A Bioactive Resveratrol Trimer from the Stem Bark of the Sri Lankan Endemic Plant Vateria copallifera

Quantitative analysis of resveratrol derivatives in the seed coats of tree peonies and their hypoglycemic activities in vitro/vivo

Tree peonies are well-known horticultural and medicinal plants. The tree peony seeds, as emerging woody oil crops, recently have attracted great attention for their metabolites and bioactivities. In this study, the phytochemicals isolated from tree peony seed coats were systematically investigated. Seven polyphenolics were separated and prepared, mainly belonging to resveratrol derivatives. There was a great variation in the seed coat polyphenolic content among eight Paeonia species, and the contents of the resveratrol trimers and dimers were significantly higher in the seed coats of Paeonia ostii than other species. Based on the HPLC fingerprint characteristics and chemometric analysis, a clear discrimination among Paeonia plants was found, including the composition patterns and contents of the constituents. Moreover, the characteristic phytochemicals (vateriferol and trans-ε-viniferin) could significantly reduce the starch-mediated levels of postprandial blood glucose in diabetic/normal mice. In addition, in vitro enzyme tests showed that the two compounds could effectively and competitively inhibit α-glucosidase, with the IC₅₀ values of 3.01 and 7.75 μM, respectively, indicating that vateriferol and trans-ε-viniferin could be therapeutic potential agents for hyperglycemia and diabetes mellitus.

Phytochemical profiles and the hypoglycemic effects of tree peony seed coats

As emerging woody oil crops, the tree peony seeds recently have been attracting great attention for their metabolites and bioactivities. In this research, the phytochemical profiles of the seed coats of tree peonies from different production regions were investigated systematically. Twelve phytochemicals were separated and prepared, mainly belonging to stilbenes. A great variation in stilbene content was detected in the three Paeonia plants, and Paeonia ostii seed coats (POSC) had significantly higher contents of the stilbene compounds than other species. There were nineteen significant correlations between ecogeographical factors and the predominant compounds. A clear discrimination among the species was observed in their HPLC fingerprint and chemometric analysis. Furthermore, POSC extracts could significantly reduce the starch mediated PBG (postprandial blood glucose) levels in normal/diabetic mice. Meanwhile, in vitro enzyme tests revealed that the predominant compounds, suffruticosol B and ampelopsin D, could effectively and competitively inhibit α-glucosidase, indicating that POSC could be a natural source of hypoglycemics in the food and drug fields.

Cysestermerol A, a rare stilbene sestermer with significant hypoglycemic activities from Cynodon dactylon

Cysestermerol A (1), a rare and new stilbene sestermer, was isolated from the whole herb of Cynodon dactylon. The planar and relative structures of 1 were elucidated based on HRESIMS, one- and two-dimensional NMR analyses, and its absolute configuration was further established by electronic circular dichroism calculations. Compound 1 obviously increased the glucose consumption in HepG2 cells equivalent to the positive control rosiglitazone and markedly inhibited the activity of α-glucosidase in vitro.