Laboratorio de Técnicas Instrumentales, Seccion Departamental de Quimica Analitica, Facultad de Farmacia, Universidad Complutense de Madrid, 28040 Madrid, Spain.
Talanta. 2003 Jun 13;60(2-3):493-503. doi: 10.1016/S0039-9140(03)00066-3.
The association characteristics of the inclusion complexes of the beta-carboline alkaloids harmane and harmine with beta-cyclodextrin (beta-CD) and chemically modified beta-cyclodextrins such as hydroxypropyl-beta-cyclodextrin (HPbeta-CD), 2,3-di-O-methyl-beta-cyclodextrin (DMbeta-CD) and 2,3,6-tri-O-methyl-beta-cyclodextrin (TMbeta-CD) are described. The association constants vary from 112 for harmine/DMbeta-CD to 418 for harmane/HPbeta-CD. The magnitude of the interactions between the host and the guest molecules depends on the chemical and geometrical characteristics of the guest molecules and therefore the association constants vary for the different cyclodextrin complexes. The steric hindrance is higher in the case of harmine due to the presence of methoxy group on the beta-carboline ring. The association obtained for the harmane complexes is stronger than the one observed for harmine complexes except in the case of harmine/TMbeta-CD. Important differences in the association constants were observed depending on the experimental variable used in the calculations (absolute value of fluorescence intensity or the ratio between the fluorescence intensities corresponding to the neutral and cationic forms). When fluorescence intensity values were considered, the association constants were higher than when the ratio of the emission intensity for the cationic and neutral species was used. These differences are a consequence of the co-existence of acid-base equilibria in the ground and in excited states together with the complexation equilibria. The existence of a proton transfer reaction in the excited states of harmane or harmine implies the need for the experimental dialysis procedure for separation of the complexes from free harmane or harmine. Such methodology allows quantitative results for stoichiometry determinations to be obtained, which show the existence of both 1:1 and 1:2 beta-carboline alkaloid:CD complexes with different solubility properties.
β-咔啉生物碱哈尔满和哈尔明与β-环糊精（β-CD）以及化学修饰的β-环糊精（如羟丙基-β-环糊精（HPβ-CD）、2,3-二-O-甲基-β-环糊精（DMβ-CD）和 2,3,6-三-O-甲基-β-环糊精（TMβ-CD））的包合特性进行了描述。结合常数从哈尔明/ DMβ-CD 的 112 变化到哈尔满/ HPβ-CD 的 418。主体和客体分子之间的相互作用的大小取决于客体分子的化学和几何特征，因此不同环糊精配合物的结合常数也不同。由于β-咔啉环上存在甲氧基，哈尔明的空间位阻较大。除了哈尔明/TMβ-CD 外，哈尔满复合物的结合比哈尔明复合物更强。在计算中使用的实验变量（荧光强度的绝对值或中性和阳离子形式对应的荧光强度比）不同时，观察到结合常数有很大差异。当考虑荧光强度值时，结合常数高于使用阳离子和中性物种的发射强度比时的结合常数。这些差异是由于在基态和激发态中同时存在酸碱平衡以及配合物平衡的结果。哈尔满或哈尔明的激发态中存在质子转移反应意味着需要进行实验透析程序以将配合物与游离的哈尔满或哈尔明分离。这种方法允许获得用于确定化学计量的定量结果，这些结果表明存在具有不同溶解度性质的 1:1 和 1:2 β-咔啉生物碱：CD 配合物。
