Non-enzymatic oxidation of the new cardiotonic agent denopamine and its derivatives: Comparison with enzymatic oxidation.
作者:TOSHIKAZU SUZUKI、YOSHIMASA HASHIMURA、SHIGEYUKI TAKEYAMA
DOI:10.1248/cpb.33.3859
日期:——
Chemical oxidation of the positive inotropic agent denopamine, (-)-(R)-1-(p-hydroxyphenyl)-2-[(3, 4-dimethoxyphenethyl) amino] ethanol, and its derivatives by Udenfriend's model system for enzymatic oxidation was studied. The oxidation products were separated and identified by gas chromatography-mass spectrometry and high-performance liquid chromatography. All the metabolites of denopamine produced by enzymatic oxidation were also formed in Udenfriend's system. However, compared to enzymatic oxidation, the chemical oxidation was less selective as to the position of demethylation : i.e., although enzymatic 4'-O-demethylation took place overwhelmingly in preference to 3'-O-demethylation, comparable amounts of the two demethylated isomers were produced in Udenfriend's system. It was also found that the chemical oxidation was more powerful than the enzymatic oxidation because hydroxylation at the ortho or para position to the methoxy group took place in all the substrates tested, while such metabolites have not been detected in biological systems. As in the enzymatic system, tetrahydroisoquinoline-type compounds were formed from substrates in which the hydroxy group was attached at the meta position of the benzene ring. This is presumably a result of Pictet-Spengler-type condensation with formaldehyde generated in the reaction mixture.
研究了正性肌力药地诺帕明、(-)-(R)-1-(对羟基苯基)-2-[(3, 4-二甲氧基苯乙基)氨基]乙醇及其衍生物在 Udenfriend 酶促氧化模型系统中的化学氧化作用。氧化产物通过气相色谱-质谱法和高效液相色谱法进行分离和鉴定。酶法氧化产生的所有地诺帕明代谢物在 Udenfriend 系统中也有形成。不过,与酶促氧化法相比,化学氧化法对去甲基化位置的选择性较低:也就是说,虽然酶促 4'-O- 去甲基化比 3'-O- 去甲基化更占优势,但在 Udenfriend 体系中产生的两种去甲基化异构体的数量相当。研究还发现,化学氧化作用比酶法氧化作用更强,因为在所有测试的底物中,甲氧基的正位或对位都发生了羟基化反应,而在生物系统中还没有检测到这种代谢物。在酶系统中,羟基连接在苯环元位置的底物会形成四氢异喹啉类化合物。这可能是与反应混合物中产生的甲醛进行 Pictet-Spengler 型缩合的结果。