Abstract The Costus speciosus belonging to family Coastaceae, is a substantial medicinal and ornamental plant used traditionally to cure different diseases. Aim: The current studies were sought to determine the antimicrobial activities of ethanolic and aqueous extracts of Costus speciosus rhizome (CSEE and CSAE) against nine bacterial strains (P. aeruginosa, S. epidermidis, S. pygenes, E. coli, K. pneumonia , S. Typhimurium, Proteus mirabillus, Bacillus species)and three fungal strains (Aspergillus fumigates, Penicillum species and Fusarium species). Method: The ethanolic and aqueous extracts were obtained by hot and cold maceration methods and the antimicrobial effect was found using well diffusion method. Results: All the nine tested bacteria and three tested fungi showed concentrations dependent susceptibility to both ethanolic extracts (CSEE). The aqueous extract on hot has antibacterial activity against P. aeruginosa, and S. aureus only and has no antifungal activity. The highest antibacterial activity was exhibited by both extracts (CSEE and CSAE) against P. aeruginosa (24mm). K. pneumonia and E. coli were susceptible to the highest concentration of on hot and on cold CSEE, while, S. Typhiwas affected by CSEE on cold and proteus mirabilis was susceptible to on hot CSEE. Additionally strong antifungal activity was exhibited by CSEE against Penicillum species, Fusarium species and Aspergillus fumigatus, thehighest inhibition zones were 37mm, 23mm and 21mm respectively. Whilst, the CSAE was not elucidate any activity against fungal strains. Overwhelmingly, the antimicrobial activities were due to biological constituents that present in C. speciosus rhizomes such as steroidal saponins (diosgenin), sesquiterpenoid compounds (costunolide and eremanthin), alkaloids, and other chemical constituents. Conclusion: On the basis of these finding, it may be inferred that ethanolic extracts of C. speciosus rhizomes on hot and on cold in high concentrations have a good antibacterial and antifungal activities against various pathogenic microorganisms. Whilst, aqueous extract on hot has antibacterial activity against P. aeruginosa, and S. aureus only and has no antifungal activity.
Keywords Costus speciosus, Pseudomonas aeruginosa, Aspergillus fumigates, Penicillum species.