Figure 1

Spectroscopic determination of curcumin content of nanocarrier formulations. (A) The keto- and enol- forms of curcumin (1,7-bis-(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione). (B) Suspensions of 4.5 mg/mL of curcumin in (left) PBS, (centre) PBS after 0.2 µm filtration to remove insoluble material and (right) in TPGS/Pluronic F127 nanoparticles after 0.2 µm filtration to remove insoluble material. (C) On dissolution in DMSO, 22 µM curcumin possesses an absorption peak of 435 nm. (D) Determination of the molar extinction coefficient of curcumin in a DMSO solvent (58,547 L.mol⁻¹.cm⁻¹) and demonstration that this accelerated oxidative degradation of curcumin at low pH⁹² results in a reduction in this molar extinction coefficient (2133 L.mol⁻¹.cm⁻¹ after 72 h incubation in 1 M sodium hydroxide solution) suggesting that spectroscopic assessment can be used to monitor both the encapsulation of curcumin and its degradation. (E) Dissolution of 5 mg/mL curcumin in 1 M sodium hydroxide solution (right) resulting in a rapid colour change compared to curcumin loaded nanocarriers (left). (F) Standard curve of known concentration of curcumin measured by HPLC.