Hartman N R, Jardine I
Biomed Environ Mass Spectrom. 1986 Jul;13(7):362-72. doi: 10.1002/bms.1200130708.
Cyclosporine (CsA, mol. wt 1202) is a cyclic undecapeptide with potent immunosuppressive properties which have made it extremely useful for preventing the rejection of transplanted organs. The drug has severe side-effects, however, which may be related to its metabolism. Sensitive methods to determine the structure of metabolites of CsA have, therefore, been developed using mass spectrometric techniques. First, the molecular weight of the metabolite is determined using fast atom bombardment mass spectrometry or thermospray liquid chromatography/mass spectrometry. The metabolite is then hydrolysed to its component amino acids, which are esterified and acylated and identified by gas chromatography/mass spectrometry. To distinguish metabolism at the four identical N-methyl leucines, the metabolite is partially hydrolysed, the resulting peptides are derivatized to the trimethylsilyl-polyamino alcohols, and these in turn are analysed by gas chromatography/mass spectrometry. These procedures have been used to determine the structure of metabolites of CsA isolated from rabbit bile. The determination of the structure of one metabolite carboxylated on the eta-carbon of amino acid 1, and of one metabolite hydroxylated on the eta-carbon of amino acid 1 and on the gamma-carbon of N-methyl leucine 9 is presented. These procedures should be generally useful for the structural analysis of microgram amounts of CsA metabolites and analogs.
环孢素（CsA，分子量1202）是一种具有强大免疫抑制特性的环状十一肽，这使其在预防移植器官排斥方面极为有用。然而，该药物有严重的副作用，这可能与其代谢有关。因此，已采用质谱技术开发出灵敏的方法来确定CsA代谢物的结构。首先，使用快原子轰击质谱法或热喷雾液相色谱/质谱法测定代谢物的分子量。然后将代谢物水解为其组成氨基酸，将这些氨基酸酯化和酰化，并通过气相色谱/质谱法进行鉴定。为了区分在四个相同的N-甲基亮氨酸处的代谢情况，将代谢物部分水解，将所得肽衍生化为三甲基硅烷基-多氨基醇，然后依次通过气相色谱/质谱法进行分析。这些方法已用于确定从兔胆汁中分离出的CsA代谢物的结构。本文介绍了一种在氨基酸1的η-碳上羧化的代谢物以及一种在氨基酸1的η-碳和N-甲基亮氨酸9的γ-碳上羟基化的代谢物的结构测定。这些方法通常应有助于对微克量的CsA代谢物和类似物进行结构分析。
