(-)-Catechin in cocoa and chocolate: Occurence and analysis of an atypical flavan-3-ol enantiomer
(-)-Catechin in cocoa and chocolate: Occurence and analysis of an atypical flavan-3-ol enantiomer
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DOI：
10.3390/12071274
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发表时间：
2007-07-01
期刊：
影响因子：
4.6
通讯作者：
Galensa, Rudolf
中科院分区：
文献类型：
--
作者：
Kofink, Michael;Papagiannopoulos, Menelaos;Galensa, Rudolf
可可含有高水平的不同类黄酮。采用毛细管电泳法对可可及可可制品中的儿茶素和表儿茶素进行了手性分离。儿茶素和表儿茶素对映体的基线分离是通过使用0.1mol中心点L-1硼酸盐缓冲液（PH8.5），12 mmol中心点L-1（2-羟丙基）-γ-环糊精作为手性选择剂，具有50 cm有效长度（75 μ mI.D.）的熔融石英毛细管，+18 kV施加电压，20 ℃的温度和280 nm处的直接UV检测。为了避免其他类似物质的共迁移或共洗脱，采用聚酰胺固相萃取和LC-MS分析对黄烷-3-醇进行分离和纯化。正如预期的那样，我们在未发酵、干燥、未烘焙的可可豆中发现了（-）-表儿茶素和（+）-儿茶素。相比之下，烘烤的可可豆和可可产品还含有非典型的黄烷-3-醇（-）-儿茶素。这通常是在生产过程中通过差向异构化形成的，将（-）-表儿茶素转化为其差向异构体（-）-儿茶素。可可豆烘焙过程中的高温，特别是可可粉的碱化是诱导差向异构化反应的主要因素。除了可可和可可产品的分析之外，还计算了峰值比率，以便更好地区分可可产品。
Cocoa contains high levels of different flavonoids. In the present study, the enantioseparation of catechin and epicatechin in cocoa and cocoa products by chiral capillary electrophoresis (CCE) was performed. A baseline separation of the catechin and epicatechin enantiomers was achieved by using 0.1 mol center dot L-1 borate buffer (PH 8.5) with 12 mmol center dot L-1 (2-hydroxypropyl)-gamma-cyclodextrin as chiral selector, a fused-silica capillary with 50 cm effective length (75 mu m I.D.), +18 kV applied voltage, a temperature of 20 degrees C and direct UV detection at 280 nm. To avoid comigration or coelution of other similar substances, the flavan-3-ols were isolated and purified using polyamide-solid-phase-extraction and LC-MS analysis. As expected, we found (-)-epicatechin and (+)-catechin in unfermented, dried, unroasted cocoa beans. In contrast, roasted cocoa beans and cocoa products additionally contained the atypical flavan-3-ol (-)-catechin. This is generally formed during the manufacturing process by an epimerization which converts (-)-epicatechin to its epimer (-)-catechin. High temperatures during the cocoa bean roasting process and particularly the alkalization of the cocoa powder are the main factors inducing the epimerization reaction. In addition to the analysis of cocoa and cocoa products, peak ratios were calculated for a better differentiation of the cocoa products.