Inclusion complexes of (-)-epicatechin gallate (ECg) as well as (+)-gallocatechin gallate (GCg) and beta-cyclodextrin (beta-CD) in an aqueous solution were investigated using several NMR techniques and a computational method. ECg and EGCg formed a 1:1 complex with beta-CD, in which the A ring and a portion of the C ring were included from the wide secondary hydroxyl group side of the beta-CD cavity, and the B and B' rings were left outside the cavity. GCg formed a 1:2 complex with beta-CD, in which the A and B rings of GCg were included by two molecules of beta-CD. The difference between the two modes of inclusion of the 1:1 complex of ECg, EGCg.beta-CD and the 1:2 complex of GCg.beta-CD might have resulted from the size of the space between the B and B' rings in aqueous solution. As a result of nuclear Overhauser effect (NOE) experiments, GCg was considered to have a large enough space between the B and B' rings to include the B ring in the beta-CD cavity; on the other hand, ECg and EGCg have no such large space.

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Rhubarb is one of the most well-known herbal medicines that constitute daiokanzoto (DKT), which is clinically effective for constipation. Sennoside A is transformed into an active metabolite, rheinanthrone, by intestinal bacteria. Sennoside A in rhubarb showed significantly accelerated metabolic activity in intestinal bacteria in comparison with sennoside A alone. In this study, we investigated the influence of rhubarb constituents on the metabolism and purgative activity of sennoside A. The 20% MeOH-eluted fraction separated by MCI-gel CHP-20P column chromatography from the water extract of rhubarb showed sennoside A metabolic activity similar to that of rhubarb extract. The 20% MeOH elute was further purified and rhein 8-O-β-D-glucopyranoside (RG) was isolated. The metabolic activity of sennoside A was significantly accelerated by increasing the level of RG. Moreover, rhein, emodin and aloe-emodin also accelerated sennoside A metabolism. The purgative activity of sennoside A was significantly accelerated when RG or rhein was concomitantly given with sennoside A in a dose-dependent manner. These results suggest that anthraquinones contribute to the purgative action of sennoside A in rhubarb. Therefore, it is assumed that the influence of anthraquinones on the fate of rheinanthrone transformed from sennoside A may promote the purgative action of sennoside A. Key words rhubarb; sennoside A; rhein 8-O-β-D-glucopyranoside; anthraquinone; daiokanzotoKampo is traditional Japanese medicine that was developed from traditional medicine originating in ancient China. Kampo medicine involves drugs based on multiple constituents, for which prescriptions are based on the combination of two or more herbal medicines. It is thought that the interaction between each herbal medicine is important for their activity, such as by reinforcing the effect of a medicine and relieving side effects, by pharmacologic or pharmacokinetic action. For example, calcium sulfate from gypsum raises ephedrine alkaloid dissolution in makyokansekito decoction.1,2) A lower glycyrrhizin content in shoseiryuto decoction is attributable to the pH of organic acids in schisandra fruit.3) In addition, the purgative activity increases 1.7-fold compared with that with each medication alone when the mixture ratio of sennosides A and C is 7 : 3. 4)Rhubarb is one of the most well-known herbal medicines that constitute daiokanzoto (DKT), which was demonstrated to be useful for constipation in a clinical double-blind study. 5)The purgative effect of rhubarb is due to sennoside A as the main laxative constituent. Sennoside A is an inactive glycoside, and is transformed to an active metabolite, rheinanthrone, by intestinal bacteria. [6][7][8] We have reported an HPLC method for the determination of sennoside A.9) This method is applicable for determination of the activity of sennoside A metabolism by anaerobic incubation of DKT with mouse feces. By using this method, we found that the activity of sennoside A metabolism in intestinal bacteria was significantly acceler...

Stereochemical structures of a 1:1 complex of (−)-epicatechin (EC) and caffeine, and a 2:4 complex of (−)-epicatechin gallate (ECg) and caffeine were determined by X-ray crystallographic analysis, and noncovalent interactions forming between EC, ECg and caffeine moieties were also elucidate.

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