Yoshihiro Mimaki

Steroidal saponins from Allium chinense and their inhibitory activities on cyclic AMP phosphodiesterase and Na+/K+ ATPase

The saponin fraction prepared from the methanolic extract of Allium chinense bulbs exhibited inhibitory activities on cyclic AMP phosphodiesterase (cAMP PDE) (43.5%) and Na+/K+ ATPase (59.3%) at a sample concentration of 100 micrograms ml-1, respectively. Attempted purification of the active fraction through column chromatography on silica gel and ODS silica gel resulted in the isolation of six steroidal saponins, one of which appeared to be a new compound and one to be the first isolation from a natural source. (25R,S)-5 alpha-Spirostan-3 beta-ol tetrasaccharide showed inhibitory activities on both cAMP PDE and Na+/K+ ATPase, while (25R)-3 beta-hydroxy-5 alpha-spirostan-6-one di- and tri-saccharides inhibited only cAMP PDE.

Phytochemicals of the Chinese Herbal Medicine Tacca chantrieri Rhizomes

The family Taccaceae is composed of two genera, Tacca and Schizocapsa, and about 10 spe‐ cies, with most distributed in tropical regions of Asia, the Pacific Islands, and Australia [1]. Tacca chantrieri Andre is a perennial plant that occurs in the southeast region of mainland China, and its rhizomes have been used for the treatment of gastric ulcers, enteritis, and hepatitis in Chinese folk medicine. According to a Chinese herbal dictionary, T. plantaginea has also been used for the same purposes as T. chantrieri [2]. The chemical constituents of T. plantaginea have been extensively examined and a series of highly oxygenated pentacyclic steroids named taccalonolids, which have a γ-enol lactone, have been isolated as characteris‐ tic components of the herb [3], but there has been only one report of the secondary metabo‐ lites of T. chantrieri, in which a few trivial sterols such as stigmasterol and daucusterol, and a diosgenin glycoside were found [4]. Therefore, we focused our attention on the constituents of T. chantrieri rhizomes, and a detailed phytochemical investigation of this herbal medicine has been carried out.

Phenolics from Glycyrrhiza glabra and G. uralensis Roots and Their PPAR-γ Ligand-Binding Activity: Possible Application for Amelioration of Type 2 Diabetes

The EtOH extract of Glycyrrhiza glabra roots and the EtOAc extract of Glycyrrhiza uralensis roots exhibited considerable PPAR-γ ligand-binding activity. Bioassay-guided fractionation of these extracts resulted in the isolation of 52 phenolics, including 11 novel ones. The PPAR-γ ligand-binding activity of more than 10 isolated phenolics at 10 μg/mL was approximately three times greater than that of 0.5 μM triglitazone. Glycyrin (44), isolated from the EtOAc extract of G. uralensis roots as a PPAR-γ ligand, reduced the blood glucose levels of genetically diabetic KK-Ay mice through its PPAR-γ ligand-binding activity.