The major commercial ginsengs are Panax ginseng Meyer (Korean ginseng), P. quinquifolium L. (American ginseng), and P. notoginseng (Burk.) FH Chen (Notoginseng). P. ginseng is the most commonly used as an adaptogenic agent and has been shown to enhance physical performance, promote vitality, increase resistance to stress and aging, and have immunomodulatory activity. These ginsengs contain saponins, which can be classified as dammarane-type, ocotillol-type and oleanane-type oligoglycosides, and polysaccharides as main constituents. Dammarane ginsenosides are transformed into compounds such as the ginsenosides $Rg_3$, $Rg_5$, and $Rk_1$ by steaming and heating and are metabolized into metabolites such as compound K, ginsenoside $Rh_1$, proto- and panaxatriol by intestinal microflora. These metabolites are nonpolar, pharmacologically active and easily absorbed from the gastrointestinal tract. However, the activities metabolizing these constituents into bioactive compounds differ significantly among individuals because all individuals possess characteristic indigenous strains of intestinal bacteria. To overcome this difference, ginsengs fermented with enzymes or microbes have been developed.