Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2006
Publication Date: 6/12/2006
Citation: Funk, C., Grabber, J.H., Weber, P., Thilker, J., Steinhart, H., Bunzell, M. 2006. Influence of lignin on the adsorption of hetero-cyclic aromatic amines by insoluble fiber. Dietary Fibre 2006, Multifunctional complex of Components, June 12-14, 2006, Helsink, Finland. 2006 CDROM.
Technical Abstract: The prevention of colon cancer by dietary fiber is widely discussed. One possible mechanism is by adsorbing carcinogens and transporting them out of the body. It was shown that several model dietary fibers are able to adsorb heterocyclic aromatic amines (HAAs), a group of carcinogens mostly found in heated, protein-rich food. These adsorption studies suggest that lignin might be an effective in-vitro adsorber. However, due to the complex composition of the investigated dietary fibers concrete conclusions about lignins' adsorption abilities are difficult. The aim of this study was to clearly delineate how lignin concentration in the fiber and lignin composition influences the adsorption of HAAs. Therefore, artificially lignified maize cell walls, so called dehydrogenation polymer (DHP)-cell walls, were synthesised. They showed a comparable protein-polysaccharide matrix, but had various, defined lignin concentrations (5 - 20 % Klason lignin) and various, defined lignin compositions (e.g. varying guaiacyl-syringyl-ratios). In-vitro adsorption studies were carried out by incubating DHP-cell walls with various HAAs (MeIQx, IQ, PhIP or A_C) under conditions simulating the small intestine. Adsorption rates of HAAs were determined by quantifying non-adsorbed HAAs by HPLC-UV. The adsorption studies showed that lignified fiber is an effective adsorber for the more hydrophobic HAAs PhIP and A_C. However, the influence of lignin on the adsorption of the hydrophobic HAAs MeIQx and IQ was rather poor. Both, lignin concentration and composition affected adsorption rates. Adsorption of HAAs generally increased with higher lignin deposition into the cell walls. PhIP and A_C were better adsorbed by guaiacyl-rich DHP-cell wall complexes compared to syringyl rich DHP walls. Studies with DHP-cells walls incorporating other minor 4-hydroxyphenylpropanoids further indicated an influence of the lignin composition on HAA adsorption. Finally, the studies showed that HAAs were not only adsorbed by lignin; considerable amounts were also adsorbed by the nonlignified cell wall matrix.