In Vitro Safety Evaluation of Caffeic Acid

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Phenolic compounds are abundant in the Brazilian plant kingdom and they are part of a large and complex group of organic substances. Cinnamic acids are part of this group of organic compounds, and caffeic acid is one of its representatives. Besides exhibiting a powerful antioxidant activity, increasing the collagen production and preventing the premature aging, caffeic acid has demonstrated antimicrobial activity and may be promising in the treatment of dermal diseases. One of the applications of caffeic acid is in emulsions, which are known to be widely used by consumers for pleasant and refreshing sensory, although few studies have reported the efficacy and safety of these products on the skin. The relevance of this study is based on evidence and to clarify the cytotoxic potential of this substance through preliminary studies in vitro. The cytotoxicity evaluation was carried out using the MTT method (3- (4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide), a colorimetric assay which determines the amount of insoluble violet crystals formed by the reduction of MTT in the mitochondria of living cells. A dose versus response curve was constructed, and it was possible to use the equation to determine the IC50 of caffeic acid or the product concentration needed to cause 50% lethality of the cells. The results are promising since caffeic acid concentration that promoted 50% toxicity in HepG2 cells (IC50=781.8 µg/mL) is approximately 330 to 400 times greater than the concentration required to inhibit 50% of DPPH (IC50 DPPH= 2.39 µg/mL) and ABTS (IC50 ABTS= 1.96 µg/mL) radicals scavenging activity, respectively. The maximum concentration of caffeic acid tested (1140 mg /mL) did not reach 50% of cell death in HaCat cells. Thus, it was concluded that the caffeic acid does not cause toxicity in HepG2 and HaCat cells in the concentrations required to promote antioxidant activity in vitro, and it can be applied in topical products.