Introduction

Psoriasis is an autoimmune long-lasting skin condition that not only affects the skin, but it is also linked to other health problems including cardiovascular and hepatic diseases, psychological challenges, and psoriatic arthritis1. Psoriasis was recognized by the World Health Organization (WHO) in 2014 as a serious non-communicable disease. Misdiagnosis, inappropriate treatment, or social stigma are factors of distress to the patient leading to health deterioration. According to the Global Burden of Disease Study in 2016, psoriasis was recognized to be responsible for around 5.6 million disability-adjusted-life-years (DALYs), which is more than the burden of inflammatory bowel disease three times2. Psoriasis pathogenesis involves a chronic inflammatory cascade and sustained immune activation in the skin epithelium3, driven prominently by infiltrating activated CD4 + T cells4. A dysregulated cytokine network, primarily mediated by T helper 1 (Th1) and T helper 17 (Th17) cells, along with keratinocytes, dendritic cells, and other immune cells, promotes keratinocyte hyperproliferation and abnormal keratinization, leading to lesion formation and progression5,6. The psoriatic cytokine profile is characterized by elevated Th1-associated cytokines (IL-2, IFN-γ, and TNF-α) and Th17-associated cytokines (IL-6, IL-17, IL-21, and IL-22), while anti-inflammatory mediators such as IL-10 are diminished7,8. Notably, IL-4 from Th2 cells can attenuate this pro-inflammatory milieu by suppressing IL-1β, IL-6, and Th17 activity9,10.

The National Institute for Health and Care Excellence (NICE) guidelines outline a stepwise approach to psoriasis management, beginning with topical therapies such as vitamin D analogues and corticosteroids, where combination regimens (e.g., calcipotriol with betamethasone) can enhance efficacy11. Traditional agents like dithranol and tar are limited by skin staining and irritation, while treatment of difficult-to-treat areas (scalp, face, palms, soles, nails, genitalia) remains challenging due to poor responsiveness and risks associated with prolonged steroid use, such as atrophy and telangiectasia1. Second-line options include phototherapy [narrowband ultraviolet B (NB-UVB) and psoralen plus ultraviolet A (PUVA)] and conventional systemic agents (ciclosporin, methotrexate, and acitretin). NB-UVB is generally favoured over PUVA due to lower associated skin-cancer risk12. Treatment success is commonly assessed using the Psoriasis Area and Severity Index (PASI), with targets such as PASI75 (75% improvement) or PASI90 (90% improvement), corresponding to absolute scores below 4 or 2, respectively13,14.

Future treatments for psoriasis are now increasingly depending on naturally derived compounds and herbal medicines15. Herbal medicines have shown fewer side effects, more availability, and easier usage in treatment than synthetic drugs, which made them gain attention as promising treatments for skin conditions and inflammatory diseases. Studies revealed that dietary and lifestyle changes can decrease the symptoms of psoriasis. This includes approaches like intermittent fasting and vegetarian and low-energy diets16. Treatments supplemented with omega-3 fatty acids and vitamin E found in fish oil proved efficiency against psoriasis due to their anti-inflammatory properties. Several bioactive components found in plant extracts can also regulate the immune system due to their anti-inflammatory properties, and thus they proved efficiency in the management of psoriasis17. All these data suggest the importance of identifying herbal sources and plant extracts with key therapeutic targets such as regulating T-cell activation, controlling T-cell trafficking, inhibiting inflammatory cytokines, and regulating immune response16.

Pomegranate peels form the outer layer of the Punica granatum L. fruit. These peels are considered waste as they are discarded after the consumption of the juicy seeds inside. Bioactive constituents extracted from pomegranate peels have gained attention for their potential applications in health due to their beneficial properties18. These bioactive constituents include flavonoids, antioxidants, polyphenols, and hydrolysable tannins, which are responsible for the coloring of the fruit. They proved effective potential as antimicrobial, anticancer, and anti-inflammatory response. Studies also showed their cardioprotective properties19. Pomegranate peel polysaccharides exhibit potent immunomodulatory and antioxidant activities, as demonstrated in cyclophosphamide-induced immunosuppressed mice20 and in hepatoprotection against CCl₄-induced liver injury21. In vitro, these polysaccharides show strong reducing and free-radical scavenging capacity against O₂⁻, OH⁻, and DPPH radicals22. These effects are attributed to the peel’s rich collection of bioactive polyphenols, particularly ellagitannins such as punicalagins and punicalins, whose hydroxyl groups and conjugated double bonds confer marked antioxidant and anti-inflammatory properties23,24. The unique molecular architecture of ellagitannins, comprising glucose units linked to ellagic acid moieties, underpins their broad bioactivity, including anti-cancer effects25, while the high fiber content contributes to gut health and cholesterol regulation26.

Traditionally used for parasitic infections and gastrointestinal disorders27, pomegranate peels are increasingly valued in dermatology and cosmetics for their ability to mitigate oxidative stress and inflammation; properties beneficial for conditions like acne, eczema, and skin aging28. Their bioactive constituents thus hold promise as therapeutic agents for chronic skin diseases19. However, clinical translation is hindered by inherent limitations: key compounds (e.g., ellagitannins, flavonoids) suffer from poor water solubility, rapid degradation, and low bioavailability, which significantly constrain their therapeutic effectiveness29.

This shed light on the potential effects of utilizing methods like nanotechnology to overcome these limitations and to form reliable therapeutic formulas to improve the stability and effectiveness of these phytochemicals30. While nanotechnology has been explored for drug delivery, few studies systematically compare nanoformulations to crude extracts in psoriasis models, particularly in modulating key cytokines (IL-17, IFN-γ) and oxidative stress markers31,32.

Therefore, the study aimed to prepare pomegranate peels nanoparticles (PGNPs) from pomegranate peels. The prepared nanoparticles were physically characterized to determine their size and surface charge (zeta potential) up to twenty-eight days after their preparation to determine their stability. The efficacy of PGNPs in the treatment of imiquimod (IMQ)-induced psoriasis in male Sprague Dawley rats was evaluated, in comparison to pomegranate peels extract (PGE), through measuring the levels of oxidative stress markers, cytokines in skin tissue homogenates and the histopathological examination of skin sections.

Materials and methods

Materials

Ethyl alcohol, hydrochloric acid (HCl, 38%), sodium hydroxide (NaOH), sulfuric acid, petroleum ether, Folin-Ciocalteu reagent (catalog #F9252), rutin standard (catalog #R5143), gallic acid standard (catalog #G7384), aluminum chloride (catalog #294713), DPPH (2,2-diphenyl-1-picrylhydrazyl) (catalog #D9132), ascorbic acid (catalog #A92902), indomethacin (catalog # I7378), MTT reagent [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] (catalog #M5655), dimethyl sulfoxide (DMSO) (catalog #D8418) and HPLC-grade methanol (catalog #34860) were obtained from Sigma-Aldrich (St. Louis, MO, USA). PTFE membrane filter (0.22 μm) was obtained from MilliporeSigma (Burlington, MA, USA). Dialysis membrane (MWCO 12–14 kDa) was obtained from Spectrum Labs (Rancho Dominguez, CA, USA). Rat epidermal keratinocytes (catalog #R2100) was purchased from ScienCell Research Laboratories (Carlsbad, CA, USA).

Preparation of pomegranate peels extract (PGE)

Fruits from pomegranate (Punica granatum L) were collected from the experimental farm of Faculty of Agriculture, Cairo University, Egypt with appropriate permission. This is standard practice for internal research projects conducted by the university’s faculty and students. The fruit peels were separated manually, cleaned with distilled water, dried at room temperature and ground into fine powder by the aid of a grinder. Peels’ powder was sieved by a mesh to remove coarse particles. One hundred g of peels’ powder was mixed with 1000 mL of ethyl alcohol and kept in a dark airtight container at room temperature overnight. The resultant peels’ extract was filtered by Whatman no. 1 filter paper; and the filtrate was allowed to evaporate in a rotatory evaporator.

Phytochemicals analysis of pomegranate peels

The proximate analysis of pomegranate peels was evaluated according to the Association of Official Analytical Chemists33. The peels were weighed and dehydrated in an oven at 100 °C until a constant weight was achieved to determine the moisture content (loss in weight between before and after dehydration). For the determination of ash content, peels were placed in a muffle furnace for six hours at 550 °C. Acid (sulfuric acid) and alkali (sodium hydroxide) digestions were used in the determination of crude fiber content. Crude protein content in the peels was determined by the Kjeldahl method, and the crude fat content was determined by the petroleum ether extraction method. The phytochemicals identification in the pomegranate peels’ extract was performed according to Balamurugan et al.34 and Sweidan et al.35. Braymer’s test was used to test the presence of tannins, where a dark green/brownish-blue-black colour indicated the presence of tannins. Polyphenols were tested by mixing 3 mL of the extract with 10 mL of ethyl alcohol, and the mixture was warmed for 10 min (in a water bath), followed by the addition of a few drops of freshly prepared ferric cyanide. The appearance of blue/green colour indicated the presence of polyphenols. Shinoda’s test was used to test the presence of flavonoids, where the extract was dissolved in ethyl alcohol (95%), followed by the addition of a small piece of magnesium, then a few drops of concentrated HCl. The appearance of an intense red colour indicated the presence of flavonoids. The frothing test was used to test the presence of saponins, where 1.5 mL of the extract was added to 5 mL of distilled water in a stoppered test-tube. The test tube was vigorously shaken and then allowed to stand until the formation of honeycomb froth, which indicated the presence of saponins. Quinones were tested in pomegranate peel extract by adding alcoholic potassium hydroxide to one mL of the extract, where the appearance of a red/blue colour indicated the presence of quinones. Two mL of the extract were mixed with chloroform (2 mL) and concentrated sulfuric acid (2 mL), where the appearance of red/yellowish green fluorescence indicated the presence of steroids. The presence of anthocyanins was indicated by blue/violet colour after mixing 2 mL of the extract with HCl (2 N) and ammonia. Coumarins were identified by mixing 2 mL of the extract with sodium hydroxide (10%, 3 mL) until the formation of a yellow colour. Wagner’s test was used to test the presence of alkaloids, where one mL of the extract was added to Wagner’s reagent [iodine (2.5 g) was dissolved in potassium iodide (12.5 g) and 250 mL of distilled water]. Brownish/red precipitate indicated the presence of alkaloids. Triterpenes were identified by the appearance of a red colour after dissolving the extract in acetic anhydride, followed by the addition of a few drops of concentrated sulfuric acid to the soluble solution formed.

Determination of the total phenolic content (TPC)

The Folin-Ciocalteu reagent was used to determine the TPC of the PGE and PGNPs in accordance with the method described by Li et al.36. Briefly, the extract (0.3 mL) was combined with Folin-Ciocalteu reagent diluted with distilled water (1.7 mL, 10%), and the mixture was incubated for 15 min at room temperature. The intensity of the resulting blue hue was measured at 760 nm. Mg gallic acid equivalents/g dry weight (mg GAE/g DW) was the unit of measurement used to express the results.

Determination of total flavonoids content (TFC)

The TFC was expressed in mg of rutin equivalent/g of extract (mg RU/g extract) and was determined using the rutin calibration curve (0.01–0.1 mg/mL) according to Djeridane et al.37 study. Methanolic aluminum chloride (0.5 mL, 10%) was mixed with the peels’ extract (1 mL) and HCl (0.5 mL, 1 M) and the mixture was kept at room temperature for half an hour. The results were measured at 425 nm.

Gas chromatography-mass spectrometry (GC-MS) analysis of PGE and PGNPs

The chemical composition of PGE and PGNPs was analyzed using GC-MS following established protocols. Samples were prepared by dissolving 1 mg of each sample in 1 mL of HPLC-grade methanol, followed by filtration through a 0.22 μm PTFE membrane. Analysis was performed using an Agilent 7890B GC system coupled with a 5977B MSD mass spectrometer, equipped with an HP-5MS capillary column (30 m × 0.25 mm, 0.25 μm film thickness) [Agilent Technologies (Santa Clara, CA, USA)]. The oven temperature program was set as follows: initial temperature of 50 °C (held for 2 min), ramped at 10 °C/min to 280 °C (held for 10 min), with a total run time of 35 min. Helium was used as the carrier gas at a constant flow rate of 1 mL/min. The injector and ion source temperatures were maintained at 250 °C and 230 °C, respectively, with a split ratio of 10:1. Mass spectra were acquired in electron ionization (EI) mode at 70 eV, scanning the m/z range of 40–600. Compounds were identified by comparing their mass spectra with the NIST 17 library and confirmed using retention indices of authentic standards when available. Quantification was expressed as % relative abundance, with each sample analyzed in triplicate to ensure reproducibility.

Preparation of pomegranate peels nanoparticles (PGNPs)

Dried pomegranate peels were cut into small pieces followed by grinding into fine powder by the aid of an electric grinder. The pomegranate peels powder was sieved to obtain particles with a uniform size. Ten g of the powder was mixed with 100 mL of HCl (38%) in a bottle that was placed on a magnetic stirrer [IKA® RCT basic (Staufen, Germany)] for continuous stirring at 1200 rpm for five days, where the optimization for the conditions of nanoparticles synthesis was according to Mostafa et al.38. PGNPs were collected as a pellet via centrifugation (15,000 rpm, 30 min, 4 °C). The pellet was stored in tightly sealed amber glass vials at 4 °C in the dark to minimize hydrolytic degradation, aggregation, and photo-oxidation of labile phytochemicals. For all subsequent applications, an aliquot of the pellet was freshly reconstituted in the appropriate aqueous vehicle (PBS or cell culture medium) using brief sonication (5 min, 40 kHz) immediately prior to use, ensuring consistent dosing and colloidal stability during experiments. The hydrodynamic size and surface charge of prepared nanoparticles were determined on the 1st, 7th ,14th and 28th days after preparation to determine their stability. The size of PGNPs was also determined by transmission electron microscope (TEM).

Determination of encapsulation efficiency and drug loading

The encapsulation efficiency (EE) and drug loading (DL) capacity of PGNPs were determined by quantifying the TPC and TFC. Following nanoparticle synthesis, the PGNPs were separated from unencapsulated compounds by centrifugation at 15,000 rpm for 30 min at 4 °C. The supernatant containing free phytochemicals was collected for the analysis. Encapsulation efficiency was calculated as [(Total TPC/TFC in PGNPs)/(Total TPC/TFC in initial extract)] × 100, while drug loading capacity was determined as [(TPC/TFC in PGNPs)/(Total weight of PGNPs)] × 100. All measurements were performed in triplicate, with appropriate blank corrections, and results were expressed as mean ± standard deviation.

In vitro release study

The in vitro release profile of PGE from PGNPs was evaluated using a dialysis method under sink conditions39. PGNPs (10 mg) were suspended in PBS (pH 7.4) and placed in a pre-soaked dialysis membrane (MWCO 12–14 kDa), which was then immersed in 50 mL of release medium maintained at 37 ± 0.5 °C with constant stirring at 100 rpm. Aliquots (1 mL) were collected at predetermined time intervals (0.5, 1, 2, 4, 6, 8, 12, 24, and 48 h) and replaced with fresh PBS to maintain the sink conditions. The released PGE was quantified using UV-Vis spectrophotometry [Shimadzu UV-1800 (Kyoto, Japan)] at 360 nm40. The cumulative release percentage was calculated by comparing the amount of PGE released at each time point to the total encapsulated PGE content. The method was designed to simulate physiological conditions while allowing for comprehensive analysis of both initial burst release and sustained release phases from the nanoparticle formulation.

Cytotoxicity test

The MTT assay was used to determine the cytotoxicity effect of PGE and PGNPs on rat epidermal keratinocytes. 105 cells were cultured and incubated for 24 h at 37 °C and CO2 (5%) [Thermo Scientific Heracell™ 150i (Waltham, MA, USA).]. The culture medium was supplemented with different concentrations of PGE or PGNPs and the cells were incubated for another 24 h at 37 °C and CO2 (5%). Twenty µL of MTT (5 mg/mL) were added to the cultures that were incubated for four hours at 37 °C and CO2 (5%); followed by the addition of DMSO and the absorbance was read at 560 nm.

Determination of the antioxidant activity

The DPPH assay was used to determine the free radicle scavenging effect of PGE and PGNPs in vitro (ascorbic acid was used as a standard). Different concentrations of PGE or PGNPs were added to methanolic solution of DPPH (0.2 mM); and the mixtures were incubated for 30 min in a dark place followed by reading the absorbance at 517 nm.

Determination of the anti-inflammatory activity

The anti-inflammatory effect of PGE and PGNPs was determined, in vitro, by the hemolysis inhibition assay (indomethacin was used as a standard). Blood sample (5 mL) was collected from rat in a heparinized tube and used in the preparation of red blood cells suspension. Briefly, blood sample was centrifuged for 10 min at 1000 rpm. The supernatant was discarded, and the pellet was washed with phosphate buffered saline several times. Finally, the pellet was suspended in a phosphate buffered saline. Different concentrations of PGE or PGNPs were mixed with phosphate buffered saline or water to form isotonic and hypotonic solutions, respectively. Red blood cells suspension (0.1 mL) was mixed with PGE or PGNPs and incubated for one hour followed by centrifugation at 1000 rpm for 10 min. The released hemoglobin was measured at 540 nm.

Experimental design

The sample size was determined by power analysis using G*Power software. Based on pilot data and effect sizes reported in comparable studies, parameters were set for a large effect size (Cohen’s f > 0.4), α = 0.05, and power (1-β) = 0.80 for one-way ANOVA. The analysis indicated that < 6 animals per group will be sufficient to detect significant differences in primary outcomes. This number also aligns with the ethical framework of the 3Rs. The present investigation employed male rats to maintain consistency with the most extensively validated preclinical model of IMQ-induced psoriasis, thereby ensuring direct comparability with established literature. This design also serves to minimize experimental variability associated with the estrous cycle, providing a more controlled and reproducible system for this initial proof-of-concept evaluation of PGNPs’ therapeutic efficacy. Twenty healthy male Sprague Dawley rats of eight weeks age and 160–170 g weight were obtained from the National Organization for Drug Control and Research. Rats were kept under controlled temperature (22 ± 2 °C), humidity and 12 h dark/light cycle. All animal experiments were complied with the ARRIVE guidelines. All experiment procedures were approved by the Institutional Animal Care and Use Committee of Cairo University (CUIF4724). Animals were divided into four groups (5 rats/group): negative control group I, untreated rats with IMQ-induced psoriasis (positive control group II), PGE (200 mg/kg) treated rats with IMQ-induced psoriasis (PGE-IMQ group III) and PGNPs (100 mg/kg) treated rats with IMQ-induced psoriasis (PGNPs-IMQ group IV). The induction of psoriasis was performed according to Horváth et al.41, 62.5 mg of Aldara cream (5% IMQ, MEDA Pharmaceuticals, Solna, Sweden) were topically administrated on the rats’ back [after shaving their hairs with a depilatory cream (one, EVA cosmetics, Egypt)] for ten successive days. After the induction of psoriasis, treatments were administrated topically for 14 successive days (twice/day). Published studies on the anti-inflammatory and antioxidant effects of pomegranate extracts commonly use doses in the range of 100–400 mg/kg20,24,42,43,44. Based on this reported therapeutic range, we selected a mid-range dose of 200 mg/kg for the crude PGE (group III) to serve as a positive treatment control. To directly test the hypothesis that nanoformulation enhances bioavailability and efficacy, the dose for PGNPs (group IV) was set at 100 mg/kg (half that of the crude extract). This comparative design aimed to demonstrate whether the nanoformulation could achieve superior therapeutic outcomes even at a reduced dose, highlighting a key potential advantage for clinical translation. Treatments were applied twice daily (approximately every 12 h) to the lesional area at doses of 200 mg/kg (PGE, group III) and 100 mg/kg (PGNPs, group IV). Clinical severity assessment of psoriatic lesions was performed using a modified rodent Psoriasis Area and Severity Index (PASI), where the three cardinal signs, erythema (redness), scaling (desquamation), and thickening (induration), were each independently scored from 0 (none) to 4 (severe) by two blinded observers. Rats were anesthetized by an intraperitoneal injection of 50 mg/kg sodium pentobarbital [Sigma-Aldrich (St. Louis, MO, USA), catalog #P3761] where skin samples from the rats’ back were collected. Skin tissue homogenates were prepared by homogenization of one g of skin in a phosphate buffered saline followed by two cycles of freeze and thaw and centrifugation for 15 min at 1200 rpm.

Determination of the effect of PGE and PGNPs on oxidative stress

The antioxidant activities of PGE and PGNPs, in vivo, were determined by measuring the level of malondialdehyde (MDA) as a marker for lipid peroxidation in skin tissue homogenates by rat ELISA kit (MBS268427, MyBioSource, USA). The antioxidant defense system was evaluated by measuring the level of the antioxidant enzymes catalase (CAT), glutathione (GSH) and superoxide dismutase (SOD) in skin tissue homogenates by rat ELISA kits (MBS726781, MBS265966 and MBS036924, MyBioSource, USA; respectively).

Determination of the effect of PGE and PGNPs on cytokines

The anti-inflammatory activity of PGE and PGNPs, in vivo, were determined by measuring the level of IL-6 (ab234570, Abcam, USA), IL-17 (MBS2022678, MyBioSource, USA), IL-10 (ab100765, Abcam, USA) and IFN-γ (ab239425, Abcam, USA) in skin tissue homogenates by rat ELISA kits.

Histopathological examination

The histopathological examination was carried out by a skilled pathologist who was blinded to the experimental design. Skin samples were fixed in 10% formalin for 24 h, dehydrated, embedded in paraffin blocks, cut into 4 μm thickness-sections that were stained by hematoxylin and eosin.

Statistical analysis

All quantitative data were presented as mean ± standard deviation (SD). Statistical significance was determined using one-way analysis of variance (ANOVA) followed by Tukey’s honestly significant difference (HSD) post-hoc test for multiple comparisons between groups. The threshold for statistical significance was set at p < 0.05. All analyses were performed using GraphPad Prism version 9.0 (GraphPad Software, San Diego, CA, USA) and Microsoft Excel with the Real Statistics Resource Pack. Exact p-values for all pairwise comparisons were reported in the results section (tables and figures).

In vitro and physicochemical assays were conducted in triplicate (n = 3), in accordance with established analytical standards for exploratory and proof-of-concept research. This approach was well-suited to robustly identify and confirm large, biologically meaningful effects, such as the enhanced antioxidant activity and phytochemical retention of PGNPs, as reflected in the low standard deviations and statistical significance of the reported data. The findings were further strengthened by their consistency across multiple independent experimental platforms (GC-MS, encapsulation efficiency, DPPH, hemolysis inhibition, and cytotoxicity assays), ensuring a reliable and reproducible demonstration of the key trends central to this study.

Results

Analysis of pomegranate peels

The proximate analysis of pomegranate peels showed the presence of crude fat (10.80%), protein (9.23%) and fibers (22.43%); in addition to a total sugar of 33.10% (32.06 and 1.03% for reducing and non-reducing sugars, respectively). The ash and moisture content in the peels were 0.53 and 0.43%, respectively (Table 1). The peels have an acidic pH of 3.03. The qualitative screening of phytochemicals confirmed the presence of tannins, polyphenols, flavonoids, saponins, quinones, alkaloids, triterpenes, courmarins, steroids and anthocyanins in the pomegranate peels extract.

Table 1 Proximate analysis of pomegranate peels.
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Results of phytochemical encapsulation in PGNPs

The encapsulation profile of PGNPs demonstrated excellent retention of bioactive compounds, as detailed in Table 2. The TPC showed high EE% of 86.04%, with PGNPs containing 260.17 ± 3.28 mg GAE/g compared to the initial PGE value of 302.36 ± 2.04 mg GAE/g, resulting in a DL% of 8.39%. Similarly, the TFC exhibited even slightly better encapsulation (EE% = 87.83%), with PGNPs containing 107.13 ± 2.25 mg RU/g versus the original PGE value of 121.96 ± 0.40 mg RU/g, achieving a DL of 3.45%.

Table 2 Phytochemical encapsulation profile of PGNPs.
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GC-MS analysis of PGE and PGNPs

GC-MS analysis revealed a highly conserved phytochemical profile between the crude PGE and its nanoformulated PGNPs. As summarized in Table 3, the relative abundances of major compound classes were remarkably similar, demonstrating the successful retention of key bioactive constituents during nanoparticle synthesis.

The most abundant compound in both extract and nanoparticles was the furan derivative 5-(hydroxymethyl)furan-2-carbaldehyde (HMF), constituting approximately 26% of the total identified area. Fatty acids and their methyl esters collectively represented the largest class of compounds, with combined abundances of 23.87% in PGE and 23.57% in PGNPs for free fatty acids, and 18.12% and 17.48% for fatty acid methyl esters, respectively. Notable anti-inflammatory fatty acids such as petroselaidic acid and palmitic acid were preserved at near-identical levels.

Nitrogenous compounds, including N⁴-acetylcytidine and homothiourea, showed a slight but consistent reduction in PGNPs (7.06% vs. 6.45%). Similarly, terpenoids and derivatives demonstrated a more pronounced decrease (1.95% vs. 1.46%), suggesting some susceptibility of these minor volatile components to the acidic hydrolysis process used for nanoparticle preparation. In contrast, sugars, amino acid derivatives, silicon-containing compounds, and hydroxy esters were well preserved, with retention exceeding 90% of their original abundance.

Overall, 95.28% of the PGE chromatogram area and 92.01% of the PGNPs chromatogram area were accounted for by the 34 identified compounds, indicating a high degree of phytochemical preservation (96.6% similarity) and validating the nanoformulation process as an effective means of stabilizing the complex bioactive profile of PGE.

Table 3 Consolidated GC-MS analysis of PGE and its nanoformulation (PGNPs).
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Physical characterization of PGNPs

TEM image showed that PGNPs have a size of 84.3–85.6 nm (Fig. 1A). The hydrodynamic size and surface charge (zeta potential) of PGNPs were determined on the 1st, 7th, 14th and 28th days after preparation to examine the nanoparticles stability. The size was 87.23 nm, on the 1st day, which increased to 91.36 and 91.43 nm on the 7th and 14th day. The same behavior was observed in the zeta potential, where a positive surface charge of 41.93 mV was measured on the 1st day. The zeta potential increased to reach 44.03 and 44.13 mV on the 7th and 14th day (Table 4). The nanoparticles stability was achieved, where the size and zeta potential on the 28th days (91.43 nm and 44.13 mV, respectively) was the same as those on the 14th days (91.43 nm and 44.13 mV, repectively).

Table 4 Physical characterization of PGNPs.
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In vitro release profile of PGE from PGNPs

The in vitro release study demonstrated a biphasic release pattern of PGE from PGNPs over 48 h (Fig. 1B). An initial burst release of 21.2 ± 0.76% was observed within the first 2 h, attributable to the rapid diffusion of surface-associated phytochemicals. This was followed by sustained release, with cumulative percentages reaching 36.7 ± 1.52% at 6 h and 45.7 ± 1.53% at 8 h. The release kinetics showed significant acceleration between 8 and 12 h (from 45.7% to 65.7%), suggesting possible matrix swelling or initial polymer degradation. The nanoparticles achieved near-complete release (85.3 ± 1.52%) by 48 h, with the release rate stabilizing after 24 h (70.8 ± 1.04%).

Cytotoxicity activity (MTT assay)

PGE showed a higher cytotoxicity % than PGNPs at all tested concentrations (11.53, 13.13, 17.53, 19.76, 25.40 and 31.20 Vs 3.60, 5.20, 6.50, 9.16, 11.40 and 15.23% for PGE and PGNPs, respectively at 31.25, 62.5, 125, 250, 500 and 1000 µg/ml). The cytotoxicity effect of both PGE and PGNPs on rat epidermal keratinocytes increased in a dose dependent manner (Fig. 1C).

Antioxidant activity (DPPH assay)

The DPPH assay was used to compare the free radical scavenging effect of PGE and PGNPs using ascorbic acid as a standard. The results showed that both PGE and PGNPs have antioxidant activities higher than that of ascorbic acid (Fig. 1D). The DPPH scavenging effect of PGNPs (45.46, 52.20, 59.93, 67.00, 74.63, 89.40 and 96.63%) was significantly higher than those of PEG (34.96, 40.66, 50.96, 59.96, 69.70, 79.60 and 90.30%) and ascorbic acid at all tested concentrations (15.62 to 1000 µg/ml).

The anti-inflammatory activity (hemolysis Inhibition assay)

The effect of PGE and PGNPs on the hemolysis of rats’ red blood cells was evaluated to determine their anti-inflammatory effects where indomethacin was used as a standard (Fig. 1E). The hemolysis inhibition % PGNPs (67.10, 72.16, 79.26, 86.03, 91.76 and 94.66%) was significantly lower than that of indomethacin (200 µg/ml) (96.03%); and significantly higher than that of PGE (63.63, 67.26, 73.43, 77.76, 84.23 and 88.23%) at all tested concentrations (100 to 1000 µg/ml).

Fig. 1
Fig. 1
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Characterization of PGNPs showing (A) TEM image, (B) in vitro release %, (C) cytotoxicity effect (MTT assay) on rat epidermal keratinocytes where * represented significance (P < 0.05) when compared to PGE, (D) the antioxidant effect (DPPH assay) where * and # represented significance (P < 0.05) when compared to ascorbic acid and PGE, (E) the anti-inflammatory effect (hemolysis inhibition test) where * and # represented significance (P < 0.05) when compared to indomethacin and PGE. Results were expressed as mean ± standard deviation (SD). Statistical significance was determined using one-way analysis of variance (ANOVA) followed by Tukey’s honestly significant difference (HSD) post-hoc test for multiple comparisons between groups. The threshold for statistical significance was set at p < 0.05.

Effect of PGE and PGNPs on oxidative stress

The effect of PGNPs on oxidative stress, in vivo, were evaluated through measuring the levels of MDA (lipid peroxidation marker) and the antioxidant enzymes (SOD, CAT and GSH) in skin tissue homogenates in comparison to PGE (Table 5). IMQ topical administration, in group II, significantly elevated the MDA (16.12 nmol/g tissue) when compared to that of control group I (6.14 nmol/g tissue); and significantly reduced the antioxidant levels when compared to control group I (SOD: 95.80 Vs 119.12 U/g tissue, CAT: 47.76 Vs 74.10 U/g tissue and GSH: 101.40 Vs 144.80 µmol/g tissue). Although PGE topical administration, in group III, significantly ameliorated the disturbance in oxidative stress parameters, however, the levels of MDA and the antioxidant enzymes remained significantly different from those of control group I. Group IV that received PNPs showed no significance difference in oxidative stress parameters when compared to control group I (MDA: 7.26 Vs 6.14 nmol/g tissue, SOD: 114.82 Vs 119.12 U/g tissue, CAT: 72.06 Vs 74.10 U/g tissue and GSH: 142.60 Vs 144.80 µmol/g tissue).

Table 5 Effect of PGE and PGNPs on oxidative stress in skin tissue homogenates.
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Effect of PGE and PGNPs on cytokines

To evaluate the anti-inflammatory effect of PGNPs, in vivo, the levels of inflammatory cytokines (IL-17 and IFN-γ), anti-inflammatory cytokine (IL-10) and IL-6 were evaluated in skin tissue homogenates (Table 6). Psoriasis induction, in group II, significantly elevated the levels of IL-6, -17 and IFN-γ (161.20, 221.40 and 479.4 pg/g tissue, respectively) when compared to control group I (129.80, 98.60 and 199.40 pg/g tissue, respectively). On the other hand, the anti-inflammatory cytokine (IL-10) level was significantly decreased in group II (48.40 pg/g tissue) when compared to group I (83.20 pg/g tissue). PGNPs administration, in group IV, significantly reduced the levels of IL-17 and IFN- γ (102.20 and 204.40 pg/g tissue, respectively); and significantly elevated the IL-10 level when compared to those of group II. No significant difference was observed in the levels of IL-17, IFN- γ and IL-10 between group I and group IV.

Table 6 Effect of PGE and PGNPs on cytokines levels in skin tissue homogenates.
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Histopathological examination

Negative control group I showed skin sections with intact keratinized epidermis, dermis with average pilosebaceous units, average collagen, and average deep dermis (Fig. 2). Positive control group II showed skin sections with ulcerated epidermis with loss of rete ridges and mild spongiosis, mild superficial inflammatory infiltrate, excess thick collagen with no pilosebaceous units, and markedly dilated congested blood vessels in deep dermis (Fig. 3). Group III, treated with PGE, showed skin sections with thick keratin, thick epidermis, atrophied pilosebaceous units and excess thick collagen (Fig. 4). Skin sections of group IV, treated with PGNPs, showed intact epidermis, mild superficial inflammatory infiltrate, atrophied pilosebaceous units and average collagen (Fig. 5).

Fig. 2
Fig. 2
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Normal skin histology in healthy control rats (Group I). Representative H&E-stained sections show: (A) Intact keratinized epidermis (black arrow), normal pilosebaceous units (blue arrow), and average collagen density (red arrow) (200×). (B) Normal hair follicles (black arrow), average collagen (blue arrow), and typical subcutis (red arrow) (200×). (C) Intact epidermis and dermal structures (black arrow), normal pilosebaceous units (blue arrow), and regular collagen (red arrow) (400×). (D) Normal pilosebaceous units (black arrow) and collagen (red arrow) (400×). (E) Typical hair follicles (black arrow) and average dermal collagen (red arrow) (400×).

Fig. 3
Fig. 3
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Psoriatic skin histopathology in IMQ-induced psoriatic untreated rats (Group II). Representative H&E-stained sections illustrate characteristic psoriasiform changes: (A) Ulcerated epidermis (black arrow), thick infected crust (blue arrow), and dermal fibrosis with absence of pilosebaceous units (red arrow) (200×). (B) Dense inflammatory infiltrate (black arrow) and markedly dilated, congested blood vessels (red arrow) (200×). (C) Thick infected crust (black arrow) overlying fibrotic dermis (red arrow) (400×). (D) Thick crust (black arrow), mild superficial inflammation (blue arrow), and excess thick collagen (red arrow) (400×). (E) Marked inflammatory infiltrate (black arrow) and pronounced collagen deposition (blue arrow) (400×).

Fig. 4
Fig. 4
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Partial histological improvement following treatment with crude PGE (Group III). Representative H&E sections demonstrate residual psoriatic features: (A) Hyperkeratosis (black arrow), acanthosis (blue arrow), atrophied pilosebaceous units (red arrow), and excess dermal collagen (yellow arrow) (200×). (B) Excessive thick collagen (black arrow), mildly dilated vessels (blue arrow), and normal subcutis (red arrow) (200×). (C) Thickened epidermis (black arrow) with mild spongiosis (blue arrow) and preserved rete ridges (red arrow) (400×). (D) Epidermal thickening with mild spongiosis (black arrow) and mild superficial inflammation (red arrow) (400×). (E) Mildly atrophied pilosebaceous units (black arrow) and persistent collagen excess (blue arrow) (400×).

Fig. 5
Fig. 5
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Near-complete histological restoration following treatment with PGNPs (Group IV). Representative H&E sections show significantly normalized skin architecture: (A) Intact epidermis (black arrow), mild residual inflammation (blue arrow), atrophied pilosebaceous units (red arrow), and normalized collagen density (yellow arrow) (200×). (B) Atrophied hair follicles (black arrow), average collagen (blue arrow), and normal subcutis (red arrow) (200×). (C) Mild spongiosis (black arrow), loss of rete ridges (blue arrow), and mild superficial inflammation (red arrow) (400×). (D) Intact epidermis with rete ridge loss (black arrow) and mild inflammation (red arrow) (400×). (E) Atrophied hair follicles (black arrow) and normal collagen (blue arrow) (400×).

Photos of rats’ back skin demonstrated the therapeutic effect of PGNPs (group IV) when compared to PGE (group III) (Fig. 6). Topical application of IMQ in positive control group II induced severe psoriatic lesions, as evidenced by high scores for erythema, scaling, and skin thickening (Fig. 6E). Treatment with crude PGE (200 mg/kg) in group III resulted in a moderate but significant improvement across all parameters compared to the untreated psoriatic group II. Notably, treatment with PGNPs (100 mg/kg) in group IV led to a dramatic and near-complete resolution of clinical symptoms. The scores for erythema, scaling, and thickening in the PGNPs-treated group were markedly lower than those in the PGE-treated group and were not significantly different from the healthy negative control group I. These results demonstrated that the nanoformulation (PGNPs) is significantly more effective than the crude extract (PGE) in ameliorating the clinical manifestations of psoriasis in this model, even when administered at half the dose (Table 7).

Fig. 6
Fig. 6
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Photos of rats’ back skin of (A) negative control group I, (B) positive control group II, (C) PGE-IMQ group III and (D) PGNPs-IMQ group IV. (E) PASI in different experimental groups. Results were expressed as mean ± SD. *,# and $ represented significance (P < 0.05) when compared to negative control group I, positive control group II and PGE-IMQ group III, respectively.

Table 7 Qualitative summary of treatment effects across experimental groups.
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Discussion

Pomegranate (Punica granatum L.) has been cultivated since around 3000 B.C. in regions including Iran, India, China, and the Mediterranean, with production now extending to North Africa, North America, Europe, and Asia45,46. Global production surpassed three million tons in 2017, reflecting its growing popularity due to flavor and nutritional value47. The fruit consists of peel, juice, and seeds, with peels representing 26–30% of the fruit’s weight as a major by-product of juicing. Rich in polyphenols, fibers, vitamins, and minerals, pomegranate peels possess broad biological activities, including anti-inflammatory and antioxidant effects, as confirmed by numerous in vitro and in vivo studies48. PGE promotes wound healing through its antibacterial, antioxidant, and anti-inflammatory properties, which attributed to constituents such as flavonoids and hydrolyzable tannins24. These bioactive compounds are also associated with protection against metabolic disorders like diabetes, heart disease, and obesity49, underscoring their potential as therapeutic agents to enhance the industrial value of pomegranate19.

The application of pomegranate peel bioactives in dermatology and cosmetics is expanding due to their ability to reduce wrinkles, inflammation, and oxidative stress. However, their translation into reliable therapies is hampered by challenges related to water solubility, biological effectiveness, and long-term stability30. Nanotechnology offers a promising strategy to overcome these limitations by improving the stability and efficacy of these valuable phytochemicals. Therefore, the study aimed to prepare PGNPs from pomegranate peels. The advantages of nanoparticles over regular sized molecules are better solubility, accessibility, and effectiveness50. Its improved physiochemical characteristics and smaller particle size increased their use in many fields like food processing, agriculture and medical fields. Furthermore, the creation of novel nanoparticles from plants waste product is recommended and has been searched in many applications51,52.

Although several studies have explored nanoformulations of pomegranate extracts, the present work distinguishes itself through several key methodological and conceptual advances. First, it specifically valorizes pomegranate peels (an abundant agricultural byproduct) using a straightforward acid hydrolysis method to generate nanoparticles, avoiding synthetic polymers or metal matrices common in other encapsulation techniques. Second, rather than focusing solely on general properties, this study provides a direct, dose-contrasted comparative evaluation of the nanoformulation versus its crude extract counterpart in a well-established IMQ-induced psoriasis model. Crucially, the nanoparticles were administered at half the dose of the crude extract, offering clear evidence of enhanced bioavailability and therapeutic efficiency. Finally, the work establishes a direct link between the nanoparticles’ extended colloidal stability (28-day monitoring) and their superior in vivo performance in modulating psoriasis-specific oxidative stress and cytokine pathways, an integrative analysis often absents in prior phytochemical nanoformulation studies.

The significantly greater anti-psoriatic efficacy of PGNPs over the crude PGE, as evidenced by the normalization of oxidative stress, cytokines, and histology, can be attributed to the fundamental advantages conferred by nanoformulation. These include: (1) enhanced penetration through the stratum corneum due to nanoscale size, (2) protection and stabilization of the core bioactive compounds (e.g., phenolics, and flavonoids), (3) improved cellular uptake and retention facilitated by the positive surface charge, and (4) sustained release kinetics ensuring prolonged therapeutic action. Collectively, these properties overcome the key limitations of poor solubility, low stability, and limited bioavailability inherent to the crude plant extract.

In this study, pomegranate peels were analyzed to identify their bioactive contents. Pomegranate peels contained crude fat, protein and fibers (10.80, 9.23 and 22.43%, respectively); in addition to 0.53% of ash and 0.43% of moisture. The total sugar content in the peels was 33.10%. The peels contained several phytochemicals (tannins, polyphenols, flavonoids, saponins, quinones, alkaloids, triterpenes, courmarins, steroids and anthocyanins).

The GC-MS analysis revealed a remarkably consistent phytochemical profile between PGE and its PGNPs, with only minor variations in compound abundances. The most abundant compound in both extracts was 5-(hydroxymethyl)furan-2-carbaldehyde (HMF), constituting approximately 26% of total detected compounds. The high retention of HMF in PGNPs (26.01 ± 0.07%) compared to PGE (26.1 ± 0.03%) suggested excellent stability during nanoparticle synthesis, supporting findings by Salem et al.32 on the protective effects of nanoencapsulation on thermolabile phytochemicals.

Fatty acid derivatives dominated both profiles, with petroselaidic acid (trans-6-octadecenoic acid) showing near-identical abundance in both extracts. This consistency is noteworthy as petroselaidic acid has demonstrated significant anti-inflammatory activity in autoimmune disorders5449. The preservation of methyl esters, including methyl stearolate (8.07% in PGE vs. 7.97% in PGNPs) and methyl (9Z)-octadecenoate (4.68% vs. 4.58%), suggested that the esterification state of these bioactive lipids was maintained during nanoparticle formulation, which is crucial for their biological activity as noted by Gunasekaran et al.55.

Nitrogenous compounds showed slightly greater variability, with N⁴-acetylcytidine decreasing from 3.92% in PGE to 3.49% in PGNPs. This modest reduction might reflect the hydrophilic nature of this nucleoside derivative, as nanoparticle encapsulation typically favours lipophilic compounds56. However, the retention of 89% of this immunomodulatory compound suggested effective nanoformulation, supporting its potential role in PGNPs’ observed anti-psoriatic effects.

The high degree of phytochemical preservation in PGNPs supports the technological advantage of this delivery system. These findings corroborate previous work by Morsy et al.31 demonstrating enhanced stability of pomegranate phytochemicals in nanoformulations. The results particularly validate the selection of PGNPs for further anti-psoriatic studies, as the maintained composition of key bioactive compounds (HMF, petroselaidic acid, and fatty acid esters) aligns with established anti-inflammatory mechanisms in psoriasis treatment14,28.

The nanoencapsulation of pomegranate peel bioactives into PGNPs proved highly effective, achieving high EE of 86.04% for TPC and 87.83% for TFC. The resultant DL capacities, 8.39% for TPC and 3.45% for TFC, fall within the optimal therapeutic nanoparticle range (5–20%), ensuring adequate bioactive delivery while preserving nanoparticle stability. The differential loading reflects the higher native concentration of phenolics (302.36 mg GAE/g) compared to flavonoids (121.96 mg RU/g) in the crude extract. These results demonstrate that PGNPs can successfully encapsulate and preserve the full spectrum of key phytochemicals, addressing a central challenge in phytopharmaceutical development and enabling the delivery of pomegranate’s complete antioxidant and anti-inflammatory profile.

The hydrodynamic size and zeta potential of PGNPs were determined on the 1st, 7th, 14th and 28th days after preparation to examine the nanoparticles stability. PGNPs showed a hydrodynamic size of 87.23 nm that increased to 91.36 nm after seven days of preparation. A positive zeta potential of 41.93 mV was measured on the 1st day that increased to reach 44.03 and 44.13 mV on the 7th and 14th day. The nanoparticles’ stability was confirmed over 28 days, with the size and zeta potential on the 28th day (91.43 nm and 44.13 mV, respectively) being like those on the 14th day, indicating no progressive aggregation or charge decay. The plateau in both size and zeta potential between day 14 and day 28 demonstrated that the nanoparticles reached a stable equilibrium state within the first two weeks, with no further changes observed over the subsequent two weeks. This 28-day data substantiates our claim of stability beyond the initial experimental timeframe and suggests that PGNPs are suitable for studies requiring storage or repeated administration over at least a one-month period. TEM image showed that PGNPs have a size of 84.3–85.6 nm which was similar to the hydrodynamic size. For the in vitro release of PGE from PGNPs, the biphasic profile, characterized by initial rapid release followed by prolonged sustained release, indicates successful encapsulation and suggests the formulation could provide both immediate and extended therapeutic effects. The high cumulative release percentage (> 85%) confirms efficient liberation of bioactive compounds from the nanoparticle matrix, while the sustained phase demonstrates the potential for reduced dosing frequency in therapeutic applications. These results compare favourably with other plant-based nanoformulations, where similar release patterns have been reported for polyphenol-loaded delivery systems.

The conversion of PGE into PGNPs conferred substantial pharmacological benefits, enhancing both efficacy and safety. In vitro, PGNPs showed significantly lower cytotoxicity than PGE on keratinocytes (p < 0.05), indicating improved dermatological biocompatibility. Antioxidant capacity (DPPH assay) was 15–20% higher for PGNPs than for PGE and ascorbic acid across all concentrations, reflecting preserved or amplified phenolic redox activity. In anti-inflammatory testing (hemolysis inhibition), PGNPs outperformed PGE while remaining less potent than indomethacin, suggesting a favourable therapeutic opportunity. Physicochemical characterization confirmed robust colloidal stability, with minimal size variation (± 4 nm) and high zeta potential (>|30 mV|) over 28 days, correlating with maintained bioactivity during storage.

These collective data demonstrate that nanoengineering converted PGE into a superior therapeutic agent with: 1- enhanced antioxidant capacity exceeding conventional standards; 2- optimized anti-inflammatory activity within a safer potency range; and 3- significantly reduced cellular toxicity. These improvements, coupled with demonstrated physical stability, position PGNPs as a promising platform for chronic inflammatory skin conditions requiring prolonged treatment, where both efficacy and safety are paramount considerations. The success of this transformation underscores the potential of nanotechnology to amplify the therapeutic index of phytochemical-rich extracts while mitigating their limitations.

This study systematically compared the efficacy of PGNPs and crude PGE in treating IMQ-induced psoriasis in Sprague Dawley rats. Four groups were used: healthy controls (I), untreated psoriatic rats (II), PGE-treated psoriatic rats (200 mg/kg, III), and PGNPs-treated psoriatic rats (100 mg/kg, IV). Psoriasis was induced via topical IMQ application (62.5 mg/day for 10 days) following established protocols41, leveraging the model’s well-characterized similarity to human psoriasis pathophysiology57,58 and its reliability for evaluating novel therapies59.

Comprehensive analysis showed PGNPs’ superior therapeutic profile. While both treatments modulated oxidative stress markers (MDA, SOD, CAT, and GSH) and inflammatory cytokines (IL-6, IL-17, and IFN-γ), PGNPs induced significantly greater improvements. PGNPs-treated animals achieved complete normalization of IL-17, IFN-γ, and IL-10 levels to near-healthy control values, whereas PGE only partially corrected these cytokines. Histopathology confirmed these findings, with PGNPs restoring near-normal skin architecture, in contrast to the persistent epidermal thickening and excess collagen seen with PGE treatment.

The agreement between histopathological findings and clinical severity scores robustly validated the therapeutic superiority of the nanoformulation. Histological analysis revealed that PGNPs treatment (group IV) restored near-normal skin architecture, characterized by intact epidermis, average collagen deposition, and only mild residual inflammation, whereas PGE treatment (group III) left notable epidermal thickening, excess collagen, and atrophied pilosebaceous units. These microscopic observations were directly reflected in the clinical PASI-based scores, where PGNPs-treated animals showed dramatic reductions in erythema, scaling, and thickening. Values that approached those of healthy controls and were significantly lower than those in the PGE-treated group. This close correlation between tissue-level repair and macroscopic symptom resolution underscores that the enhanced bioavailability and targeted delivery afforded by nanoencapsulation not only modulate molecular markers (cytokines and oxidative stress) but also translate into tangible, holistic restoration of skin structure and function, offering a comprehensive therapeutic outcome that closely mimics the treatment goals in human psoriasis management.

The superior modulation of all measured parameters, including pro-inflammatory cytokines (IL-6, IL-17, and IFN-γ), anti-inflammatory cytokine (IL-10), and oxidative stress markers (MDA, SOD, CAT, and GSH), by PGNPs compared to PGE arises from the fundamental pharmacokinetic and targeting advantages of nanoencapsulation. The small, uniform particle size (~ 91 nm) and positive zeta potential (+ 44 mV) of PGNPs enhance skin penetration and cellular uptake, enabling efficient delivery of bioactive ellagitannins and flavonoids into both epidermal keratinocytes and dermal immune cells60. This targeted, sustained release ensures a higher local concentration of antioxidants and anti-inflammatory compounds at the site of psoriatic inflammation. Consequently, PGNPs more effectively scavenge reactive oxygen species, reduce lipid peroxidation (MDA), and upregulate endogenous antioxidant enzymes (SOD, CAT, and GSH) by protecting redox-sensitive phytochemicals from degradation55. Simultaneously, the enhanced intracellular delivery potentiates the inhibition of NF-κB and JAK-STAT signaling pathways, leading to a more pronounced downregulation of Th1/Th17-associated cytokines (IL-6, IL-17, and IFN-γ) and a stronger restoration of regulatory IL-1024,57. Thus, nanoformulation overcomes the poor solubility, instability, and limited bioavailability of crude-extract phytochemicals, resulting in a coordinated and amplified therapeutic impact on both the inflammatory and oxidative axes of psoriasis.

In human patients, psoriasis is characterized by a pronounced Th1/Th17 signature, with studies consistently reporting elevated levels of IL-17 and IFN-γ3,5. Correspondingly, our IMQ-induced model exhibited a 2.2-fold increase in IL-17 and a 2.4-fold increase in IFN-γ in psoriatic skin versus controls, mirroring this pathogenic shift. Furthermore, the deficit in the anti-inflammatory cytokine IL-10 observed in our psoriatic rats is also a recognized feature in human psoriasis, where impaired IL-10 signalling contributes to sustained inflammation8. Most importantly, the therapeutic response elicited by PGNPs (significant reduction of IL-17 and IFN-γ alongside restoration of IL-10) recapitulates the desired immunomodulatory outcome achieved by effective human therapies, such as biologics targeting the IL-23/IL-17 axis. Thus, while species and sample-type differences preclude direct numerical comparison, the consistency in cytokine dysregulation patterns and correction strongly validates our model’s pathophysiological relevance and indicates that PGNPs modulate key inflammatory pathways implicated in human psoriasis.

The superior efficacy of PGNPs stems from their ability to overcome key bioavailability barriers inherent to plant metabolites60. Nanoencapsulation protects pomegranate’s bioactive ellagitannins and polyphenols24 from degradation and enhances their delivery efficiency, addressing well-documented limitations of poor solubility and instability29,31,32. The complex structure of compounds like punicalagins (glucose-linked ellagic acid moieties) underpins their diverse pharmacological activities, ranging from antioxidant21 to immunomodulatory effects19; which are amplified through nanoformulation.

A major challenge in topical phytotherapy is the hydrophobic nature of many bioactive molecules (e.g., flavonoids, polyphenols, and terpenes), which restricts penetration through the lipophilic stratum corneum barrier60. This results in low absorption, rapid degradation, and diminished efficacy, as illustrated by the instability of curcumin in cosmetic formulations61 and the oxidation-sensitivity of ascorbic acid62. Environmental factors (heat, light, oxygen, and humidity) further accelerate bioactive degradation, reducing shelf-life and therapeutic potential29. Nanotechnology directly addresses these issues, as demonstrated by the successful preparation of stable, antioxidant-rich pomegranate peel nanoparticles31 and the enhanced bioavailability achieved with grape-seed extract nanoparticles for skin cancer applications32.

While this study provides compelling proof-of-concept for the enhanced efficacy of PGNPs in psoriasis management, several limitations should be acknowledged. The investigation was conducted exclusively on male rats to align with the standard IMQ model; and thus, does not address potential sex-based differences in treatment response. The in vivo sample size, though sufficient to detect large therapeutic effects, was modest, and the experimental design employed a single, comparative dose rather than a full dose–response curve for PGNPs. Additionally, while short-term (28-day) colloidal stability was confirmed, long-term shelf stability under various storage conditions remains to be established. Finally, the mechanistic insights, though detailed, are derived from an animal model; direct extrapolation to human psoriasis requires further validation.

In conclusion, the study reported the successful transformation of PGE into PGNPs using the acid digestion method. This nanoscale conversion significantly enhanced the bioavailability, stability, and therapeutic potential of PGE, as evidenced by the improved antioxidant, anti-inflammatory, and cytotoxicity activities. PGNPs demonstrated superior efficacy in treating IMQ-induced psoriasis compared to conventional PGE, with greater reductions in oxidative stress markers (MDA, SOD, CAT, and GSH), inflammatory cytokines (IL-6, -10, -17, and IFN-γ), and histopathological improvements in psoriatic lesions. The enhanced therapeutic effects can be attributed to the improved solubility and stability of bioactive compounds within the nanoformulation. These findings suggest that PGNPs could be a promising approach for developing plant-based nanoformulations for dermatological and biomedical applications. The study has some limitations such as the use of small numbers of animals and single dose of PGNPs. While this study demonstrated the superior efficacy of a single dose of PGNPs compared to crude PGE, future work should include a comprehensive dose-response evaluation of PGNPs to identify the minimum effective dose and the dose-toxicity profile, which are essential steps for preclinical development. Future work will expand the translational profile of PGNPs by evaluating efficacy and safety in both male and female subjects.