Carboxyl-glucuronidation of mitiglinide by human UDP-glucuronosyltransferases

Mitiglinide (MGN) is a new potassium channel antagonist for the treatment of type 2 diabetes mellitus. In the present study, a potential metabolic pathway of MGN, via carboxyl-linked glucuronic acid conjugation, was found. MGN carboxyl-glucuronide was isolated from a reaction mixture consisting of MGN and human liver microsomes fortified with UDP-glucuronic acid (UDPGA) and identified by a hydrolysis reaction with beta-glucuronidase and HPLC-MS/MS. Kinetic analysis indicated that MGN from four species had the highest affinity for the rabbit liver microsomal enzyme (K(m)=0.202 mM) and the lowest affinity for the dog liver microsomal enzyme (K(m)=1.164 mM). The metabolic activity (V(max)/K(m)) of MGN to the carboxyl-glucuronidation was in the following order: rabbit>dog>rat>human. With the assessment of MGN glucuronide formation across a panel of recombinant UDP-glucuronosyltransferase (UGT) isoforms (UGT1A3, UGT1A4, UGT1A6, UGT1A9, and UGT2B7), only UGT1A3 and UGT2B7 exhibited high MGN glucuronosyltransferase activity. The K(m) values of MGN glucuronidation in recombinant UGT1A3 and UGT2B7 microsomes were close to those in human liver microsomes. The formation of MGN glucuronidation by human liver microsomes was effectively inhibited by quercetin (substrate for UGT1A3) and diclofenac (substrate for UGT2B7), respectively. The MGN glucuronidation activities in 15 human liver microsomes were significantly correlated with quercetin (r(2)=0.806) and diclofenac glucuronidation activities (r(2)=0.704), respectively. These results demonstrate that UGT1A3 and UGT2B7 are catalytic enzymes in MGN carboxyl-glucuronidation in human liver.     

杏香兔耳风高效液相色谱-光电二极管矩阵检测器法的指纹图谱研究

目的 研究用高效液相色谱-光电二极管矩阵检测器法（HPLC—PDAD）建立杏香兔耳风指纹图谱的分析方法 ,为杏香兔耳风的质量鉴定提供依据。方法 色谱条件为：色谱柱为Nucleosil C18柱（4．6mm×250mm,5μm）,以乙腈-缓冲溶液（乙酸-NaH2PO4,0．1mol／L,pH=2．5）为流动相,梯度洗脱,流速1．0mL／min,柱温30℃,检测波长356nm。结果 用上述方法 确定了12批不同品种杏香兔耳风的11个共有峰,其相识度均大于0．91,精密度、稳定性、重复性试验、各共有峰相对保留时间和相对峰面积的RSD均小于2．5％,各色谱峰分离效果良好,符合指纹图谱要求。结论 该方法 精密度、稳定性和重复性均较好,为杏香兔耳风的质量控制标准提供了参考。     

蒙药小白蒿中总黄酮的提取及其抗氧化活性研究

目的:研究蒙药小白蒿中总黄酮的抗氧化作用。方法:以芦丁、Vc为对照,测定小白蒿总黄酮对超氧阴离子自由基(O 2-.)、羟自由基(.OH)及二苯代苦味酰基苯肼自由基(DPPH.)的清除率。结果:小白蒿总黄酮具有不同程度的清除自由基能力,而且对DPPH.,O 2-.和.OH的清除率均优于Vc,芦丁。结论:小白蒿总黄酮具有较强的抗氧化能力。