The Wall-Bound Phenolics of Chinese Water Chestnut (Eleocharisdulcis)

Abstract

Chinese water chestnut (CWC) is a vegetable in which the edible storage parenchyma exhibits thermal stability to texture. This property has been attributed to the presence of large quantities of simple phenolics which exhibit pH-dependent autofluorescence. The identities of the major phenolic components were assessed by reverse-phase HPLC after sequentially extracting them with increasing strengths of alkali from purified CWC cell wall material. The levels of cold-alkali-liberated phenolics were very high (12.2 mg g -1 cell wall material). Ferulic acid dominated the monomeric phenol fraction (7.2 mg g -1 ), although small quantities of aldehydes were also released. A number of different diferulic acids were also identified, of which the 8-0-4'-linked form was the major component (2.8 mg g -1 ), with 8,5'-diferulic acid and the familiar 5,5'-form also present in smaller quantities (910 and 988 μg g -1 , respectively). Hence, approximately 40% of the ferulic acid in the wall was present as dimers which are potentially available to form extensive, heat-resistant cross-links between polysaccharides within the wall, and between cells.