Waterstraat Martin, Bunzel Mirko
Department of Food Chemistry and Phytochemistry, Institute of Applied Biosciences, Karlsruhe Institute of Technology, Karlsruhe, Germany.
Front Chem. 2018 Jun 8;6:190. doi: 10.3389/fchem.2018.00190. eCollection 2018.
Ferulate-mediated cross-linking of plant cell wall polymers has various implications on the quality of plant based food products, forage digestibility, and biomass utilization. Besides dehydrodiferulic acids (DFA), dehydrotriferulic acids (TriFA) gained increasing interest over the past two decades, because they potentially cross-link up to three polymers. Here, we describe a separation strategy to obtain several TriFA as analytical standard compounds from a reaction mixture after radical coupling of ethyl ferulate. By using silica flash chromatography, Sephadex LH-20 chromatography, and reversed phase HPLC, six known TriFA as well as three previously unidentified ferulic acid trimers were obtained, and their structures were characterized by mass spectrometry and NMR spectroscopy (H, HSQC, COSY, HMBC, and NOESY). The novel trimers were identified as 5-5/8-8(cyclic)-, 8-8(noncyclic)/8-O-4-, and, tentatively, 5-5/8-8(noncyclic)-TriFA. Natural occurrence of these TriFA in plant cell walls was demonstrated by LC-MS/MS analyses of alkaline cell wall hydrolyzates.
阿魏酸介导的植物细胞壁聚合物交联对植物性食品质量、饲料消化率和生物质利用具有多种影响。除了脱氢二阿魏酸（DFA），在过去二十年中，脱氢三阿魏酸（TriFA）越来越受到关注，因为它们可能交联多达三种聚合物。在此，我们描述了一种分离策略，用于从阿魏酸乙酯自由基偶联后的反应混合物中获得几种TriFA作为分析标准化合物。通过使用硅胶快速色谱法、葡聚糖凝胶LH-20色谱法和反相高效液相色谱法，获得了六种已知的TriFA以及三种先前未鉴定的阿魏酸三聚体，并通过质谱和核磁共振光谱（H、HSQC、COSY、HMBC和NOESY）对其结构进行了表征。新型三聚体被鉴定为5-5/8-8（环状）-、8-8（非环状）/8-O-4-，以及初步鉴定的5-5/8-8（非环状）-TriFA。通过对碱性细胞壁水解产物的LC-MS/MS分析证明了这些TriFA在植物细胞壁中的天然存在。
