Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/21/2005
Publication Date: 2/4/2006
Citation: Funk, C., Weber, P., Thilker, J., Grabber, J.H., Steinhart, H., Bunzel, M. 2006. Influence of lignification and feruloylation of maize cell walls on the adsorption of heterocyclic aromatic amines. Journal of Agricultural and Food Chemistry. 54:1860-1867. Interpretive Summary: Dietary fiber is thought to protect against colorectal and possibly other forms of cancer by adsorbing carcinogens and transporting them out of the body. Fiber it is composed primarily of polysaccharides (polymers of sugar molecules) cemented together with a polymer known as lignin. Many types of fiber also contains ferulates, small molecules that knit polysaccharides together in fiber. The aim of our study was to clearly delineate how lignin and ferulates affect the adsorption of carcinogens found in protein rich-foods like meat or fish. Using conditions that mimic the small intestine, we measured the absorption of four carcinogens to nonlignified corn (Zea mays L.) fiber with varying ferulate levels and to corn fiber containing various types and quantities of lignin. Nonlignified fiber adsorbed moderate quantities of carcinogens. Variations in ferulate concentrations had no effect on carcinogen adsorption. Incorporating lignin into fiber enhanced the adsorption of carcinogens, especially types that have low solubility in water. The chemical makeup of lignin also influenced the binding of some types of carcinogens. This study provides the best evidence to date that fiber, particularly lignified fiber, is effective for binding carcinogens found in protein rich foods. Additional research of this type may reveal strategies for using dietary fiber as a means of reducing the risk of cancer in humans.
Technical Abstract: Both epidemiological and experimental data indicate that a diet rich in fiber may reduce cancer risk. One possible mechanism is by adsorbing carcinogens and transporting them out of the body without metabolic activation. We investigated the role of fiber lignification and feruloylation on the adsorption of four of the most relevant heterocyclic aromatic amines in food: 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and 2-amino-9H-pyrido[2,3-b]indole (A_C). Adsorption experiments, under conditions mimicking the small intestine, were carried out using nonlignified and artificially lignified primary maize walls with defined lignin and ferulate/diferulate concentrations and defined lignin compositions. Lignin concentration and composition both influenced the adsorption of heterocyclic aromatic amines, especially the more hydrophobic types. Heterocyclic aromatic amine adsorption increased with lignin concentration. 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine and 2-amino-9H-pyrido[2,3-b]indole were better adsorbed by guaiacyl-rich lignins, 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline by syringyl-rich lignins, whereas the adsorption of 2-amino-3-methylimidazo[4,5-f]quinoline was not clearly influenced by lignin composition. Nonlignified cell walls adsorbed lesser amounts of heterocyclic aromatic amines. Variations in cell wall feruloylation had no effect on heterocyclic aromatic amine adsorption.