Sanguinarine (1) and chelerythrine (2) are two quaternary benzo[c]phenanthridine alkaloids (QBAs). Eighteen derivatives of 1 and 2 were synthesized by modification of C=N+ bond and evaluated for their in vitro acaricidal activity against Psoroptes cuniculi, a mange mite. A new method was developed to prepare 6-alkoxy dihydro derivatives of 1 and 2 (1a–e, 2a–e). Among all the compounds, only 6-alkoxy dihydrosanguinarines (1a–e) showed significant acaricidal activity at 5.0 mg/mL and 1a possessed the strongest activity (50% lethal concentrations (LC50)=339.70±0.75 mg/L, 50% lethal time (LT50)=6.53±0.04 h), comparable with a standard drug ivermectin (LC50=168.19±11.79 mg/L, LT50=16.54±0.11 h). The iminium moiety in 1 and 2 was proven to be the determinant for their acaricidal properties. 6-Alkoxy dihydro derivatives (1a–e, 2a–e) were prodrugs of 1 and 2. Compared with 7,8-dimethoxy groups, 7,8-methylenedioxy group was able to significantly improve the bioactivity. The present results suggested that QBAs are promising candidates or lead compounds for the development of new isoquinoline acaricidal agents.
血根碱(1)和
白屈菜红碱(2)是两种季
铵基
苯并[c]菲啶生物碱(QBAs)。通过C=N+键的修饰合成了1和2的18个衍
生物,并评估了它们对兔耳螨(Psoroptes cuniculi)的体外杀螨活性。开发了一种新方法制备1和2的6-烷氧基二氢衍
生物(1a–e,2a–e)。在所有化合物中,只有6-烷氧基二氢
血根碱(1a–e)在5.0 mg/mL浓度下显示出显著的杀螨活性,其中1a具有最强的活性(50%致死浓度(LC50)=339.70±0.75 mg/L,50%致死时间(LT50)=6.53±0.04 h),与标准药物伊维菌素(LC50=168.19±11.79 mg/L,LT50=16.54±0.11 h)相当。1和2中的
亚胺基团被证实是其杀螨活性的决定因素。6-烷氧基二氢衍
生物(1a–e,2a–e)是1和2的前药。与7,8-二甲氧基相比,7,8-甲基二氧基能显著提高
生物活性。现有结果表明,QBAs是有前景的候选化合物或开发新型
异喹啉杀螨剂的先导化合物。