In vitro lipase inhibitory effect and kinetic properties of di-terpenoid fraction from Calotropis procera (Aiton)

Calotropis procera Aiton (Asclepiadaceae) root extract was investigated as an inhibitor of pancreatic lipase (PL) and its kinetic parameters were studied in an attempt to explain its hypolipidemic activity. The purified di-terpenoid fraction showed highest inhibition with an IC50 of 9.47 µg/mL in comparision with a standard inhibitor, Orlistat (IC50 0.15 µM). In the presence of purified di-terpenoid fraction, the value of apparent Km (Kmapp) was found to be increased whereas apparent Vmax (Vmaxapp) remained unchanged. Inhibition constant (Ki) of purified di-terpenoid fraction was found to be significantly lower than the positive control (Orlistat). Moreover, in the presence of purified di-terpenoid fraction, substantial decrease was noticed in specificity constant (Kcat/Km). Based on kinetic data, the inhibition was found to be of competitive type. The bioactivity was discussed in terms of bioactive metabolites present in the extracts. Our results demonstrated that the antihyperlipidaemic effects of C. procera root extract can be partly attributed to the inhibition of PL by di-terpenoids present in it.