vitisin-a and hopeaphenol

Ethanol extracts (Et) from the stem (S) and leaf (L) of Vitis thunbergii var. taiwaniana (VTT) were used to investigate yeast α-glucosidase and porcine kidney dipeptidyl peptidase-IV (DPP-IV) inhibitory activities. Both VTT-Et showed complete α-glucosidase inhibition at 0.1 mg/mL; VTT-S-Et and VTT-L-Et showed 26 and 11% DPP-IV inhibition, respectively, at 0.5 mg/mL. The VTT-Et interventions (20 and 50 mg/kg) resulted in improvements in impaired glucose tolerance of diet-induced obese rats. (+)-Hopeaphenol, (+)-vitisin A, and (-)-vitisin B were isolated from the ethyl acetate fractions of S-Et and showed yeast α-glucosidase inhibition (IC50 = 18.30, 1.22, and 1.02 μM) and porcine kidney DPP-IV inhibition (IC50 = 401, 90.75, and 15.3 μM) compared to acarbose (6.39 mM) and sitagliptin (47.35 nM), respectively. Both (+)-vitisin A and (-)-vitisin B showed mixed noncompetitive inhibition against yeast α-glucosidase and porcine kidney DPP-IV, respectively. These results proposed that VTT extracts might through inhibitions against α-glucosidase and DPP-IV improve the impaired glucose tolerance in diet-induced obese rats.

Topics: alpha-Glucosidases; Animals; Benzofurans; Dipeptidyl Peptidase 4; Dipeptidyl-Peptidase IV Inhibitors; Glucose Intolerance; Glycoside Hydrolase Inhibitors; Kinetics; Male; Obesity; Phenols; Plant Extracts; Plant Leaves; Rats; Rats, Wistar; Saccharomyces cerevisiae; Stilbenes; Swine; Vitis

It has been reported that resveratrol (trans-3,5,4'-trihydroxystilbene) from Vitis plants has various cardioprotective effects. Vitis plants also include various resveratrol tetramers. The aim of our study is to clarify the pharmacological properties of resveratrol tetramers. We isolated two resveratrol tetramers as major products of Vitis plants. One is vitisin A, a complex of two resveratrol dimers, (+)-epsilon-viniferin and ampelopsin B, and the other is hopeaphenol, composed of 2 mol ampelopsin B. Vitisin A (30-300 nM) unexpectedly dose-dependently facilitated swelling and depolarization of mitochondria and cytochrome c release from mitochondria, which are indices of cardiomyocyte apoptosis. Furthermore, vitisin A induced apoptosis in the primary culture of adult rat ventricular myocytes. On the other hand, hopeaphenol (1-10 microM) dose-dependently inhibited Ca(2+) (30 microM)-induced mitochondrial depolarization and cytochrome c release from mitochondria but had not affected mitochondrial swelling. Moreover, hopeaphenol inhibited vitisin A-induced apoptosis. In structural and functional studies, we further confirmed that vitisin B, one of the resveratrol tetramers having (+)-epsilon-viniferin unit, induces mitochondrial swelling and cytochrome c release from mitochondria like vitisin A and that vitisifuran A, one of the resveratrol tetramers having the ampelopsin B unit, inhibits Ca(2+)-induced cytochrome c release from mitochondria like hopeaphenol. These results show that resveratrol tetramers have at least two opposite effects on cardiomyocytes; the one having the (+)-epsilon-viniferin unit induces cardiomyocyte apoptosis, and the other having ampelopsin B but not (+)-epsilon-viniferin unit inhibits it.

Topics: Animals; Antioxidants; Apoptosis; Benzofurans; Calcium; Cytochromes c; Heart; Intracellular Membranes; Membrane Potentials; Mitochondria, Heart; Mitochondrial Swelling; Myocardium; Myocytes, Cardiac; Phenols; Rats; Rats, Wistar; Resveratrol; Stilbenes