Osamu Iida

Flavonol Caffeoylglycosides as α-Glucosidase Inhibitors from Spiraea cantoniensis Flower

In the screening experiments for rat intestinal alpha-glucosidase inhibitors in 218 plants cultivated in the Japanese temperate region, potent maltase-inhibiting activity was found in the extract of flowers of Spiraea cantoniensis. The enzyme assay guided fractionation of the extract led to the isolation of three flavonol caffeoylglycosides, quercetin 3- O-(6- O-caffeoyl)-beta-galactoside ( 1), kaempferol 3- O-(6- O-caffeoyl)-beta-galactoside ( 2), and kaempferol 3- O-(6- O-caffeoyl)-beta-glucoside ( 3), as rat intestinal maltase inhibitors. This is the first report on the alpha-glucosidase-inhibitory activity of those flavonol caffeoylglycosides. Comparison in the activity of the isolates indicated the importance of caffeoyl substructures in the molecule for the alpha-glucosidase-inhibiting activity. The relatively high contents of the active isolates in the plant suggest that S. cantoniensis could be physiologically useful for treatment of diabetes.

Methyl Caffeate as an α-Glucosidase Inhibitor from Solanum torvum Fruits and the Activity of Related Compounds

In screening experiments for rat intestinal α-glucosidase (sucrase and maltase) inhibitors in 325 plants cultivated in Japan’s southern island, of Tanegashima, marked inhibition against both sucrase and maltase was found in the extract of the fruit of Solanum torvum. Enzyme-assay guided fractionation of the extract led to the isolation of methyl caffeate (1) as a rat intestinal sucrase and maltase inhibitor. We examined 13 caffeoyl derivatives for sucrase- and maltase-inhibitory activities. The results showed that methyl caffeate (1) had a most favorable structure for both sucrase and maltase inhibition, except for a higher activity of methyl 3,4,5-trihydroxycinnamate (14) against sucrase. Its moderate inhibitory action against α-glucosidase provides a prospect for antidiabetic usage of S. torvum fruit.

Highly oxygenated monoterpene acylglucosides from Spiraea cantoniensis.

Six new monoterpene acylglucosides named kodemariosides A-F (1-6) were isolated from the leaves and flowers of Spiraea cantoniensis. Their absolute structures including a highly oxygenated monoterpene aglycon part were determined by NMR experiments and chemical derivatization.

Construction of Prediction Models for the Transient Receptor Potential Vanilloid Subtype 1 (TRPV1)-Stimulating Activity of Ginger and Processed Ginger Based on LC-HRMS Data and PLS Regression Analyses

To construct a model formula to evaluate the thermogenetic effect of ginger (Zingiber officinale Roscoe) from the ingredient information, we established transient receptor potential vanilloid subtype 1 (TRPV1)-stimulating activity prediction models by using a partial least-squares projections to latent structures (PLS) regression analysis in which the ingredient data from liquid chromatography-high-resolution mass spectrometry (LC-HRMS) and the stimulating activity values for TRPV1 receptor were used as explanatory and objective variables, respectively. By optimizing the peak extraction condition of the LC-HRMS data and the data preprocessing parameters of the PLS regression analysis, we succeeded in the construction of a TRPV1-stimulating activity prediction model with high precision ability. We then searched for the components responsible for the TRPV1-stimulating activity by analyzing the loading plot and s-plot of the model, and we identified [6]-gingerol (1) and hexahydrocurcumin (3) as TRPV1-stimulating activity components.

Influence of genetic factors on the ephedrine alkaloid composition ratio of Ephedra plants

We investigated the ephedrine alkaloid [(−)-ephedrine and (+)-pseudoephedrine] composition ratio of a crude Chinese herbal drug described in the Japanese Pharmacopoeia ‘Ephedra herb (Chinese name: Mahuang)’. There were marked changes in the alkaloid composition ratio of wild plants in areas where both male and female clusters coexisted. However, in genetically homogeneous areas with the growth of male or female clusters alone, all of the coefficients of the regression lines were positive, but each gradient varied. This suggests that the alkaloid composition ratio has a clear tendency in each individual. Based on this, we cultivated individuals for vegetative propagation, and evaluated the alkaloid content ratio. Those propagated by separating the roots showed a specific tendency regardless of the cultivation area (Wakayama, Tanegashima). Those propagated by separating the herbaceous stem showed a specific tendency regardless of the soil or harvest time. In addition, we surveyed the (−)-ephedrine content ratio of 3- to 6-year-old strains. There was a high positive correlation coefficient between the previous and subsequent years. These findings suggest that the ephedrine alkaloid composition ratio of Ephedra herb depends on genetic factors, but not on environmental factors or the growth period.