CHROMATOGRAPHIC SEPARATION OF CERTAIN CHEMICAL CONSTITUENTS OF SALIX MUCRONATA AND EVALUATING THEM AS ANTIOXIDANT AND ANTIMICROBIAL AGENTS

Abstract

- In the present study, extracts of different percentages of methanol and water of Salix mucronata leaves were prepared and evaluated as antioxidant agents using three in-vitro techniques which are; DPPH radical scavenging activity, ABTS/TEAC (Trolox-equivalent antioxidant capacity( and Total antioxidant capacity (Phosphomolybdenium assay). Also, their antimicrobial activity was determined using disc diffusion assay (DDA). - Owing to the high activity of 85% methanolic extract, the defatted 85% methanolic extract was submitted to fractionation process using chloroform (CHCl3), ethyl acetate (EtOAc) and n-butanol (n-BuOH). These fractions were evaluated as antioxidant and antimicrobial agents. The results revealed that the EtOAc and n-BuOH fractions have high antioxidant and antimicrobial activities. - The total phenolic and flavonoid contents of 85% methanolic extract and fractions derived from it were also determined. The results revealed that there is a positive correlation between the phenolic and flavonoid contents and the antioxidant activity of the tested extracts. - Separation of certain chemical constituents from the EtOAc and n-BuOH fractions derived from 85% methanolic extract was achieved using different chromatographic techniques. - Identification and structure elucidation of the pure isolated compounds were taken place by using different spectroscopic analyses such as UV, 1H NMR and 13C NMR as well as acid hydrolysis. - Six compounds were isolated from the EtOAc fraction derived from 85% methanolic extract of S. mucronata leavesand their structures were identified 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). - Five compounds were isolated from the n-BuOH fraction derived from 85% methanolic extract of S. mucronata leaves 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).