This study was conducted to identify and compare natural antioxidant based plant sources. Polyphenols are the main constituents of the natural antioxidants obtained from fruits, leaves, and seeds etc. In this work, four types of seeds from Trachyspermum ammi (Ajwain), Brassica alba (Mustard), Trigonella foenum graecum (Fenugreek) and Papaver somniferum (Poppy) were selected and their extracts were tested for antioxidant activity (AOA) by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and chelating methods. Total phenolic contents were found in the range of 1015-6900 mg/100 g (p<0.5). Antioxidant activity by DPPH radical scavenging and chelating methods was found to be in the range of 44-95% and 33-77% (p<0.5), respectively. This study revealed that T.ammi is a potent source of natural antioxidant and can be used to replace synthetic antioxidant. However mustard, fenugreek and poppy have also proved to be the potential sources of phenolics.