Enantiomeric Separation of Adrenergic Amines in Citrus Species, Related Genera and Dietary Supplements by Capillary Electrophoresis

Citrus aurantium L. (Rutaceae) fruit extracts have recently been used for weight loss. Among the adrenergic amines the most important active constituent is the sympathomimetic compound synephrine and commercially available extracts are standardized for their content of this active principle. A capillary electrophoresis method was developed for the quantitative and qualitative determination of d-synephrine, l-synephrine, d-octopamine, l-octopamine, tyramine, n-methyl tyramine and hordenine. The electrophoretic separation was performed using a 75 cm × 50 µm ID (66.5 cm effective length) fused silica capillary. The samples were injected by pressure for 5s at 50 mbar and the running voltage was 30 kV at the injector end of the capillary. The method developed was successively applied to the determination of the adrenergic amines in dietary supplements, in various Citrus species including Citrus aurantium, jams and juices. Synephrine was the main component and present in the levels from 0.02–0.17% in various Citrus species and 0.42–69.28 mg in dietary supplements claiming to contain Citrus aurantium. Parameters affecting the resolution between (+) and (−)-enantiomers, such as pH, cyclodextrin concentration, temperature, organic modifier, buffer concentration and capillary dimensions were reported.     

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

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.     

Determination of bitter orange alkaloids in dietary supplement Standard Reference Materials by liquid chromatography with atmospheric-pressure ionization mass spectrometry

A liquid chromatographic atmospheric-pressure ionization electrospray mass spectrometry (LC–API–ES–MS) method has been developed for the determination of five bitter orange alkaloids (synephrine, octopamine, n-methyltyramine, tyramine, and hordenine) in bitter orange-containing dietary supplement standard reference materials (SRMs). The materials represent a variety of natural, extracted, and processed sample matrices. Two extraction techniques were evaluated: pressurized-fluid extraction (PFE) and sonication extraction. The influence of different solvents, extraction temperatures, and pH were investigated for a plant material and a processed sample. The LC method uses a new approach for the separation of highly polar alkaloids. A fluorinated, silica-based stationary phase separated the five alkaloids and the internal standard terbutaline in less than 20 min. This method enabled the determination of the dominant alkaloid synephrine and other minor alkaloids in a variety of dietary supplement SRMs.     

流动注射双安培法测定辛弗林

基于辛弗林在经预阳极化的铂电极上的催化氧化和不可逆电对的双安培检测原理,建立了流动注射双安培直接检测辛弗林的电化学分析新方法.本法使用经过恒电位预阳极化处理的双铂电极,在外加电位差为0 V时,通过偶合辛弗林在一支电极上的氧化和氧化铂在另一支电极上的还原两个不可逆电极过程,构成流动注射双安培检测体系.实验发现,在pH=10.88的BR缓冲溶液中,测得氧化电流与辛弗林浓度在6.0×10-6～1.0×10-3 mol/L范围内呈良好的线性关系(r=0.9990,n=8).检出限为2.0×10-6 mol/L.连续20次测定5.0×10-4 mol/L辛弗林,电流值的相对标准偏差(RSD)为2.2%.方法用于香砂养胃丸中辛弗林含量的测定,结果满意.     

Rapid simultaneous determination of amines and organic acids in citrus using high-performance liquid chromatography

Rapid analytical method for the simultaneous separation and determination of amines and organic acids is a vital interest for quality control of citrus and their products. In the present study, a simultaneous high performance liquid chromatography (HPLC) method for the rapid separation of three amines and two organic acids was developed. Chromatographic separation of compounds was achieved using Xbridge C₁₈ column at ambient temperature, with an isocratic mobile phase of 3 mM phosphoric acid at a flow rate of 1.0 mL min⁻¹. A photodiode array (PDA) detector was used to monitor the eluent at 223 nm and 254 nm with a total analysis time of 10 min. Extraction of amines and organic acids from citrus juice was optimized. The method was validated by tests of linearity, recovery, precision and ruggedness. The limit of detection (LOD) and limit of quantification (LOQ) for amines and ascorbic acid were determined to be 5 ng and 9.8 ng, respectively. All calibration curves showed good linearity (R² ≥ 0.9999) within the test ranges. The recoveries of the amines and organic acids ranged between 84% and 117%. The identity of each peak was confirmed by mass spectral (MS) analysis. The developed method was successfully applied to analyze the content of amines and organic acids in six different species and two varieties of citrus. Results indicate that mandarin and Marrs sweet orange contain high level of amines, while pummelo and Rio Red grapefruit had high content of ascorbic acid (137-251 μg mL⁻¹) and citric acid (5-22 mg mL⁻¹). Synephrine was the major amine present in Clementine (114 μg mL⁻¹) and Marrs sweet orange (85 μg mL⁻¹). To the best of our knowledge, this is the first report on simultaneous separation and quantification of amines and organic acids in Marrs sweet orange, Meyer lemon, Nova tangerine, Clementine, Ugli tangelo and Wekiwa tangelo.     

毛细管电泳电化学检测法测定中药枳实和枳壳中的辛弗林和3种黄酮

采用毛细管电泳电化学检测法同时测定了枳实和枳壳中的辛弗林和3种黄酮即橙皮甙、柚皮素和柚皮甙的含量。考察了工作电极的氧化电位、分离电压和进样时间,运行缓冲的浓度和pH值对分离和检测的影响。在优化条件下,以300μm直径的碳圆盘电极为检测电极,检测电位为 0.85 V(vs.SCE),在80 mmol/L硼酸盐(pH 8.45)的运行缓冲液中,被测物浓度与峰电流在3个数量级范围内呈良好线性,检出限(S/N=3)在1×10-4~5×10-4g/L之间,该法简单、可靠、快速,单次测定可在20 m in内完成,已经成功应用于实际样品枳实和枳壳中4组分的测定,样品处理简单,无须预富集,检测结果令人满意。     

超高效液相色谱-串联质谱测定减肥保健食品中辛弗林及其电喷雾质谱裂解途径研究

建立了测定减肥保健食品中辛氟林的超高效液相色谱-串联质谱分析方法。不同类型减肥保健食品经超声提取,固相萃取净化后,以ACQUITY UPLC BEH HILIC色谱柱分离,采用多反应监测正离子模式检测,监测离子对为m/z168/150和m/z168/135,定量离子对为m/z168/150。结果表明,辛氟林在0.03～50μg/L的范围内与其峰面积呈良好的线性关系,相关系数为0.9990。在低、中、高3个添加水平范围内的平均回收率为80.3%～98.4%。同时研究了辛弗林的电喷雾电离串联质谱特征,推测其裂解途径。该方法准确、灵敏度高、操作简便,可用于不同减肥保健食品中辛弗林的检测。     

毛细管电泳法测定中药艾叶中的脱氧肾上腺素和柚皮素

采用毛细管区带电泳法测定了艾叶中的辛弗林和柚皮素。在30mmol／L Na2B4O7缓冲溶液（pH10．00）的条件下,实现了被测组分的有效分离。为中药艾叶的质量控制提供了新的方法。