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Background and Objective: The SU84 was isolated from the rhizosphere of Curcuma longa and identified to be Streptomyces sp. via analysis of its 16S rDNA sequence, chemotaxonomy and morphology. This study aimed to isolate major compounds from the extract culture of strain SU84 and evaluate their antibacterial activity. Materials and Methods: The TLC and silica gel column chromatography were used to purify major compounds, elucidate 1,3-dihydroxy-,2',2'-dimethylpyrano-(5,6)-xanthone (compound 1) and lupeol (compound 2) using mass spectrometry and nuclear magnetic resonance. One new chemical, compound 1, was first isolated from microbial sources. Antibacterial, antioxidant and cytotoxic properties of these compounds were carried out. Results: Various bioassays showed that compound 1 displayed antibacterial property against Gram-positive bacteria, with a minimum inhibitory concentration of 8-32 μg/mL and minimum bactericidal concentration of 32-128 μg/mL. In addition, the purified compounds were tested against normal cell lines using tetrazolium assay. The results did not show cytotoxic property against L929 and Vero cells, with IC50 values of >512.00 μg/mL. Compounds 1 and 2 have also antioxidant properties, with IC50 values of 16.67±7.48 and 38.86±8.45 μg/mL, respectively. Conclusion: The findings suggested that compounds of Streptomyces sp. SU84 displayed antibacterial and antioxidant properties without cytotoxic activity. Extensive studies of compound 1 may be useful for the advancement of improved methods for avoidance, control and management of bacterial infections and metabolic-related free radical contribution.
Taechowisa et al. (Thu,) studied this question.