7-(4-Chlorophenyl)-1-hydroxy-5-methylpyrido[3,4- d ]pyridazin-4(3 H )-one: synthesis, solvatomorphism, in vitro anti-inflammatory and cytotoxic activity studies and in silico analysis

The newly obtained compound 7-(4-chlorophenyl)-1-hydroxy-5-methylpyrido[3,4- d ]pyridazin-4(3 H )-one ( CPM ) was crystallized as two new variable solvates, namely, the dimethyl sulfoxide monosolvate, C 14 H 10 ClN 3 O 2 ·C 2 H 6 SO ( I ), and the sesquisolvate, C 14 H 10 ClN 3 O 2 ·1.5C 2 H 6 SO ( II ), and their structures were confirmed by single-crystal X-ray diffraction analysis. In previous work, 1-hydroxy-5-methyl-7-phenylpyrido[3,4- d ]pyridazin-4(3 H )-one ( PM ) was found to display anticancer activity. In the next step of our studies, we synthesized a new derivative of PM , introducing a Cl atom into the PM structure, obtaining CPM , which showed not only anticancer but also anti-inflammatory activity. CPM and the new semi-products of each step of the synthesis were examined by 1 H NMR, 13 C NMR and FT–IR spectroscopic analyses, and mass spectrometry. CPM forms ( I ) and ( II ) crystallize in the triclinic P 1 and monoclinic C 2/ c space groups, respectively, and differ in the stoichiometry of the CPM and DMSO molecules in the crystal lattice, being 1:1 and 1:1.5 for ( I ) and ( II ), respectively. A powder X-ray diffraction analysis was performed only for solvate ( I ) due to the lack of stability of solvate ( II ). The potential cytotoxicity of CPM was evaluated against the normal cell lines L929 and RPTEC, as well as the cancer cell lines A172, AGS, CACO-2 and HepG2. The anti-inflammatory activity of CPM was also evaluated using colorimetric assay for the inhibition of COX-1 and COX-2. The same biological tests were carried out for PM to compare the activities of both compounds. The biological studies revealed that CPM does not exhibit more activity than PM . Moreover, in silico analysis of the bioavailability and molecular docking were performed.