Integrated study of toxicity, antitumor potential and biochemical changes induced by melatonin in <i>Nauphoeta cinerea</i>

Oxidative stress denotes an imbalance between the production of reactive oxygen species (ROS) and the body's ability to neutralise them effectively. These ROS play a direct role in pathophysiological mechanisms and have been linked to a wide range of diseases. Therefore, this study evaluated the biochemical effects and toxicity of melatonin in <i>Nauphoeta cinerea</i>, focusing on its antioxidant properties and potential toxicological risks. Melatonin was applied to the third abdominal segment of <i>N. cinerea</i>, and after 24 h, biochemical assays were performed following toxicity monitoring and <i>in silico</i> analyses of toxicity, biological interaction and antitumor. Melatonin exhibited dose-dependent toxicity, with notable effects on hepatotoxicity, neurotoxicity, respiratory toxicity, immunotoxicity, and ecotoxicity. It also demonstrated potential endocrine-disrupting activity and interactions with hepatic enzymes. <i>In addition,</i> it demonstrated selective cytotoxicity against several tumour cell lines, particularly pulmonary and uterine adenocarcinomas, while displaying minimal toxicity to normal gastric cells. Despite its low activity in the DPPH assay, melatonin influenced oxidative stress markers <i>in vivo</i>, reducing malondialdehyde levels and altering iron and protein thiol concentrations (500 μg/mL), indicating a complex role in oxidative metabolism. These findings suggest the potential of melatonin as an antitumor agent but also highlight the need for caution due to its toxicological profile in application to the abdomen of <i>N. cinerea</i>.