We describe herein the design, synthesis, and pharmacological evaluation of novel series of imidazolopyridinyl indole analogues as potent antioxidants and antimicrobials. These novel compounds (3a–i) were synthesized by reacting 3,5-disubstituted-indole-2-carboxylic acid (1a–i) with 2,3-diamino pyridine (2) in excellent yield. The novel products were confirmed by their IR, 1H NMR, 13C NMR, mass spectral, and analytical data. These compounds were screened for their antioxidant and antimicrobial activities. Among the compounds tested, 3a–d showed the highest total antioxidant capacity, scavenging, and antimicrobial activities. Compounds 3c-d and 3g-h have shown excellent ferric reducing activity. 1. Introduction The continuous search for novel agents which target pathological processes of human carcinogenesis has led to the synthesis of small molecules which may modulate cell cycle [1]. Free radicals are referred to as oxidizing agents because they tend to cause other molecules to donate their electrons [2]. Reactive oxygen species (ROS) are a product of normal cellular metabolism [3]. ROS plays a vital physiological role in several intracellular signaling and regulations [4]. Antioxidants have the ability to neutralize free radicals and prevent the damage caused by them [5]. Antioxidants, even at low concentration, significantly delay or prevent the oxidation of easy oxidizable substrates [6]; when in high concentrations, ROS can damage cell structures, nucleic acids, lipids, and proteins [7]. In the normal metabolism status, the level of free radicals and antioxidants in humans is maintained in balance, which is important for sustaining optimal physiological conditions [8]. The reactive oxygen species (ROS) are implicated in numerous pathological conditions such as diabetes, liver damage [9], inflammation, aging, atherosclerosis, carcinogenesis [10, 11], and neurodegenerative [12] disorders like Parkinson’s, Alzheimer’s, and amyotrophic lateral sclerosis (ALS) [13]. The treatment of infectious microbial disease remains a pressing problem worldwide [14, 15]. A major research emphasis to counter this growing problem is the development of antimicrobials structurally unrelated to the existing molecules. One possibility to achieve this goal is the combination of a molecule with structural elements possessing appropriate biological activities [16, 17]. Nitrogen-bridgehead fused heterocycles containing an imidazole ring is a common structural component in pharmacologically important molecules, with activities spanning an assorted range of targets [18], such as
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