The root of Panax ginseng CA Meyer is an established traditional herbal medicine in Asia, having been used for thousands of years, and is now used worldwide as a nutraceutical source to improve physical performance, boost resistance against infection, reduce risk of cancer, and support current therapeutic modalities for some chronic diseases [1],[2]. The biological actions of ginseng are unclear, but it appears that some of its effects are related to immunomodulation [3].

More than 100 different chemical entities of biological Interest, including ginsenosides, polysaccharides, polyacetylenes, and peptides, have been derived from ginseng species and their metabolites [4]. Among them, the polysaccharides have been shown to have effects on immunologic defense functions [5],[6]. The mechanisms of action have not been fully elucidated at the molecular level, but these have been shown to activate many of the diverse types of cells in the immune system [7],[8] and stimulate production of various cytokines [9]-[12]. A number of pharmacologically active polysaccharides with molecular weights ranging from 3500 to 160,000 Da have been identified. Importantly, these polysaccharides consist primarily of neutral sugars with various molar ratios depending on the specific ginseng of origin [4].

Ginsan is an acidic polysaccharide with a molecular weight of 150,000 Da, isolated from the aqueous Korean Panax ginseng extract [13],[14]. Previous studies have shown that Ginsan induces the proliferation of lymphocytes [15] and maturation of bone-marrow derived dendritic cells [16],[17] as well as stimulates the phagocytic activity of macrophages [18],[19]. These processes include Ginsan-induced generation of cytokines, including interleukin-1β, interleukin-2, interleukin-6, interleukin-12 (IL-12), interferon-γ, and tumor necrosis factor-α (TNF-α) [14],[16],[18]-[24]. In addition, Ginsan enhances the antibody response to orally administered Salmonella antigen in a mouse model [25]. Finally, pretreatment of Ginsan protects mice from lethality induced by Staphylococcus aureus infection [26],[27]. This survival benefit is associated with enhanced bacterial clearance from circulation and attenuation of the acute elevation of cytokines in the early septic phase, the uncontrolled response of which may be harmful to the host. Taken together, these observations strongly suggest that Ginsan mediates a significant modulatory effect on the immune system. However, the efficacy of Ginsan has not been studied in clinical trials.

Ginsan is currently available as an over-the-counter preparation and is used as a natural alternative to proactively strengthen immunity. The present study performed a randomized, placebo-controlled clinical trial to evaluate the safety and beneficial effects of Ginsan, denoted as Y-75, on immune function in a group of healthy adults aged between 50 and 75 years. The focus of this trial was modulation of innate immunity, comprising cytotoxic activity of natural killer (NK) cells, phagocytic activity of polymorphonuclear (PMN) leukocytes and mononuclear phagocytes, and serum levels of monocyte-derived mediators.

Considerable current interest has focused on health products that are believed to enhance immunity, and ginseng is the most studied herbal medicine in this context. However, consumption of whole ginseng extract has limited clinical utility due to variations in pharmacological effects depends on preparations [2],[28]. Thus, efforts have been made to purify the active components of ginseng in order to isolate its pharmacological constituents and achieve a more predictable outcome after administration. Several immunomodulatory polysaccharides have been isolated such as ginsenans [29]-[31], CVT-E002 [32], and Ginsan [13]. Currently, CVT-E002 is the only purified polysaccharide preparation for which safety and therapeutic effectiveness have been demonstrated in clinical trials [33]-[36].

In the current study, we characterized the safety and efficacy of Y-75, a novel candidate of immune modulator, in 72 healthy volunteers. Administration of Y-75 for 8 and 14 weeks safely increased NK cell activity by 35.2% and 40.2%, respectively, from baseline without altering white blood cell differential count, electrolytes, or vital signs or causing significant side effects. Importantly, compared with placebo, NK cell activity was increased by 27.6% and 29.6% at 8 and 14 weeks, respectively. Secondary efficacy variables, phagocytosis of E. coli by phagocytes from peripheral blood and serum level of the representative monocyte-derived mediator TNF-α, were also significantly increased by Y-75. These findings are consistent with previous preclinical laboratory studies on Ginsan.

In the current 14-week study, administration of Y-75 was well tolerated, with no discontinuation of therapy due to adverse effects. The most commonly experienced adverse events associated with usage of ginseng products include headache, sleep disturbance, and gastrointestinal disorders [37]. Long-term abuse of ginseng is associated with hypertension, gastrointestinal disturbances, insomnia, nervousness, confusion, and depression [38]. However, the number of clinical events that occurred during this trial was small, and their distribution indicated that there were no treatment-related adverse events. This high degree of safety of Y-75 was expected based on clinical literature showing that ginseng products are rarely associated with adverse effects [39].

We did not address mechanisms of action in terms of a target immune organ in the study design. Considering its high molecular weight, Y-75 is unlikely to be absorbed from the digestive tract into systemic circulation. However, in vitro evidence for gastrointestinal epithelial transfer of oligosaccharides has been reported [40]. Therefore, probable absorption of integrated molecule or digested fragment with active moiety should not be excluded. Furthermore, because the gastrointestinal tract is the largest immune organ in the body, it is interesting to speculate that this organ may be a direct target of Y-75 [41].

The pharmacokinetic profile of Y-75 after ingestion in unknown, and thus there are several limitations in this study. First, although preclinical laboratory observations showed direct stimulation of immune effector cells by Y-75, we cannot exclude the involvement of another unknown substance or substances generated through metabolism or transformation in the digestive system, as in the case of ginsenosides [42]. Second, we were also limited by uncertainty as to whether the designed dosing schedule was optimized for a primary outcome. Another limitation is gender imbalance between the groups. Male subjects (n = 2) were included only in Y-75 group. We re-analyzed the primary efficacy excluding the male subjects, and obtained the similar results; 51.3 ± 13.7% of NK cell activity with Y-75 versus 40.8 ± 14.6% with placebo at week 8 (P = 0.0028), and 53.4 ± 13.1% versus 41.6 ± 15.5% at week 14 (P = 0.0010). However, a study including a similar number of male in the both groups is needed to exclude gender effect. Next limitation is that the findings presented in this study, did not directly reflect clinical utility as an anti-tumor or anti-septic alternative. Therefore, further investigation in larger trials designed with respect to therapeutic outcome is needed. Finally, the short study duration did not allow for prediction of the long-lasting effects on the immune system or the exclusion of emerging adverse events after long-term administration.

Administration of Y-75 for 14 weeks induced augmentation in NK cell and phagocyte activities and cytokine release without affecting white blood cell differential counts in healthy volunteers. In addition, we found no significant adverse effects associated with Y-75. So far, these findings are valid for normal individuals only. However, this study provides the foundation for future clinical trials aimed at assessing the therapeutic outcomes of Y-75 as an anti-tumor or anti-septic clinical utility.