Glucose Tolerance-Improving Activity of Helichrysoside in Mice and Its Structural Requirements for Promoting Glucose and Lipid Metabolism.

An acylated flavonol glycoside, helichrysoside, at a dose of 10 mg/kg/day per os for 14 days, improved the glucose tolerance in mice without affecting the food intake, visceral fat weight, liver weight, and other plasma parameters. In this study, using hepatoblastoma-derived HepG2 cells, helichrysoside, trans-tiliroside, and kaempferol 3-O-ß-D-glucopyranoside enhanced glucose consumption from the medium, but their aglycones and p-coumaric acid did not show this activity. In addition, several acylated flavonol glycosides were synthesized to clarify the structural requirements for lipid metabolism using HepG2 cells. The results showed that helichrysoside and related analogs significantly inhibited triglyceride (TG) accumulation in these cells. The inhibition by helichrysoside was more potent than that by other acylated flavonol glycosides, related flavonol glycosides, and organic acids. As for the TG metabolism-promoting activity in high glucose-pretreated HepG2 cells, helichrysoside, related analogs, and their aglycones were found to significantly reduce the TG contents in HepG2 cells. However, the desacyl flavonol glycosides and organic acids derived from the acyl groups did not exhibit an inhibitory impact on the TG contents in HepG2 cells. These results suggest that the existence of the acyl moiety at the 6'' position in the D-glucopyranosyl part is essential for glucose and lipid metabolism-promoting activities.

Flavonol glycosides with lipid accumulation inhibitory activity and simultaneous quantitative analysis of 15 polyphenols and caffeine in the flower buds of Camellia sinensis from different regions by LCMS.

A simultaneous quantitative analytical method for 15 major polyphenols, e.g. five catechins (1-5) and 10 flavonols (6-15), as functional constituents in the extracts of "tea flowers", the flower buds of Camellia sinensis (Theaceae), has been developed. The content of caffeine (16), which showed similar chromatographic behaviour under the analytical conditions, was also determined. To approve the validity of the newly developed protocol, thirteen extracts of the plant's flower buds collected from different regions, i.e. China, Taiwan, Japan and India, were evaluated. The results indicated that the assay was reproducible and precise, and could be readily underutilised for the quality evaluation of tea flowers on the basis of polyphenols' contents. It was noteworthy that the contents of two major constituents, kaempferol 3-O-ß-D-glucopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→6)-ß-D-glucopyranoside (10) and kaempferol 3-O-ß-D-glucopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→6)-ß-D-galactopyranoside (11), varied by region where the flower buds were produced. A new flavonol glycoside, chakaflavonoside B (17), which was isolated in the course of this analytical study, was found to show oleic acid-albumin-induced lipid accumulation inhibitory activity.

Quantitative analysis of catechin, flavonoid, and saponin constituents in "tea flower", the flower buds of Camellia sinensis, from different regions in Taiwan.

Using the recently developed two analytical protocols, distributions were analyzed of five catechins (1-5), ten flavonoids (6-15), caffeine (16), and nine saponins (17-25) in 12 samples of flower buds of Camellia sinensis (L.) O. Kuntze, collected at different points in Taiwan. Characteristic tendencies with respect to the distribution of these constituents were observed according to the region of collection. Among the catechins, (-)-epigallocatechin 3-O-gallate (5) was the major constituent in all the samples. Notably, the content of 5 was higher in samples from the mountain regions in the middle and northern Taiwan than in samples from other regions. As for the principal flavonoids, the content of 10 was higher than that of 11 in most of the samples except those of Sijichun tea. For the saponin contents, the following trends were observed: (1) contents of chakasaponins I-III (17-19) were higher in samples from the mountain region in the middle and northern areas; and (2) contents of floratheasaponins A-F (20-25) were higher in the samples from central and southern areas.

Quantitative analysis of acylated oleanane-type triterpene saponins, chakasaponins I-III and floratheasaponins A-F, in the flower buds of Camellia sinensis from different regional origins.

A quantitative analytical method was developed for the determination of acylated oleanane-type triterpene saponins, chakasaponins I-III (1-3) and floratheasaponins A-F (4-9), found in Camellia sinensis (Theaceae). The practical conditions for separation and detection of these saponins were established on an ODS column with methanol containing 5 mM trifluoroacetic acid as a mobile phase, and the detection and quantitation limits of the method were estimated to be 1.1-3.8 and 3.5-12.5 ng, respectively. The relative standard deviation values of intra- and interday precision were lower than 2.35 and 6.12%, respectively, overall mean recoveries of all saponins being 94.7-108.8%, and the correlation coefficients of all the calibration curves showed good linearity within the test ranges. To approve the validity of the protocol, extracts of 13 kinds of C. sinensis collected in China, Taiwan, Japan, and India were evaluated. The results indicated that the assay was reproducible and precise, and could be readily utilized for the quality evaluation of tea flowers. It was noteworthy that the distinct regional difference was observed with respect to the content of chakasaponins and floratheasaponins, more chakasaponins being contained in the extracts of tea flowers from Fujian and Sichuan provinces, China than those from Japan, Taiwan, and India. Optimum conditions for the extraction process were also established.