Newboulasides A and B, two new caffeic acid glycosides from Newbouldia laevis with α-amylase inhibitory activity

Abstract

Chemical investigation of the ethanol extract of the leaves of Newbouldia laevis (P. Beauv) led to the isolation of two new caffeic acid glycosides, Newboulasides A (1) and B (2). The structures of these compounds were determined on the basis of extensive spectroscopic methods, including 1D-, 2D-NMR and MS data. The extracts and fractions and the isolated compounds were evaluated for their inhibition of α-amylase enzyme activity. The extract showed inhibition of α-amylase activity with IC50 value of 102.91 µg/mL, while the isolated compounds (1 and 2) exhibited pronounced inhibition with IC50 values of 4.95 and 4.44 µg/mL respectively, comparable to the standard – Acarbose with IC50 value of 4.05 µg/mL. Our findings demonstrated that the inhibition of α-amylase activity may be part of the mechanisms through which N. leavis exhibits antidiabetic effect.