Introduction

Nanotechnology is an emerging scientific field that focuses on manipulating matter at the atomic and molecular scales. This interdisciplinary field has opened new avenues for creating materials with extraordinary properties. Nanoparticles, which typically range from 1 to 100 nm in size, have a wide range of applications across various scientific disciplines, including medicine, chemistry, and biotechnology1. Owning to their high surface-to-volume ratio, these materials are particularly appealing for applications such as drug delivery, gene therapy, and biosensing2.

Nanoparticles can be synthesized through chemical, physical, and biological methods. While physicochemical methods, such as hydrothermal synthesis, sol-gel synthesis, laser ablation, and lithography are commonly used, they often require sophisticated equipment and can have detrimental environmental and health impacts3. In contrast, green synthesis offers a cost-effective, non-toxic, and biodegradable alternative. This eco-friendly approach utilizes natural resources such as plant extracts, microorganisms, and other biological materials to reduce the use of hazardous chemicals4,5.

Owning to their low melting points, very high surface areas values and the special optical, catalytic and magnetic properties6 these materials have attracted much interest from the scientific community so far. These nanoparticles are used in numerous industrial areas such as food, space-age, agriculture, chemicals and medicine. This process is much more environmentally friendly than traditional methods of nanoparticle synthesis, researchers said. Kirubakaran et al.7 and Al-darwaish et al.8, also presented several novel studies on the green synthesis of metal oxide nanoparticles, where the green production approach was considered as relevant topic and emphasized that oxides of metals such as zinc, cobalt copper and gold, among others, have gained prominence in these recent years.

Current reports include natural methodological guidance pertaining to the eco-friendly synthesis of zinc nanoparticles prepared with an extract from the leaves of binary compounds. ZnO nanoparticles are one kind of metal oxides that are superior to others in terms of electron mobility, exciton binding energy, bandgap and optical transmittance9,10. In this study, a sustainable synthesis method of ZnO nanoparticles was investigated by employing a botanical sample, M. oleifera which is commonly known as “Sohanjna”. Moringa is one among the most versatile trees from the global perspective where nearly every component of the tree can be applied for nutritional or beneficial purposes.

M. oleifera is a nutritious plant high in essential minerals, amino acids, and antioxidants, which promotes optimal nourishment and healing. Its bioactive components have anti-aging and anti-inflammatory qualities, making it the nickname “miracle tree”11. Leaves are conventionally used to treat sores, inflammation and scabies12,13. It is worth mentioning that due to the presence of bioactive molecules in M. oleifera seed protein, it has been used as a reducing agent for generation of silver nanoparticles14. Moreover, Zn2+ ions are released more quickly from spherical NPs than from rod-shaped of ZnO-NP and also because smaller particles have greater permeability to the bacterial membrane15.

This study reports the green synthesis of zinc oxide nanoparticles (ZnO-NPs) using M. oleifera leaf extract, a plant known for its high phytochemical content and nutritional benefits. The synthesized ZnO-NPs were characterized via various techniques, including UV-Vis spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and Fourier transform infrared spectroscopy (FTIR). Furthermore, we evaluated the antibacterial and antioxidant properties of the synthesized nanoparticles, demonstrating their potential applications in biomedical fields.

Materials and methods

Plant leaf collection

Leaves of M. oleifera were collected during the rainy season from a farm at the University of Agriculture in Faisalabad to take advantage of the their relatively high phytochemical content and bioactive component availability, which can improve the synthesis of zinc oxide nanoparticles. The leaves were identified by a taxonomist from the Department of Botany at Government College Women University Faisalabad (GCWUF). Zinc nitrate hexahydrate (98% purity) was prepared in the laboratory for the synthesis process (Fig. 1).

Fig. 1
figure 1

Green Synthesis Mechanism for Producing ZnO Nanoparticles.

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Leaf extract preparation

The leaves were thoroughly rinsed with distilled water to remove contaminants, air-dried, and then washed with methanol. Fifty grams of leaves were weighed, minced, and crushed using a mortar and pestle. The crushed leaves were mixed with water and boiled for 15 min to release the cellular contents. 15 mL of the extract was filtered through Whatman No. 1 filter paper and centrifuged at 2400 rpm for 5 min to remove debris. The supernatant was collected for further use (Fig. 2).

Fig. 2
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Stages of green synthesis of Zinc oxide nanoparticles from Zinc nitrate precursor using the plant extract of Moringa oleifera as a reducing agent.

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Green synthesis of ZnO nanoparticles

A simple and environmentally friendly method, called “green synthesis,” was used to create tiny particles of zinc oxide (ZnO) was used. This method is based on a procedure developed by Nayak et al.16. First, a special mixture was mixed with ice-cold acetone, and then, the mixture was spun very fast (15,000 times per minute) for 20 min to separate the different parts. The clear liquid was removed and heated gently in a water bath. After the mixture was left overnight, we obtained a pale yellow product. Finally, the mixture was heated it to a high temperature (400 °C) for 2 h to remove any impurities and obtain pure ZnO nanoparticles.

Mechanism of the plant-mediated approach

Phytochemicals present in the plant extracts serve as reducing agents which play a major role in the conversion of metal precursors into metal nanoparticles. The pH, temperature, contact time, metal salt concentrations and the phytochemical contents of the extracts affect their ability to synthesize nanoparticles effectively as well stabilize them leading total nanoparticle production17. In three steps for their stabilization, the goal of a single study was to allude that once reduced by plant extracts ions metal ions would be encapsulated in an organic covering18.

The experimental steps are simple to perform, metal ion reduction and reduced metal ions nucleation activation phase; growth phase (associated with nanoparticle stability) section; and the structure of the formed nanoparticles constitutes the termination phase.

They act on metals such as Zn (zinc), Cu (copper), Au (gold), Ag (silver), Fe (iron) and Ni (nickel) to form metal oxides. It helps in the development and stabilization of metal ions, which then occur through phytochemicals. This process is then followed by the formation of oxygen, which results in a specific structure in which the metal ions are bound together, (1) preparation of the plant extract, (2) mixing of the metallic solution with the prepared plant part for reduction and synthesis of the nanoparticles, and (3) production of biocompatible nanoparticles. UV/Vis, FTIR, SEM and XRD techniques were used for the characterization of the nanoparticles. A graphical representation is shown in Fig. 3.

Fig. 3
figure 3

Factor influencing sustainable ZnO-NP synthesis, a graphical representation.

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ZnO nanoparticle characterization

UV/Visible spectroscopy

In this study, we have investigated the optical properties of ZnO nanoparticles synthesized at various concentrations and temperatures via UV/visible spectroscopy. The absorption spectra of the samples were noted on a Cary series spectrophotometer (Agilent Technology) over a wavelength range of 200–800 nm.

Scanning electron microscopy

Scanning electron microscopy (SEM) A Nova Nano SEM-450 was used to obtain morphological and compositional images of the biologically synthesized zinc oxide nanoparticles.

X-ray diffractogram

X-ray powder diffraction data of the crystalline material were collected on a Bruker AXS D8 Advance (Cu k-alpha radiation, λ = 1.5402 Å).

Energy-dispersive spectrometers

The elemental information of the nanomaterials and their composition were investigated by energy dispersive spectrometry.

Fourier transform infrared spectroscopy (FTIR)

Fourier transform infrared spectroscopy was used to determine the molecular interactions and chemical makeup of the synthesized nanoparticles. The FTIR spectra were acquired using a Thermo Fisher Scientific Nicolet iS50 spectrophotometer. The IR absorption spectra revealed peaks corresponding to several functional groups, providing important information about the chemical bonds found in the nanoparticles.

Antioxidant and antibacterial activity

The antioxidant activity of the synthesized ZnO-NPs was evaluated using the DPPH radical scavenging assay. The antibacterial activity of the ZnO-NPs was assessed using the disk diffusion method against gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacteria. The zones of inhibition were measured and compared with standard antibiotics. The DPPH assay was used to assess the radical scavenging capacity of the ZnO-NPs mediated by M. oleifera extract. The various concentrations between 10 and 100 g/mL were used.

Results

UV/Visible spectroscopy

The presence of secondary metabolites in plants causes the reduction of zinc ions in the solution to form zinc oxide. The plant extract serves not only as a reducing agent but also as a stabilizing agent. This was verified through UV/Visible spectrum analysis conducted within the wavelength range of 200–800 nm. The spectrum exhibited a distinct peak at 320 nm, characteristic of ZnO nanoparticles. For ZnO nanoparticles, the absorbance peak typically falls within the wavelength range of 310 nm to 340 nm. The energy band gap (Eg) of the ZnO nanoparticles was calculated using the equation Eg = 1240/λ eV, where λ represents the wavelength corresponding to the absorption peak. The λ value was determined from the UV/Visible spectrum analysis, which revealed a distinct peak at 320 nm (Fig. 4A). This peak was identified as the absorption wavelength (λ) used in the calculation. However, to improve accuracy, the λ value can be determined more precisely using methods such as linear extrapolation or curve fitting to identify the exact wavelength corresponding to the absorption edge.

Fig. 4
figure 4

A–B: UV/Vis spectra for ZnO Nanoparticles (A). X-ray diffraction spectrum of ZnO Nanoparticles (B).

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Structural analysis

An X-ray diffraction spectrophotometer was used to examine the structural characteristics of the produced nanoparticles. Cu Kα radiation in 2θ (2 theta) configurations was used to calibrate the XRD equipment at 40 kV and 30 mA of current. X-ray diffraction alignment of the prepared ZnO-NPs revealed that the peaks agreed with the standard data. XRD reveals the crystalline nature of the ZnO nanoparticles. The diffractogram shows the intensity of the diffracted rays as a function of the diffraction angle. The spectra show the details of the crystal planes (Fig. 4B). X-ray diffraction peaks were obtained at various angles (Table 1). The size of the nanoparticles was measured via the Debye-Scherrer equation: Dhkl = 0.89λ/βcosθ.

Table 1 Results of XRD analysis at various diffraction angles.
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where D is the average crystalline particle size, λ is the X-ray wavelength (1.5406 Å), k is the shape factor or Scherer’s constant (0.89), θ is Bragg’s diffraction angle, and β is the full width at half maximum of the XRD peak. Using Scherrer’s formula, the average crystalline size of the NPs formed was estimated and found to be 52.24 nm. The shape of the nanoparticles was found to be hexagonal in nature, with lattice parameters a (= b) equal to 3.2568 A0 and c equal to 5.2125 A0.

Scanning electron microscopic analysis of the ZnO-NPs

After that, the X-ray diffraction results were confirmed, and the samples were sent for further analysis by scanning electron microscopy (SEM). The image captured by the scanning electron microscope (Fig. 5) shows the size, shape, and morphology of the zinc oxide nanoparticles. The synthesized products are flower-like structures with crystal arrangements, according to detailed structural characterizations, and their measured diameters are approximately 50 nm. SEM images were captured at various magnifications to analyse the size and shape of the produced nanoparticles. The production of nanoparticles in their agglomerated form was confirmed by the surface morphology (Fig. 5).

Fig. 5
figure 5

Scanning Electron Microscope (SEM) Images of Zinc Oxide Nanoparticles.

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Energy dispersive X-ray analysis

EDX revealed a high signal for zinc and oxygen, which confirms the presence of zinc in the oxide form. The composition of each element contained in the analyte was obtained via energy dispersive X-ray spectroscopy (EDX), which revealed strong peaks of 76.26% for zinc and 22.78% for oxygen. Two strong peaks were identified for zinc at 1 eV and 8.6 eV for oxygen, and the signal was evident at 0.5 eV. These values are specific for zinc and oxygen, which confirms the elemental composition of the synthesized compounds (Fig. 6A).

Fig. 6
figure 6

A–C: EDX spectrum of synthesized ZnO Nps (A), FTIR spectrum of synthesized ZnO Nanoparticles (B), Antioxidant scavenging activity of ZnO-NPs (C).

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Fourier transform infrared spectroscopy analysis

FTIR was used to determine the composition and formation of functional groups in the synthesized ZnO nanoparticles. This finding also suggests that the formation of ZnO nanoparticles is due to the interaction of phenolic compounds, alkynes, terpenoids, and flavonoids. Figure 6B shows the FTIR spectra of the synthesized ZnO nanoparticles in the range of 500–4000 cm−1. The functional groups were responsible for reducing zinc ions to ZnO, which were observed as bands. Each of the bands corresponds to various stretching modes.

The broad peak in the higher energy region at 3331–3414 cm−1 is due to the stretching vibration of the O-H group. At approximately 2233–2345 cm−1, the C-H stretching vibration band appears and indicates the presence of an alkane group. The peaks near 1391–1415 cm−1 and 1633–1647 cm−1 are caused by the amide I and amide II regions, which are typical of proteins and enzymes. The presence of alcohols and carboxylic acid groups is indicated by the strong bands observed at 1020–1060 cm−1 attributed to the C-O stretching vibration. The FTIR spectra, which have absorption bands at 3314, 2345, 1391, 1647 and 436 cm−1, respectively, indicate the structure on the basis of functional groups of M. oleifera. These peaks were caused by M. oleifera, a plant that is rich in phytochemicals such as amino acids, alkaloids and flavonoids. Overall, these observations prove the existence of some phenolic compounds, terpenoids or proteins that are bound to the surface of the ZnO-NPs.

The changes observed in the FTIR spectra of the green synthesized ZnO-NPs after bioreduction indicated the participation of polyols, terpenoids and proteins with functional groups of amines, alcohols, ketones and carboxylic acids in the bioreduction reactions. Terpenoids are poorly water soluble and hence may not be among the prime moieties involved in bioreduction reactions.

Antioxidant activity of the ZnO-NPs

A stable free radical called DPPH typically absorbs at 517 nm according to UV-Vis analysis. By monitoring the decrease in DPPH absorbance, the ability of environmentally friendly ZnO-NPs to scavenge free radicals was assessed. The DPPH assay was used to assess the radical scavenging capacity of the ZnO-NPs mediated by M. oleifera extract. The results at various concentrations between 10 and 100 g/mL were as follows:

100 µg/mL (67%) > 90 g/mL (66%) > 80 g/mL (60%) > 70 g/mL (53%) > 60 g/mL (51%) > 50 g/mL (39%) > 40 g/mL (33%) > 30 g/mL (27%) > 20 g/mL (22%) > 10 g/mL (11%), (Fig. 6C).

The increase in the concentration of the ZnO-NPs correlated with an increase in the radical scavenging activity, with a peak of 67% observed at 100 µg/mL. Key phytochemical components such as 1, 15-pentadecanediol and 1, 10-decanediol found in M. oleifera leaf extracts may contribute to the increased antioxidant properties. The increased antioxidant capabilities facilitated by the ZnO-NPs can be attributed to the stimulation of reactive oxygen species (ROS) production, ultimately leading to cellular death.

Antibacterial activity of the ZnO-NPs

A dose-dependent antibacterial activity of the ZnO-NPs from M. oleifera leaf extract was observed against gram-positive (Bacillus subtilis and Staphylococcus aureus) and gram-negative (E. coli and P. aeruginosa) strains of bacteria. The antibacterial activity increased significantly (p < 0.05) with increasing concentrations of ZnO-NPs from 10 µg/mL to 100 µg/mL. The zones of inhibition for each bacterial strain were measured and compared using one-way ANOVA, followed by Tukey’s post-hoc test. The results presented that at 100 µg/mL, the ZnO-NPs exhibited maximum zones of inhibition for Bacillus subtilis (15 mm), P. aeruginosa (15 mm), S. aureus (17 mm), and E. coli (17 mm) (Table 2). In contrast, the control antibiotic disc showed no inhibition. Statistical analysis revealed that the ZnO-NPs derived from M. oleifera were significantly more effective (p < 0.01) against all the bacterial strains tested than the control.

Table 2 Antibacterial activity of different organisms tested for ZnO-NPs nanoparticles.
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Bacteria of both gram-positive and gram-negative types display zones of inhibition (Fig. 7). At dosages of 75 and 100 g, both gram-positive and gram-negative bacteria showed significant antibacterial action. With 100 g of ZnO-NPs, the maximum zones of inhibition for B. subtilis (15 mm), P. aeruginosa (15 mm), S. aureus (17 mm), and E. coli (17 mm) were all reached (Table 2). On the control antibiotic disc, there was no indication of inhibition. The results showed that M. oleifera-derived ZnO-NPs are more effective at killing bacteria than all the strains used in the test.

Fig. 7
figure 7

Antibacterial Activity of ZnO-NPs on (a) E. coli, (b) Pseudomonas aeruginosa, (c) Staphylococcus aureus and (d) Bacillus subtilis.

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Discussion

UV/Visible spectroscopy

The UV/visible spectroscopy results confirmed the effective production of ZnO nanoparticles from M. oleifera leaf extracts. The UV/Vis spectrum shows a definite peak at 320 nm for ZnO nanoparticles, which falls within the predicted wavelength range of 310–340 nm. The computed energy band gap (Eg) of the ZnO nanoparticles offers useful information about their optical characteristics. Our results were similar to those of previous studies conducted by Arias et al.6 and Tiwari et al.19. The bandgap energy was calculated using Eg = 1240/λ eV and was found to be 3.8 eV, which is comparable to the previously reported values of the energy bandgap for ZnO nanoparticles20,21.

X-ray diffraction study

The diffractogram demonstrates the crystalline nature of the nanoparticles, with peaks matching the standard data. The XRD peaks at various angles, demonstrate the presence of distinct crystal planes (Table 1). The average crystalline particle size of ZnO-NPs was calculated to be 52.24 nm using the Debye-Scherrer equation. Furthermore, the lattice characteristics point to a hexagonal form for the nanoparticles. The results reveal the effective fabrication of crystalline ZnO nanoparticles with a well-defined structure.

The nanoparticles’ hexagonal form and crystalline composition may help them find applications in a variety of sectors, including biomedicine and food packaging22. Using Scherrer’s formula, the average crystalline size of the NPs formed was estimated and found to be 52.24 nm. The shape of the nanoparticles was found to be hexagonal in nature, with lattice parameters a (= b) equal to 3.2568 A0 and c equal to 5.2125 A0, which matches the values previously reported23.

Scanning electron microscopic analysis of the ZnO-NPs

The scanning electron microscopy (SEM) confirmed the structural properties of the synthesized zinc oxide nanoparticles. The SEM images showed that the characteristic flower-like appearance of nanoparticles, with crystal configurations that support the XRD data. The reported sizes of around 50 nm are comparable with the typical crystalline particle size obtained by XRD analysis (52.24 nm). The SEM images also presented the nanoparticles’ agglomerated shape, as evidenced by their surface morphology24. The combined XRD and SEM investigations provide a thorough understanding of the structural and morphological aspects of the synthesized ZnO nanoparticles. The production of nanoparticles in their agglomerated form is confirmed by the surface morphology. Several studies have investigated the relationship between surface shape and the synergistic action of ZnO-NPs25,26.

Energy dispersive X-ray analysis

The energy dispersive X-ray (EDX) spectrum shows high peaks for zinc and oxygen confirming the presence of zinc in its oxide form. Zinc and oxygen have specific energy values of 1 eV and 8.6 eV, respectively, with a signal at 0.5 eV. These findings support the XRD and SEM data, providing a complete picture of the composition and structure of the synthesized ZnO nanoparticles. The composition of each element contained in the analyte was obtained via energy dispersive X-ray spectroscopy (EDX), which revealed strong peaks of 76.26% for zinc and 22.78% for oxygen, whose weight% peaks are comparable to those reported earlier for the synthesis of ZnO-NPs27. Two strong peaks were identified for zinc at 1 eV and 8.6 eV for oxygen, and the signal was evident at 0.5 eV28. These values are specific for zinc and oxygen, which confirms the elemental composition of the synthesized compounds.

Fourier transform infrared spectroscopy analysis

The FTIR analysis offers vital information on the composition and functional groups found in the synthesized ZnO nanoparticles. The FTIR spectra show a number of absorption bands corresponding to different stretching modes, suggesting the presence of various functional groups. The detected bands point to the participation of phenolic chemicals, alkynes, terpenoids, and flavonoids in the production of ZnO nanoparticles. The FTIR spectra show the presence of O-H, C-H, amide I and II, and C-O stretching vibrations, which are typical of alcohols, carboxylic acids, proteins, and enzymes. The absorption bands are due to the structure of M. oleifera. Overall, the FTIR examination shows the existence of functional groups bonded to the surface of the ZnO-NPs, including phenolic chemicals, terpenoids, and proteins.

Proteins compared to terpenoids seem to have little importance in the biosynthesis of nanoparticles, as reported previously29,30. Therefore, water-soluble phenolic acid and flavonoid compounds are believed to play a major role in bioreduction reactions. The reduction mechanism of tannins with zinc nitrate may also involve the reduction of zinc nitrate to zinc nanoparticles31,32. The possible mechanism for the green synthesis of ZnO-NPs involves the reduction of zinc nitrate ions that can form intermediate complexes with phenolic OH groups present in hydrolysable tannins, which subsequently undergo oxidation to quinine forms with the consequent reduction of zinc to zinc oxide nanoparticles33,34. The formation of ZnO-NPs can be related to the interactions between reducing phenolic acids such as ascorbic acid, cardiac glycosides, gallic acid and zinc ions. However, the possible mechanism is still unclear and needs further investigation35,36.

Antioxidant activity of the ZnO-NPs

The antioxidant activity of the ZnO-NPs synthesized using M. oleifera extract was evaluated using the DPPH assay, which measures the scavenging of free radicals. The results show a concentration-dependent increase in radical scavenging activity. This suggests that the ZnO-NPs exhibit potent antioxidant properties, which can be attributed to the presence of phytochemical components in the M. oleifera leaf extract. The enhanced antioxidant capabilities of the ZnO-NPs may be due to their ability to stimulate reactive oxygen species (ROS) production, leading to cellular death.

The increased antioxidant capabilities facilitated by the ZnO-NPs can be attributed to the stimulation of reactive oxygen species (ROS) production, ultimately leading to cellular death. Previous studies have highlighted the antioxidant effects of plant extract-containing ZnO-NPs37.

Plant-based production of ZnO nanoparticles employs phytochemicals as reducing and stabilising agents, altering nanoparticle size, shape, and biological activity38. Because of their increased biocompatibility, these green-synthesized ZnO-NPs have promising biomedical uses, including antibacterial, anti-inflammatory, and anticancer activities39,40. ZnO-NPs from M. oleifera exhibit equivalent or higher antioxidant activity to standard chemical antioxidants, presenting a natural, biocompatible option for combatting free radicals41.

Antibacterial activity of the ZnO-NPs

The antibacterial activity of ZnO-NPs synthesized using M. oleifera leaf extract was evaluated against both gram-positive and gram-negative bacterial strains. The results demonstrate a dose-dependent antibacterial activity, with significant increases in zones of inhibition observed with increasing concentrations of ZnO-NPs. Statistical analysis revealed that the ZnO-NPs derived from M. oleifera were significantly more effective (p < 0.01) against all bacterial strains compared to the control antibiotic disc, which showed no inhibition. These findings suggest that the ZnO-NPs synthesized using M. oleifera leaf extract possess potent antibacterial properties, effective against a broad spectrum of bacterial strains. The observed antibacterial activity may be attributed to the unique physicochemical properties of the ZnO-NPs, such as their small size, high surface area, and reactivity.

At dosages of 75 and 100 g, both gram-positive and gram-negative bacteria showed significant antibacterial action42,43. With 100 g of ZnO-NPs, the maximum zones of inhibition for B. subtilis (15 mm), P. aeruginosa (15 mm), S. aureus (17 mm), and E. coli (17 mm) were all reached. On the control antibiotic disc, there was no indication of inhibition. The results showed that M. oleifera derived ZnO-NPs are more effective at killing bacteria than all the strains used in the test44,45.

The bacterial cell wall is broken down as a result of the contact of ZnO-NPs with them, releasing ions and producing ROS, which is the mechanism underlying their antibacterial activity. Because of their antibacterial qualities, ZnO-NPs are better materials for use in the development of bioactive food packaging substances that prolong the shelf-life of food and provide germ resistance46,47,48. The study by Kirubakaran et al.49 reports the green synthesis of zinc oxide nanoparticles (ZnONPs) using Acmella caulirhiza leaf extract, confirming their stability, spherical morphology, and crystalline nature. The bio-fabricated ZnO-NPs demonstrated strong antibacterial, antioxidant, anti-inflammatory, and biocompatible properties, highlighting their potential for biomedical applications49,50,51. The optimal concentration of ZnO-NPs for significant antibacterial activity is 100 µg, as it exhibited the maximum zones of inhibition against all tested bacterial strains52.

Conclusion

This study demonstrated a simple, eco-friendly, and cost-effective method for synthesizing ZnO-NPs from M. oleifera leaf extract. The green synthesis of ZnO-NPs from M. oleifera leaf extract represents a promising approach for development of eco-friendly and cost-effective nanomaterials. The excellent antibacterial and antioxidant properties of these nanoparticles make them suitable for various biomedical applications, including wound healing, drug delivery, and food packaging. Future research directions could focus on exploring the potential of ZnO-NPs in these applications, as well as exploring the mechanisms underlying their biological activities. Additionally, scaling up the green synthesis process could pave the way for industrial-scale production of ZnO-NPs, offering a sustainable alternative to conventional methods.

Recommendations and future perspectives

Future research directions could include surface modification, doping with other metals, and developing hybrid nanocomposites to enhance the stability and effectiveness of ZnO NPs. Scalable synthesis methods and in vivo studies could also be explored. The use of only two bacterial strains and potential interference from the M. oleifera extract limits this research. Further studies with a broader range of microorganisms and control experiments are recommended.