Anti-diabetic, anti-hyperlipidaemic and anti-oxidant effects of saponins fractions of Irvingia gabonensis stem bark in streptozotocin diabetic female rats

Abstract

Background: Irvingia gabonensis aqueous stem bark extract possesses significant long term (24 weeks) hypoglycaemic /antidiabetic, hypolipidaemic and antioxidant effects. Preliminary phytochemical analysis revealed the presence of saponins in I. gabonensis stem bark. Saponins from various plant sources have been shown to also possess these effects.

Objectives: The aim of this study was therefore to ascertain the contribution of I. gabonensis total saponins fractions (ITSF) to the observed antidiabetic, antihyperlipidaemic and antioxidant effects of the crude aqueous extracts.

Methods: ITSF was extracted from I. gabonensis stem bark by sequential solvent extraction and chromatographic methods. Twenty (25) Wistar rats in five groups (normal control, diabetic control, 10mg saponins/kg b. w. treated diabetic rats, 20mg saponins/kg b. w. treated diabetic rats and 40mg saponins/kg b. w. treated diabetic rats) were used in this study. After twenty-eight (28) days of ITSF administration; the fasting blood sugar (FBS), serum lipid profile and oxidative status of streptozotocin-diabetic female rats were assessed.

Results: I. gabonensis saponins slightly reduced the FBS of STZ diabetic female rats. Higher concentrations of saponins (20 and 40 mg/Kg body weight) caused reductions in serum total cholesterol, LDL-cholesterol and triglycerides, while HDL-cholesterol concentrations were significantly (P<0.05) increased in the saponins treated diabetic female rats (TDFR). The higher concentrations of the saponins caused significant (P<0.05) reductions in serum and tissue MDA concentrations, while SOD, CAT, GST and GSH levels were mostly increased in the TDFR.

Conclusion: Our findings showed that ITSF had only a marginal short-term anti diabetic effect, but exhibited substantial anti-hyperlipidaemic and anti-oxidant effects. It is possible that the phytochemicals found in I. gabonensis bark, including saponins, may act synergistically to exert its anti-diabetic effect; there is also the possibility that it may take a longer period of time for the anti-diabetic effects of I. gabonensis saponins to become evident.

Keywords:  Irvingia gabonensis; Saponins; Anti-diabetic; Anti-hyperlipidaemic; Anti-oxidant