Hypoglycaemic potential of leaf extracts of Lonchocarpus cyanescens (Schum. and Thonn) Benth

Abstract

This study evaluated the in vitro inhibitory effects of different extracts of L. cyanescens leaf on the activities of diabetes-related enzymes (α-amylase and α-glucosidase) and the effect of its ethanol extract on postprandial hyperglycaemia in starch-loaded rats. Results of this study revealed ethanol extract as the most potent inhibitor of α-amylase (IC₅₀: 3.69 mg/ml) and α-glucosidase (IC₅₀: 0.13 mg/ml). Lineweaver–Burk plots of the enzyme kinetics showed that the mode of inhibition of α-amylase by the ethanol extract of L. cyanescens is competitive, while it inhibited α-glucosidase non-competitively. Administration of ethanol extract of L. cyanescens leaf to starch-loaded Wistar rats significantly (p < 0.05) reduced the postprandial blood glucose level of the rats within two hours compared to the control animals. This study suggests that ethanol leaf extract of L. cyanescens possessed hypoglycaemic effect, and that one of the mechanisms by which this extract elicited its hypoglycaemic property may be through the inhibition of diabetes-related enzymes (pancreatic α-amylase and intestinal α-glucosidase) activities.

Keywords:

• hyperglycaemia
• Lonchocarpus cyanescens
• α-amylase
• α-glucosidase
• antidiabetic agents

ACKNOWLEDGEMENT

The authors are grateful to the Mangosuthu University of Technology, Umlazi 4031, Durban, South Africa for the postdoctoral fellowship granted to Dr M.I. Kazeem. The support of Lagos State University, Lagos, Nigeria is also acknowledged.

DECLARATION OF INTEREST

The authors declare no conflict of interest.

ORCID

Mutiu Idowu Kazeem http://orcid.org/0000-0002-8058-1938