Cytotoxicity and antibacterial activities of crude extract of Streptomyces sp. W08, an endophyte of Amomum krervanh Pierre

Abstract

Strain W08 was isolated from the pseudostem tissue of Amomum krervanh Pierre (Zingiberaceae) and identified as Streptomyces sp. by analyzing its morphology, chemotaxonomy, and 16SrDNA sequence. It was shown to exert bactericidal effects against Bacillus cereus, Bacillus subtilis, Staphylococcus aureus, and methicillin-resistant S. aureus. Crude extract of its culture inhibited the tested bacteria, with minimum inhibitory concentrations of 32-128 µg/ml. The cytotoxicity of the crude extract was also assessed against cell lines using [3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide] colorimetric assay. The crude extract showed weak cytotoxic activity on L929 and Vero cells with IC50 values of 453.22 and >512.00 µg/ml, respectively. The most powerful cytotoxicity of the crude extract was observed in human cervical carcinoma cells and human breast carcinoma cells with IC50 values of 78.45 and 106.50 µg/ml, respectively, while the IC50 value of human hepatocellular carcinoma cells was 425.86 µg/ml. The bioactive compounds in the extract were isolated by column chromatography and thin-layer chromatography, which were revealed by IR and NMR analyses to be 1-hydroxy-2-methyl-6-methoxyanthraquinone (1) and 6-methoxy-2-methylquinizarin (2). The findings showed that the crude extract of Streptomyces sp. W08 containing the bioactive compounds exhibited antibacterial activity and selective cytotoxicity toward some cancer cells. The studies on these compounds could thus lead to useful approaches for managing some bacterial infections and cancers in the future.