The synthesis, characterization and biological evaluation of a series of novel N-substituted phthalazine sulfonamide (5a-1) are disclosed. Phthalazines which are nitrogen-containing heterocyclic compounds are biologically preferential scaffolds, endowed with versatile pharmacological activity, such as anti-inflammatory, cardiotonic vasorelaxant, anticonvulsant, antihypertensive, antibacterial, anti-cancer action. The compounds were investigated for the inhibition against the cytosolic hCA I, II and AChE. Most screened sulfonamides showed high potency in inhibiting hCA II, widely involved in glaucoma, epilepsy, edema, and other pathologies (K(i)s in the ranging from 6.32 +/- 0.06 to 128.93 +/- 23.11 nM). hCA I was inhibited with K(i)s in the range of 6.80 +/- 0.10-85.91 +/- 7.57 nM, whereas AChE in the range of 60.79 +/- 3.51-249.55 +/- 7.89 nM. ADME prediction study of the designed N-substituted phthalazine sulfonamides showed that they are not only with carbonic anhydrase and acetylcholinesterase inhibitory activities but also with appropriate pharmacokinetic, physicochemical parameters and drug-likeness properties. Also, in silico docking studies were investigated the binding modes of selected compounds, to hCA I, II, and AChE.