Optimization of total phenol and anthocyanin extraction from the peels of eggplant (Solanum melongena L.) and biological activity of the extracts

Abstract

Anthocyanins are biologically active compounds with high antioxidant capacity, found in many fruits and vegetables. In this study, optimizations of total anthocyanin (TA) and total phenolic content (TPC) in the extracts from peels of Solanum melongena L. (eggplant) were investigated by considering eight independent variables including: alcoholic solvent type (methanol or ethanol), volume ratio of alcohol to water, acid type (acetic acid or hydrochloric acid), acid volume, ratio of solid mass to solvent volume (w/v), particle size of solid, temperature and extraction time. Effects of these variables on the extraction yields were investigated using Plackett–Burman factorial design with sixteen experimental runs. Results indicated that the ratio of solid mass to liquid volume and temperature had significant positive effects on the total extraction yield, while the solvent volume ratio showed significant negative effect. Acid volume ratio, temperature and time improved independently anthocyanins extraction yield, while temperature and acid volume ratio had significant positive effects on the extraction yield of phenolic contents. Statistical analysis showed that temperature influenced most significantly both TA and TPC response variables. Maximum TA yield recorded was about 431.58 mg/100 g dry (in conjunction with highest TPC yield), and biological tests carried out for this anthocyanin-rich extract, showed potent antioxidative properties (IC50 of 11.23 ± 1) compared to BHT (IC50 of 16.54 ± 0.07) and β-carotene oxidation being effectively inhibited (88.37 ± 1.21% inhibition). In-vitro cytotoxicity of the sample was also evaluated against brine shrimp larvae and human breast cancer cells with LC50 of 125 µg/mL and growth inhibition percentage of 80%, respectively.