Isolation of endophytic Xylaria spp. from Trad province and their metabolites with anti-cervical cancer activity

Abstract

Metabolites from microorganisms are considered to be a rich source of novel lead compounds for drug development. Endophytic fungi are increasingly used to screen for such compounds because they are relatively unexplored until now. In this study, we isolated endophytic Xylaria spp. from plant leaves sampling in Trad Province in eastern Thailand, and screened for biological activity of the isolated fungal metabolites. A total of 83 isolates included 41 Xylaria spp., 5 Daldinia spp., 1 Fusarium spp., 1 Collectotrichum spp., 4 Pestalotiopsis spp., 2 Phomopsis spp., 2 Phyllosticta spp., 1 Trichoderma spp., 4 Nigrospora spp. and 22 Mycelia sterilia. Crude extracts with ethyl acetate of all endophytic Xylaria spp. were screened for antimicrobial activity against 5 reference pathogenic bacteria and yeast. Moreover, nine crude extracts with strong antimicrobial activity were tested for cytotoxicity against human papiloma virus positive cervical cancer cell line, CaSki. Among these isolates, endophytic fungi isolate X-17 showed both strong antimicrobial and anticancer activity. Crude extract from X-17 showed cytotoxic activity against human cancer cell line, with the inhibitory concentration 50 (IC50) of 10.05±0.28 µg/ml. Detailed study on the cytotoxicity of the X-17 against CaSki cell line demonstrated that this extract induced cell cycle arrest and apoptosis. Therefore, it was chosen for further test for anti-inflammatory activity. Nevertheless, crude extract from X-17 did not show anti-inflammatory activity. Purification of bioactive compounds from this extract was carried out by liquid chromatography and two pure compounds were obtained that were identified as cytochalasin D and 2-p-tolylethanol. In addition, morphology, cultural characteristics and ITS (internal transcribe spacer) sequencing analysis of endophytic isolate X-17 confirmed that it belongs to Xylaria laevis.