A new triterpenoid saponin from Anemone raddeana

Review of Anemone raddeana Rhizome and its pharmacological effects

The chemical compositions of Anemone raddeana Rhizome, a kind of traditional Chinese medicine, were reviewed, along with its bioactivity and pharmacological properties and method improvements of extracting and detecting triterpenoid saponins. A. raddeana Rhizome is used to treat neuralgia and rheumatism, and is rich in triterpenoid saponins, most of which are pentacyclic, with oleanane as the nucleus. So far, 37 triterpenoid saponins have been determined from the herb. Its reported bioactivity and pharmacological properties have been described as anticancerous, antimicrobial, anti-inflammatory, analgesic, antipyretic, anticonvulsive, antihistaminic, and sedative. It has also been used for the induction of the humoral immune response and treatment of liver fibrosis in chronic hepatitis. However, the herb also has hemolytic effects and can be toxic, which limits its clinical application. Further studies are needed on the pharmaceutical functions, mechanisms, and immunological responses to contribute to the herb's clinical applications.

Identification of RL-TGR, a coreceptor involved in aversive chemical signaling

Chemical signaling plays an important role in predator-prey interactions and feeding dynamics. Like other organisms that are sessile or slow moving, some marine sponges contain aversive compounds that defend these organisms from predation. We sought to identify and characterize a fish chemoreceptor that detects one of these compounds. Using expression cloning in Xenopus oocytes coexpressing the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel, the beta-2 adrenergic receptor (beta(2)AR), and fractions of a zebrafish cDNA library, we isolated a cDNA clone encoding receptor activity-modifying protein (RAMP)-like triterpene glycoside receptor (RL-TGR), a novel coreceptor involved in signaling in response to triterpene glycosides. This coreceptor appears to be structurally and functionally related to RAMPs, a family of coreceptors that physically associate with and modify the activity of G protein-coupled receptors (GPCRs). In membranes from formoside-responsive oocytes, RL-TGR was immunoprecipitated in an apparent complex with beta(2)AR. In HEK293 cells, coexpression of beta(2)AR induced the trafficking of RL-TGR from the cytoplasm to the plasma membrane. These results suggest that RL-TGR in the predatory fish physically associates with the beta(2)AR or another, more physiologically relevant GPCR and modifies its pharmacology to respond to triterpene glycosides found in sponges that serve as a potential food source for the fish. RL-TGR forms a coreceptor that responds to a chemical defense compound in the marine environment, and its discovery might lead the way to the identification of other receptors that mediate chemical defense signaling.

Triterpenoids

This review covers the isolation and structure determination of triterpenoids including squalene derivatives, protostanes, lanostanes, holostanes, cycloartanes, dammaranes, euphanes, tirucallanes, tetranortriterpenoids, lupanes, oleananes, friedelanes, ursanes, hopanes, isomalabaricanes and saponins; 574 references are cited.