Synthesis and Antioxidant Activity of (E) ω-Formylcamphene-Based Thiazole Hydrazone Derivatives

(E) ω-formylcamphene was synthesized from α-pinene, the main component of turpentine, and then reacted with thiosemicarbazide to obtain (E) ω-formylcamphene thiosemicarbazide 3, which was reacted with 14 α-bromoacetophenone compounds to obtain 14 (E) ω-formylcamphene thiazole hydrazone compounds 5a–5n; the yields were all above 80%. The structures of the target compounds were characterized by IR, 1H-NMR, 13C-NMR, and HR-MS analyses. Then, 500, 250, 125, 62.5, and 31.25 mg/L drug solutions were prepared. Free radical scavenging experiments of 1, 1-diphenyl-2-picrylhydrazyl (DPPH) and 2, 2-bis (3-ethyl-benzothiazole-6-sulfonic acid) diammonium salt (ABTS) were carried out with Trolox and L-ascorbic acid as the control samples. The scavenging rates of 14 compounds for DPPH and ABTS free radicals were obtained; the IC50 values of scavenging free radicals were fitted using SPSS software. The results show that 14 (E) ω-formylcamphene-based thiazole hydrazone compounds exhibited good scavenging effects on the two free radicals, especially when the concentration of the drug solution was 125 and 62.5 mg/L; most compounds exceeded the scavenging efficiency of Trolox and L-ascorbic acid.