Novel Imidazo [1, 2-a] Pyrazine Derivatives: Design, Synthesis, Antioxidant and Antimicrobial Evaluations

A series of imidazo[1,2-a] pyrazine derivatives were synthesized and evaluated for antioxidant activity based on the recently reported active colenterazine derivatives. The substitutions have been introduced at C2 C3, C8 positions of imidazo [1,2-a] pyrazine framework. All the compounds were screened for their in vitro antioxidant, antibacterial and antifungal, activities. Compounds 4c, 4f, 5a, 5b, 5c, 5d, 5f, 5h and 6b, displayed promising free radical scavenging activity and were found to be effective antioxidant when compared with standard ascorbic acid (vitamin C). Subsequently the effect of C2 C3, C8 substituents on the antioxidant activity has been investigated. The SAR reveals that amination at C8 position improves the activity. The above new chemical entities are screened for cytotoxicity on HeLa and MCF7 cancer cell lines. But they have not exhibited any cancer activity against cervical and breast cancer cell lines on human cancer cell lines at 10 μg/mL concentration. The series of compounds were also evaluated for their antimicrobial activity. Compounds 4f, 4a, 5g, 6b, and 6c display pronounced antibacterial activity against Staphylococcus aureus at 100 μg/mL concentration. Compounds 5h, 6b, 4f, 6c showed excellent zone of inhibition against both fungi Candida albicans, and Aspergillus niger at 50 μg/mL compared to the reference drugs. Compound 5h was found to be a good antioxidant as well as good antifungal agent. The low cytotoxicity of the title compounds can stand as good antioxidant and antimicrobial agents.