Costus speciosus (Koen ex.Retz.) is an ornamental plant and has also been used in traditional medicinal systems, mainly in India and Sri Lanka. This research article reveals the antibacterial activity of the leaves of Costus speciosus (Koen.) and its efficacy in different solvents, acetone, ethanol and sterilized distilled water (aqueous), against selected human pathogenic bacteria, Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The leaves were tested for antibacterial activity, using agar well diffusion method at the test concentrations of 25, 50 and 75mg/100?l of these solvents, separately. The maximum inhibitory action was observed in ethanol extracts against both bacterial strains at 75mg/100?l concentration. The Minimum Inhibitory Concentration (MIC) for Acetone and ethanol extracts of Costus speciosus were 12.5mg/100?l and 6.25mg/100?l respectively against E. coli whereas it was 12.5mg/100?l against S. aureus for both extracts. The aqueous, ethanol and acetone extracts showed concentration-dependent antibacterial activity against the tested bacteria with the zone of inhibition. Among the solvents used, the acetone showed higher inhibitory activity yet clear and significant inhibition zones were also observed from the aqueous and ethanol leaf extracts. Thereby, the results revealed the medicinal potential of the leaf extracts of Costus speciosus (Koen.) against various infectious diseases to develop a drug with appropriate solvents.

Staphylococcus aureus

Escherichia coli