| Summary: | 碩士 === 台北醫學院 === 生藥學研究所 === 90 === Monoamine oxidase (MAO) is a flavin-containing enzyme, which catalyzes the oxidation of a variety of amine-containing neurotransmitters (such as serotonin, dopamine and norepinephrine) to yield the corresponding aldehydes and the coproducts hydrogen peroxide (H2O2) and ammonia. It exists MAO-A and MAO-B forms. The attenuation of MAO-B activity may provide protection against oxidative neurodegeneration for treatment of Parkinson’s and Alzheimer’s patients. Gou-teng，the hook of Uncaria rhynchophylla（Miq.）Jacks., is a Chinse herb used for an antihypertensive therapy . The herb also has sedative, anticonvulsive, and antispasmodic effects on smooth muscles. In this study, we isolated the active fractions from U. rhynchophylla by fluorometric method for the measurement of monoamine oxidase B activity. The methanol extract of Gou-teng showed the significant inhibitory effect (86.90%) on MAO-B activity at dose of 200 μg/ml and was fractionated into n-hexane, dichloromethane, ethyl acetate, and n-butanol soluble parts. The ethyl acetate soluble part exhibited obviously inhibitory effect on MAO-B activity, as well as chromatographed over Diaion HP-20 and ODS columns by bio-guide isolation. The active fractions were purified by preparative HPLC to yield two know compounds, (+) catechin (1) and (-) epicatechin (2). Their structures were identified by comparison of spectroscopic data of the literatures. The IC50 values of (+) catechin (1) and (-) epicatechin (2) were 98.96 μM and 85.32 μM in the dose-dependent manner on MAO-B inhibitory activity. We performed a kinetics analysis of the two components in each IC50 concentration. By the Lineweaver-Burk plot to know the Ki values of (+) catechin (1) and (-) epicatechin (2) were 73.97 and 21.26 μM, respectively. They show the mixed type inhibition MAO-B for two compounds. By 5﹪native-PAGE analysis, the inhibitory effects of these two compounds on MAO-B activity were also found. In this study, the inhibitory effects of (+) catechin (1) and (-) epicatechin (2) from U. rhynchophylla on MAO-B activity was investigated. As results, these two compounds might protect neurodegeneration and the molecular mechanisms were deserved to be further studied.
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