New laxative constituents of rhubarb. Isolation and characterization of rheinosides A, B, C and D

Phytochemical and Antioxidant Studies on a Rare Rheum cordatum Losinsk. Species from Kazakhstan

An optimisation of extraction towards an increased antioxidant capacity and the study on the extracts' composition by HPLC-ESI-Q-TOF-MS were performed on different organs of a rarely studied plant: Rheum cordatum Losinsk (Polygonaceae) growing in Kazakhstan. More than 20 compounds from anthraquinones and phenolics were identified in an optimised method. The plant was proven to contain a wide variety of phenolic compounds (catechins, flavonoids, and their glucosides and phenolic acids) in contrast to the anthraquinone composition, which was mainly represented by emodin and its analogues. The results of the studies could determine the plant as a rich source of pharmacologically precious polyphenols. It was evidenced that the extracting solvents, the time of collection, and the organs tested affected both the chemical content and the antioxidant potential of the extracts. Ethanol : water (50 : 50 v/v) was selected as the most beneficial extractant for all metabolites, and based on the principal component analysis of raw data, the radical scavenging potential of the plant was strictly related to the presence of epicatechin gallate (ECG), kaempferol glucoside, and epigallocatechin gallate (EGCG) occurring in this extract at the concentration of 1.69-5%, 0.16-0.47%, and 0.001-2.93%, respectively.

Activity of Wen-Pi-Tang, and Purified Constituents of Rhei Rhizoma and Glycyrrhizae Radix against Glucose-Mediated Protein Damage

Wen-Pi-Tang, an Oriental medical prescription composed of Rhei Rhizoma, Ginseng Radix, Aconiti Tuber, Zingiberis Rhizoma and Glycyrrhizae Radix, is used clinically as a medicine to treat renal failure. This study was conducted to examine the inhibitory activity of the five crude drug components of Wen-Pi-Tang and several pure compounds isolated from Rhei Rhizoma and Glycyrrhizae Radix against the protein glycation reaction. Rhei Rhizoma exerted the most potent activity, Zingiberis Rhizoma and Glycyrrhizae Radix showed relatively moderate activity, whereas Aconiti Tuber and Ginseng Radix showed weak activity. On the other hand, of 20 compounds obtained from Rhei Rhizoma and Glycyrrhizae Radix, tannins, especially rhatannin, RG-tannin and procyanidin B-2 3,3′-di-O-gallate, showed significantly strong activities that were more effective than the positive control, aminoguanidine. Some flavones such as licochalcone A and licochalcone B, and anthraquinones such as emodin and aloe-emodin, also showed inhibitory activity. These findings may help to explain, at least in part, certain pharmacological activities of Wen-Pi-Tang, whose clinical efficacy against renal failure is already recognized.

Development of eastern blotting technique for sennoside A and sennoside B using anti-sennoside A and anti-sennoside B monoclonal antibodies

INTRODUCTION

Rhubarb, senna and sennoside-containing preparations are currently widely employed as purgatives. The major active components of these medications are sennoside A (SA) and sennoside B (SB).

OBJECTIVE

To develop an eastern blotting technique for the specific visualisation and easy determination of SA and SB in plant extracts for application in the standardisation and authentication of rhubarb and senna.

METHODOLOGY

SA and SB were separated by TLC, transferred to a PVDF membrane, treated with 1-ethyl-3-(3'-dimethylaminopropyl)-carbodiimide hydrochloride solution and finally treated with bovine serum albumin (BSA). The resulting membrane-bound SA-BSA and SB-BSA conjugates were linked to anti-SA and anti-SB monoclonal antibodies (MAbs) and then to secondary antibodies labelled with peroxidase. SA and SB were detected by visualisation of the peroxidase reaction products.

RESULTS

The limit of detection of the eastern blotting was 62.5 ng for both sennosides. The method was applied to the immunohistochemical localisation of SA in fresh rhubarb root. Phloem and radiate wood were found to contain higher concentrations of SA compared with other tissues (pith and bud) in agreement with results obtained by ELISA. The concentrations of SA in the phloem, radiate wood, pith and bud were 64.4, 48.1, 15.0 and 1.8 ng/mg fresh weight, respectively.

CONCLUSION

The technique described permitted the visualisation of small molecular weight compounds that had been bound to a membrane, using immunostaining. Owing to the specificity of the MAbs, the eastern blotting may prove to be a useful method for the identification of SA and SB in a background containing large amount of impurities.

Anthrone C-glucosides from Rheum emodi

In a study of the anthraderivatives in roots of Rheum emodi, three new anthrone C-glucosides, named 10-hydroxycascaroside C (1), 10-hydroxycascaroside D (2) and 10R-chrysaloin 1-O-beta-D-glucopyranoside (3) were isolated besides the rare compounds cascaroside C (4), cascaroside D (5) and cassialoin (6). Additionally the investigation resulted in the isolation of an acetylated chrysophanol glucoside, 8-O-beta-D-(6'-O-acetyl)glucopyranosyl-chrysophanol (7). The structures were established by comprehensive spectroscopic investigations.

A new stilbene diglycoside from Rheum undulatum

A new stilbene diglycoside, piceatannol-3, 4'-O-beta-D-diglucopyranoside (I), together with desoxyrhaponticin (II), emodin-1-O-beta-D-glucopyranoside (III), and physcion-8-O-b-D-glucopyranoside (IV), were isolated from the rhizomes of cultivated Korean rhubarb rhizomes (Rheum undulatum), Jong DaeWhang, and the structures of I-IV were identified on the basis of chemical and spectral evidences.

Effects of a rhubarb (Rhei rhizoma) solution and its fractions on the formation of calcium phosphate precipitates

Inhibitory effects of a rhubarb (Rhei rhizoma) solution and its fractions on the formation of calcium phosphate precipitates were studied. The rhubarb solution inhibited both the amorphous calcium phosphate (ACP) formation and the rate of hydroxyapatite (HAP) transformation, and extended the induction time. When the solution was fractionated using membrane filters, a filtrate with the molecular weight between 3 and 10 kDa (with 2/3 recovery of polyphenols) was found to be responsible for both the ACP formation and the extension of the induction time. Another filtrate with the molecular weight below 3 kDa (with 1/3 recovery of polyphenols) may be responsible for the inhibition of both the ACP formation and the rate of HAP transformation, and the extension of the induction time. When the extract of rhubarb was fractionated using a Sephadex LH-20 column chromatography, fraction IV greatly inhibited the formation of calcium phosphate precipitates, while fractions I, II and III slightly inhibited that reaction. Our finding suggests that fraction IV may contain useful substance(s) for the prevention of oral calcium phosphate precipitation (calculus formation). However, strong calcium chelating properties would limit the concentration that could be safely employed.