Research on the Toxic Effects on Human Cells of Natural Melanogenic Substance Ellagic Acid in Reservoirs of Eucalyptus Forest Area

Water sources used for rural residential water in reservoirs of the southern Eucalyptus forest area are clearly exposed to natural melanogens such as tannins, ellagic acid and other polyhydroxyphenolic compounds and their iron salt complexes during autumn and winter, making it necessary to evaluate the effect of natural melanogens on human health. In this study, by simulating the natural melanogenic substances from reservoir waters in southern Eucalyptus forests with different concentrations of ellagic acid, trivalent iron were used to evaluate the general cytotoxicity, intracellular reactive oxygen species (ROS) levels, and cellular morphological changes after exposing to ellagic acid (EA) and/or trivalent iron (Fe³⁺) on colorectal adenocarcinoma epithelial cells (DLD1) , hepatocytes (LO2) , and human renal epithelial cells (293T) . The results showed cytotoxicity in most cases under both individual and combined exposure conditions. Cell viability was significantly reduced in the higher concentration of EA (1 mg/L, 10 mg/L) combined with 1 μmol/L Fe³⁺ treatment group, which was more toxic than EA exposure alone. The cell viability of LO2 and 293T cells did not change significantly in the combined exposure group, but they were decreased when compared with that of Fe³⁺ exposure alone. The results of oxidative stress assays found that both EA and/or Fe³⁺ exposure significantly increased ROS levels compared with DMSO controls. The ROS results for DLD1, LO2 may suggest that co-exposure had a greater effect on intracellular ROS secretion than when EA was exposed alone. In addition, no significant changes of cell morphology were observed in all treated groups, but the expression of actin F-actin in LO2 was significantly inhibited. The results of this study indicate that ellagic acid and trivalent iron exposure alone or in combination have deleterious effects on human cells, and the toxic effects in order are sorted as follows: hepatocytes (LO2) > intestinal cells (DLD1) > kidney cells (293T) . This study provided an important basis for the precise control of contaminants in southern rural water sources.