Kinetics of Non-Enzymatic Synthesis of Dipeptide Cbz-Phe-Leu with AOT Reversed Micelles

The non-enzymatic synthesis of N-benzyloxycarbonyl-L-phenylalanyl-L-leucine (Cbz-Phe-Leu) from lipophilic N-benzyloxycarbonyl-L-phenylalanine (Cbz-Phe) and hydrophilic L-leucine (Leu), by N, N’-dicyclohexylcarbodiimide (DCC) as a condensing agent, was carried out using a reversed micellar system composed of bis(2-ethylhexyl) sodium sulfosuccinate (AOT) as a surfactant and isooctane. We successfully synthesized Cbz-Phe-Leu in a short time and investigated the effects of its operational conditions, the DCC concentration, w0, and the pH on the kinetic parameters and the maximum yields. For dipeptide synthesis, we had to add an excess of DCC with the substrates because of the side reactions of Cbz-Phe. From the pH dependency of the reactivity, a partially cationic form of Leu was better for a synthesis reaction because of the enrichment of Leu at the interface by anionic AOT. The optimum water content on the dipeptide synthesis was w0 = 28 due to the competition of the peptide synthesis and the side reactions. The maximum yield of Cbz-Phe-Leu was 0.565 at 80 h under optimum experimental conditions.

UV-Vis Spectrophotomertic Investigation of β-Carotene and Morin in Presence of AOT/Ethanol System

The precise measurements of β-carotene and morin absorbance in the presence of surfactant/ethanol at 25°C by UV-vis technique are reported. The surfactant used in the study was sodium bis(2-ethylhexyl) sulfosuccinate (Aerosol-OT or AOT) and the solvent was ethanol. For the system AOT/ethanol/β-carotene, surfactant concentration varied from 0.002 to 0.23 [mol/kg]; whereas in case of AOT/ethanol/morin system, it was between 0.001 and 0.25[mol/kg]. In all cases during UV- vis measurements β-carotene concentration was 0.0018[mol/kg] and morin concentration was 0.0094[mol/kg]. In UV-vis experiment, β-carotene or morin absorbance was measured as a function of surfactant concentration. Assuming the solute distribution between solvent and the AOT reversed micelles according to Nernstian law, the results were analysed with the help of a Non Linear Regression Procedure, in which a β-carotene and morin binding constants and distribution constants were obtained. Computed data indicate that in case of β-carotene the location of the molecules might not only in palisade layer of AOT reversed micelles but also in the interior whereas in case of morin, the only possible location seems to be the AOT palisade layer.

Determination of rhodamine B in lipsticks by high performance liquid chromatography after extraction with AOT reversed micelles

In this study, we investigated the possibility of reverse micelles which were used for the determination of rhodamine B in lipsticks followed by high performance liquid chromatography (HPLC).