The six novel 4-methylcoumarins bearing different functionalities such as amino, hydroxy, N-acetyl, acetoxy and nitro have been synthesized and confirmed on the basis of their spectral data (1H-, 13C-NMR, UV, IR and EI mass). They were examined for the first time for their effect on NADPH dependent liver microsomal lipid peroxidation in vitro, and the results were compared with other model 4-methylcoumarin derivatives to establish the structure-activity relationship. Our studies demonstrated that amino group is an effective substitute for the hydroxyl group for antioxidant property and produced a dramatic inhibition of lipid peroxidation. Ortho dihydroxy and ortho hydroxy-amino coumarins were found to possess highest antioxidant and radical scavenging activities.