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.

Antibacterial and antifungal activities of the polyphenolic fractions isolated from the seed coat of Abrus precatorius and Caesalpinia crista.

Crude seed coat extracts from Abrus precatorius and Caesalpinia crista were purified into four different fractions namely phenolic acids, flavonols, flavanols and anthocyanin which were then examined for their polyphenol contents and antimicrobial potentials. The fractions derived from seed coat of A. precatorius were found more potent with high phenolic and flavonoid contents as compared to C. crista fractions. The significant antibacterial activity was observed against all strain tested by the fractions of both samples apart from anthocyanin fraction. It was interesting to note that the phenolic acid fractions of both samples was found more active against gram-negative bacteria, while gram-positive bacteria were found to be more sensitive towards flavonol fractions. The phenolic acid and flavonol fractions being potent antibacterial were selected to demonstrate the antifungal capacity of two samples. Among them, phenolic acid fraction of both samples was found active towards all the fungal strain.