Isolation and Identification of Certain Phenolic Compounds from Salix mucronata Leaf Extracts and Evaluation Them as Antimicrobial Agents

Background: In recent years, plant extracts are considered as an important source of many drug formulations for treatment of human beings from infection diseases. The objective of this study was to evaluate the antimicrobial activity of Salix mucronata leaves extracts and isolate their bioactive phytochemicals. Methods: The dry powder of Salix mucronata was extracted with different aqueous methanol concentrations. The 85% methanolic extract was further fractionated using different organic solvents. The antimicrobial activity of different extracts and fractions was evaluated. The most bioactive fractions were submitted for chromatographic isolation and structure elucidation of their phytochemicals using chromatographic and spectroscopic methods. Results: The ethyl acetate and the butanolic fractions derived from 85% MeOH extract gave a high antimicrobial activity with inhibition zones ranging between 10 mm and 26 mm and minimum inhibitory concentration (MIC) value of 8 mg/mL. While the butanolic fraction showed zones of inhibition ranging between 10 mm and 25 mm with MIC 8 mg/mL. Six compounds were isolated from ethyl acetate fraction and their structures were elucidated as; apigenin (1), quercetin (2), quercetrin (3), rhamnazin -3-O-β-D-glucopyranoside (4), Chrysoeriol-7-O-β-D-glucuronoid- 6 -methyl ester (5), and tremuloidin (6). Also, five compounds were isolated from the butanolic fraction and their structures were elucidated as; kaempferol (7), luteolin (8), luteolin-3 - methoxy-4 - O-β-D- glucopyranoside (9), isorhamnetin -3-O-β -D-glucopyranoside (10) and salicin (11). Conclusion: The results of the present study showed that the ethyl acetate and the butanolic fractions contain high flavonoids and salicinoids compounds which may attribute to their potential as antimicrobial agents.