The structure activity relationship study for the synthesized eight compounds has been divided into two series: 2-substituted and 4-substituted phenyl ureas having variable atoms in (X). X=O (urea) and X=S (thiourea) for carboxylic acid and carboxamide substitutions in phenyl ring produces open chain ureas which have been screened for CNS depression study by using closed chain ureas to identify the correlation analogy between closed chain and open chain ureas on CNS depression and sleeping time potentiation. But in the present study we have taken the part of work related to the “invitro antioxidant assay” by using DPPH. This approach is there to support and serve as a tool for doing antioxidant assay at laboratory level to get a basic and preliminary conclusion for the potency of the compounds as an antioxidant. It may be a useful tool for a researcher and scientist to ascertain the antioxidant potential of synthesised compounds in rapid way.