| Summary: | 碩士 === 台北醫學院 === 藥學研究所 === 85 === Part I. The Constituents of Prunus phaeosticta (HANCE) MAXIM.
Prunus phaeosticta (HANCE) MAXIM. is a novel Prunus plant of
Rosaceae in Taiwan. Prunus plants have been used as nourish the
lung, resalve sputum, for treatment of dryness-syndrome, also as
diuretic, tonic, astringent and for treatment of benign prostate
hyperplasia. In this study, the constituents of the plant were
isolated, and compared with the constituents of other Prunus
spp. By variaus column chromatography, seven compounds were
isolated from the chloroform soluble fraction. Three compounds,
beta-amyrin(1), taraxerol(2) and beta-sitosterol-3-O-beta-D-
glucoside(3) were characterized by spectroscopic data and
chemicalmethods, and four constituents remain to be analyzed.
Part II. Inhibition of Xanthine Oxidase by the Constituents of
Prunus phaeosticta (HANCE) MAXIM. and Benzothiazinone Analogues.
According to the literature, xanthine oxidaseis related to
several diseases such as gout, tissue reperusion iniuries, brain
tumors, acute pancreatitis and hepatitis. In this study, the
constituents of Prunus phaeosticta (HANCE) MAXIM., thiazoles and
benzothiazinones have been tested for their inhibitory, effects
on xanthine oxidase:determination of percent inhibition, IC50,
mode of inhibition and the apparent inhibition constant (Ki). It
is expected that xanthine oxidase inhibitors are useful for the
treatment or prevention of these diseases mentioned as above.
The enzyme, xanthine oxidase catalyses the oxidation of
hypoxanthine to xanthine and of xanthine to uric acid which has
wavelength of 295 nm. Uric acid was thus forming basis for a
spectrophotometric assay of the activity of xanthineoxidase.
According to the Lineweaver-Burk plot equation, mode of
inhibition andthe apparent inhibition constants (Ki) were
estimated. The results showed that the constituents of Prunus
phaeosticta (HANCE) MAXIM. showed very weak inhibitory effect on
xanthine oxidase. On the other hand, benzothiazinone analogues,
2-amino-4H-1,3-benzothiazin-4-one (IC50-5.54uM, Ki=5.12uM) and
2-guanidino-4H-1,3-benzothiazin-4-one (IC50=5.60uM, Ki=19.47uM)
displayed potent activities on xanthine oxidase inhibition. They
induced noncompetitive and mixed (non-competi tive-uncompective)
type inhibitions respectively, with respect to the substrate
xanthine. Rhodanine (IC50=121.40uM, Ki=206.23uM) also showed
moderate effects on xanthine oxidase inhibition, and induced
mixed (non-compective-uncompetitive) type inhibition of the
enzyme with respect to the substrate xanthine.
|
|---|
