Antibacterial and Antibiotic Modifying Potential of Crude Extracts, Fractions, and Compounds from Willd. against MDR Gram-Negative Bacteria.

The present study aimed to assess the antibacterial and antibiotic modifying activities of methanol extracts prepared from the leaf (APL) and bark (APB) of , fractions (APLa-d) and compounds isolated from APL against a panel of multidrug resistant (MDR) Gram-negative bacteria. Leaf extract was subjected to column chromatography for compounds isolation; antibacterial assays were performed on samples alone and with an efflux pump inhibitor (EPI), respectively, and several antibiotics on the tested bacteria. The phytochemical investigation of APL led to the isolation of stigmasterol (), -amyrin (), 3---glucopyranosylstigmasterol (), 3-O-methyl-D-chiro-inositol (), epicatechin (), quercetin-3--glucoside (), 3--[--xylopyranosyl-(1→4)---galactopyranosyl]-oleanolic acid (), and 3--[-galactopyranosyl-(1→4)---galactopyranosyl]-oleanolic acid (). APL and APB had minimal inhibitory concentration (MIC) values ≤ 1024 g/mL on 73.3% and 46.7% of the tested bacteria, respectively. APLb and APLd were effective against 88.9% of tested bacterial species with compound 8 showing the highest activity inhibiting 88.9% of tested bacteria. The EPI, phenylalanine-arginine--naphthylamide (PAßN), strongly improved the activity of APL, APLb, APLd, and compound on all tested bacteria. Synergistic effects were obtained when APL and compounds and were combined with erythromycin (ERY), gentamycin (GEN), ciprofloxacin (CIP), and norfloxacin (NOR). The present study demonstrates the antibacterial potential of and its constituents to combat bacterial infections alone or in combination with EPI.