involved in regulation of serum uric acid, xanthine oxidase (XO) is the best pharmacological target to control the levels of serum uric acid as it catalyzes the final steps in uric acid production. In the current study, a systemic search for the inhibitors of xanthine oxidase, starting from synthesis to in vitro screening and leading to in vivostudies is presented. Benzylidene nicotino/isonicotinohydrazides