The study aims to develop a rapid, sensitive and specified method of liquid chromatography with heated electrospray ionization tandem mass spectrometry (LC-HESI/MS/MS) for simultaneous determination of amlodipine, benazepril and benazeprilat in human plasma using amlodipine-d4 and ubenimex as internal standards (ISs). Selected reaction monitoring (SRM) with heated electrospray ionization (HESI) was used in the positive mode for mass spectrometric detection. Analytes and ISs were extracted from plasma by simple protein precipitation. The reconstituted samples were chromatographed on a C18 (100 mm x 4.6 mm, 5 microm) column with mixture of methanol-acetonitrile-5 mmol.L- ammonium acetate-formic acid (30 : 30 : 40 : 0.1) as mobile phase at a flow rate of 0.6 mL.min-1. The standard curves were demonstrated to be linear in the range of 0.02 to 6.00 ng.mL-1 for amlodipine, 0.2 to 1,500 ng.mL-1 for benazepril and benazeprilat with r2>0.99 for each analyte. The lower limit of quantitation was identifiable and reproducible at 0.02, 0.2 and 0.2 ng mL-1 for amlodipine, benazepril and benazeprilat, respectively. The intra-day and inter-day precision and accuracy results were within the acceptable limit across all concentrations. The plasma samples were stable after four freeze-thaw cycles and being stored for 93 days at -20 degrees C. The method was applied to a pharmacokinetic study of a fixed-dose combination of amlodipine and benazepril on Chinese healthy volunteers.

Objective To evaluate the effect of Eucommia on hyperlipidemia and related indexes in rats, and provide animal data useful for the clinical experimental studies on hyperlipidemia.Methods Seventy-two healthy male SD rats were used in this study.One group of 12 rats fed with normal diet was chosen as normal control group, and other 60 rats were fed with high fat diet for two weeks to generate rat models of hyperlipidemia.48 of the hyperlipidemic model rats were taken and divided randomly into 4 groups, including model group, high dose Eucommia, moderate dose Eucommia, and low dose Eucommia groups.The last three groups were gavaged different dose of Eucommia, respectively.Druing this period, the other groups except the normal control group were fed with high fat diet continuously.The levels of serum TC, TG, LDL-C, and HDL-C of rats were measured on day 30 and 45.Results The serum levels of TC and LDL-C of the rats in the model group were obviously higher than those in the normal control group.The rat models of hyperlipidemia were established successfully.The three dose groups had a tendency of lowing blood lipid after 30 days.At 45 days, the levels of serum TC and LDL-C in the low and high dose groups were lower than those in the model group (P<0.01, P<0.05), (P<0.01, P<0.01).TG in the high, moderate and low dose groups were lower than that in the model group (P<0.01, P<0.01, P<0.01), but the level of the serum HDL-C was not significantly lower than that in the model group (P>0.05, P>0.05, P>0.05).Conclusions Eucommia in a dose of 0.43 g/kg, 0.86 g/kg and 1.71 g/kg administered for 30 days have a tendency to reduce the level of serum TC, TG, and LDL-C.When Eucommia is administered in a dose of 0.43 g/kg, 1.71g/kg and 3.42 g/kg for 45 days, it shows an adjuvant hypolipidemic effect.