Phenylaminojuglone AJ-2

Phenylaminojuglone AJ-2 is a nitric oxide synthase inhibitor that can interact with soluble guanylate cyclase, β-adrenergic receptors, CaV1.2 calcium channels, KV channels, and KCa channels. It blocks extracellular Ca2+ influx, regulates the NO−sGC−cGMP signaling pathway activity, and inhibits both pharmacological and electromechanical contraction of smooth muscle. Phenylaminojuglone AJ-2 is utilized in studies related to intestinal spasms.

Phenylaminojuglone AJ-2 exhibits high affinity binding to M2, M3, β2, β3, nitric oxide synthase, guanylate cyclase, and Ca v 1.2 L-type voltage-gated calcium channels, with binding energies ranging from -8.3 to -10.0 kcal·mol⁻¹. At concentrations of 10⁻⁸ to 10⁻⁴ M, administered at 3-minute intervals, it induces strong, concentration-dependent relaxation of isolated rat ileum smooth muscle, achieving an 87.7% relaxation rate and an AUC₀₋ₜ of 303.6 at 10⁻⁴ M. When applied sequentially after stable contraction induced by acetylcholine (ACh) or potassium chloride (KCl), it significantly relaxes pre-contracted smooth muscle, with relaxation rates of 77.9% (AUC₀₋ₜ 346.6) and 107.7±5.3% (AUC₀₋ₜ 392.1±17.7 arbitrary units), respectively, at 10⁻⁴ M. Preincubation with 10⁻⁵ to 10⁻⁴ M concentrations for 20 minutes results in concentration-dependent inhibition of ACh-induced and KCl-induced contractions, reducing the contraction amplitude to 64.0±12.1% (AUC₀₋ₜ 164.1±27.6) and 34.0±2.7% (AUC₀₋ₜ 78.6±8.5 arbitrary units) at 10⁻⁴ M. The relaxation effect, partly mediated by β-adrenergic receptors and the NO-sGC-cGMP signaling pathway, is reduced in the presence of propranolol, L-NAME, and methylene blue. Additionally, the activation of K Ca and K V potassium channels mediates relaxation, as demonstrated by decreased relaxation and AUC₀₋ₜ in the presence of TEA and 4-AP. Involvement of the inhibition of extracellular calcium influx through Ca v 1.2 L-type voltage-gated calcium channels was evidenced by reduced relaxation in the presence of verapamil and reduced contraction in a calcium-free solution with CaCl₂ induction.