Preparation and bioactivity of the rare ginsenosides Rg3 and Rh2: An updated review

Ginseng, an ancient medicinal herb, is used in oriental medicine for the treatment of various diseases. Saponins are the main bioactive components of ginseng, but the multiple glucosyl side chains on its molecules prevent ginsenosides from entering the blood through the intestinal membrane, thus reducing the efficacy. The prepa-ration of rare ginsenosides, which are easy to be absorbed by human body and have higher drug activity, has been widely practiced by removing the sugar group of natural ginsenosides in vitro. Rare ginsenosides Rg3 and Rh2 have been approved as drugs or health supplements to improve immune function. This review summarizes the preparation methods of ginsenoside Rg3 and Rh2 in recent years. Ginsenoside Rg3 and Rh2 were prepared by biotransformation of protopanaxadiol type ginsenoside, with the highest conversion rate of 98.19% and 95.89% in the laboratory, respectively. At present, improving the conversion rate and reducing the production cost are still the bottleneck of industrial scale production of Rg3 and Rh2 through the deglycosylation directly from Rb1, Rb2, Rb3, Rc and Rd in the crude extract of ginseng. In addition, ginsenosides Rg3 and Rh2 play anti-inflammatory, anticancer, cardiovascular protective, immunomodulatory, neuroprotective, anti-diabetic, anti -fatigue, anti-allergic, anti-aging, antioxidant and other pharmacological effects by activating AMPK, JNK, NF-kappa B, MAPKs, P13K/AKT/mTOR and other signaling pathways. As potential drugs for prevention and treatment of various diseases, ginsenoside Rg3 and Rh2 need to further clarify other underlying mechanisms of action through in vitro and in vivo experiments.