The in vitro α-glucosidase and α-amylase inhibitory activity and in vivo postprandial antihyperglycemic activity of Ficus nota Blanco Merr. and Ficus septica Burm. F. leaf methanolic extracts

Abstract

Background: One of the therapeutic strategies for type 2 diabetes mellitus involves suppressing postprandial hyperglycemia by inhibiting key enzymes in carbohydrate digestion, α-glucosidase and α-amylase. While such inhibitors are commercially available, some researchers have turned to plants for potentially cheaper and safer alternatives.

Objectives: The study aimed to investigate the in vitro α-glucosidase and α-amylase inhibitory activities of the leaf methanolic extracts of two native Philippine plants Ficus nota Blanco Merr. and Ficus septica Burm F, as well as their effects on postprandial blood glucose levels in a mouse model.

Methodology: The in vitro activities of the leaf methanolic extracts were evaluated against porcine pancreatic α-amylase and yeast α-glucosidase. The most active extract was partially purified into fractions by sequential solvent partitioning and subjected to in vitro testing. Postprandial antihyperglycemic activity was then assessed in normoglycemic ICR mice. Phytochemical analysis was also performed.

Results: The most active extract and fraction in vitro were FS-crude and FS-HexF, respectively, having significantly more potent α-glucosidase inhibitory activity than the commercial drug acarbose. FS-crude and FS-HexF exhibited strong inhibition of α-glucosidase and weak inhibition of α-amylase, which is considered favorable for novel inhibitors as it is hypothesized to reduce gastrointestinal adverse effects. However, FS-crude and FS-HexF did not significantly attenuate postprandial blood glucose levels in the oral starch tolerance test. Phytochemical analysis of FS-HexF putatively identified 6-gingerol as one of the possible bioactive components.

Conclusion: F. septica could be a potential source of glycoside inhibitors as it showed promising in vitro inhibition of α-amylase and α-glucosidase. While it did not exhibit significant postprandial antihyperglycemic activity in this study, more robust testing is recommended to make a definitive conclusion.