Licorice root extract found to inhibit replication of the SARS virus

Spirulina is a blue-green algae that grows in lakes and other bodies of water. In recent years, it has become popular as a dietary supplement because it has been found to be a rich natural source of nutrients.

The sudden outbreak of SARS led to a flurry of research to find an antiviral agent that could reduce the severity of the disease and promote recovery. The virus responsible for SARS was found to belong to the coronavirus, a family that also includes the cold and flu viruses.

A German study evaluated the efficacy of various agents, including interferon, to inhibit viruses isolated from SARS patients. One of the agents evaluated was glycyrrhizin, an extract of the herb licorice root, and this particular substance proved to be the most effective one of all those tested.

Researchers found that, in addition to inhibiting replication of the virus more effectively than any other drugs, glycyrrhizin also inhibited ability of the virus to infect healthy cells. The authors also commented that glycyrrhizin had previously been used in the treatment of patients with HIV and chronic hepatitis C. Compared with the other agents tested, glycyrrhizin has the lowest occurrence of side effects: only increased blood pressure in susceptible individuals with long-term use. (The Lancet, June 2003; 361 (9374): 2045-6)

Licorice root standardized for its glycyrrhizin content can be purchased in the United States over the counter as a dietary supplement. Although the SARS epidemic seems to be behind us, glycyrrhizin can be considered as part of a strategy to address a variety of chronic and acute viral conditions in both children and adults.

Other herbal extracts have also been shown to be active against viruses. These can be combined with glycyrrhizin to obtain a synergistic effect at lower doses, thus reducing the risk of side effects and possibly even increasing effectiveness.

I will review a few of these herbs briefly:

Elderberry extract has been used traditionally to protect from the flu and other viral conditions.

Chinese skullcap (Scutellaria baicalensis) has been shown to inhibit the replication of influenza viruses A and B (Boil Pharm Bull 1995;18(2):295-9). It has also been shown to inhibit HIV proliferation in animal studies (Cell Mol Biol Res 1993;39(2):119-24), and Epstein-Barr virus in humans (Chem Pharm Bull (Tokyo) 1992;40(2):531-3).

Astragalus has been used traditionally in Chinese medicine for a variety of viral conditions. Research has shown its ability to correct deficient T cells (immune cells) in cancer patients (J Clin Lab Immunol 1988;25:119-23).

Berberine, an extract of several herbs, has been shown to have strong inhibiting effects against various fungal, bacterial and viral organisms (Can J Microbiol 1969;15(9):1067-76, J Prosthet Dent 1990;64(6):691-4).

Hypericin, extracted from St. John’s wort, has been shown to be effective against herpes simplex virus I and II and Epstein-Barr virus, among others. It received a European patent as an antiviral drug, but is available in this country as a dietary supplement.

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