Humic acids are known for their overall positive health and productivity effects in animal feeding trials and, controversially, as an aetiological factor of
cancer. We tried to assess the in vitro effect of
humic acids from a selected source in Slovakia when used at recommended prophylactic dosage. We investigated
antioxidant properties, enzymatic and non-enzymatic
antioxidant defence system in liver mitochondria and cultured
cancer cell lines in vitro. We observed a significant decrease in
superoxide dismutase activity after
humic acids treatment irrespective of dissolving in
dimethyl sulphoxide or direct addition to mitochondria
suspension in a respiration medium. Activities of other
antioxidant enzymes measured, such as
glutathione peroxidase and
glutathione reductase, showed no significant differences from the control as well as the
reduced glutathione content. Percentage of inhibition by
humic acids of
superoxide radical indicated lower efficacy compared with that of
hydroxyl radical. Survival of six different
cancer cells lines indicated that only the acute T lymphoblastic leukaemia cell line was sensitive to the tested
humic acids. Despite relatively low solubility in aqueous solutions,
humic acids from the selected source participated in redox regulation. By recapturing the radicals,
humic acids reloaded the
antioxidant defensive mechanism. Results from in vitro study conducted with
humic acids from the natural source showed potential of these substances as promising immunity enhancing agents.