Discovery of a new pyrido[2,3-d]pyridazine-2,8-dione derivative as a potential anti-inflammatory agent through COX-1/COX-2 dual inhibition.

In this paper, we present the design and synthesis of a novel series of pyrido[2,3-d]pyridazine-2,8-dione derivatives via the annulation of the 2-pyridone pattern. The synthesized derivatives were evaluated for in vivo anti-inflammatory activity using an ear edema model. Compound 7c, which showed a greater inhibition of ear edema (82%), was further tested for its in vitro COX-1/COX-2 inhibitory activity. Compound 7c showed similar inhibitory activities against COX-1 and COX-2 isoenzymes. The structural features that ensure the dual inhibition of COX-1 and COX-2 were elucidated using molecular docking studies. Overall, the ring closing of 2-pyridone pattern I transformed this highly selective COX-2 inhibitor into a dual COX inhibitor (7c), which could serve as a model for determining selectivity for COX-2.

Discovery of 1,3,4,5-tetrasubstituted pyrazoles as anti-trypanosomatid agents: Identification of alterations in flagellar structure of L. amazonensis.

Trypanosoma cruzi and Leishmania species are causative agents of Chagas disease and Leishmaniasis, respectively, known as Neglected Tropical Diseases. Up to now, the treatments are inadequate and based on old drugs. Thus, we report herein the discovery of 1,3,4,5-tetrasubstituted pyrazole derivatives that presented potent and selective inhibition against promastigote forms of L. amazonensis, and epimastigote forms of T. cruzi. The structure-activity relationship led to the identification of three compounds (2m, 2n and 2p) with an in vitro IC50 of 7.4 µM (selective index - SI ≥ 133.0), 3.8 µM (SI in the range of 148.4 to 200.8), and 7.3 µM (SI in the range of 87.2 to 122.4) against L. amazonensis, respectively. Also, those compounds exhibited in vitro IC50 of 9.7 µM (SI ≥ 101.5), 4.5 µM (SI in the range of 125.3 to 169.6) and 17.1 µM (SI in the range of 37.2 to 52.2) against T. cruzi, respectively. A preliminary study about the reaction mechanism in promastigotes showed that 2n caused an increase of the production of ROS and of lipid storage bodies. Furthermore, 2n induced abnormalities in the flagellum that may have an impact on the parasite motility.

Synthesis and antifungal activity of new hybrids pyrimido[4,5-d]pyridazinone-N-acylhydrazones.

Paracoccidioidomycosis is an endemic mycosis in Latin America for which there is a high mortality rate and limited treatment options. There are no specific drugs to treat the systemic disease. Thus, there is a need for further studies focused on the development of specific drugs. In this work we synthesized new hybrids pyrimido[4,5-d]pyridazinone-N-acylhydrazone (5a-p) by simple methodologies with good yields. The antifungal activity of compounds was evaluated against P. brasiliensis (Pb18) and Candida spp. Compounds 5a, 5f, 5i, 5 k, 5m and 5n showed significant inhibition against Pb18 with MIC of 0.125 to 64 µg mL-1. Compound 5a is the most promising, showing potent fungicidal profile with MFC of 0.5 µg mL-1, synergic effect with amphotericin B, besides showing no toxicity against HeLa and Vero cells.

Synthesis of novel 3,5,6-trisubstituted 2-pyridone derivatives and evaluation for their anti-inflammatory activity.

The inflammatory response is the reaction of living tissue to an injury of a foreign nature, such as infection and irritants, and occurs as part of the body's natural defence response. Compounds capable of inhibiting cyclooxygenase (COX) enzymes, especially COX-2, have great potential as anti-inflammatory agents. Herein we present the regioselective synthesis of 49 novel compounds based on the 2-pyridone nucleus. The topical anti-inflammatory activity of seventeen compounds was evaluated in mice by croton oil (CO) induced ear edema assay. Most of the compounds exhibited a high level of in vivo anti-inflammatory activity, reducing ear edema and myeloperoxidase (MPO) activity. The most active compounds (2a and 7a) were inhibitors of COX enzymes. Compound 2a selectively inhibited the COX-2, while 7a was nonselective. Further, the compound 2a showed effective binding at the active site of COX-2 co-crystal by docking molecular study.

Unconventional Method for Synthesis of 3-Carboxyethyl-4-formyl(hydroxy)-5-aryl-N-arylpyrazoles.

An alternative highly regioselective synthetic method for the preparation of 3,5-disubstituted 4-formyl-N-arylpyrazoles in a one-pot procedure is reported. The methodology developed was based on the regiochemical control of the cyclocondensation reaction of ß-enamino diketones with arylhydrazines. Structural modifications in the ß-enamino diketone system allied to the Lewis acid carbonyl activator BF3 were strategically employed for this control. Also a one-pot method for the preparation of 3,5-disubstituted 4-hydroxymethyl-N-arylpyrazole derivatives from the ß-enamino diketone and arylhydrazine substrates is described.

Synthesis and evaluation against Leishmania amazonensis of novel pyrazolo[3,4-d]pyridazinone-N-acylhydrazone-(bi)thiophene hybrids.

A new series of pyrazolo[3,4-d]pyridazin-7-one derivatives were synthesised and evaluated for their in vitro antileishmanial activity against Leishmania amazonensis promastigote and axenic amastigote forms. The results showed that the pyrazolo[3,4-d]-pyridazin-7-one-N-acylhydrazone-(bi)thiophene hybrids 5b, 6b and 6d exhibit better antileishmanial activity with IC50 84.96, 3.63 and 10.79 µM, against the promastigote form and IC50 32.71, 2.32 and >100 µM against the axenic amastigote form, respectively. The active compounds had their cytotoxicity tested against macrophages and fibroblast cells with a higher selectivity index than 10 for compounds 6b and 6d. Molecular docking studies were performed for all active compounds using the enzyme trypanothione reductase (TR) to investigate a possible action mechanism. The results suggested that active compounds had interactions with the residues of amino acids Gly 13, Thr 51, Thr 160, Gly 161, Tyr 198, Arg 287, Asp 327, Thr 335, which may inhibit the enzyme TR.