PEAT HUMIC ACIDS – PROSPECTIVE BIOLOGICALLY ACTIVE SUBSTANCES WITH ANTIOXIDANT ACTIVITY FOR THE DEVELOPMENT OF PROTECTIVE AGENTS

Abstract

A present study was carried out to investigate the antioxidant activity (AOA) of humic acids (HA) isolated by sodium hydroxide and sodium pyrophosphate from nine peat species of the Tomsk region different by botanical composition, degree of decomposition and ash content. All HA samples had shown the AOA in the study. As the results of four research methods, it was found that HAs are highly effective in inhibiting the free ABTS•+ radical cation, superoxide anion radical O2-•, hydroxyl radical HO•, and are able to bind Fe2+ in a wide range of concentrations. The activity of HAs in different tests was not equal between samples; HAs isolated by sodium hydroxide have had a higher AOA in inhibition of the superoxide anion–radical O2-• in the model reaction compared to HAs isolated by sodium pyrophosphate within the same peat species. In the study of iron binding activity, an inverse relationship was observed. In the model reactions of the free ABTS•+ radical cation and the hydroxyl radical HO• inhibition, a comparable level of activity was registered between the HA samples isolated by different solutions. Such an uneven distribution of the activity between various HA samples can be explained by the unequal chemical parameters of their structure, which depend on their origin and method of isolation. Using of such classical antioxidants with an established mechanism of action as comparison drugs, as a water-soluble analogue of tocopherol - "Trolox", a water-soluble antioxidant – ascorbic acid, a classic chelator – ethylenediaminetetraacetic acid (EDTA), a classic trap of a hydroxyl radical – mannitol, it is possible to conclude that the investigated HAs are effective antioxidants belonging to the groups of proton donors and complexing agents.