A Test of the Melanoidin Hypothesis: ABSTRACT

Abstract

Marine and terrestrial humic acids are thought to differ in structural composition owing to differences in precursors and formation pathways. It has been proposed that marine humic acids are formed by the polymerization of sugars and amino acids (the melanoidin pathway) while terrestrial humic acids result primarily from the condensation of lignin-derived phenols and amino acids. In this study, four marine and three terrestrial humic acids have been isolated, and a series of polymers have been made by the reaction of either glucose or catechol with alanine or ammonia. Chemical and spectroscopic measurements of the natural and synthetic polymers have been made, including elemental analysis, carbon isotope ratios and IR, UV-visible, UV-fluorescence, and ESR scans. In additi n, degradative analyses of marine and terrestrial humic acids together with the synthetic polymers have been performed to determine (1) if characteristic structural differences exist between marine and terrestrial humic acids and (2) if similarities between the degradative products of synthetic and natural polymers reflect biologic precursors and reaction pathways. End_of_Article - Last_Page 704------------