Immune Stimulants and Antiviral Botanicals: Echinacea and Ginseng

Preparations of echinacea and ginseng likely comprise the most popular and commercially successful combination of medicinal plant products in North America. Interestingly, the development of Echinacea species for medicinal purposes stems from use by indigenous American people, but research has been conducted predominantly in Germany (Bauer and Wagner 1991). On the other hand, the reputation of ginseng is firmly planted in China and has spread west in modern times, research in China, Japan, and Korea, being bolstered by European investigations of mainly extracts of the Asian species, Panax ginseng. Following its discovery outside present-day Montreal, Quebec, in 1716 (Foster 1992), the trade in North American ginseng, Panax quinquefolius, grew steadily and now constitutes a considerable market in the Orient, where roughly 90% of Canadaand US-grown root is sold. Only one of the additionally recognized Panax species, namely Panax notoginseng (Sanchi or Tienchi ginseng), is of commercial significance, primarily in Asia, where it finds application as a hemostatic, cardiotonic, and anti-infective agent (Gao et al. 1996). The traditional use of echinacea by native Americans as a topical anti-infective and snake-bite remedy, and to assuage coughs associated with colds, was presumably the impetus for investigation of its anti-microbial potential. Anti-bacterial, anti-fungal and anti-viral activities were subsequently assessed for a variety of preparations, the identity of the particular Echinacea species being still somewhat equivocal (Bauer and Wagner 1991). Latterly, attention has concentrated on the plant’s application to the treatment of symptoms of cold and other influenza-like infections, the basis for its economic success; any effectiveness in such conditions is widely attributed to effect on the immune system—potentiation or “stimulation” being generally regarded more particularly as “immunomodulation” (Bauer and Wagner 1991). Any benefit deriving from treatment with echinacea preparations is thought to be due to such stimulation of the immune system, rather than to any direct anti-viral effect. Ginseng (P. ginseng) has a traditional reputation as a tonic and drug of longevity in Asia, where it has also long been used to treat a variety of diseases, including cancer and diabetes, as well as various infections; in modern times, it has been characterized as an ‘adaptogen’ or anti-stress agent, exerting a non-specific normalizing effect on bodily functions. Ginsenosides, also termed panaxosides, are triterpene saponins regarded as the main active constituents of Panax species; hydrophilic bioactive polysaccharides are held responsible for anti-complementary and anti-tumor activities (Gao et al. 1991). However, while the attention of the herbal industry has focused almost exclusively on ginsenosides, almost all investigations of the immunomodulatory effects of ginseng have involved crude extracts of P. ginseng (see later) and polysaccharide fractions of Panax species (Yun et al. 1993; Gao et al. 1996). The results of one human study with a proprietary P. ginseng extract, support the claim of enhancement of immune response against influenza and colds, after vaccination (Scaglione et al. 1996).