Exploring the possible metabolism mediated interaction of Glycyrrhiza glabra extract with CYP3A4 and CYP2D6

The rhizome of Glycyrrhiza glabra L. (licorice) is used very widely in Indian and Chinese traditional medicine, and it is a popular flavor ingredient of drinks, sweets and candies. Its medicinal uses include treating bronchitis, dry cough, respiratory infections, liver disorders and diabetes. Glycyrrhizin is normally considered to be its biologically active marker, so a rapid RP‐HPLC method was developed for the quantitative estimation of glycyrrhizin in the extract. The effect of the standardized extract and its marker on drug metabolizing enzymes was evaluated through CYP3A4 and CYP2D6 inhibition assays to evaluate the safety through its drug interaction potential. The inhibition of CYP3A4 and CYP2D6 isozymes was analysed by the fluorescent product formation method. In the CYP450‐CO assay, the interaction potential of the standardized extract and pooled microsomes (percentage inhibition 23.23 ± 1.84%), was found to be less than the standard inhibitor. In the fluorimetric assay, G. glabra extracts showed higher IC₅₀ values than their positive inhibitors, ketoconazole and quinidine for CYP3A4 and CYP2D6, respectively. Furthermore, the interaction potential of the plant extract was greater than the pure compound. The results demonstrate that G. glabra and its principle bioactive compound, glycyrrhizin, when co‐administered with conventional medicines showed only a weak interaction potential with drug metabolizing enzymes. Copyright © 2011 John Wiley & Sons, Ltd.