ANIMAL BIOAVAILABILITY OF A 3,4-DICHLOROANILINE LIGNIN METABOLITE FRACTION FROM WHEAT

Treatment of intact wheat plants and excised shoot tissues with [U-C-14]-3,4-dichloroaniline led to 55-65% incorporation of the radioactivity into the "insoluble" residue. A sequential solubilization procedure revealed that approximately 85% of the C-14-label was associated with the operationally defined lignin fraction. When the "insoluble' wheat metabolite residue was fed to rats and lambs, 11-20% of the bound radioactivity was released in soluble form. Refeeding the lamb fecal residue to rats released another approximately 7% of the bound radioactivity. A 3,4-dichloroaniline-lignin metabolite prepared enzymatically has previously been shown to be more extensively solubilized by rats (approximately 66%). Mild acid hydrolysis under simulated stomach conditions (0.1 N HCl, 37-degrees-C) resulted in a "burst" release of free 3,4-dichloroaniline (approximately 30%) only from the previously used lignin metabolite. The presence of 4-hydroxybenzylamine linkages in only the lignin metabolites prepared enzymatically under mild conditions is proposed to explain the different degrees of solubilization in the digestive tract of animals. Animal bioavailability results can thus strongly depend on the methods used to prepare the "bound" metabolite fraction.