In this study, two researchers from the Indonesian Institute of Sciences and Ehime University in Japan isolated, identified, and characterized an endophytic fungus from the stem of Quercus gilva Blume (Ichiigashi oak) and investigated its bioactivity. Their results, which highlighted the alpha-glucosidase inhibitory effect of the extracts obtained from the fungus, were published in the journal Food Science and Human Wellness.
- In their previous study, the researchers found that Q. gilva and Quercus phillyraeoides A. Gray (Ubame oak) are rich sources of catechins and epicatechins, which are known antioxidants, and tiliroside, a potent alpha-glucosidase inhibitor.
- Several studies have also reported that endophytic fungi contain bioactive compounds with antioxidant, antiviral, and antimicrobial activities.
- For this study, the researchers isolated an endophytic fungus from the stem of Q. gilva and identified it as Xylariaceae sp. QGS 01.
- They used ethyl acetate as an extraction solvent and obtained extracts from the mycelium of Xylariaceae sp. QGS 01.
- They isolated active components from the mycelium extracts using a bioassay-guided fractionation technique.
- The researchers used a glucosidase enzyme isolated from the yeast Saccharomyces cerevisiae for the in vitro assay.
- The researchers obtained an isocoumarin derivative, 8-hydroxy-6,7-dimethoxy-3-methylisocoumarine (1), after further separating and purifying the active fraction using silica gel chromatography.
- They also obtained a fatty acid mixture that contained two saturated fatty acids, palmitic acid (24.1 percent) and stearic acid (7.5 percent), and three unsaturated fatty acids, namely, oleic acid (29.8 percent), linoleic acid (3.6 percent), and linolenic acid (33.7 percent).
- They reported that 8-hydroxy-6,7-dimethoxy-3-methylisocoumarine (1) showed the highest alpha-glucosidase inhibitory activity (41.75 micrograms per milliliter [ug/mL], IC50).
- The fatty acids with double bonds (unsaturated) had stronger alpha-glucosidase inhibitory activities than fatty acids without double bonds (saturated).
Based on these results, the researchers concluded that Xylariaceae sp. QGS 01 from Ichiigashi oak is a rich source of antidiabetic compounds.
Read the full study at this link.
Journal Reference:
Indrianingsih AW, Tachibana S. ALPHA-GLUCOSIDASE INHIBITOR PRODUCED BY AN ENDOPHYTIC FUNGUS, XYLARIACEAE SP. QGS 01 FROM QUERCUS GILVA BLUME. Food Science and Human Wellness. June 2017;6(2):88–95. DOI: 10.1016/j.fshw.2017.05.001