Onion is one of the major sources
of various biologically active phytomolecules, e.g., phenolic acids,
flavonoids, cepaenes, thiosulfinates and anthocyanins (Singh
et al., 2009). The major flavonoids found in the dry peel of the
onion, which has usually been considered to be waste, contain
large amounts of quercetin, quercetin glycoside and their oxidative
products, which are effective antioxidants against the lethal effect
of oxidative stress