Coumarin-1,2,4-triazole hybrids: Recent advances in synthesis and medicinal applications

Coumarin and 1,2,4-triazole compounds have been widely used in drug design and development due to their widespread biological applications. Combination of these two pharmacophores with or without linker moiety through the hybridization drug design strategy results in the hybrid molecules that can exhibit high therapeutic potential, likely due to synergistic effects as a mono compound or the two pharmacophores reach different target sites in the presence of a metabolically unstable linker and acts as a multi-target drug. Thus, chemists across the world have synthesized numerous coumarin-1,2,4-triazole hybrids and studied their biological applications. Comprehensive synthesis and biological applications with detailed structure-activity relationship studies of these hybrids have not been reported. Therefore, we here present a review focusing on the detailed synthesis of coumarin-1,2,4-triazole hybrids and their biological activities such as antimicrobial, anticancer, antioxidant, anti-tuberculosis, etc. with structure-activity relationship studies. The coumarin-1,2,4-triazole hybrids have been categorized as fused hybrids, direct-linked hybrids, and spacer-linked hybrids. The direct-linked and spacerlinked hybrids have further sub-grouped based on the position of 1,2,4-triazole on coumarin moiety. Numerous hybrid molecules have been identified as promising antifungal, antibacterial, anticancer, antioxidant, antihaemolytic, antitubercular, alpha-amylase inhibitor, anti-lipase, anti-inflammatory, and analgesic agents. The potent molecules presented in this review hold the potential of being lead molecules for further in vivo studies in the animal models of various diseases. We hope this review may assist synthetic and medicinal chemists across the world to better design and develop highly efficient drug molecules containing coumarin and 1,2,4-triazole moieties.