A fast-track research letter published in this week’s issue of THE LANCET suggests that the antiviral agent glycyrrhizin derived from the roots of the liquorice plant could be more effective than other antivirals in tackling severe acute respiratory syndrome (SARS).
Professor Jindrich Cinatl and his colleagues at Frankfurt University Medical School in Germany, assessed the antiviral potential of five compounds: ribavirin, 6-azauridine, pyrazofurin, mycophenolic acid, and glycyrrhizin. They tested them against two isolates of the SARS coronavirus from patients with SARS who had been admitted to the clinical centre of Frankfurt University.
Ribavirin, which is the most commonly used antiviral for treating SARS infection, had no effect on SARS-associated coronavirus replication in the Frankfurt study.
Among the antivirals tested, glycyrrhizin was the most active in inhibiting replication of the virus. Glycyrrhizin at a concentration of 4,000 mg/L completely blocked replication and was considerably more active than at 1,000 mg/L. The activity of glycyrrhizin points to an increase in nitric oxide synthesis as the mechanism for its action.
The investigators consider their findings "suggest that glycyrrhizin should be assessed for treatment of SARS."
The authors describe side-effects, for example raised blood pressure and hypokalaemia (low blood potassium) found after several months of glycyrrhizin treatment in patients with HIV-1 or chronic hepatitis C. However, if used in treatment of SARS, this would be only for a short time.
"The side effects of this compound are known and can be controlled" the authors assert, "proper monitoring could lead to effective use of glycyrrhizin as a treatment for SARS."
Ribavrin is known to have many toxic effects when given to patients with SARS, including haemolysis and a drastic reduction of haemoglobin.
About liquorice and glycyrrhizin
Glycyrrhizin is an antiviral agent with proven efficacy in treating HIV-1 and hepatitis C infection. The ingredient in liquorice (glycyrrhiza glabra) of particular interest is the alkaloid glycyrrhizin, which takes its name from the biological name of the plant.
The Chinese name for liquorice is "gan cao", meaning "sweet weed." Glycyrrhizin is about fifty times sweeter than sugar, conferring a sweet taste to infusions, tinctures or other products made from the liquorice root.
Reference
Cinatl, J, Morgenstern B, Bauer G, Chandra P, et al., Glycyrhizin, an active component of liquorice roots, and replication of SARS-associated coronavirus. Lancet, June 14, 2003; Vol 361, 2045-2046
Keywords : Frankfurt University Medical School Germany SARS-associated coronavirus Glycyrrhizin Liquorice plant root glycyrrhiza glabra Nutraceutical Inhibition of virus replication HIV-1 Hepatitis-C Ribavirin Side-effects
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