The nutraceutical benefit, part II: ginseng.

For more than 2000 y, ginseng has been consumed for medicinal purpose in Asian countries, including China, Korea, and Japan. Accumulated data show that ginseng has immunostimulatory and anticarcinogenic properties. The mechanisms of these functions have been gradually revealed through a series of immunologic and molecular biological studies. The main immunologically active constituents of Panax ginseng is ginsenoside.1–3 Ginseng modulates both humoral and cellmediated immune function. Jie et al. and Kenarova et al. examined the effect of ginseng on such immune functions.2,3 The results showed that oral administration of 250 mg/kg ginseng for 6 d into Balb/C mice2 and intraperitoneal administration of 10 mg/kg ginsenoside Rg1 for 3 d also into Balb/C mice3 before immunization increased plaque-forming cell counts to 128% and over 200% of the control, respectively. They also examined natural killer cell activity. Jie et al. showed that at an oral dose of 250 mg/kg ginseng for 5 d and with an effector-to-target cell ratio of 6, natural killer cell activity increased to 251% of the control in spleen cells of C57 B1/6J nu/nu mice when using Cr-labeled YAC-1 cells as the target. Kenarova et al. showed that the natural killer cell activity of the splenocytes measured when using chick erythrocytes as target cell 5 d after ginsenoside Rg1 treatment increased three-fold as compared with control (57.8% versus 21.6%). Furthermore, Kenarova et al. reported that after ginsenoside Rg1 treatment the number of T-helper cells increased to 83.6% of the whole T-cell number versus that of the control (62.9%). Yang et al. also reported that ginseng enhances phagocytosis of macrophages and mitogen-induced mitogenesis of both T and B lymphocytes and increases production of antibodies.4 In mice whose bone marrow was suppressed by cyclophosphamide injection, ginseng administration partly restored the number and colonyforming activity of bone marrow cells and enhanced the production of interleukin (IL)-1, IL-3, and IL-6 factors from immune cells. Yang et al. hypothesized that ginsenoside increases cGMP levels in immune cells by increasing the ratio of cGMP/cAMP in T cells stimulating T-cell proliferation.4 Figure 1 shows the site of action of ginseng to enhance the cell-mediated and humoral immune system. Ginseng has anticarcinogenic properties that have been demonstrated by human epidemiologic and animal studies. A prospective cohort study in Korea showed a decreased risk of non-specific cancers in various organs with a rise in the frequency of ginseng intake, in a dose-dependent manner.5 In this study, 3267 ginseng consumers in a group of 4634 people older than 40 y who had completed a questionnaire on ginseng intake had a decreased risk as compared with non-consumers (relative risk 5 0.40). In experimental animal studies, the anticarcinogenic capacity of ginseng has been shown. In Swiss Webster mice subcutaneously administrated 1 mg of urethan, a known carcinogen, the incidence of lung adenoma was significantly depressed, by a treatment consisting of ginseng extract in drinking water, to 50% and 27% at 6 and 12 wk, respectively, after treatment as compared with treatment of urethan alone.6 The lower incidence of lung adenoma induced by urethan administration treated with ginseng was associated with increased natural killer cell activity (20% and 29% increase at 6 and 12 wk, respectively, after treatment as compared with urethan treatment alone), suggesting that the anticarcinogenic capacity of ginseng is due to enhancement of natural killer cell activity.6 Another possible mechanism of ginseng’s anticarcinogenic property was demonstrated by Sohn et al.7 In this experiment, the cell cycle of human renal carcinoma cells was analyzed after treatment with ginseng extract. Results showed that S-phase cells decreased and G0/G1-phase cells increased in a dosedependent manner as compared with control cells, indicating that ginseng components inhibit proliferation of tumor cells by blocking cell-cycle progression at the G1to S-phase transition.7 Ginseng may be useful for prevention of cancer and to boost immune cells in immunodepressive diseases. For a better understanding of the immunostimulatory and anticarcinogenic properties of ginseng, further studies need to be performed.