Anti-inflammatory efficacy and relevant SAR investigations of novel chiral pyrazolo isoquinoline derivatives: Design, synthesis, in-vitro, in-vivo, and computational studies targeting iNOS

Abstract

Isoquinoline alkaloids are a rich source of multimodal agents with distinctive structural specificity and various pharmacological activities. In the present report, we propose a combination of design, synthesis, computational study, primary in-vitro screening using the lipopolysaccharide (LPS)-induced RAW 264.7 cell line, and in-vivo evaluation in mice models as a novel approach to speed up anti-inflammatory drugs discovery. The nitric oxide (NO) inhibitory effect of new compounds revealed that all of them displayed the potent NO inhibitory ability in a dose-dependent manner with no obvious cytotoxicity. A series of the model compounds 7a, 7b, 7d, 7f, and 7g have been identified as the most promising, with IC50 values of 47.76 μM, 33.8 μM, 20.76 μM, 26.74 μM, and 47.8 μM respectively in LPS-induced RAW 264.7 cell line. Structure-activity relationship (SAR) studies on a range of derivatives aided in identifying key pharmacophores in the lead compound. Western blotting data of 7d identified that our synthesized compounds can down-regulate and suppress the expression of the key inflammatory enzyme, inducible nitric oxide synthase (iNOS). These results suggested that synthesized compounds may be potent anti-inflammatory agents, inhibiting the NO-release, in turn, iNOS inflammatory pathways. Furthermore, in-vivo anti-inflammatory detection via xylene-induced ear edema in mice revealed that these compounds could also inhibit swelling in mice, with model compound 7h showing an inhibition activity (64.4%) at a concentration of 10 mg/kg comparable to the reference drug celecoxib. Molecular docking results showed that shortlisted compounds (7b, 7c, 7d, 7e, and 7h) had a potential binding affinity for iNOS with low energies, with S-Score to be −7.57, −8.22, −7.35, −8.95, −9.94 kcal/mol, respectively. All results demonstrated that the newly synthesized chiral pyrazolo isoquinoline derivatives are highly potential anti-inflammatory agents.