Determination of cytotoxic doses of selected plants in human liver cells

Abstract

Background: HepG2 cells are widely used as an in vitro model for investigating alterations in hepatic cellular metabolism. Studies evaluating the biological activities of plant-derived compounds using HepG2 cells have also increased. Strawberry (Fragaria orientalis), lingonberry (Vaccinium vitis-idaea), radish (Raphanus sativus), and blue honeysuckle (Lonicera caerulea L.) contain polyphenols, flavonoids, anthocyanins, and other secondary metabolites. The biological activities of these plants may vary depending on species, plant tissue, growing conditions, and extraction methods. Prior to evaluating the biological activities of plant extracts, it is essential to assess their cytotoxic effects on cells and determine appropriate concentrations for subsequent experiments. Therefore, evaluating the effects of plant extracts on the viability of HepG2 cells, a human hepatocellular carcinoma cell line, is of considerable importance. Aim: To evaluate the effects of aqueous and ethanolic extracts of strawberry, lingonberry, radish, and cultivated and wild blue honeysuckle on HepG2 cell viability and to determine concentrations exhibiting cytotoxic effects. Materials and Methods: A total of 18 plant extracts were prepared using water and ethanol as extraction solvents. The extracts were obtained from strawberry leaves, lingonberry leaves, radish, and the fruits, stems, and leaves of cultivated and wild blue honeysuckle. The extracts were subsequently dried. HepG2 cells maintained in the Cell Biology Laboratory of the Institute of Biomedical Sciences were revived, stabilized, and used for the experiments. The plant extracts were prepared at concentrations of 6.25, 12.5, 25, 50, 100, 200, and 300 μg/mL and used to treat HepG2 cells. Cell viability was assessed using the Cell Counting Kit-8 (CCK-8) assay. Cytotoxicity was defined as a reduction in cell viability of more than 30% compared with the control group. Results: The aqueous extract of cultivated blue honeysuckle and the ethanolic extracts of its fruits and stems maintained HepG2 cell viability above 70% across the concentration range of 6.25–300 μg/mL, indicating relatively low cytotoxicity. In contrast, the ethanolic extract of cultivated blue honeysuckle leaves reduced cell viability at higher concentrations. The aqueous and ethanolic extracts of fruits and stems of wild blue honeysuckle showed no apparent cytotoxic effects, whereas both aqueous and ethanolic extracts of its leaves reduced cell viability to approximately 65% at 300 μg/mL, indicating relatively higher cytotoxicity. Most aqueous and ethanolic extracts of strawberry, radish, and lingonberry maintained cell viability above 70% and showed no cytotoxic effects. The ethanolic extract of strawberry leaves reduced cell viability to approximately 63% even at the lowest concentration of 6.25 μg/mL; however, cell viability tended to increase with increasing extract concentration. Conclusion: The effects of plant extracts on HepG2 cell viability varied depending on plant species, tissue type, extraction solvent, and concentration. Most extracts of strawberry, lingonberry, radish, and the fruits and stems of cultivated and wild blue honeysuckle exhibited relatively low cytotoxicity at concentrations ranging from 6.25 to 300 μg/mL. However, the ethanolic extract of cultivated blue honeysuckle leaves at 200 μg/mL and the aqueous and ethanolic extracts of wild blue honeysuckle leaves at 300 μg/mL reduced cell viability by more than 30%, indicating relatively higher cytotoxicity.