Diversity And Antidiabetic Activities of Fungal Leaf Endophytes Associated with Antidesma Bunius (L.) Spreng (Bignay)

Plant-associated fungal endophytes continue to be valuable sources of bioactive natural products. Of particular interest are fungal endophytes associated with the endemic and medicinal Philippines plants. Antidesma bunius, locally known as bignay, is known for its blood sugar-lowering activities, but no reports yet on the antidiabetic activities of its fungal endophytes. In this study, we investigated the diversity of fungal endophytes associated with young, mature and old leaves of bignay. Our results showed the isolation of 94 fungal endophytes from the three different leaf stages. Colonization rate and taxonomic diversity was influenced by leaf age. A higher colonization rate and number of isolated morphospecies were recorded in mature leaf type (CR: 100%, 27 morphospecies) followed by the old leaf type (CR: 100%, 19 morphospecies). The young leaf type had the least colonization rate and number of isolated fungi (CR: 16.6%, 3 morphospecies). Confirmation of species identities was done through sequence analysis of the ITS genes. We also conducted secondary metabolite profiling of the fungal crude culture and plant extracts using TLC. Major detected compounds were fatty acids, triterpenes, phenols, flavonoids, and phenolics. Selected fungi were also evaluated for their antidiabetic properties based on alpha-glucosidase assay. We hypothesized the antidiabetic activities of our isolated fungal endophytes as its host plant also exhibited similar properties. Our results showed that the bignay leaf extract had 95.6% inhibitory activity while the crude culture extracts of eight fungal endophytes had a range of 37.9 -71.8% inhibitory activity of the enzyme alpha-glucosidase, confirming our hypothesis.