Metabolic Profiling for Evaluating the Dipeptidyl Peptidase-IV Inhibitory Potency of Diverse Green Tea Cultivars and Determining Bioactivity-Related Ingredients and Combinations

There
are numerous cultivars of tea (Camellia sinensis L.), but the differences in their anti-hyperglycemic-related effects
are largely unknown. The inhibition of the dipeptidyl peptidase (DPP)-IV
enzyme plays an essential role in controlling hyperglycemia in diabetes
by blocking the degradation of incretin hormones, which is necessary
for insulin secretion. In this study, we examined the DPP-IV inhibitory
activity of leaf extracts from diverse Japanese green tea cultivars.
The inhibitory rates differed among tea extracts. Metabolic profiling
(MP), using liquid chromatography–mass spectrometry, of all
cultivars revealed compositional differences among cultivars according
to their DPP-IV inhibitory capacity. Epigallocatechin-3-O-(3-O-methyl)­gallate, kaempferol-3-O-rutinoside, myricetin-3-O-glucoside/galactoside,
and theogallin were newly identified as DPP-IV inhibitors. The bioactivity
of a tea extract was potentiated by adding these ingredients in combination.
Our results show that MP is a useful approach for evaluating the DPP-IV
inhibitory potency of green tea and for determining bioactivity-related
ingredients and combinations.