STUDIES ON PECTIC SUBSTANCES FROM DIETARY FIBER SOURCES. PART I. IDENTIFICATION OF CAPROLACTAM METABOLITES. PART II. (CABBAGE, CARROT, APPLE, ORANGE PEEL)

Pectic substances were isolated from four dietary fiber sources (cabbage, carrot, apple, and orange peel) using mild methods for sample preparation and polysaccharide isolation. The pectic polysaccharides extracted from the four fiber sources with cyclohexanediaminetetraacetic acid (CDTA) contained 77 to 87 mole % of uronic acid.;Further fractionation by DEAE-cellulose chromatography of the precipitated complexes yielded a galacturonan containing 91 to 96 mole % uronic acid with minor amounts of arabinose and galactose. This galacturonan may exist independently within these plant cell walls not covalently bound to rhamnogalacturonan. Carbohydrate composition was determined for all fractions and degree of esterification is reported for acidic fractions.;In a separate study, the metabolites of caprolactam excreted in the urine by the rat were investigated. Four ninhydrin-positive components were noted in the amino acid profile from the basic column of an amino acid analyzer. Three of these were identified as 6-aminohexanoic acid, the hydrolysis product of caprolactam, 6-amino-4-hydroxyhexanoic acid, and 6-amino-1,4-caprolactone. The two hydroxylated metabolites formed an equilibrium mixture. The structural identity of these components was confirmed by comparison of chromatographic and spectroscopic properties of the urine-derived samples with synthetic 6-amino-1,4-caprolactone.;A galacturonan fraction containing 82 to 92 mole % uronic acid was precipitated from the CDTA extracts with ytterbium acetate at pH 6.8 and room temperature. The ytterbium selectively precipitated galacturonans of low degree of esterification.