Chung Mi Ja, Sung Nak-Ju, Park Cheon-Seok, Kweon Dong-Keon, Mantovani Alberto, Moon Tae-Wha, Lee Sung-Joon, Park Kwan-Hwa
Division of Food Bioscience and Technology, College of Life Science and Biotechnology, Institute of Biomedical Sciences and Food Safety, Korea University, Seoul 136-713, South Korea.
Eur J Pharmacol. 2008 Jan 14;578(2-3):159-70. doi: 10.1016/j.ejphar.2007.09.036. Epub 2007 Oct 5.
Puerarin is an isoflavone derived from Kudzu roots and has antioxidant and hypocholesterolemic effects; however, its insolubility often limits its biological availability in vivo. Using a novel transglycosylation process, the solubility of puerarin glycosides was increased >100-fold, but it was not known whether these modified puerarin glycosides maintained biological activities. We found that water-soluble puerarin glycosides fully maintained antioxidant activities compared with puerarin assessed by radical scavenging activity, reducing power assay, superoxide dismutase activity, and non-site-specific hydroxyl radical scavenging activity. Both puerarin and its glycosides also significantly reduced low-density lipoprotein (LDL) oxidation. Mice fed with puerarin glycosides (0.1% w/w) showed significantly reduced plasma total cholesterol levels, thus, we further investigated their hypocholesterolemic mechanisms by assessing several key gene expressions both in vitro and in vivo. Puerarin and its glycosides induced multiple changes in hepatic cholesterol metabolism. The LDL receptor promoter activity was increased dose-dependently in puerarin glycosides-treated HepG2 cells. Accordingly, the expression of LDL receptor mRNA and protein were also significantly increased in HepG2 cells and mouse livers. The transcription and translation of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase were down-regulated both in vitro and in vivo. The cholesterol 7alpha-hydroxylase (CYP7A1) mRNA levels were not affected in vitro but significantly up-regulated in the mouse livers. Collectively, our results show that puerarin and its glycosides are biologically fully active isoflavone and have antioxidant and hypocholesterolemic effects in HepG2 cells and in C57BL/6J mice. In the livers, hypocholesterolemic effects of puerarin glycoside may be achieved by multiple mechanisms including increasing LDL uptake, reducing cholesterol biosynthesis, and possibly enhancing cholesterol degradation.
葛根素是一种从葛根中提取的异黄酮，具有抗氧化和降胆固醇作用；然而，其不溶性常常限制其在体内的生物利用度。通过一种新型转糖基化工艺，葛根素糖苷的溶解度提高了100多倍，但尚不清楚这些修饰后的葛根素糖苷是否保持生物活性。我们发现，与通过自由基清除活性、还原能力测定、超氧化物歧化酶活性和非位点特异性羟基自由基清除活性评估的葛根素相比，水溶性葛根素糖苷完全保持了抗氧化活性。葛根素及其糖苷还显著降低了低密度脂蛋白（LDL）的氧化。喂食葛根素糖苷（0.1% w/w）的小鼠血浆总胆固醇水平显著降低，因此，我们通过在体外和体内评估几个关键基因的表达，进一步研究了它们的降胆固醇机制。葛根素及其糖苷引起了肝脏胆固醇代谢的多种变化。在葛根素糖苷处理的HepG2细胞中，LDL受体启动子活性呈剂量依赖性增加。相应地，HepG2细胞和小鼠肝脏中LDL受体mRNA和蛋白的表达也显著增加。3-羟基-3-甲基戊二酰辅酶A（HMG-CoA）还原酶的转录和翻译在体外和体内均下调。胆固醇7α-羟化酶（CYP7A1）mRNA水平在体外未受影响，但在小鼠肝脏中显著上调。总体而言，我们的结果表明，葛根素及其糖苷是具有生物活性的异黄酮，在HepG2细胞和C57BL/6J小鼠中具有抗氧化和降胆固醇作用。在肝脏中，葛根素糖苷的降胆固醇作用可能通过多种机制实现，包括增加LDL摄取、减少胆固醇生物合成以及可能增强胆固醇降解。
