Abstract:

The inhibitory effect of the polysaccharide secreted by the endophytic fungus Chaetomium JY25 isolated from
Gymostamma pentaphyllum on α-glucosidase was explored to provide basic data for the application of this endophytic fungal
polysaccharide. To this end, the conditions for colorimetrically detecting α-glycosidase activity using 4-N-trophenyl-α-Dglu-
copyranoside (PNPG) as a substrate were optimized and the evaluation of α-glucosidase inhibitory effect was performed
using acarbose as a positive control. At the same time, the inhibition type and inhibition constant were determined, and
the inhibitory effect of the fungal polysaccharide on α-glycosidase derived from Caco-2 cells was measured in vitro. The
results showed the optimum conditions for colorimetric determination of α-glycosidase activity were found to be reaction for
30 min at 44 ℃ with an initial pH of 6.8 and a substrate (PNPG) concentration of 5 mmol/L. The polysaccharide secreted by
JY25 at 6.15 mg/mL showed the strongest inhibition against α-glucosidase with a percentage inhibition of 68.21%. The IC50
value of the polysaccharide was (2.46 ± 0.42) mg/mL, and the inhibition constant was 1.15 mg/mL in a competitive manner.
The percentage inhibition of α-glycosidase derived from Caco-2 cells cultured for 16 days reached 16.48% in the presence
of 10.00 mg/mL JY25 polysaccharide. Therefore, the exopolysaccharide produced by the endophytic fungus JY25 has
inhibitory activity on α-glycosidase in vitro in a competitive manner.

Key words: endophytic fungal polysaccharide, Gynostemma pentaphyllum, α-glycosidase, inhibitory effect