Abstract:

Ethanol extraction was employed to extract total flavonoids from the leftover residue of a Chinese herbal medicine combination consisting of lotus leaves, cassia seeds, hawthorn fruit and oriental water plantain rhizome after supercritical carbon dioxide extraction. The optimal conditions for the extraction of total flavonoids were explored by response surface methodology. Box-Behnken design was applied to provide experimental data for establishing a mathematical regression model describing the relationship between the extraction rate of total flavonoids and four independent variables including material-to-liquid ratio, ethanol concentration, extraction temperature and extraction time. Correlation analysis of the established model was performed, and the results indicated that it could be employed to optimize the ethanol extraction of total flavonoids from the start material. Material-to-liquid ratio of 1:20, ethanol concentration of 50%, extraction temperature of 80 ℃ and extraction time of 80 min were found optimum. The experimental values of the extraction rate of total flavonoids under these optimum conditions were in good agreement with the predicted ones.

Key words: response surface methodology, flavonoids, residue