Comparative Study on the Antidiabetic Efficacy of Unripe and Ripe Fruit Extracts of Siraitia grosvenorii and the Possible Mechanism of Action

Aims: The ripe fruit of Siraitia grosvenorii (Swingle) C. Jeffrey (Cucurbitaceae) is used in Traditional Chinese Medicine (TCM) for treatment of diabetes. The ripe fruit is very edible, nutritious and of high sweet taste, while the unripe fruit which is usually very bitter and not edible, has not been widely studied. Therefore, the aim of this study is to evaluate the antidiabetic activity of the unripe fruit of S. grosvenorii and to compare it with that of the ripe fruit as well as to determine their possible mechanism of action.

Methodology: The method of streptozotocin-nicotinamide induced diabetic animal model in mice was employed and mice with blood glucose greater than 9.0 mmol/l were selected for treatment with unripe fruit extract (UFE) and ripe fruit extract (RFE) for 24 days. Alpha-glucosidase and alpha amylase enzymes inhibitory assays for determination of possible mechanism of action, were performed.

Results: The RFE exhibited better efficacy in antidiabetic activity than the UFE, though the later displayed better potency in activity. The RFE, UFE (300 mg/kg) and glibenclamide exhibited significant (P<0.05) percentage blood glucose reduction (PBGR) of 67.04, 60.69 and 62.88%, respectively, in diabetic mice. Alpha glucosidase assay showed median inhibitory concentration (IC50) value of 7.60 and 6.62 mg/ml for RFE and UFE, respectively, while the alpha amylase inhibitory assay exhibited percentage inhibition of 84.78 and 95.10% for RFE and UFE (25 mg/ml), respectively.

Conclusion: The ripe and unripe extracts of S. grosvenorii exhibited antidiabetic activities, and RFE proved a better efficacious activity than UFE, which showed more potent activity. In addition, the antidiabetic activity is likely being mediated through alpha glucosidase and alpha amylase enzymes inhibition.