title: Determination of angiotensin converting enzyme inhibitory activity by high-performance liquid chromatography/electrospray-mass spectrometry.
abstract: A sensitive and rapid method for determination of angiotensin converting enzyme (ACE) inhibitory activity was developed based on a combination of enzymatic reaction followed by high performance liquid chromatography/electrospray-mass spectrometry (HPLC-ESI-MS) determination of its product. The most commonly used substrate hippuryl-histidyl-leucine (HHL) or hippuryl-glycyl-glycine (HGG) hydrolysis catalyzed by purified rabbit lung ACE or human plasma ACE was investigated in the presence of benazeprilat. The incubation time was 8 min for purified lung ACE, and 16 min for human plasma ACE. The produced hippuric acid (HA) was separated from substrate HHL or HGG by HPLC on a C(18) column with isocratic elution within 6.5 min, and quantified by electrospray ionization mass spectrometry (ESI-MS) with p-phthalic acid as an internal standard (IS). The limit of detection of HA was 6.0 ng/ml. HHL or HGG hydrolysis catalyzed by purified lung ACE displayed excellent accuracy and reproducibility. The small total reaction volume, the low concentration of substrate, and the simple treating procedures present the advantages of the new method. Furthermore, the total time of the whole procedure for one sample with the novel method is less than 1/2 of that of the conventional HPLC or spectrophotometry method, while the accuracy and the precision of the new method are almost the same as the conventional HPLC method with UV detection.
authors.affiliation: Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research, Ministry of Education, Hunan Normal University, Changsha 410081, PR China.
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Xiao
authors.forename: Xubiao
authors.initials: X
authors.lastname: Luo
authors.forename: Bo
authors.initials: B
authors.lastname: Chen
authors.forename: Shouzhuo
authors.initials: S
authors.lastname: Yao
mesh_terms: D000806:Angiotensin-Converting Enzyme Inhibitors / Q000032:analysis*; D000818:Animals; D002138:Calibration; D002384:Catalysis; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D006801:Humans; D006868:Hydrolysis; D007703:Peptidyl-Dipeptidase A / Q000378:metabolism; D011817:Rabbits; D012015:Reference Standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D007703:Peptidyl-Dipeptidase A