Antidiabetic activity of a xanthone compound, mangiferin.

Flavonoids from Ziziphus jujuba Mill var. spinosa

Mangiferin, three catechins, and two catechin dimers were isolated from the roots of Salacia reticulata (SRE), and examined their inhibitory activities against several carbohydrate metabolize enzymes (sucrase, maltase, isomaltase, alpha-amylase, and aldose reductase). Among them, mangiferin was found to inhibit sucrase, isomaltase, and aldose reductase from rat with IC50 values of 87, 216 and 1.4 micrograms/ml, respectively. The inhibitory activities of mangiferin are competitive for sucrase and isomaltase with inhibitor constant (Ki) 55 micrograms/ml and 70 micrograms/ml, respectively. In order to determine the mangiferin contents in the water extracts from the roots of S. reticulata, a quantitative analytical method by means of HPLC was developed and the mangiferin contents in SRE were determined to be in the range of 0.9-2.3% by the application of this method. A high linear correlation (r = 0.934) was observed between the mangiferin contents and the sucrase inhibitory activity. In addition, this analytical procedure of mangiferin was found to be applicable for other Salacia species (S. oblonga, S. chinensis, and S. prinoides). Thus, the quantitative HPLC analysis of mangiferin was supposed to be suitable for the quality control of Salacia species and its products.

Salacia属植物のポリフェノール成分:α-グルコシダーゼ及びアルドースレダクターゼ阻害活性成分,Mangiferin,の定量分析

The antidiabetic activity of the rhizoma of Anemarrhena asphodeloides was investigated in KK-Ay mice, an animal model of genetic type 2 diabetes. The water extract of the rhizoma (AA) (90 mg/kg) reduced blood glucose levels from 570±29 to 401±59 mg/dl 7 h after oral administration (p<0.05) and also tended to reduce serum insulin levels in KK-Ay mice. AA-treated KK-Ay mice had significantly reduced blood glucose levels in an insulin tolerance test. Based on these results, the antidiabetic mechanism of AA may be due to decreased insulin resistance. In addition, the active components of AA were confirmed to be mangiferin and its glucoside.

Antidiabetic Activity of the Rhizoma of Anemarrhena asphodeloides and Active Components, Mangiferin and Its Glucoside

Quality evaluation of Rhizoma Belamcandae (Belamcanda chinensis (L.) DC.) by using high-performance liquid chromatography coupled with diode array detector and mass spectrometry.

Four C-glucosylxanthones [Mangiferin (3), isomangiferin (2), 4 and 5] and three C-glucosylflavones [swertisin (6), isoswertisin (7) and isoswertiajaponin (8)] were isolated from the fresh leaves of Iris florentina L. (Iridaceae). The structures of 4 and 5 were shown to be 7-O-methylmangiferin and 7-O-methylisomangiferin, respectively, by chemical and spectroscopic methods. In addition, the 13C nuclear magnetic resonance chemical shifts of aryl carbons in these C-glucosylxanthones (2-5) were assigned. On the basis of the co-occurrence of several types of xanthone and flavone C-glucosides, the biosynthetic relationship between both C-glucosides is briefly discussed.

Masao Fujita

Papers

Studies on the Constituents of Iris florentina L. II. C-Glucosides of Xanthones and Flavones from the Leaves