Phenylaminojuglones were synthesized under solvent-free conditions via silica gel-mediated aza-Michael addition between juglone and substituted anilines, namely, aniline, 4-methoxyaniline, and 3,4,5-trimethoxyaniline. Among the synthesized derivatives, phenylaminojuglone (AJ-2) exhibited the most potent spasmolytic activity on rat ileal smooth muscle. Molecular docking studies revealed that AJ-2 exhibits potential binding affinities with multiple targets implicated in smooth muscle contraction, including muscarinic receptors, β-adrenergic receptors, nitric oxide synthase, guanylate cyclase, and the CaV1.2 calcium channel. Absorption, distribution, metabolism, excretion, and toxicity predictions indicated that AJ-2, AJ-8, and AJ-11 comply with Lipinski's rule of five and do not present major predicted toxicity liabilities, supporting their pharmacological viability. Functional assays demonstrated that AJ-2 significantly inhibited both pharmacomechanical (ACh-induced) and electromechanical (KCl-induced) contractions. Mechanistic studies suggested that its relaxant effects might be mediated by the activation of β-adrenergic receptors, the NO-sGC-cGMP signaling pathway, and the opening of KV and KCa channels. AJ-2 also inhibited extracellular Ca2+ influx, as shown by its interaction with verapamil and attenuation of CaCl2-induced contractions. These findings support AJ-2 as a promising multifunctional spasmolytic agent derived from green chemistry principles and highlight the pharmacological relevance of phenylaminojuglones as novel modulators of the intestinal smooth muscle tone.
Benites et al. (Fri,) studied this question.