| Glycyrrhizin (or Glycyrrhizic acid,GL) which is the main ingredient of Licorice (or liquorice,whose Latin name is Glycyrrhiza glabra.L.) , is a triterpeniod saponin consisting of a glycyrrhetic acid(GA)and a β(1→2)-linked disaccharide of glucuronic acids. It is known that GL has a variety of biological activities such as anti-inflammatory, hypolipidemic, anti-ulcer, anti-viral effects and immuno -modulating activities. The inhibitory effects of GL to some protein kinases were also reported. GL has been used intravenously to treat chronic hepatitis for many years. GL occours in the form of two stereoisomers, 18β-H-(cis) and 18α-H-(trans)-glycyrrhizic acid, the former one is the main ingredient and can transform to the later one by chemical conversion. Two GL stereosiomers possessed close physicochemical properties, but 18α-GL differs from 18β-GL for its better affinity with the ligand, which resulted in stronger pharmacological activities.With the high hydrophilicity, GL molecules have a lower membrane permeability attributed mainly to its lower partition into the lipid memebrane, so it is hard to be absorbed via transcellular route; and with the large molecular weight, it is also hard to be absorbed via paracellular route. Thus poor bioavailability limits GL for oral use. GL and GA sometimes induce pseudoaldosteronism, edema, hypertension, and hypokalemia in patients treated with higher doses and long-term administration.Now GL is a noteworthy drug among phtotherapeutics and its chemical modification is the perspective route to design novel bioactive compounds for medicine. To receive new bioactive compounds for medicine, chemical modifications of GL carboxyl and hydroxyl groups have been modified with the introduction of...
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