Abstract

Context: Crotalaria incana L. (Fabaceae) is used for various traditional medicinal treatments such as astringent, jaundice and palpitation, inflammation, skin disease and purgative. Aims: To investigate the phytochemical constituents and evaluate the antibacterial activity of seed and pod extracts of C. incana. Methods: Phytochemical screening tests were conducted to identify the class of compounds present in the dichloromethane/methanol (1:1) extracts of seed and pod. Silica gel column chromatographic technique was applied to separate the constituents of the extracts. Various spectroscopic techniques (IR, NMR (1H, 13C and DEPT-135) were applied to determine the structures of isolated compounds. Antibacterial activities were evaluated via disc diffusion method. Results: Preliminary phytochemical screening of seed and pod extracts of C. incana L. revealed the presence alkaloids, flavonoids, triterpenes, tannins and steroids and absence of anthraquinones. Silica gel column chromatography separation of the extract yielded a known steroid β-sitosterol (1) and 1-nonadecanol (2). Evaluation of antibacterial activity of crude extract via disc diffusion method against Escherichia coli, Staphylococcus aureus, Klebsiella pneumonia and Salmonella typhi showed moderate susceptibility of this selected Gram-positive and Gram-negative bacteria strains, comparable to the activity of the antibiotic (gentamicin). Conclusions: The compound (2) (1-nonadecanol) was isolated for the first time from the C. incana. These results proved that polar extracts of the seeds and pods of C. incana possess antibacterial activity.

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