A promising approach for treating diabetes mellitus (DM) is to decrease postprandial
hyperglycaemia by suppressing carbohydrate digestion using a-glucosidase inhibitors.
Pluchea indica leaf extracts possess inhibitory activity against intestinal maltase.
Enzyme assay-guided fractionation by chromatography yielded five active
caffeoylquinic acid derivatives (1–5). Their structures were elucidated by mass
spectrometry and NMR analysis and completed by comparison with reference data.
3,5-Di-O-caffeoylquinic acid (1), 4,5-di-O-caffeoylquinic acid methyl ester (2), 3,4,5-
tri-O-caffeoylquinic acid methyl ester (3), 3,4,5-tri-O-caffeoylquinic acid (4) and
1,3,4,5-tetra-O-caffeoylquinic acid (5) were isolated. Comparison of the activities of
each isolate suggested that both methyl esterification of quinic acid and the number of
caffeate groups in the molecule were important for the inhibitory activity. This study
provides basic information for further examination of the suitability of P. indica as a
functional food and medicinal supplement for the treatment and prevention of diabetes.