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

ObjectiveTo 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.MethodsThe 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.ResultsThe 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.ConclusionThe 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.