Biological properties of baicalein in cardiovascular system.

The dried roots of Scutellaria baicalensis (S. baicalensis) Georgi (common name: Huangqin in China) have been widely employed for many centuries in traditional Chinese herbal medicine as popular antibacterial and antiviral agents. They are effective against staphylococci, cholera, dysentery, pneumococci and influenza virus. Baicalein, one of the major flavonoids contained in the dried roots, possesses a multitude of pharmacological activities. The glycoside of baicalein, baicalin is a potent anti-inflammatory and anti-tumor agent. This review describes the biological properties of baicalein (Table 1), which are associated with the prevention and treatment of cardiovascular diseases. Baicalein is a potent free radical scavenger and xanthine oxidase inhibitor, thus improving endothelial function and conferring cardiovascular protective actions against oxidative stress-induced cell injury. Baicalein lowers blood pressure in renin-dependent hypertension and the in vivo hypotensive effect may be partly attributed to its inhibition of lipoxygenase, resulting in reduced biosynthesis and release of arachidonic acid-derived vasoconstrictor products. On the other hand, baicalein enhances vasoconstricting sensitivity to receptor-dependent agonists such as noradrenaline, phenylephrine, serotonin, U46619 and vasopressin in isolated rat arteries. The in vitro effect is likely caused by inhibition of an endothelial nitric oxide-dependent mechanism. The anti-thrombotic, anti-proliferative and anti-mitogenic effects of the roots of S. baicalensis and baicalein are also reported. Baicalein inhibits thrombin-induced production of plasminogen activator inhibitor-1, and interleukin-1beta- and tumor necrosis factor-alpha-induced adhesion molecule expression in cultured human umbilical vein endothelial cells. The pharmacological findings have highlighted the therapeutic potentials of using plant-derived baicalein and its analogs for the treatment of arteriosclerosis and hypertension.