Acylated flavonol monorhamnosides, α-glucosidase inhibitors, from Machilus philippinensis

Guided by a bioassay against α-glucosidase, two active kaempferol- 3-O-α-l-rhamnopyranoside coumaroic acid esters (1 and 2) with IC50 values of 6.1 and 1.0 μM, respectively, were isolated from the leaf extract of Machilus philippinense. Additional seven isomers, of which three were hitherto unknown, were identified by application of an HPLC-SPE-NMR technique.