Anti-inflammatory activity and cheminformatics analysis of new potent 2-substituted 1-methyl-5-nitroindazolinones

After the identification of the anti-inflammatory properties of VA5-13l (2-benzyl-1- methyl-5-nitroindazolinone) in previous investigations, some of its analogous compounds were designed, synthesized and evaluated in two anti-inflammatory methods: LPS-enhanced leukocyte migration assay in zebrafish; and 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced mouse ear edema. The products evaluated (3, 6, 8, 9 and 10) showed the lower values of relative leukocyte migration at 30 μM (0.14, 0.07, 0.10, 0.13 and 0.07, respectively), while in ear edema and myeloperoxidase activity methods, all the compounds reduced inflammation, only 4 and 16 yielded unsatisfactory results. The relationship linking structure and activity (SAR analysis) was determinate by using SARANEA software. The importance of the 5-Nitro group of the indazole ring for the activity was evident, and showed modest reduction when benzyl (Bn) is changed by alkyl group. A substituted Bn moiety at N2 (R) is the best substituent (5-10); nevertheless, if methylene group of Bn is deleted, the activity is affected. Also, introduction of halogen atoms mainly at positions 3 or 4 of the benzyl moiety (6 and 10) leads in general to strong activities. In fact, compounds 7 and 8 (R = 4-FBn or 4-ClBn, respectively) exhibit satisfactory results in in vivo tests and appear promising. The production of IL-6 at all doses assayed was significantly reduced, except with 16. Nonetheless, the production of TNF-α was significantly inhibited only by this chemical (16) at concentration of 50 μM. On the other hand, compound 2 was the one that mostly inhibited the expression of COX-2 and iNOS. From these results, it can be concluded that the inhibition in the release of cytokines can be one of the mechanisms of action responsible for the anti-inflammatory effect for 2-benzyl derivates while other 2-alkyl derivatives can inhibit production of NO. Therefore, nitroindazolinone chemical prototype could be an interesting structural group with anti-inflammatory purposes in the therapeutic.