酸提高绿茶提取物对脂肪酸合酶的抑制活性

脂肪酸合酶和肥胖、癌症等人类重大疾病相关.获取高活性脂肪酸合酶抑制剂有重要应用价值.50％乙醇的绿茶提取物具有抑制脂肪酸合酶和经口服降低大、小鼠体重的功能.该提取物在酸的作用下可明显地提高其抑制脂肪酸合酶的能力.采用1 mol/L硫酸或盐酸在100℃下处理绿茶提取物，发现该提取物对脂肪酸合酶的抑制活性随时间逐步提高.在25℃至120℃温度下，提高处理温度使抑制活性提高的速度加快和程度加大. 用1 mol/L盐酸120℃处理35 min或3 mol/L盐酸100℃处理30 min可使绿茶提取物抑制脂肪酸合酶的半抑制浓度下降20倍左右，达到1 μg/ml以下.用pKa值4.76至1.27的1 mol/L浓度的4种有机酸在100℃作用150 min使绿茶提取物抑制活性分别提高到1.48至5.84倍.提高酸的浓度也使被作用的提取物的抑制活性提高的更多.表现抑制活性提高的速度及程度和氢离子浓度正相关.判断绿茶提取物在酸作用下抑制活性的提高来源于其中所含儿茶素在氢离子作用下发生了化学变化.初步实验表明其变化过程比较复杂，确定其分子机制还需进一步的研究工作.

Enhancement of Inhibitory Activity of Green Tea Extract on Fatty Acid Synthase by Hydrogen Ion

Fatty acid synthase (FAS) is a potential therapeutic target for obesity and cancer and therefore development of high efficient inhibitors is of vital importance Treatment with 50%ethanol extract of green tea inhibited this enzyme and reduced body weight of rats and mice upon oral administration. The inhibitory activity of the extract onFAS was enhanced markedly in the acidic medium. The increasing inhibitory activity was time dependent by 1 mol/L H2SO4 or HCl at 100℃. Ranging from 25℃to 120℃,increasing temperature raised the speed of enhancement of the inhibitory activity and augment of the final inhibitory capacity. The concentration required for half inhibition of green tea extract decreased by 20 folds and reduced to less than 1 μg/ml by treatment of 1 mol/L HCl in 120℃ for 35 min or 3 mol/L HCl in 100℃ for 30 min. The action by each of four different organic acids with 1 mol/L concentration and pKa value of 4.76 to 1.27 in 100℃ for 150 min enhanced the inhibitory activity of green tea extract to 1.48—5.84 folds, respectively. Higher concentration of hydrogen ion induced more inhibitory effect of the treated extract. The results showed that the speed and degree of the enhancement of inhibitory activity of the extract positively related to the concentration of hydrogen ion in the reaction solution. It is suggested that the enhancement of inhibitory activity of green tea extract in acid roots in some chemical modification of catechins in the extract by hydrogen ion. The primary experiments showed that the reaction was a complicated process. Further investigation is needed to determine the molecular mechanism.