Endophytic fungi from Rafflesia cantleyi: species diversity and antimicrobial activity

The Rafflesia flower is the largest single flower in the world, a parasitic flowering plant found only in Borneo, Indonesia, Malaysia and Philippines. This study was undertaken to isolate, identify and evaluate antimicrobial activity of endophytic fungi from Rafflesia cantleyi, a Malaysian endemic species. Different parts of the flower and bud collected in Perak, Malaysia, were surface sterilized and plated onto potato dextrose agar. Fungal isolates recovered were cultured in potato dextrose broth for antimicrobial activity screening and solvent extraction. Fungal 5.8S gene and flanking internal transcribed spacer regions of rDNA were sequenced for construction of phylogenetic trees. Eight endophytic strains obtained from R. cantleyi were categorized as seven morphotypes. Three isolates inhibited the growth of Candida albicans with IC50 values of 3.5-8.2 mu g/ml for crude fungal extracts. Based on morphological study, the endophytes were identified as belonging to Colletotrichum, Cytospora and Gliocladiopsis. Phylogenetic analysis of fungal rDNA internal transcribed spacer sequences confirmed the three active isolates were Colletotrichum siamense, Colletotrichum sp. and Cytospora sp. while other isolates were identified as Colletotrichum siamense, Colletotrichum sp. and Gliocladiopsis sp. Endophytic fungi isolated from Rafflesia cantleyi produce bioactive metabolites which may contribute to the plant's medicinal properties.