Tryptophan browning products

A stirred solution of mono-A-Boc-l,5-pentanediamine (6.3 mmol) and D,L-tryptophan (7.0 mmol) in 30 ml THF was treated with dicyclohexylcarbodiimide (7.5 mmol) at ambient temperature and stirred 1 hour. The mixture was filtered, concentrated, and warm diethyl ether added to the residue. Upon cooling, crystallization occurred and the product isolated as a light brown powder, mp = 97-98°C. 

In our investigation on the effect of Maillard reaction products on the absorption of tryptophan (36), the kinetics of the absorption of tryptophan in the presence of Maillard reaction products formed in the glucose-tryptophan system was studied by bott vitro everted gut sac method and vivo catherization of the portal vein. Fructose-L-tryptophan (Amadori compound) appeared to be the major fraction of the reaction products when fractionated using a cellulose column eluted by water-saturated n-butanol. The absorption of L-tryptophan was partially inhibited vitro and vivo by fructose-L-tryptophan in a competitive manner with an inhibitor constant (Ki) of l.lmM. The relative absorption rate of L-tryptophan was significantly lower in the presence of the Maillard reaction products than in the presence of fructose-L-tryptophan indicating the presence of other inhibitory factors in the reaction products. The in vivo absorption of fructose-L-tryptophan was almost negligible compared to that of tryptophan. The inhibited absorption by Maillard reaction products, may have contributed in part to an incomplete recovery in the growth of the rats when fed a supplemented browned synthetic amino acid diet. 

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