Immunomodulators are agents that exert a general net effect (positive or negative) on the activity of the immune system or on a specific immune function. Immunomodulators have the potential to be of clinical use in the enhancement (e.g., for treating AIDS) or therapeutic suppression (e.g., for treating organ transplant rejection or autoimmune disease) of immune function. Some compounds that have been isolated from herbs used in traditional Chinese medicine (TCM) have been shown to have immunomodulating activity.

More than 70 compounds have been isolated from the poisonous liana Tripterygium wilfordii Hook.f., Celastraceae, largely alkaloids and terpenoids. Many have been shown to be immunosuppressors in vitro and in vivo. T. wilfordii has been used in TCM to treat fever, chills, edema, and inflammation, and extracts of the plant's xylem have been used for rheumatoid arthritis, chronic nephritis, skin diseases, and immunological disorders.

Artemisinin, known as qing haosu in TCM, a sesquiterpene lactone isolated from Artemisia annua (Sweet Annie, Artemisia annua "Qing-Hao" L., Asteraceae), is an antimalarial drug. Recent clinical studies have found it to be an immunomodulator, and that it can be effective in the treatment of systemic lupus erythematosis, psoriasis, and other autoimmune-related disorders. Arteether, a semisynthetic analogue of dihydroartemisinin (an artemisinin derivative), is being developed by the World Health Organization to treat malaria. Another compound, artemether (a homologue of arteether), is proving to have more potent antimalarial activity than artemisinin.

The fruits of Sophora alopecuoides (Fabaceae) and the roots of S. flavescens are used in TCM for their antipyretic (fever reducing) effects. Alkaloids isolated from these plants have been shown both to be immunosuppressors (at high doses) and immunostimulators (at low doses). Diterpenoid alkaloids isolated from the axial roots of Aconitum species used in TCM have shown anti-inflammatory, analgesic, antipyretic and immunomodulatory activity. The sinomenine alkaloids, derived from Sinomenium acutum Diels. (Menispermaceae), have been shown to be clinically effective in arthritis and rheumatoid arthritis.

In addition to these compounds, several polysaccharides, such as those from the fruiting bodies of Ganoderma lucidum (Reishi mushroom), ling chih (Leyss. ex Fr., P. Karst., Ganodermataceae), the fruits of Lycium barbarum L. Solanaceae, the whole plants of Epimedium koreanum Berberidaceae nec pubescens, the roots of Panax ginseng C. A. Mey., Araliaceae, Acanthopanax obovatus nec senticosus, and Achyranthes bidentata L., Amaranthaceae, have been found to be immunostimulators.

[Zhang, Ling-Hua, Yi Huang, Li-Wei Wang, and Pei-Gen Xiao. 1995. Several Compounds from Chinese Traditional and Herbal Medicine as Immunomodulators. Phytotherapy Research, Vol. 9, 315-322.]

Article copyright American Botanical Council.

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By Ginger Webb