Besides ferulate dimers, higher oligomers of ferulic acid such as trimers and tetramers were previously demonstrated to occur in plant cell walls. This paper reports the identification of two new triferulic acids. 8-O-4/8-5(cyclic)-triferulic acid was synthesized from ethyl ferulate under oxidative conditions using copper(II)–tetramethylethylenediamine [CuCl(OH)–TMEDA] as a catalyst, whereas 8-8(cyclic)/5-5-triferulic acid was isolated (preparative size exclusion chromatography, reversed-phase HPLC) from saponified insoluble maize fiber. Structures of both trimers were unambiguously elucidated by high-resolution LC-ToF-MS/MS and one- (¹H) and two-dimensional (HSQC, HMBC, COSY, NOESY) NMR spectroscopy. The newly described trimers were identified by LC-MS/MS in alkaline hydrolysates of insoluble fibers from maize, wheat, and sugar beet, indicating that ferulic acid cross-links between cell wall polymers are more diverse than previously recognized. Saponification experiments also suggest that the newly identified 8-O-4/8-5(cyclic)-triferulic acid is the naturally occurring precursor of the previously identified 8-O-4/8-5(noncyclic)-triferulic acid in plant cell walls.

中文翻译：

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鉴定天然存在于单子叶和双子叶植物细胞壁中的8-O-4 / 8-5（环）-和8-8（环）/ 5-5-偶合的脱氢三铁酸

除阿魏酸二聚体外，先前已证明在植物细胞壁中存在阿魏酸的高级低聚物，如三聚体和四聚体。本文报道了两种新的三阿魏酸的鉴定。以铜（II）-四甲基乙二胺[CuCl（OH）-TMEDA]为催化剂，由阿魏酸乙酯在氧化条件下合成了8-O-4 / 8-5（环）-三阿魏酸，而8-8（环）/从皂化的不溶性玉米纤维中分离出5-5-三铁酸（制备尺寸排阻色谱法，反相HPLC）。高分辨率LC-ToF-MS / MS和一种（（¹H）和二维（HSQC，HMBC，COSY，NOESY）NMR光谱。通过LC-MS / MS在来自玉米，小麦和甜菜的不溶性纤维的碱性水解物中鉴定了新描述的三聚体，表明细胞壁聚合物之间的阿魏酸交联比以前所认识的要多样化。皂化实验还表明，新发现的8-O-4 / 8-5（环状）-三阿魏酸是植物细胞中先前发现的8-O-4 / 8-5（非环状）-三阿魏酸的天然前体。墙壁。