thromboxane-b2 and isoliquiritigenin

Glycyrrhiza glabra and its phytoconstituents have been known to possess widespread pharmacological properties as an anti-inflammatory, anti-viral, antitumour and hepatoprotective drug. In this study, we examined the inhibitory potential of extract of G. glabra (GutGard™) root and its phytoconstituents (glabridin, glycyrrhizin, and isoliquiritigenin) on both cyclooxygenase (COX) and lipoxygenase (LOX) products in order to understand the mechanism of its anti-inflammatory action. Inhibitory effect of GutGard™ and its phytoconstituents on lipopolysaccharide (LPS) induced prostaglandin E(2) (PGE(2)), calcimycin (A23187) induced thromboxane (TXB(2)), and leukotriene (LTB(4)) release was studied using murine macrophages (J774A.1) and human neutrophil (HL-60) cells. Results revealed that, G. glabra and glabridin significantly inhibited PGE(2), TXB(2) (COX) and LTB(4) (LOX), while, isoliquiritigenin exerted inhibitory effect only against COX products but failed to suppress LOX product. However, glycyrrhizin at the tested concentrations failed to exhibit inhibitory effect on both COX and LOX products. Here, we report for the first time that G. glabra (almost devoid of glycyrrhizin) exhibits anti-inflammatory property likely through the inhibition of PGE(2), TXB(2) and LTB(4) in mammalian cell assay system, which could be influenced in part by glabridin and isoliquiritigenin.

Topics: Animals; Anti-Inflammatory Agents; Calcimycin; Cell Line; Chalcones; Dinoprostone; Glycyrrhiza; Glycyrrhizic Acid; HL-60 Cells; Humans; Isoflavones; Leukotriene B4; Lipopolysaccharides; Lipoxygenase; Mice; Phenols; Plant Extracts; Plant Roots; Prostaglandin-Endoperoxide Synthases; Thromboxane B2

The mechanism was studied by which isoliquiritigenin, a new aldose reductase inhibitor purified from licorice (Glycyrrhizae radix), inhibits platelet aggregation. This new agent significantly inhibited the phosphorylation of 40,000- and 20,000-dalton proteins, and inhibited the formation of 12 (S)-hydroxy-5,8,10-heptadecatrienoic acid, 12-hydroxyeicosatetraenoic acid and thromboxane B2. The inhibitory effect of isoliquiritigenin on platelet aggregation in vitro was comparable to that of aspirin. Our findings may indicate that isoliquiritigenin elicits an anti-platelet action by inhibiting not only cyclooxygenase but also lipoxygenase or peroxidase activity in platelets. Isoliquiritigenin also showed an anti-platelet action in vivo. Isoliquiritigenin appears to be the only aldose reductase inhibitor with a significant anti-platelet action. Since the hyperaggregability of platelets has been implicated in the pathogenesis of diabetic complications, isoliquiritigenin may offer a unique benefit as an aldose reductase inhibitor.

Topics: Aldehyde Reductase; Blood Platelets; Blood Proteins; Chalcone; Chalcones; Fatty Acids, Unsaturated; Glycyrrhiza; Humans; Hydroxyeicosatetraenoic Acids; Molecular Weight; Phosphorylation; Plants, Medicinal; Platelet Aggregation Inhibitors; Thromboxane B2