Uptake of Heterocyclic Aromatic Amine by Insoluble Dietary Fiber in Artificial Gastric and Intestinal Juice

ABSTRACT

Objectives: The purpose of the present in vitro study was to predict to what extent dietary fiber (DF) takes up heterocyclic aromatic amine (HAA) and how DF acts to intercept HAAs in vivo. Methods: The sorption isotherms of 2-amino-3-methyl-3H-imidazo[4,5-f]quinoline (IQ), 2-amino-3,4-dimethyl-3H-imidazo[4,5-f]quinoline (MeIQ), 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole acetate (Trp-P-1), and 3-amino-1-methyl-5H-pyrido[4,3-b]indole acetate (Trp-P-2) for DF were measured in artificial intestinal juice (AIJ) and artificial gastric juice (AGJ) at 37°C. The desorption of HAA from DF was measured in AGJ and AIJ. Results: The sorption isotherms were statistically classified into four types. The percentage of Trp-Ps taken up by carboxymethylated cellulose (CMC) and agar in AGJ (pH, 1.2) was 52-56% and 58-78%, respectively. On the other hand, the percentage of Trp-Ps taken up by CMC and agar in AIJ (pH, 6.8) was 97-98% and 87-89%, respectively. The percentage of IQ and MeIQ sorbed by CMC was 21-27% in AGJ and 100% in AIJ. Collagen and chitin did not remove any HAAs in AGJ, but removed 4-69% in AIJ. In the four-component solution, the percentage of HAA taken up by DF was almost the same or significantly increased, with a few exceptions, as compared with that in the one-component solution. Conclusion: The results indicated that MeIQ is mainly held on the surface of CMC in AIJ, and that Trp-P-1 and Trp-P-2 are mainly held in the interior of agar in AGJ and AIJ. The results on sorption-desorption in vitro indicate that sorbed HAAs in the stomach are held more firmly by agar than by CMC while DF passes through the human intestinal tract. CMC and agar would be expected to be more useful than collagen and chitin as agents intercepting HAAs.