Zhang Yong-He, Fang Lian-Hua, Lee Myung-Koo, Ku Bao-Shan
Department of Pharmacology, Peking University, School of Basic Medical Science, Beijing 100083, P.R. China.
Phytother Res. 2003 Sep;17(8):967-9. doi: 10.1002/ptr.1292.
The aqueous extract of Mallotus japonicus (Euphorbiaceae) showed an inhibitory effect on bovine adrenal tyrosine hydroxylase (TH), the rate-limiting enzyme in the biosynthesis of catecholamine. The present study was undertaken to investigate the effects of bergenin and norbergenin, constituents of the aqueous extract of Mallotus japonicus on bovine adrenal TH. Bergenin and norbergenin inhibited the TH activity by 29.0% and 53.4% at a concentration of 20 microg/mL, respectively, and exhibited noncompetitive inhibition of TH activity with the substrate l-tyrosine. The inhibition of TH activity and the inhibitory effect of norbergenin was more potent than that of bergenin. From these results, it is presumed that bergenin and norbergenin may be the active components of Mallotus japonicus in inhibiting TH, and these inhibitory effects may be partially responsible for the clinical use of Mallotus japonicus in treating peptic ulcer by reducing the availability of dopa/dopamine in vivo.
大戟科植物野桐的水提取物对牛肾上腺酪氨酸羟化酶（TH）有抑制作用，酪氨酸羟化酶是儿茶酚胺生物合成中的限速酶。本研究旨在探讨野桐水提取物的成分岩白菜素和去甲岩白菜素对牛肾上腺TH的影响。岩白菜素和去甲岩白菜素在浓度为20μg/mL时，分别使TH活性抑制29.0%和53.4%，并对底物L-酪氨酸表现出非竞争性抑制TH活性。TH活性的抑制以及去甲岩白菜素的抑制作用比岩白菜素更强。从这些结果推测，岩白菜素和去甲岩白菜素可能是野桐抑制TH的活性成分，这些抑制作用可能部分解释了野桐在体内通过降低多巴/多巴胺的可用性来治疗消化性溃疡的临床应用。
