Antispasmodic activity of a series of cyclic imides (phthalimides) derivatives

This study aimed to evaluate the potential antispasmodic activity of 15 cyclic imides, focusing on their effects on muscarinic receptor-mediated contractions and smooth muscle relaxation in isolated rat jejunum. The compounds were tested in vitro, with rats jejunal segments pre-contracted using acetylcholine to assess relaxant activity, and during acetylcholine-induced contractions to evaluate their inhibitory effects. Structural variations among the compounds included modifications in aromatic substituents, electronegativity, and steric hindrance, which were analyzed for their impact on biological activity. The in silico analysis of overall profiles, which balanced efficacy prediction and safety, identified compounds 09, 12, 14, and possibly 01-04 as particularly promising. All tested compounds demonstrated smooth muscle relaxant activity in pre-contracted jejunal segments. Notably, compounds 01, 02, 03, 04, 06, 13, and 15 significantly inhibited acetylcholine-induced contractions. Structural analysis revealed that electronegative groups such as nitro and sulfur or bulky aromatic substituents contributed to enhanced antispasmodic effects, potentially due to increased interaction with muscarinic receptors. These findings align with literature suggesting phthalimide derivatives may modulate muscarinic receptors through allosteric or direct binding mechanisms. The results suggest that specific structural features of cyclic imides influence their antispasmodic efficacy, possibly via interactions with muscarinic receptors. These findings provide valuable insights into the design of novel therapeutic agents targeting smooth muscle disorders, emphasizing the relevance of structural optimization for enhanced pharmacological activity.