Study on the racemization of synephrine by off-column chiral high-performance liquid chromatography

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• 作者：Federica Pellati ; Giuseppe Cannazza ; Stefania Benvenuti
• 关键词：Citrus aurantium ; Phenethylamine alkaloids ; Synephrine ; Enantiomer ; Racemization ; Chiral-CBH
• 刊名：Journal of Chromatography A
• 出版年：2010
• 出版时间：21 May 2010
• 年：2010
• 卷：1217
• 期：21
• 页码：3503-3510
• 全文大小：548 K

文摘

In this study, the racemization kinetic parameters of R-(−)-synephrine, the active phenethylamine alkaloid of Citrus aurantium L., were determined by means of an off-column HPLC method. Enantioseparation was carried out in different buffer solutions and solvents on a chiral stationary phase (CSP) with cellobiohydrolase as the chiral selector (Chiral-CBH, 100 mm × 4.0 mm i.d., 5 μm). The mobile phase was 10 mM sodium phosphate buffer (pH 6.0)-2-propanol (95:5, w/w), with 50 μM disodium EDTA, at 0.8 mL/min. The column was thermostatted at 20 °C and detection was set at 225 nm. The influence of pH value, ionic strength, temperature and addition of organic modifier on the rate constant, the half-life of racemization and the free energy barrier of racemization of R-(−)-synephrine were determined. Among the different chemical and physical parameters evaluated as affecting the racemization of naturally occurring R-(−)-synephrine, pH, temperature and addition of an organic co-solvent appear to have the strongest effect, while ionic strength does not exert a significant influence on the racemization rate. The results of the present study indicated that synephrine racemization is possible at high temperature at both acidic and basic pH values; therefore, the extraction procedure of R-(−)-synephrine from the plant material should be carried out under specific conditions to preserve the stereochemical integrity and the biological activity of this secondary metabolite.