柿单宁的体外降胆固醇作用

采用分光光度法和气相色谱法研究了柿单宁对胰脂酶活性和胆固醇酯酶活性的抑制作用，以及柿单宁与胆汁酸、胆固醇的结合能力。结果表明：柿单宁对胰脂酶具有显著的抑制效果，其半数抑制浓度（half inhibitoryconcentration，IC50）为（0.445±0.021） mg/mL；抑制类型为非竞争性抑制，抑制常数Ki为0.406 mg/mL；柿单宁对胆固醇酯酶也具有显著的抑制作用，其半数抑制浓度IC50为（0.442±0.017）mg/mL，抑制类型为非竞争性抑制，抑制常数Ki为0.488 mg/mL。不同质量浓度的柿单宁对胆酸（cholic acid，CA）、脱氧胆酸（deoxycholic acid，DCA）都有一定的结合能力，10 mg/mL的单宁与CA、DCA的结合率分别为58%和94%；柿单宁对胆固醇胶束化溶液有较强的结合能力，0.20 mg/mL的单宁对其抑制率达到了67%。另外，在不同的pH值下，柿单宁对胆固醇都有一定的结合作用，其中pH 7.0时的结合能力明显强于pH 2.0时的结合能力。总之，柿单宁可抑制胰脂酶活性和胆固醇酯酶活性，并与胆固醇和胆汁酸结合，减少胃肠道对脂肪的吸收，这可能是柿单宁在体内发挥强降胆固醇作用的原因之一。

Cholesterol-Lowering Effect of Persimmon Tannin in Vitro

This study investigated the inhibitory effect of persimmon tannin on pancreatic lipase and pancreatic cholesterol
esterase activities. The binding capacity of persimmon tannin to cholesterol and bile acids was also determined by
spectrophotometry and gas chromatography. The results indicated that persimmon tannin significantly inhibited the activity
of pancreatic lipase with an IC50 value of (0.445 ± 0.021) mg/mL in an un-competitive manner, and the inhibitory constant
(Ki) was 0.406 mg/mL. Meanwhile, it also showed a strong inhibitory effect on pancreatic cholesterol esterase in an
un-competitive manner with an IC50 value of (0.442 ± 0.017) mg/mL and a Ki value of 0.488 mg/mL. At the concentration
of 10 mg/mL, the binding rates of persimmon tannin to cholic acid (CA) and deoxycholic acid (DCA) were 58% and 94%,
respectively. Persimmon tannin also could inhibit cholesterol micellization effectively, and the percentage inhibition was
found to be 67% when the concentration was 0.20 mg/mL. In addition, the cholesterol binding ability of persimmon tannin
was stronger at pH 7.0 than pH 2.0. These results suggested that persimmon tannin might decrease lipid absorption through
inhibiting the activities of pancreatic lipase and pancreatic cholesterol esterase, and binding cholesterol and bile acids. This
may explain the strong cholesterol-lowering effect of persimmon tannin in vivo.