Screening eco-friendliness tire antioxidants alternatives: functional 2,2,4-trimethyl-1,2-dihydroquinoline derivatives design and toxicity evaluation

Antioxidants which are indispensable functional additives used in rubber tires, are released into aquatic habitats from tire wear particles (TWP), collected in water bodies, and threaten the aquatic ecosystem. This study aimed to design eco-friendly derivatives of 2,2,4-trimethyl-1,2-dihydroquinoline (TMQ) with increased antioxidant activity to use as tire antioxidants. Initially, seventy highly efficient derivatives of TMQ were designed by hydroxylation modifications at multiple sites. The antioxidant activity of hydroxyl derivatives was characterized based on DFT method and compared with TMQ. Twenty derivatives showing a significant (greater than 9%) increase in antioxidant activity compared to TMQ were selected for the next stage. The toxicity risk of these twenty TMQ derivatives was assessed using various toxicokinetic methods. Finally, six TMQ derivatives with significantly lower toxicity risk compared to that of TMQ were evaluated for potential developmental toxicity. They were characterized using molecular docking and molecular dynamics techniques to assess the developmental toxicity risk in silver salmon by absorption of their ROO·, HO·, O 2 · – and O 3 derivatives. TMQ-6 and TMQ-48 showed the lowest toxicity among all TMQ derivatives by a rather large margin. The study throws light on the path of future endeavors to develop highly efficient and greener tire antioxidants.