Sequential Solvent Extraction of Red-Onion (Allium cepa L) Skin: Influence of Solvent Polarity on Antioxidant and Radical Scavenging Activity

The present study was performed to evaluate the influence of solvent polarity on antioxidant and radical scavenging activity of the extracts of red onion skin. Extracts were obtained using sequential extraction method with various solvents namely ethyl acetate, n-butanol, methanol and water. Ethyl acetate and n-butanol extracts demonstrated the highest total phenolic (577.310±9.2 and 441.379±7.3 mg GAE/g extract, respectively) and flavonoids contents (36.188±5.1 and 33.844±4.6 mg QE/g extract, respectively), as well asthe highest antioxidant capacity compared to methanolic and waterextracts through all antioxidant assays.The results showed that all extracts exhibited antioxidant activity in a concentration-dependent manner. Significant correlation was obtained between antioxidant activities and total flavonoids.The highest DPPH and nitric oxide radical scavenging were acquired for n-butanol extract.Furthermore, ethyl acetate extract displayed the most reducing power.The results indicated that the components with antioxidant properties in onion skin were extracted in non-polar solvents more than polar solvents.