Extraction of saponin from Camellia oleifera cake and evaluation of its antioxidant activity

Summary Response surface methodology was employed to optimise extraction conditions of saponins from Camellia oleifera cake. Optimal conditions were extraction at 82.2 °C for 3.3 h with an 8.6:1 ratio (mL g −1 ) of solvent to solid. The saponin extract was further extracted with n‐butanol, and nine saponins were found as the main components. The identification of these saponins was carried out by HPLC–ESI–MS, and their possible structures were given. Antioxidant activities of the saponins were evaluated in vitro by 1,1‐diphenyl‐2‐picryl‐hydrazyl (DPPH), 1, 2, 3‐phentriol self‐oxidation and metal chelating activity assays. IC 50 value of each assay was 3866 ± 3, 4744 ± 2 and 2389 ± 2 μg mL −1 , respectively. The effects of environmental factors on antioxidant activity of saponins from C. oleifera cake were studied for the first time. The antioxidant activity is pH dependent with 9.0 as the optimal pH and is also temperature independent.