Design and synthesis of some substituted 1 H-pyrazolyl-thiazolo[4,5- d]pyrimidines as anti-inflammatory–antimicrobial Agents

Abstract

The synthesis of two novel series of structurally related 1 H-pyrazolyl derivatives of thiazolo[4,5- d]pyrimidines is described. All the newly synthesised compounds were examined for their in vivo anti-inflammatory activity in two different bioassays namely; cotton pellet-induced granuloma and carrageenan-induced paw edema in rats. The in vitro inhibitory activity of the most active compounds towards human COX-1 and COX-2 enzymes was also estimated. In additon, the ulcerogenic effects and acute toxicity (LD 50) values of these compounds were determined. The same compounds were evaluated for their in vitro antimicrobial activity against Escherichia coli, as an example of Gram negative bacteria, Staphylococcus aureus as an example of Gram positive bacteria, and Candida albicans as a representative of fungi. The results revealed that compounds 5a, 9a, 9b, 10b and 12a exhibited anti-inflammatory activity comparable to that of indomethacin in both local and systemic in vivo animal models with no or minimal ulcerogenic effects (0–10%) and high safety margin (LD 50>500 mg kg −1). In addition, most of them displayed appreciable antibacterial activities when compared with ampicillin, especially against S. aureus. Compounds 9a and 12a are the most distinctive derivatives identified in the present study because of their remarkable in vivo and in vitro anti-inflammatory activity in addition to their pronounced antibacterial activities comparable to ampicillin against Gram positive and -negative bacteria. Therefore, they are considered as successful dual anti-inflammatory–antimicrobial candidates.