Isolation and bioactivity of endophytic filamentous actinobacteria from tropical medicinal plants

Abstract

Endophytic microorganisms are rich sources for drug discovery. Isolation of actinomycetes from the surface-sterilized tissues of 12 medicinal plants in Hainan, China, was carried out using different media of American Type Culture Collection (ATCC) 172 agar, Gauze’s No. 2 agar, glucose-asparagine agar, humic acid-vitamin agar, and starch-casein-mineral salts agar. Of the 280 isolates recovered, 154 were from roots, 73 from stems and 53 from leaves. Bioactivity test of crude fermentation extracts were performed on all the isolates. About 41.1% of the extracts showed activity against liver cancer cell SMMC-7721, 19.3% against Candida albicans ATCC10231, and 10.0% against Staphylococcus aureus ATCC 51650. In addition, metabolites of nine isolates inhibited caspase 3, a protein related to neurodegenerative diseases, and three inhibited protein tyrosine phosphatase 1B (PTP1B), a protein related to diabetes. Based on their phenotypic and genotypic characteristics, endophytic actinomycetes were classified to actinobacterial genera including Streptomyces, Micromonospora, Nocardia, Nonomuraea and Amycolatopsis spp. The high bioactivity percentage, broad bioactivities and the novel taxa of the isolated endophytic actinomycetes presented their potential in pharmaceutical utilization.

Key words: Filamentous actinomycetes, medicinal plants, antimicrobial activity, anti-tumor cell activity, protein tyrosine phosphatase 1B, caspase 3.