Hjelmeland Anna K, Zweigenbaum Jerry, Ebeler Susan E
Department of Viticulture and Enology, University of California, Davis, Davis, CA, 95616, USA; Food Safety and Measurement Facility, University of California, Davis, Davis, CA, 95616, USA.
Agilent Technologies, Inc., Wilmington, DE, 19808, USA.
Anal Chim Acta. 2015 Aug 5;887:138-147. doi: 10.1016/j.aca.2015.06.026. Epub 2015 Aug 11.
In this work we present a novel approach for the identification of plant metabolites using ultrahigh performance liquid chromatography coupled to accurate mass time-of-flight mass spectrometry. The workflow involves developing an in-house compound database consisting of exact masses of previously identified as well as putative compounds. The database is used to screen accurate mass spectrometry (MS) data to identify possible compound matches. Subsequent tandem MS data is acquired for possible matches and used for structural elucidation. The methodology is applied to profile monoterpene glycosides in Vitis vinifera cv. Muscat of Alexandria grape berries over three developmental stages. Monoterpenes are a subclass of terpenes, the largest class of plant secondary metabolites, and are found in two major forms in the plant, "bound" to one or more sugar moieties or "free" of said sugar moieties. In the free form, monoterpenes are noted for their fragrance and play important roles in plant defense and as attractants for pollinators. However, glycoconjugation renders these compounds odorless, and it is this form that the plant uses for monoterpene storage. In order to gain insight into monoterpene biochemistry and their fate in the plant an analysis of intact glycosides is essential. Eighteen monoterpene glycosides were identified including a monoterpene trisaccharide glycoside, which is tentatively identified here for this first time in any plant. Additionally, while previous studies have identified monoterpene malonylated glucosides in other grapevine tissue, we tentatively identify them for the first time in grape berries. This analytical approach can be readily applied to other plants and the workflow approach can also be used for other classes of compounds. This approach, in general, provides researchers with data to support the identification of putative compounds, which is especially useful when no standard is available.
在这项工作中，我们提出了一种使用超高效液相色谱与精确质量飞行时间质谱联用技术来鉴定植物代谢物的新方法。该工作流程包括开发一个内部化合物数据库，其中包含先前鉴定出的以及推测的化合物的精确质量。该数据库用于筛选精确质量质谱（MS）数据，以识别可能匹配的化合物。随后，对可能的匹配物获取串联MS数据，并用于结构解析。该方法应用于分析亚历山大麝香葡萄（Vitis vinifera cv. Muscat of Alexandria）浆果在三个发育阶段的单萜糖苷。单萜是萜类化合物的一个亚类，萜类是植物次生代谢物中最大的一类，在植物中以两种主要形式存在，“结合”到一个或多个糖部分上，或者“游离”于所述糖部分。以游离形式存在时，单萜因其香味而闻名，在植物防御中发挥重要作用，并作为传粉者的引诱剂。然而，糖基化结合使这些化合物无味，而植物正是以这种形式储存单萜。为了深入了解单萜生物化学及其在植物中的命运，对完整糖苷的分析至关重要。鉴定出了18种单萜糖苷，包括一种单萜三糖糖苷，这是首次在任何植物中初步鉴定到。此外，虽然先前的研究在其他葡萄组织中鉴定出了单萜丙二酰化葡萄糖苷，但我们首次在葡萄浆果中初步鉴定到它们。这种分析方法可以很容易地应用于其他植物，并且该工作流程方法也可用于其他类别的化合物。总体而言，这种方法为研究人员提供了支持推测化合物鉴定的数据，在没有标准品可用时尤其有用。
