Ferulic acid and diferulic acids as components of sugar-beet pectins and maize bran heteroxylans

Enzymatic hydrolysis of sugar-beet pulp, and subsequent isolation of ferulo ylated oligosaccharides, has shown that ferulic acid groups are ester-linke d mainly on O-2 of arabinose residues and on O-6 of galactose residues in t he pectin side-chains. After saponification of sugar-beet pulp enzymatic di gests, dehydrodiferulic acids (0.14%,w/w) have also been identified and cha racterised as 8-5', 5-5', 8-8' and 8-O-4' isomers, suggesting that covalent cross-linking of pectic polysaccharides through diferulic bridges occurs i n sugar-beet pulp. Feruloylated oligosaccharides from the side-chains of he teroxylans have been isolated from maize bran by acid hydrolysis. Ferulic a cid is esterified on O-5 of arabinofuranose residues. 8-8', 8-5', 8-O-4' an d 5-5' coupled dimers, which represent 2.5% (w/w) of the bran, have also be en detected. It has been calculated that, in the cell wall, each heteroxyla n macromolecule bore similar to 75 esterified ferulic acid groups and could be cross-linked through similar to 30 diferulic bridges. This result sugge sts a high degree of cross-linking of heteroxylans chains through ferulic a cid in maize bran cell walls. (C) 1999 Society of Chemical Industry.