Structure‐Based Assessment of the Toxicity and Cytoprotective Effects of a Series of Small Molecule Polyphenolic Compounds

Abstract

ObjectivePolyphenols are widely known to possess antioxidant and anti‐inflammatory properties, but are also capable of eliciting toxicity at higher doses. This goal of this project was to investigate whether a structure‐toxicity relationship exists among five polyphenolic compounds: trans‐cinnamic acid (tCA), p‐coumaric acid (COU), caffeic acid (CAF), resveratrol (RES), and phloretin (PHL). Each compound is relatively similar in structure, but varies in the number of phenolic groups it contains (tCA=0, COU=1, CAF=2, RES=3, PHL=4).MethodsPolyphenol toxicity was measured by determining the median lethal dose (LC50) and toxicant threshold concentration (LC1) for each compound using an in vitro mouse liver model (TAMH; transforming growth factor‐α transgenic mouse hepatocytes). TAMH cells were cultured and exposed to varying concentrations of each compound for 24‐hours followed by a test for cell viability using resazurin dye. Subsequent hepatoprotective studies based on LC1 values were then conducted by incubating TAMH cells with each polyphenol for 24 h prior to a hepatotoxic dose of diquat (18μM). Changes in cell viability were again measured using the resazurin‐based assay. Data analysis was performed using SPSS to calculate the LC50 and LC1 values for each compound. Significance was determined using one‐way analysis of variance (ANOVA) and post‐hoc Least Significant Difference tests with a fold cut‐off of p < 0.05.ResultstCA and COU were relatively non‐toxic (LC50 > 5mM) compared to the compounds with multiple phenolic groups. In fact, addition of phenolic groups directly correlated with a decrease in the LC50 value indicating that as the number of phenolic groups increased so did the toxicity for this series of compounds. For the hepatoprotection studies, significant increases in cell viability were observed across only some of the polyphenolic compounds; however, this protection did not correlate with phenolic group number.ConclusionsWhile greater toxicity was associated with an increase in the number of phenolic groups based on the LC50 determinations, no common trend was observed relating phenolic group number and hepatoprotective ability using an LC1‐based dosing regimen. Perhaps this suggests that subtle differences in the carbon skeleton among the polyphenols tested influences protective ability. Future work is currently underway to investigate the mechanistic features differentiating the degree of cytoprotection between the polyphenolic compounds.Support or Funding InformationSource of Research Support: This work was supported by the Pacific University Research Incentive Grant Program and an ASPET Summer Undergraduate Research Fellow (SURF) Individual Award.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.