Rheum palmatum

The plant Rheum palmatum, called Indian rhubarb in North America and also used in traditional Chinese medicine, is rich in anthraquinones and other biologically active compounds.

Phytochemicals in Rheum species

Recently, advanced analytical chemical methods were applied to different rhubarb species.

hese species belong to the section deserticola Maxim. of the Polygonaceae family, including Rheum racemiferum Maxim., R. nanum Siev. ex Pall., R. delavayi Franch., R. sublanceolatum C. Y. Cheng et T. C. Kao and R. pumilum Maxim. A total of 101 phenolic compounds, including sennosides, anthraquinones, stilbenes, glucose gallates, naphthalenes, procyanidins and chromones were identified or tentatively characterized based on their ultraviolet and mass spectral data from the methanol extracts. These chemical constituents were compared with those of an official species (R. palmatum l.). The results showed that most sennosides and procyanidin derivatives were only present in R. palmatum rather than in the unofficial species; stilbenes and chromones were only found in the sect. deserticola species; while anthraquinones, glucose gallates and naphthalenes could be detected in all studied species. For anthraquinone glycosides, only emodin O-glucosides were detected in the sect. deserticola species. Moreover, remarkable difference was observed among unofficial species. These results may be useful for the quality control of rhubarb in order to guarantee its clinical effects, and may also be helpful for the further clarification of the taxonomic relationship of the plants in the sect. deserticola.

Sennosides are the active principle in the laxative, senna extract. Stilbenes contain 1,2-diphenylethylene as a functional group; they include hormones such as diethylstibestrol and hormone modulators such as tamoxifen .

Procyanidins are dimers and oligomers of flavan-3-ol units (catechin analogs) linked mainly through C4 to C8 bonds to leucoanthocyanidins. They are structurally similar to anthocyanins but are the result of a different fork in biosynthetic pathways.

Antiviral activity

Extracts of the plant have shown activity against hepatitis B virus.

Chromones are 1,4-Benzopyrones that include cromolyn sodium and flavonoids.

Antineoplastic activity

Aloe-emodin (1,8-dihydroxy-3-(hydroxymethyl)-anthraquinone) is an active component from the root and rhizome of R. palmatum. Activation of caspase-3, caspase-8, and caspase-9 is an important determinant of apoptotic death induced by aloe-emodin. These results suggest that aloe-emodin induces cell death in a human lung squamous cell carcinoma line, CH27, by the Bax and Fas death pathway.

Indian rhubarb is a constituent of the herbal cancer treatment, Essiac.