Screening and Bioassay-guided Isolation of Antimicrobial Components from Laggera mollis

Abstract

There are about 20 identified species in the genus Laggera and only few have been extensively investigated. The study was aimed at evaluation the antimicrobial activity of Laggera mollis and isolation of the bioactive component(s) for new potent antimicrobial agent. Four fractions each from the leaves and stem-root of the plant were sequentially extracted with petroleum ether, chloroform, ethyl acetate and ethanol using soxhlet extraction scheme, while the marcs were decocted for the aqueous extracts. Phytochemical screening of four extract fractions each from the leaves and stem-root of the plant revealed the presence of alkaloids, tannins, flavanoids, saponins, steroids, terpenoids and reducing sugar distributed across the fractions. Disc diffusion method of Antimicrobial Sensitivity Test (ATS) was adopted in testing the bioactivity of the plant extracts against seven bacteria and one fungus. Bioassay-guided isolation from the petroleum ether fraction (LM1-01) of the leaves of the Laggera mollis using column chromatography, led to the isolation of two pure compounds. The results of the antimicrobial activity of the isolated compounds indicted that LM1-1-10 was more potent against Salmonella typhi (11 mm) at 40 μg/disc followed by Streptococcus pyogens (10 mm) at 40 μg/disc and Staphylococcus aureus (10 mm) at 40 μg/disc. The spectra of the activity exhibited by the isolates signified their potency for the development of therapeutic agents against these pathogenic microorganisms.

Keywords: Bioassay-guided isolation, antimicrobial activity, Laggera mollis, clinical isolates, extracts.