Antimicrobial activity of 7,3ʹ,4ʹ-trihydroxyflavonol isolated from Acacia nilotica var. ad stringens

Abstract

Acacia species (Mimosaceae) is widely distributed in tropical and subtropical countries and has a variety of ethnomedicinal uses. There is inadequate laboratory investigation to identify bioactive compounds and therapeutic effect of Acacia nilotica var. ad stringens. This research has been conducted to extract, isolate and identify major compounds from heartwood of Acacia nilotica var. ad stringens and to test them against representative bacteria. Powdered air-dried heartwood of A. nilotica var. ad stringens has been extracted with methanol/water, 4:1 and the extract has been then purified using chromatographic techniques (column and paper chromatography). A pure flavonoid compound has been isolated and the structure has been elucidated based on extensive spectroscopic analysis procedures (IR, UV, ¹H NMR, and mass spectrometery). The isolated compound has then been evaluated for antimicrobial potential against Gram-negative (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive bacteria (Bacillus subtilis, Bacillus cereus, and Staphylococcus aureus) using cup-plate agar diffusion method. The spectroscopic analysis of the isolated compound has led to its identification as 7,3ʹ,4ʹ-trihydroxyflavonol. The compound shows varying antimicrobial responses with high potency against Gram-negative human pathogens. The Gram-positive bacteria which are inhibited are Bacillus cereus, Corynebacterium sp., Enterococcus faecalis, Staphylococcus aureus , and Streptococcus agalactiae. The Gram-negative bacteria are Acinetobacterbaumannii , Acinetobacter sp. , Escherichia coli, Pseudomonas aeruginosa and yeasts are Candida albicans and Cryptococcus neoformans. The present study has demonstrated that 7,3ʹ,4ʹ-trihydroxyflavonol is an effective antimicrobial compound. If applied in suitable pharmaceutical formulations it could be valuable for treating various bacterial infections or introduced as adjunct treatment along with standard agents.