Antiproliferative and Cytotoxic Effects of Schinus terebinthifolia Leaf Extract on Thyroid Follicular Cells

Schinus terebinthifolia Raddi, Anacardiaceae, is a Brazilian plant species, with anti-inflammatory and healing properties. This plant is popularly used for the treatment of several disorders, including thyroid dysfunctions. However, its influence on thyroid physiology is not fully understood. This study investigated the effects of a S. terebinthifolia leaf methanolic extract on the proliferation, viability, and reactive oxygen species (ROS) level of rat thyroid follicular cells. For this, PCCL3 cells were treated with different concentrations of the extract (1–100 μg/ml) and times of exposure (24, 48, and 72 h). The 30 μg/ml concentration significantly reduced cell viability. Thyrocytes treated with the extract presented altered cell morphologies and evidence of oxidative stress. The 50 μg/ml concentration of the extract elicited a pronounced increase in ROS level. The results demonstrated that S. terebinthifolia leaf is harmful to thyroid cells after exposure to high concentrations for prolonged periods. These potentially harmful effects should be considered when this medicinal plant is used in humans. This observation is particularly relevant to individuals with an increased risk of thyroid dysfunctions.