Abstract: AIMIn search of more potent, less toxic and selective potassium channel openers. METHODS According to the structure-activity relationships of benzopyran compounds and the features of structures of aprikalim, dofetilide and nifekalant, twenty benzopyran-4-one hydrazone derivatives have been designed and synthesized from 4-cyanophenos through acetylation, Fries rearragment, cyclization, hydrazone, substitution reaction and so on. The compounds were tested for their vasorelaxant activity in low (30 mmol·L^-1) and high (80 mmol·L^-1) KCl-induced contraction of rat aorta to identify potential potassium channel openers in vitro. RESULTSThree series of twenty benzopyran-4-one hydrazone derivatives, nominated N-aminoacetyl-(6-cyano-3,4-dihydrospiro ［2H-1-benzopyran -2,1′-cyclohexane］-4)-one hydrazone (I), 2-(6-cyano-3,4-dihydro-2H-1-benzopyran-4-ylene) hydrazinethiocarboxamide derivatives (II) and N-(2-arylethyl) aminoacetyl-(6-cyano-3,4-dihydro-2H-1-benzopyran)-4-one hydrazone (III), have been synthesized. They (I_1～9, II_1～4 and III_1～7) are new compounds. Their chemical structures were determined by IR, 1HNMR, MS and elemental analysis. The vasorelaxant effects of those novel compounds indicated that some of the compounds have vasorelaxant activities at 1×10^-6 mol·L^-1. CONCLUSIONThe vasorelaxant activities of compounds I9, III₂ and III₅ in inhibiting low KCl-induced vasocontraction at 1×10^-6 mol·L^-1 are less potent than the reference compound emakalim. However they are more potent than emakalim to inhibition high concentration KCl-induced vasocontraction at 1×10^-5 mol·L^-1 .It is worthy of further study.