10.22376/ijpbs.2019.10.1.p1-12 Volume 10 Issue 1 2019 (January - March) A series of some novel pyridazinone compounds were synthesised. The reaction of mucochloric acid and 3-chloro phenylhydrazine hydrochloride has led to the formation of 4,5-dichloro-2-(3-chloro-phenyl)-6-(substituted-benzyl)-2H-pyridazin-3-one derivatives 2a-k in the presence of substituted aldehydes. These derivatives carry 3-chloro phenyl moiety on lactam nitrogen and substituted benzyl moiety attached at sixth position in the pyridazinone ring. Antimicrobial activity of newly synthesized compounds were investigated and C-6 benzyl substituted pyridazinone derivatives showed moderate to good antibacterial activity against Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa and antifungal activity against Candida albicans and Aspergillus niger. Compound 2f exhibited good antimicrobial activity against all the strains (MIC 25-50μg/ml). Compound 2d exhibited good antimicrobial activity against all the strains except E. coli. The in vitro antioxidant activity of the novel 4,5-dichloro-2-(3-chloro-phenyl)-6-(substituted-benzyl)-2H-pyridazin-3-one were assayed by the quantitative 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity method. The compound 2k proved to be the most active, showing the highest capacity to deplete the DPPH radicals. The chemical structures were confirmed by IR, lessThan sup greaterThan 1 lessThan /sup greaterThan HNMR, lessThan sup greaterThan 13 lessThan /sup greaterThan C-NMR, MS, and elemental analysis. Molecular docking studies of the synthesized compounds were done with the help of V-Life Science MDS 4.6 software using GRIP batch docking method to find out which derivative had a better docking. The compounds which showed the highest negative score in docking have also exhibited good antibacterial and antifungal activity. DINESH KUMAR MEHTA, MINAXI SAINI Antibacterial activity, Antifungal activity, Pyridazinone 127-140