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United States Department of Agriculture

Agricultural Research Service

Title: Disinapic Acids-Natural Products Or Artifacts?

Authors
item Bunzel, Mirko - UNIV. HAMBURG, GERMANY
item Ralph, John
item Kim, Hoon - UNIV. WISCONSIN-MADISON
item Steinhart, Hans - UNIV. HAMBURG, GERMANY

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: September 5, 2002
Publication Date: N/A

Technical Abstract: Considerable quantities of cell-wall-bound hydroxycinnamic acids exist in cereal grains. Ferulic acid plays a large role in the cross-linking of cell wall polysaccharides, influencing the physiochemical characteristics of fiber. Cell-wall-bound sinapic acid is also found in some grains, but no cell-wall-bound disinapates analogous to the diferulates have been previously identified. In 1969 Thomasidioic acid was identified in aqueous extract from the wood of Ulmus thomasii coffin. Thomasidioic acid is an 8-8´-linked cyclic disinapic acid, a product that can arise from radical coupling. In recent investigations, however, it has been shown that Thomasidioic acid can derive from sinapic acid during the extraction process. After alkaline hydrolysis of different grain fibers, two 8,8´-linked disinapic acids were provisionally identified by GC-MS. Syntheses of the assumed products were developed. Through comparison of the retention times and mass spectra with which the synthetic substances, the 8,8´-linked disinapic acids were identified as Thomasidioic acid (cyclic form) and a non-cyclic 8,8´-dehydrodimer (8,8´-DSAnc). To elucidate whether the identified dimers were natural products present in the fiber or extraction artifacts, we carried out the isolations analogously from free sinapic acid, sinapate esters, and a polysaccharide matrix. Under the same conditions, even with unrealistically large quantities of added sinapic acid, only traces of Thomasidioic acid and no 8,8´-DSAnc were observed. The investigations suggest that disinapates cross-link cell wall, and that they are probably formed analogously to diferulates.

Last Modified: 4/16/2014
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