3,5-dimethoxy-4’-o-(2”,3”-dihydroxy-3”-methylbutyl)- dihydrostilbene isolated from the aerial parts of <i>Indigofera pulchra</i> potentiates the antimicrobial activities of ciprofloxacin and fluconazole

Abstract

Bacterial and fungal infections continue to present a major threat to human health leading to serious injuries. Microorganisms’ resistance to currently existing drugs is an increasingly problematic issue that leads to millions of deaths in the world every year. This study examined the microbial inhibitory potential of 3,5-dimethoxy-4’-O-(2”,3”-dihydroxy-3”-methylbutyl)-dihydrostillbene isolated from the aerial parts of Indigofera pulchra (Willd) and its ability to enhance the activities of Ciprofloxacin and Fluconazole against bacteria and fungi respectively. The aerial parts were extracted by cold maceration using ethyl alcohol to obtain the crude extract which was further separated by liquid-liquid fractionation to afford the hexane, chloroform, ethylacetate and butanol fractions. Extensive phytochemical investigation of chloroform fraction using column and thin-layer chromatographic techniques led to the isolation of 3,5-dimethoxy-4’-O-(2”,3”-dihydroxy-3”- methylbutyl)-dihydrostillbene. The structure was elucidated using IR, 1H-NMR, 13C-NMR and DEPT techniques. Results of the antimicrobial study indicated that the isolated compound inhibited the growth of the test microorganisms (MRSA, S. aureus, E. coli, P. mirabilis, C. albicans and C. tropicalis) with maximum zone of inhibition of 37 mm, and was found to be greater than that observed for ciprofloxacin (33 mm) and fluconazole (26 mm). The isolated compound was observed to enhance the antimicrobial activities of ciprofloxacin and fluconazole when combined from a range of 25 – 33 mm to a range of 25 – 40 mm. The result of this study had justified the use of Indigofera pulchra in traditional medicine for the treatment of bacterial and fungal infections and the isolated compound can be used for clinical trials to develop a new drug, more potent and effective for the treatment of microbial infections.