Abstract
Abstract The results of studies on the physicochemical and antioxidant properties of humic acids (HAs) and hymatomelanic acids (HMAs) from brown coals of deposits in the Republic of Kazakhstan are presented. It was found that the molecular structure of HAs from coals of the Oy-Karagay and Kiyakty deposits has functional groups of carbonyl, hydroxyl, and aliphatic nature as structural elements. The test samples of coals and HAs were characterized by the occurrence of paramagnetic centers (PMCs) with the Lande spectroscopic splitting factor values above 2.00, which indicate the presence of free radicals caused by a strongly delocalized electron cloud in the molecules of coals and HAs. The results of the amperometric determination of the antioxidant properties of HMAs indicated that the HMAs exhibit antioxidant activity, which will allow them to be used as a biologically active additive in the production of pharmaceutical preparations.