Isolation and identification of α-glucosidase inhibitory constituents from the seeds of <i>Vigna nakashimae</i>: Enzyme kinetic study with active phytochemical

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>The α-glucosidase inhibition effects of the 80% ethanol extracts in the seeds of five <I>Vigna</I> species (<I>V. nakashimae</I>, <I>V. nipponensis</I>, <I>V. umbellate</I>, <I>V. radiate</I>, and <I>V. angularis</I>) were evaluated and their half-maximal inhibitory concentration (IC<SUB>50</SUB>) values showed considerable differences (<I>p</I> < 0.05) ranging from 7.3 to >900 μg/ml. <I>V. nakashimae</I> exhibited the most potent inhibition with IC<SUB>50</SUB> value of 7.3 ± 1.1 μg/ml, followed by <I>V. nipponensis</I> (184.0 ± 9.5 μg/ml) and <I>V. umbellata</I> (520.0 ± 8.1 μg/ml). Bioactivity-guided fractionation of <I>V. nakashimae</I> seeds yielded three phenolics by silica gel chromatography and their structures were elucidated as gambiriin D (<B>1</B>), luteoliflavan-7-<I>O</I>-glucopyranoside (<B>2</B>), and catechin-7-<I>O</I>-glucopyranoside (<B>3</B>) using nuclear magnetic resonance (NMR) spectroscopy. In particular, gambiriin D (<B>1</B>) possessed strong inhibition activity with IC<SUB>50</SUB> of 36.8 ± 2.3 μM through simple reversible slow-binding inhibition (kinetic parameters: <I>k</I> <SUB>4</SUB> = 0.0048 μM<SUP>−1</SUP>s<SUP>−1</SUP>; <I>K</I> <SUB>i</SUB> <SUP>app</SUP> = 48 μM). Furthermore, this compound inhibited recombinant human aldose reductase with IC<SUB>50</SUB> value of 12.0 ± 0.7 μM. Results suggest that <I>V. nakashimae</I> may be a potent α-glucosidase inhibition for health products.</P> <P><B>Highlights</B></P> <P> <UL> <LI> <I>V. nakashimae</I> seeds showed potent α-glucosidase inhibition (IC<SUB>50</SUB> = 7.3 ± 1.1 μg/ml). </LI> <LI> Three phenolic compounds were identified from the seeds of <I>V. nakashimae</I>. </LI> <LI> Gambiriin D inhibited α-glucosidase with reversible slow-binding mode (IC<SUB>50</SUB> = 36.8 ± 2.3 μM). </LI> <LI> Gambiriin D inhibited human aldose reductase with IC<SUB>50</SUB> value of 12.0 ± 0.7 μM. </LI> </UL> </P>