The chemical composition, antifungal, antioxidant and antimutagenicity properties of bioactive compounds from fungal endophytes associated with Thai orchids

Abstract

Some plant-derived bioactive compounds produced by fungal endophytes have been proven to have antimicrobial and antioxidant activities. In this study, endophytic fungi were isolated from 20 orchid samples collected in northern Thailand from 12 genera of orchids. In total, 97 isolates were isolated from the leaves (44.3%), stems (40.2%) and flowers (15.5%) of the orchid samples. The antifungal activity was investigated of the endophytic isolates against the plant pathogenic fungi. The results showed that 13 endophytic isolates provided antifungal activities against Fusarium sp., Colletotrichum sp. and Curvularia sp. The endophyte CK F05-5, which was isolated from the flower part of Dendrobium lindleyi, was chosen for further testing because it the highest level of antifungal activity against Fusarium sp. The isolate CK F05-5 was identified as Fusarium oxysporum on the basis of its ITS sequences of 5.8 s rRNA, and phytochemical analysis revealed the presence of coumarins. The ethyl acetate extract of CK F05-5 was examined for its total phenolic content and antioxidant activity using Folin–Ciocalteu's reagent and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay, respectively. The phenolic content was 160.51 mg of GAE/g of extract, and the free radical scavenging activity was 89.61 µg/ml at the half maximal inhibitory concentration (IC50). The antimutagenic potential of the ethyl acetate extract of CK F05-5 against Trp-P-1 mutagenic substances was determined using the Ames test which revealed that the extract of CK F05-5 at 10 mg/plate had the highest antimutagenic activity against Trp-P-1 (51.2%) and 39.6% for strains TA98 and TA100, respectively. The active compounds present in the acetate extract of CK F05-5 were examined using GC-MS analysis, which displayed the presence of gibepyrone A, pyrrolo [1, 2-a] pyrazine-1, 4-dione, hexahydro-3-(2-methylpropyl) and indoleacetic acid as major components. Based on the results, this endophytic fungus contains various bioactive components that have various biological activities. This useful information could help in producing potentially valuable and novel pharmaceutical products.