Abstract
It has been suggested that marine humic and fulvic acids are formed by a condensation of sugars with amino acids or proteins via Maillard reaction. In order to investigate this hypothesis a series of melanoidins were synthesised under laboratory conditions and their structure compared with natural humic acids. An extensive collaborative research programme on the chemical and physical properties of natural and synthetic humic substances has been undertaken using spectroscopic (IR, UV,
13C-CP/MAS NMR, ESR), chromatographic (GC and GC/MS), thermogravimetric (TG, DTG, TG-EGD-MS), pyrolytic (stepwise, Rock Eval, Curie point) oxidative (KMnO
4) and isotopic methods. The results indicate that various heterocyclic moieties are the main building blocks of humic substances rather than aromatic benzenoid structures. It seems possible that significant portions of humics of Lake Haruna (Japan) as well as of Lake Hula (Israel) are composed of melanoidins and/or pseudomelanoidins. The extent of this contribution has not yet been determined.