Antibacterial and cytotoxic activity of seeds of white hyacinth bean (Lablab purpureus L. sweet ‘white’)

Seeds of white hyacinth bean available in Khulna, Bangladesh were investigated to assess bioactivities such as antibacterial and cytotoxic properties. For the evaluation of bioactivities solvent extraction was performed by using 50% ethanol and 50% methanol. In the present study , in vitro antibacterial screening was done by the method known as disc diffusion assay. Additionally, the cytotoxic activity was screened by using brine shrimp lethality bioassay. Both the extracts exhibited excellent activity against both gram positive and gram negative bacteria. For ethanolic extract of white hyacinth bean, maximum zone of inhibition was found 17.75 mm at 1000 μg/disc against Staphylococcus epidermidis and 16.75 mm against Staphylococcus aureus. On the other hand, for methanolic extract the maximum zone of inhibition was found as 17.25 mm for 1000 μg/disc against Escherichia coli and 16.75 mm against Pseudomonas aeruginosa. In comparision to ethanolic extract, methanolic extract was found to be more active against all tested microorganisms. Compared to vincristine sulphate (with LC50 of 0.99 μg/ml) both ethanolic and methanolic extracts of hyacinth bean seeds showed toxicity lower than 100 μg/ml and they were 34.67 μg/ml and 45.5 μg/ml, respectively. The LC50 values suggest moderate cytotoxicity of the tested samples. The experimental findings could be correlated with the traditional medicinal uses of the seeds of this plant and showed the rational for further investigation which would be required for isolating the possible bioactive constituents responsible for such activities.