Determination of radical scavenging activities of some pyrimidine derivatives

Purpose: To synthesize some pyrimidine derivatives and investigate their radical scavenging activities. Methods: A series of newly pyranopyrimidines derivatives and dithiopyridopyrimidinediones were synthesized by condensation of barbituric acid, malononitrile and different substituted benzaldehydes reacted with 1,4-Diazabicyclo[2.2.2] octane (DABCO) as a base. Compounds P1-7 (series 1),  S1-11 (series 2) Scheme 1 and 6-amino-2-thiouracil with aromatic aldehydes in glacial acetic acid under reflux J1-13 (series 3) Scheme 2. 1H & 13C NMR, CHN, GC-MS and IR were used to characterize the compounds and were also screened for radical scavenging activity using 2,2-diphenyl- 1-picrylhydrazyl (DPPH) radical scavenging activity (IC50 = 50 μg/ml). Results: The potency of radical scavenging activity was ranked as series 1 > series 3 > series 2. Compounds P3, J4, S10, P5, P7 with inhibitory  concentration at 50 % level (IC50) of 12, 40, 48, 50, and 54 μg/ml, respectively, showed radical scavenging activity equal or more potent than the standard antioxidant, ascorbic acid (IC50 = 50 μg/ml). Conclusion: Series of newly pyranopyrimidines and dithiopyridopyrimidinediones derivatives have been successfully synthesized, and they  demonstrate good radical scavenging activity. Keywords: Pyranopyrimidine, Dipyrimidines, Anti-oxidant, DPPH, Ascorbic acid, Radical scavenging