Metabolic disposition in rats of regular and enzymatically depolymerized sodium carboxymethylcellulose

Partially enzyme-hydrolysed sodium carboxymethylcellulose (CMC-ENZ), which holds promise as a new, functional food ingredient, is obtained from sodium carboxymethylcellulose (CMC) by enzymatic hydrolysis with a cellulase preparation from Trichoderma longibrachiatum. In the safety evaluation of CMC-ENZ, a comparative disposition study on 14C-labelled CMC and CMC-ENZ was conducted in conventionally kept rats. The 14C label was in the two C atoms of the carboxymethyl group. Two groups of four male and four female rats each were fed diets with 5% unlabelled CMC or CMC-ENZ for a 2-wk adaptation period. A single oral dose of 14C-CMC or 14C-CMC-ENZ solution was then given by gavage (500 mg/kg body weight). Respiratory CO2, urine and faeces were collected at regular intervals, and after 120 hr organs, tissues and the carcass were sampled as well. For both experimental groups, total mean recovery of 14C was 98%, about 95% of the label being excreted with the faeces, 2% or less in the urine, 1% or less with CO2 and a small fraction being retained in the body (CMC, 0.58%; CMC-ENZ, 0.75%). Tissue retention of 14C was highest in the liver of rats of both experimental groups. Only about 49 and 65% of the faecal 14C was extracted with water in the 14C-CMC and 14C-CMC-ENZ dosed rats, respectively. Gel permeation chromatography (GPC) of the dosing solutions and the faecal extracts revealed that CMC is depolymerized during intestinal passage whereas CMC-ENZ is excreted nearly unchanged. Consequently, the molecular weight distribution of the 14C-CMC and 14C-CMC-ENZ faecal excretion products was similar. It is concluded that there is no toxicologically relevant difference between the disposition of CMC and CMC-ENZ.