Spectrophotometric method for the simultaneous determination of Epigallocatechin-3-gallate and Curcumin in a thermoresponsive anti-psoriatic in-situ sustained release topical hydrogel: Application of GAPI and AGREE greenness assessment tools

Introduction: Epigallocatechin-3-gallate (EGCG) and Curcumin (CUR), the primary active components in Green Tea Extract (GTE) and Turmeric Extract (TE), respectively, have shown efficacy in the treatment of psoriasis. An antipsoriatic thermoresponsive in-situ gel containing both extracts has been developed in-house. However, simultaneous estimation of these drugs from the dosage form is challenging due to overlapping spectra. Aim: To develop and validate simple, efficient, and environment friendly spectrophotometric methods for the simultaneous estimation of EGCG and CUR in the developed formulation. Materials and Methods: Vierordt’s equation method, quotient absorbance ratio method, and dual-wavelength method were developed. The wavelength maxima (λmax) of CUR was found at 425 nm, where interference from EGCG was negligible at lower concentrations, whereas at 276 nm (λ max of EGCG), CUR showed significant interference. The isosbestic point was observed at 300 nm, and wavelengths of 276 nm and 310 nm were selected for the dual-wavelength method. Laboratory-prepared mixtures were analyzed to assess reliability, followed by application to the formulation. Validation was performed as per International Council for Harmonisation guidelines. Results: The methods demonstrated acceptable accuracy, precision, and reliability for simultaneous estimation of EGCG and CUR. Validation parameters were within acceptable limits. Greenness assessment using the Analytical Greenness metric approach and the Green Assessment Profile Index indicated satisfactory environmental performance. Conclusion: The proposed methods provide a simple, cost-effective, and environmentally sustainable approach for routine analysis of EGCG and CUR in thermoresponsive in-situ gel formulations.