Phytochemistry of Red Ginseng, a Steam-Processed Panax ginseng

Asian ginseng, the root of Panax ginseng C.A. Meyer, occupies a prominent position in the list of best-selling natural products in the world. There are two major types of ginseng roots: white ginseng and red ginseng, each with numerous preparations. White ginseng is prepared by air-drying fresh Asian ginseng roots after harvest. Red ginseng is prepared by steaming roots in controlled conditions using fresh or raw Asian ginseng. Red ginseng is commonly used in Asian countries due to its unique chemical profile, different therapeutic efficacy, and increased stability. Compared with the widespread research on white ginseng, the study of red ginseng is relatively limited. In this paper, after a botanical feature description, the structures of different types of constituents in red ginseng are systematically described, including naturally occurring compounds and those resulting from the steam processing. In red ginseng phytochemical studies, the number of published reports on ginsenosides is significantly higher than that for other constituents. Up to now, 57 ginsenosides have been isolated and characterized in red ginseng. The structural transformation pathways during steaming have been summarized. In comparison with white ginseng, red ginseng also contains other constituents, including polyacetylenes, Maillard reaction products, other types of glycosides, lignans, amino acids, fatty acids, and polysaccharides, which have also been presented. Appropriate analytical methods are necessary for differentiating between unprocessed white ginseng and processed red ginseng. Specific marker compounds and chemical profiles have been used to discriminate red ginseng from white ginseng and adulterated commercial products. Additionally, a brief phytochemical profile comparison has been made between white ginseng and black ginseng, and the latter is another type of processed ginseng prepared from white or red ginseng by steaming several times. In conclusion, to ensure the safe and effective use of red ginseng, phytochemical and analytical studies of its constituents are necessary and even crucial.