本實驗目的是探討體內補充順式-(cis-cinnamic acid, c-CA)與逆式-肉桂酸(trans-cinnamic acid, t-CA)在給予高膽固醇飲食大鼠的脂質代謝和抗氧化系統的影響。順式-肉桂酸是依孫芳明等人於2003年發表的方法來製備與純化。28隻大鼠平均分配於四組中，控制組給予每公斤含1.2公克的膽固醇的飼料連續5星期；其餘三組則分別給予含t-CA、維生素C (Vit C)或c-CA (0.1 g/100 g)的高膽固醇飼料5星期。動物於犧牲後，我們測量血漿或肝臟樣品中之總膽固醇 (Total-C)、高密度脂蛋白膽固醇 (HDL-C)、三酸甘油脂(TG)、動脈硬化指數(AI)、脂質過氧化物質指標 (TBARS)以用來測試c-CA對於大鼠脂質代謝之影響。另外其對大鼠肝臟的抗氧化系統 (catalase, and superoxide dismutase) 之影響則由西方墨點法 (Western blot analysis) 來評估。在Vit C組與c-CA組的大鼠之血漿Total-C濃度顯著低於控制組。在Vit C組的大鼠之血漿HDL-C/Total-C之比例顯著高於t-CA；所以AI於此2組之間是顯著相反的。然而在血漿HDL-C與TG濃度在四組之間沒有明顯的差異。根據實驗結果顯示，在t-CA與c-CA組的大鼠之肝臟TBARS顯著低於Vit C組。在肝臟之Total-C與TG卻是控制組顯著低於t-CA或c-CA組。在抗氧化酵素含量 (CAT and SOD) 於四組之間卻沒有差異性。結果指出c-CA在降低血漿Total-C濃度與肝臟TBARS含量比t-CA或Vit C組更有影響。 The purpose of this study was to investigate the effects of cis- and trans- cinnamic acid (c-CA and t-CA) supplementation on the lipid metabolisms and antioxidant systems of rats fed a high-cholesterol diet in vivo. The c-CA was prepared and purified by the method developed by Sun et al. (2003). The rats (n = 28) were randomly assigned to four groups and given a diet containing 1.2 g cholesterol/kg for 5 weeks. The control group only received a high cholesterol diet, whereas the other three groups received a diet including t-CA or Vitamin C (Vit C)or c-CA (0.1 g/100 g). The total cholesterol concentrations (Total-C), high-density lipoprotein-cholesterol concentrations (HDL-C), triglyceride concentrations (TG), atherogenic index (AI) and thiobarbituric acid reactive substances level (TBARS) of plasma and/or hepatic samples were determined to test the effects of c-CA on the lipid metabolisms of rats. The levels of hepatic antioxidant enzymes (catalase, and superoxide dismutase) were also evaluated by Western blot analysis. The plasma Total-C was significantly lowered in the Vit C and c-CA than in the control group. The plasma ratio of HDL-C/Total-C was significantly higher in the Vit C than in the t-CA group, so the AI was reversed in these two groups. The plasma HDL-C and plasma TG were not appreciably different among four groups. According to this study, the hepatic TBARS significantly was reduced in the c-CA than in the Vit C group. The hepatic TBARS was significantly lowered in the c-CA than in the Vit C group. The hepatic Total-C was significantly lowered in the control than in the t-CA group. The hepatic TG was significantly lowered in the control than in c-CA. There were no significant differences in the levels of hepatic antioxidant enzymes (catalase and superoxide dismutase) among the four groups. These results indicate that c-CA was more effective in lowering the plasma cholesterol and hepatic TBARS content than t-CA or Vit C.