Antibacterial and Anticandidal Activities of New Flavonoids from Streptomyces sp. HK17; an Endophyte in Curcuma longa Linn.

Aims: The purpose of this study was to investigate the antibacterial and anticandidal activities of new flavonoids from Streptomyces sp. HK17 which was isolated from the root tissue of Curcuma longa Linn. Study Design: Experimental study. Place and Duration of Study: The study was carried out at the Department of Microbiology and Department of Chemistry, Faculty of Science, Silpakorn University, between February and May 2014. Methodology: The major active ingredients from the crude extract were purified by silica gel column chromatography, thin-layer chromatography. The diameters of the zones of inhibition and the Minimum Inhibitory Concentration (MIC) were determined using the paper disc diffusion and the microbroth dilution methods respectively. Results: The crude extract and purified compounds were tested for their antibacterial activity against Staphylococcus aureus ATCC25932, Bacillus cereus ATCC7064 and Bacillus subtilis ATCC6633, Escherichia coli ATCC10536 and Pseudomonas aeruginosa ATCC27853 and anticandidal activity against Candida albicans ATCC190088. The crude extract showed the highest activity against S. aureus and C. albicans, with MIC values of 32 μg/ml. The purified compounds 3 showed the lowest MIC (32 μg/ml) and Minimum Microbicidal Concentration (MMC) (128 μg/ml) against S. aureus and C. albicans with corresponding large diameter of the zone of inhibitions (25.5 and 25.2 mm respectively). Conclusion: This study has shown that the new flavonoids were first isolated and identified. These flavonoids produced by Streptomyces sp. HK17 have potential in antibacterial and anticandidal activities.