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Response surface optimization of ethanol extraction of total flavonoids from coffee leaf by RSM and study on hydroxyl radicals scavenging effect

Li Hui-Duan

Response surfacemethodology and Box-Benhnken Designwere employed to optimize the ethanol extraction of total flavonoids fromcoffee leaf. Based on the single-factor experimental results, ethanol concentration of 60~80%, solid-liquid ratio of 2.0:20~3.0:20 g·mL-1, extraction temperature of 40 ~ 60ï‚°C and time of 1.5 ~ 2.5h were selected as the independent variables and scope for BBD. The optimum extract conditions were ultimately determined as ethanol concentration of 73%, solid-liquid ratio of 2.56:20 g·mL-1, extraction temperature of 50ï‚°C and extraction time of 2.0 hwith responding extraction ratio of 4.838%for coffee leaf. The experimental extraction ratiosmatched well with the theoretical values by solving the multiple regression equation, which confirms that RSM could be successfully used to optimize the extraction process and the fitted quadraticmodel had a predictive effect on target extracts. Hydroxyl radicals scavenging effect of Coffee leaf extracts and BHTwere alsomeasured in this paper, the experimental results showed a significant dose-effect relationship.