Differentiation of volatile aromatic isomers and structural elucidation of volatile compounds in essential oils by combination of HPLC separation and crystalline sponge method
Differentiation of volatile aromatic isomers and structural elucidation of volatile compounds in essential oils by combination of HPLC separation and crystalline sponge method
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HPLC分离与结晶海绵法相结合区分挥发性芳香异构体并解析精油中挥发性化合物的结构
DOI：
10.1016/j.chroma.2016.10.072
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发表时间：
2016-11-25
影响因子：
4.1
通讯作者：
Di, Bin
中科院分区：
文献类型：
--
作者：
Gu, Xiao-Fei;Zhao, Yue;Di, Bin
由于挥发性芳香族异构体具有相似的结构和相似的极性，即使借助质谱和核磁共振（NMR）光谱等多种光谱技术，在痕量水平上对其进行结构解析也一直被认为是一项难以捉摸的任务。单晶x射线衍射（SCD）被认为是最强大的结构解析技术之一。最近开发的结晶海绵方法克服了SCD的固有限制，即目标分子必须是单晶，可以分析非结晶和微量化合物，而无需任何特殊处理。为了探讨结晶海绵法是否可以用于密切相关的异构体或其他挥发性甚至油性化合物在复杂混合物中痕量水平的结构解析，我们将高效液相色谱分离与结晶海绵法结合进行x射线晶体学分析。本文首先用高效液相色谱法分离出asarone顺式/反式异构体、carvacrol和百里香酚位置异构体两对挥发性芳香异构体，并将其包封到结晶海绵中，并用x射线晶体学分析对其进行鉴定。通过x射线晶体学直接观察这些挥发性化合物，只使用微克量，没有结晶或衍生化。在没有参考标准的情况下，实现了这些化合物的明确鉴定。该策略提供了一个有前景的平台，能够提供密切相关的异构体以及其他挥发性甚至油性化合物在微克级复杂混合物中的高可信度详细结构信息。(C) 2016 Elsevier B.V.版权所有
Structure elucidation of volatile aromatic isomers at trace level has long been considered as an elusive task, due to their structural similarities and similar polarities, even with the aid of many spectroscopic techniques such as mass spectrometry and nuclear magnetic resonance (NMR) spectroscopy. Single crystal X-ray diffraction (SCD) is recognized as one of the most powerful structural elucidation techniques. The recently developed crystalline sponge method overcomes the intrinsic limitation of SCD that the target molecules must be single crystals, being able to analyze non-crystalline and trace-amount compounds without any special treatment. In order to investigate whether the crystalline sponge method could be used for the structure elucidation of closely related isomers or other volatile and even oily compounds in complex mixtures at trace level, we combined HPLC separation with the crystalline sponge method for X-ray crystallographic analysis. In this paper, two pairs of volatile aromatic isomers including cis/trans isomers of asarone and positional isomers of carvacrol and thymol, as well as the main volatile component in essential oil extracted from Acorus Tatarinowii, were first isolated by HPLC and encapsulated into the crystalline sponge then elucidated by X-ray crystallographic analysis. Direct observation of these volatile compounds by X-ray crystallography was achieved using only microgram quantities without crystallization or derivatization. Unambiguous identification of these compounds was realized without reference standards. This strategy offers a promising platform capable of providing high-confidence detailed structural information of closely related isomers as well as other volatile and even oily compounds in complex mixtures in microgram quantities. (C) 2016 Elsevier B.V. All rights reserved.