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. adstringens. This research was conducted to extract, isolate and identify major compounds from heartwood of Acacia nilotica var. adstringens and to test them against representative bacteria. Powdered air-dried heartwood of A. nilotica var. adstringens was extracted with methanol/water, 4:1 and the extracted was then purified using chromatographic techniques (column and paper chromatography). A pure flavonoid compound was isolated and the structure was elucidated based on extensive spectroscopic analysis procedures (IR, UV, 1H-NMR, and MS spectrometery). The isolated compound was then evaluated for antimicrobial potential against Gram-negative (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive bacteria (Bacillus subtilis, Bacillus cereus, and Staphylococcus aureus) using cub-plate agar diffusion method. The spectroscopic analysis of the isolated compound led to its identification as 7, 3`, 4`-trihydroxyflavonol. The compound showed varying antimicrobial responses with high potency against Gram-negative human pathogens. The Gram-positive bacteria which were inhibited were Bacillus cereus, Corynebacterium sp., Enterococcus faecalis, Staphylococcus aureus, and Streptococcus agalactiae. The Gram-negative bacteria were Acinetobacter baumannii, Acinetobacter sp., Escherichia coli, Pseudomonas aeruginosa and yeasts were Candida albicans and Cryptococcus neoformans. The present study demonstrated that 7, 3`, 4`-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.