Antibacterial and antioxidant potential of the phenolic extract and its fractions isolated from Allium ascalonicum (onion) peel

Aqueous methanolic (20:80) crude extract of the outer peel of Allium ascalonicum (onions) was fractionated into anthocyanin (II), acidic (i.e., phenolic acids, Ia), neutral A (i.e., flavanols, Ib) and neutral B (i.e., flavonols, Ic) phenols using C-18 and hydrophilic-lipophilic balanced (HLB) Co-polymer cartridges. The fractions were analysed for total phenolic, total flavonoids, antibacterial activity, antioxidant potential and lipoxygenase (LOX) inhibition. The recovery of total phenols and bio functional activity in all fractions were found to be more in HLB. All fractions showed antimicrobial activity against tested strains with phenolic acids (Ia) being most active and flavanol (Ib) least active, while the highest free radical scavenging, reducing power and LOX inhibition was exhibited by flavonol (Ic) and least by flavanols (Ib). HPLC analysis revealed the presence of vanillic acid and quercetin in non-anthocyanin I and cyanidin in anthocyanin II.

Automated summary

The aqueous methanolic extract of the outer peel of onions was fractionated into anthocyanin, acidic phenols, flavanols, and flavonols, with the HLB fractions showing higher total phenols and bio functional activity. All fractions exhibited antimicrobial activity, with phenolic acids being the most active and flavanols the least. Flavonols showed the highest antioxidant potential and LOX inhibition. HPLC analysis revealed the presence of specific compounds in different phenolic fractions.