Antioxidant Activity of Ethanolic Onion Skin Extracts Produced by Microwave Assisted and Conventional Extraction Methods

Abstract

This experiment focused on determination of antioxidant activity of onion skin (OS), extracted by three techniques i.e. Microwave Assisted Extraction (MAE), Soxhlet and Maceration with three different ethanol (EtOH) concentrations. Total Phenolic Content (TPC) and Total Flavonoid Content (TFC) were estimated by Folin-ciocaltteu method and Aluminium Chloride method respectively. Antioxidant activity (AOA) was assessed by Diphenyl Picryl Hydrazyl (DPPH) method and Half-maximal inhibitory concentration (IC50) value was recoded. The maximum TPC and TFC were found as 519.25 mg/g gallic acid equivalent (GAE) and 120.975 mg/g Quercetin equivalent (QE) respectively, using 90% EtOH concentration with microwave at 300W. EtOH (90%) OS extracts showed the highest free radical scavenging activity with power of 400W of 86.980% with an IC50 value of 38.516µg/ml. In all of assay, 90% EtOH OS extracts with MAE showed higher TPC, TFC and antioxidant activity, suggesting that MAE is a suitable method for extraction of antioxidant component from OS.