Recovery of bioactive compounds from red onion skins using conventional solvent extraction and microwave assisted extraction

Abstract

In this study two extraction methods, such as conventional solvent extraction (CSE) and microwave assisted extraction (MAE) were used for bioactive compounds extraction from red onion skins. The effects of several extraction parameters on the phytochemical content were investigated to discover which combination of parameters led to the highest concentration of phytochemicals. The results revealed that the optimal conditions for anthocyanin extraction (1.75±0.04 mg C3G/g DW) by CSE was achieved at 70% ethanol acidified with 0.1 N hydrochloric acid after 120 minutes of extraction at 25 °C. Also, the highest antioxidant activity (32.18±1.75 mM of Trolox/g DW) was obtained with 96% ethanol acidified with glacial acetic acid, after 3 hours of extraction at 25 °C. Meanwhile, for MAE the highest anthocyanin content of 1.60±0.05 mg C3G/g DW was found when using 50% ethanol acidified with 99.5% citric acid, at 735 W microwave power for 15 seconds of extraction. MAE with 96% ethanol and glacial acetic acid had the highest yield of antioxidant activity (33.41±0.59 mM of Trolox/g DW) at 315 W microwave power after 10 seconds of extraction. Therefore, the bioactive compounds from red onion skins might be available as a source of functional compounds useful in the pharmaceutical and food industry.