Naturally Occurring Coumarins as Promising Antimicrobial Agents: Latest Progress

One of the twenty-first century's most significant threats to human health is the rise of microbial diseases. Infectious diseases are caused mainly by microorganisms, including bacteria, viruses, fungi, and protozoa. These organisms are responsible for significant increases in morbidity and mortality worldwide. Since the discovery of penicillin, antibiotics have been used to treat microbial illnesses. Antibiotic abuse and overuse in humans, animals, and plants, as well as in the treatment of non-microbial disorders, have led to the fast development of multidrug-resistant and high-virulence pathogens in recent decades. Microbes with greater pathogenicity and virulence have emerged due to antibiotic resistance. Most antibiotics remain ineffective in treating resistant pathogens and require high doses or combination therapy to overcome antimicrobial resistance. Since most synthetic antimicrobials have acquired resistance, natural products (NPs) offer more effective alternatives to overcome the resistance and can sensitize the microbes to antibiotics. Coumarin-based scaffolds possess several pharmacological properties, including antimicrobial, antiviral, antiprotozoal, and antiparasitic activities. Notably, most coumarins exhibit antimicrobial activity through distinct pathways from conventional antibiotics; thus, they can help address antibiotic resistance and effectively treat human infections. This review discusses the recently identified natural coumarins, their antibacterial, antiviral, antifungal, and antiprotozoal activities, their action as efflux pumps and as biofilm inhibitors, and their formulations as potential means to combat microbial infections. We also provide detailed coverage of the coumarin-based patents and the gain of market exclusivity. The discussed natural coumarin-based compounds could be promising agents for treating microbial diseases.