Antioxidant, antimicrobial and anti-quorum sensing compounds from Salix babylonica
Gehad Abdel Wahab, Amal Sallam, Abdelaziz Elgaml, M. Lahloub, Mohamed Afifi
Abstract
Phytochemical investigation of the leaves and bark of Salix babylonica L. trees yielded 11 compounds; catechol (1), methyl trans-4-hydroxycinnamate (2), luteolin (3), apigenin-7-O-β–d-(4″-p-coumaroyl) glucoside (4), populoside B (5), salicin (6), luteolin-7-O-β-d-glucoside (7), catechin (8), acmophyllin B (9), 1-O-p-coumaroyl-β-d-glucopyranoside (10) and chrysoeriol-7-O-β-d-glucuronyl methyl ester (11). Their structures were established using 1D and 2D NMR spectroscopic techniques. Compounds 2, 4, 5 and 8–10 are reported from S. babylonica L. for the first time in this study. Antioxidant activity was determined using in vitro ABTS radical scavenging assay. Compounds 8, 7 and 4 exhibited potent antioxidant activities compared with ascorbic acid. The isolated compounds were screened for their antimicrobial activity. Amongst the tested compounds; compounds 3, 7 and 2 showed the strongest antibacterial activity against Staphylococcus aureus with MIC values of 0.55, 0.70 and 0.88 μmole/L, respectively. Compound 8 exhibited potent anti-quorum sensing activity followed by compounds 7 and 3. Compound 11, which is a new compound and is thought to be formed as an artifact during the extraction process by the action of the methanol used for extraction, showed cytotoxic activity against HepG2 liver cancer cells and MCF-7 breast cancer cells (IC50 = 0.210 ± 0.151 and 0.437 ± 0.251 μmole/L, respectively) compared with the standard 5-FU (IC50 = 0.869 ± 0.066 and 1.257 ± 0.128 μmole/L, respectively).