Valorization of Onion Peelings: Screening Phytochemical, Antioxidant Activity and Antimicrobial Propriety

Abstract

Onion is a vegetable with important nutritional and therapeutic properties. Nutritionally, onion is an excellent source of nutrients. As part of our contribution to enhance the value of this plant, we performed physicochemical and phytochemical analysis and evaluated the antioxidant and antimicrobial activity of various onion peel extracts. The physicochemical analysis revealed that the plant is rich in primary metabolites, namely 1.19% fat, 3.23% protein and 8.62% total sugars. Extraction was carried out by shaking immersion using different solvents (70% methanol, 70% ethanol and 70% acetone). The yields obtained were 13.94%, 14.36% and 15.9%, respectively. The quantification of total polyphenols, flavonoids and condensed tannins in the three extracts using colorimetric methods showed that this species is rich in secondary metabolites. The antioxidant activity was evaluated using different assays (DPPH, TAC). Methanol, ethanol and acetone extract showed DPPH radical scavenging capacity with IC50 of 2.63, 3.37, and 1.37 mg/ml, respectively. The antibacterial activity of the extracts was evaluated by the diffusion method against five bacteria (Enterococcus faecolis, Mycobacteruim avium, E. coli and S. aureus, CA) method. All extracts showed good antimicrobial activity. At the end of this work, we can conclude that the studied plant possesses significant biological activity and can serve as an excellent candidate for pharmaceutical applications. Key words: onion peels, polyphenols, flavonoids, condensed tannins, antioxidant activity, antimicrobial activity.