Isolation and Screening of Endophytic Actinonycetes and Characterization of Their Bioactive Compounds

Abstract

Thirty eight endophytic actinomycetes were isolated from leaves, pseudoster as rhizomes and roots of three medicinal plants, Amomum krervanh Pierre., Etlingera pavieana (Pierre ex Gagnep.) R.M. Smith and Zingiber zerumbet (L.) Smith by using surface-sterilize technique and isolated on humic acid-vitamin agar. For screening of antimicrobial activity, only 13 isolates have a potential for growth inhibition of the test microorganism, against Gram positive bacteria, strains W14 showed potent antimicrobial activity against Bacillus cereus, Bacillus subtilis TISTR 1248 and Staphylococcus cureus ATCC 2592 and the highest inhibition ratio. Strain V14 was identified as Streptomyces based on phenotypic and genotypic characteristics. On the basis of 16S rRNA gene sequences analysis, Streptomyces, W14 was similar to Streptomyces malaysiensis NBRC 16446T (99.65%). The ethyl acetate extraction from the culture of W14 showed a potential of antibacterial and antioxidan: activity. And then, purification and structure elucidation of crud extract of W14 was performed by column chromatography afford SM01 and SM02. Both were identified as known compound, SM01 was methyl 5-(hydroxymethy1)furan-2carboxylate, the toxin of fungal Curvularia lunata, while SM02 was geldanamycin. Only SM02 showed a potential of anti-inflammatory activity, inhibit the production of nitric oxid (NO) in culture medium and suppress the expression of inducible nitric oxide symhase (iNOS) and proinflammatory cytokine gene in mRNA level ofRAW264.7 cells. Whereas, SM01 exhibition against S. aureus ATCC 25923, MRSA and BCG. Since, SM02 is the major ingredient in sufficient quantities to be semisynthesized to obtain new derivatives. SM02 was reacted with tryptamine or 5- methoxytryptamine, and then purification and structure elucidation afford two derivatives, SMO2T and SM02mT. Derivative SM02mT is a substance that has never been synthesized before. But the two derivatives are not yet examined for biological activity which is suggested to future study in future.