High-performance thin-layer chromatography method for determination of rosmarinic acid in the optimized extracts of Rosmarinus officinalis L and its antioxidant activity

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This study aims to determine the most effective method for extracting rosmarinic acid (RA) from Rosmarinus officinalis L. (R. officinalis) leaves using Response Surface Methodology (RSM). Additionally, it seeks to quantify RA through High-Performance Thin Layer Chromatography (HPTLC) and evaluate its antioxidant properties. RSM was employed to optimise the extraction parameters like extraction time, temperature and drug solvent ratio. to maximise the RA yield. HPTLC densiometric method was used to quantify the RA. Furthermore, its antioxidant activity was assessed using the 2,2-diphenyl-1-picrylhydrazyl assay.A quadratic polynomial model was found to be the most suitable method for predicting RA yield, with an R² value of 0.9421 and a %CV of 9.19. The adjusted R², predicted R², and signal-to-noise ratio were 0.8677, 0.7481, and 10.2822, respectively, indicating a good model fit and an adequate signal. The optimized HPTLC procedure used a solvent system of toluene and ethyl acetate, yielding an Rf value of 0.55 ± 0.2 for RA. This research established an optimized extraction method for RA and verified its antioxidant properties. The findings contribute to enhancing RA extraction techniques and advancing research on its biological functions, particularly in combating oxidative stress, reducing inflammation, and supporting neuroprotection.