Acylated flavonol monorhamnosides, α-glucosidase inhibitors, from Machilus philippinensis
Journal
Phytochemistry
Journal Volume
69
Journal Issue
12
Pages
2347-2353
Date Issued
2008
Author(s)
Abstract
Bioassay-guided fractionation and isolation of the active constituents from the leaf extract of Machilusphilippinense Merr. yielded two active compounds, kaempferol-3-O-alpha-L-rhamnopyranoside 3'',4''-di-E-P-coumaroic acid ester (1) and 3''-E,4''-Z-di-p-coumaroic acid ester (2) when tested against a Bacillus stearothermophilus, a alpha-glucosidase type IV. The IC50 values of 1 and 2 were 6.10 and 1.00microM, respectively. Further application of the HPLC-SPE-NMR hyphenated technique in the on-line characterization of other active ingredients present in the CH2Cl2 - soluble fraction led to identification of luteolin (3) and seven additional 3-O-(coumaroyl-rhamnopyranosyl)-flavonols (4-10). Their structures were determined mainly by 1H NMR spectroscopic analyses. Among the compounds identified, compounds 2, 4, 5, and 7 were hitherto unknown natural products.
Type
journal article