Ginsenosides or panaxosides are a class of natural product steroid glycosides and triterpene saponins. Compounds in this family are found almost exclusively in the plant genus Panax (ginseng), which has a long history of use in traditional medicine that has led to the study of pharmacological effects of ginseng compounds. As a class, ginsenosides exhibit a large variety of subtle and difficult-to-characterize biological effects when studied in isolation.
Ginsenosides can be isolated from various parts of the plant, though typically from the roots, and can be purified by column chromatography. The chemical profiles of Panax species are distinct; although Asian ginseng, Panax ginseng, has been most widely studied due to its use in traditional Chinese medicine, there are ginsenosides unique to American ginseng (Panax quinquefolius) and Japanese ginseng (Panax japonicus). Ginsenoside content also varies significantly due to environmental effects.
Ginsenosides are named according to their retention factor value in thin layer chromatography (TLC). They can be broadly divided into two groups based on the carbon skeletons of their aglycones: the four-ring dammarane family, which contains the majority of known ginsenosides, and the oleanane family. The dammaranes can be further subdivided into two main groups, the protopanaxadiols and protopanaxatriols, with other smaller groups such as the ocotillol-type pseudoginsenoside F11 and its derivatives.
The biosynthetic pathway of ginsenosides is not entirely characterized, though as steroids they derive from pathways that lead to the synthesis of isoprene units. A proposed pathway converts squalene to 2,3-oxidosqualene via the action of squalene epoxidase, at which point dammaranes can be synthesized through dammarenediol synthase, oleananes through beta-amyrin synthase, and another class of molecules, the phytosterols, through cycloartenol synthase.
Ginseng is generally consumed orally as a dietary supplement, and thus its component ginsenosides may be metabolized by gut flora. This process is known to vary significantly between individuals. In some cases the metabolites of ginsenosides may be the biologically active compounds.
Most studies of the biological effects of ginsenosides have been in cell culture or animal models and thus their relevance to human biology is unknown. Effects on the cardiovascular system, the central nervous system, the immune system have been reported, primarily in rodents. Antiproliferative effects have also been described.
Two broad mechanisms of action have been suggested for ginsenoside activity, based on their similarity to steroid hormones. They are amphiphilic and may interact with and change the properties of cell membranes. Some ginsenosides have also been shown to be partial agonists of steroid hormone receptors. It is not known how these mechanisms yield the reported biological effects of ginsenosides. The molecules as a class have low bioavailability due to both metabolism and poor intestinal absorption.
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