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

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, 1 H 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.