Antioxidant and inhibitory properties of Clerodendrum volubile leaf extracts on key enzymes relevant to non-insulin dependent diabetes mellitus and hypertension

Objective: To characterize the interaction of phenolic (free and bound) extracts from white butterfly (Clerodendrum volubile P. Beauv) leaves with key enzymes relevant to non-insulin dependent diabetes mellitus (α-amylase and α-glucosidase) and hypertension (Angiotensin-I converting enzyme) and their antioxidant properties in vitro. Methods: The effects of the extracts on enzymes [α-amylase, α-glucosidase, Angiotensin-I converting enzyme (ACE)], some pro-oxidant (Fe2+- and sodium nitroprusside-induced lipid peroxidation in the pancreas (in vitro)) and antioxidant properties and HPLC analysis of the extracts were investigated. Results: The phenolic extracts inhibited α-amylase, α-glucosidase, ACE and some pro-oxidants (Fe2+- and sodium nitroprusside-induced lipid peroxidation in the pancreas (in vitro)). Bound phenolics had significantly higher (P < 0.05) α-glucosidase inhibitory effects compared to free phenolics and acarbose (a standard drug). However, captopril, a synthetic ACE inhibitor, showed a higher ACE inhibitory activity compared with both the free and bound phenolics, whereas there was no significant difference (P > 0.05) in their α-amylase inhibitory activities. The stronger inhibition of α-glucosidase and ACE compared to α-amylase by both extracts may be of pharmacological relevance. Reversed-phase HPLC analysis of the extracts revealed the presence of quercetin, rutin, kaempferol, and chlorogenic and caffeic acids as the main components of both the free and bound extracts. Conclusion: The inhibitory properties of phenolic rich extracts on α-amylase, α-glucosidase, ACE, and Fe2+- and sodium nitroprusside-induced lipid peroxidation in the pancreas could be attributed to the antioxidant properties of the extracts and their phenolic composition. The stronger action of the bound phenolic extract on α-glucosidase may provide the possible bioactivity at the brush border end of the intestinal wall. This study may thus suggest that leaves represent a functional food and nutraceutical in the management of non-insulin dependent diabetes mellitus and hypertension.