Abstract

Quercetin, a bioflavonoid extracted from red onion peel, has a marked inhibitory activity against phosphodiesterase 5A. Mechanical shredding of red onion peel increased its total flavonoid content two fold compared to control. Change in individual flavonoid content was studied using HPLC. Quercetin 4'-O-β-glucopyranoside showed the highest increase in content after shredding with slight change in quercetin content. Radical scavenging activity was assayed using DPPH. Extract of the shredded peel showed lesser activity (19.7%) compared to the control (31.2%).

Key words: Allium cepa, Alliacea, red onion peel, flavonol, quercetin 4'-O-ß-glucopyranoside.