Antidiabetogenic oligostilbenoids and 3-ethyl-4-phenyl-3,4-dihydroisocoumarins from the bark of Shorea roxburghii.

A methanol extract of the bark of Shorea roxburghii (Dipterocarpaceae) was found to inhibit plasma glucose elevation in sucrose-loaded mice. From the extract, three new 3-ethyl-4-phenyl-3,4-dihydroisocoumarins, 1'S-dihydrophayomphenol A(2) (1) and phayomphenols B(1) (2) and B(2) (3), were isolated together with 24 known compounds including 20 stilbenoids and oligostilbenoids. The structures of 1-3 were determined on the basis of their spectroscopic properties as well as of chemical evidences. Among the isolates, (-)-hopeaphenol (6), hemsleyanol D (8), (+)-α-viniferin (15), and (-)-balanocarpol (18) showed inhibitory activity against plasma glucose elevation in sucrose-loaded rats at doses of 100-200mg/kg, p.o. To clarify the mode of action of the antihyperglycemic property, effects of these oligostilbenoids on gastric emptying in mice, those on glucose uptake in isolated intestinal tissues as well as inhibitory activities against rat intestinal α-glucosidase and rat lens aldose reductase were examined.

Medicinal flowers. XXXIII. Anti-hyperlipidemic and anti-hyperglycemic effects of chakasaponins I-III and structure of chakasaponin IV from flower buds of Chinese tea plant (Camellia sinensis).

Effects of principal saponins, chakasaponins I-III, from the flower buds of Camellia sinensis cultivated in Fujian province, China on plasma triglyceride (TG) and glucose levels in olive oil or sucrose-loaded mice were examined. Chakasaponins I-III at 50 and 100 mg/kg significantly inhibited increases in plasma TG and glucose levels. Furthermore, they prevented gastric emptying, suggesting that the former inhibitory effect is partly dependent on the inhibition of gastric emptying. In addition, the chemical structure of a new acylated oleanane-type triterpene oligoglycoside, chakasaponin IV, was elucidated on the basis of chemical and physicochemical evidence.

Adipogenic effects of piperlonguminine in 3T3-L1 cells and plasma concentrations of several amide constituents from Piper chaba extracts after treatment of mice.

In our previous study, piperlonguminine from the fruit of Piper chaba was reported to promote adipogenesis in 3T3-L1 cells like the peroxisome proliferator-activated receptor-γ (PPARγ) agonist, troglitazone. In the present study, the mode of action of piperlonguminine in cells was examined. Piperlonguminine increased mRNA levels of adiponectin, glucose transporter 4, and fatty acid-binding protein (aP2). It also increased mRNA levels of PPARγ2 but, unlike troglitazone, piperlonguminine did not activate PPARγ directly in a nuclear receptor cofactor assay. Analyses of plasma from mice treated with piperlonguminine, piperine, and retrofractamide A, and an extract of the fruit, showed that concentrations of piperlonguminine were higher than those of piperine and retrofractamide A, and that the "area-under-the-curve" of piperine increased following in vivo administration of the extract.