Day S T, Crouthamel W G, Martinelli L C, Ma J K
J Pharm Sci. 1978 Nov;67(11):1518-23. doi: 10.1002/jps.2600671107.
Tetracycline complexation with calcium and organic ligands was studied using fluorescence, circular dichroism, and solvent extraction methods. The results were used to interpret the mechanism of the commonly used fluorometric methods for the analysis of tetracycline in biological fluids. Tetracycline formed ternary calcium complexes with barbital sodium and L-tryptophan in alkaline solutions. The circular dichroism studies indicate that the calcium ion in these complexes is bound to the C-4 dimethylamino and the C-12a hydroxyl groups of tetracycline. These ternary complexes are strongly fluorescent and can be extracted easily into 1-butanol or ethyl acetate. Based on the characteristics of the ternary complexes and of the tetracycline degradation products, it is concluded that only the active form of tetracycline can be complexed and extracted for fluorescence analysis.
采用荧光、圆二色性和溶剂萃取法研究了四环素与钙及有机配体的络合作用。这些结果用于解释生物流体中四环素分析常用荧光法的作用机制。四环素在碱性溶液中与巴比妥钠和L-色氨酸形成三元钙络合物。圆二色性研究表明，这些络合物中的钙离子与四环素的C-4二甲氨基和C-12a羟基结合。这些三元络合物具有强烈的荧光，并且可以很容易地萃取到正丁醇或乙酸乙酯中。基于三元络合物和四环素降解产物的特性，得出结论：只有四环素的活性形式才能被络合和萃取用于荧光分析。
