Cudina Olivera, Janković Ivana, Comor Mirjana, Vladimirov Sote
Institute of Pharmaceutical Chemistry and Drug Analysis, Faculty of Pharmacy, Vojvode Stepe 450, P.O. Box 146, 11000 Belgrade, Serbia and Montenegro.
J Colloid Interface Sci. 2006 Sep 15;301(2):692-6. doi: 10.1016/j.jcis.2006.05.025. Epub 2006 May 16.
In this study, the interaction of the anion of quinapril (QUIN), angiotensin converting enzyme (ACE) inhibitor, with cationic surfactant cetyltrimethylammonium bromide (CTAB) was investigated. The effect of cationic micelles on the spectroscopic and acid-base properties of QUIN was studied at pH 8. The binding of QUIN anion to CTAB micelles implied a shift in drug acidity constant (pK(a)(water)-pK(a)(micelle)=1.39) proving the great affinity of negatively charged QUIN ion for the positively charged CTAB micelle surface. The strong dependence of the partition coefficient K(x) on QUIN concentration, obtained by using pseudo-phase model, is consistent with an adsorption-like phenomenon. From the dependence of differential absorbance at lambda=272 nm on CTAB concentration, by using mathematical model that treats the solubilization of QUIN anion as its binding to specific sites in the micelles (Langmuir adsorption isotherm), the binding constant K(b)=(2.3+/-0.4)x10(3) mol(-1)dm(3) was obtained. QUIN-CTAB binding constant was also calculated from micellar liquid chromatography (MLC) and this method was found to be not accurate enough for its determination.
在本研究中，对血管紧张素转换酶（ACE）抑制剂喹那普利（QUIN）的阴离子与阳离子表面活性剂十六烷基三甲基溴化铵（CTAB）之间的相互作用进行了研究。在pH值为8的条件下，研究了阳离子胶束对QUIN光谱和酸碱性质的影响。QUIN阴离子与CTAB胶束的结合意味着药物酸度常数发生了变化（pK(a)(水)-pK(a)(胶束)=1.39），这证明带负电荷的QUIN离子对带正电荷的CTAB胶束表面具有很强的亲和力。通过使用假相模型得到的分配系数K(x)对QUIN浓度的强烈依赖性与类似吸附的现象一致。根据在λ = 272 nm处的微分吸光度对CTAB浓度的依赖性，采用将QUIN阴离子的增溶视为其与胶束中特定位点结合的数学模型（朗缪尔吸附等温线），得到结合常数K(b) = (2.3 ± 0.4)×10³ mol⁻¹ dm³。还通过胶束液相色谱法（MLC）计算了QUIN - CTAB结合常数，发现该方法用于其测定时不够准确。
