Phenolic Composition of Leaf extracts of Ailanthus altissima (Simaroubaceae) with Antibacterial and Antifungal Activity Equivalent to Standard Antibiotics

Abstract

Extracts of fresh and dry Ailanthus altissima leaves from Croatia were evaluated for their phenolic composition, antioxidant and antimicrobial activities. The methanolic extract had a higher concentration of total phenolics, flavonoids and non-flavonoids, as well as a higher antioxidant capacity than water extracts. Flavonoids identified in A. altissima leaves belong to two groups: flavones (glycosides of apigenin and luteolin) and flavonols (glycosides of quercetin and kaempferol). They were mainly present as glycosides, quercetin-3- O-glucoside was the predominant flavonoid. Only traces of aglycones were detected even after extract hydrolysis. Caffeic acid was the predominant phenolic acid both before and after hydrolysis, followed by chlorogenic acid after hydrolysis. The concentration of chlorogenic acid significantly increased soon after tissue fragmentation suggesting this compound is involved in rapid response against mechanical wounding in A. altissima. Therefore, to increase the chlorogenic acid concentration, mechanical wounding could be applied. The acetone leaf extract was as active against Escherichia coli as the positive control gentamicin. Both acetone and methanol:dichloromethane extracts had a higher activity against Candida albicans than a standard drug amphotericin B. Therefore, A. altissima could serve as a valuable resource for antimicrobial activity, which makes this species interesting for further investigation and possible pharmaceutical application.