Since ancient times, root extract of Glycyrrhiza glabra (liquorice) was used medicinally for treatment of a large range of diseases. Recently, it has been reported that constituents isolated from liquorice have antiplatelet, antitumorigenic, antimicrobial, antiviral, and also antioxidants activities. Interestingly, glycyrrhizin and its aglycone, glycyrrhetinic acid, the major components of G. glabra, were known to exhibit cardio-protective properties. The aim of this research was to explore, in rat hearts (Langendorff technique), the biological activity of glycyrrhizin and glycyrrhetinic acid under basal conditions.

Both glycyrrhizin and glycyrrhetinic acid influenced cardiac contractility and lusitropism. In particular, glycyrrhizin induced significant positive inotropic and lusitropic effects starting from very low concentrations, while glycyrrhetinic acid administration induced opposite effects. In fact, both inotropism and lusitropism were negatively affected by treatment with glycyrrhetinic acid. Only the effects of glycyrrhizin was evident at very low concentrations, and this reflects the in vivo situation after liquorice ingestion.

In conclusion, our preliminary data reveal, for the first time, that both glycyrrhizin and glycyrrhetinic acid directly affect cardiac performance potently acting on both inotropism and lusitropism.