Synthetic and Natural Xanthones as Antibacterial Agents—Review

Xanthones, a class of polyketide derivatives characterized by a dibenzo-γ-pyrone core structure, are aromatic oxygenated cyclic compounds extensively found in nature. They are known for their diverse biological activities, including anti-Alzheimer, antitumor, and antidiabetic properties, which have spurred extensive research into their therapeutic potential. One of the most significant challenges facing mankind currently is the development of antibiotic resistance in pathogenic microbes making microbial infections increasingly difficult to treat. The formation of biofilms enhances bacterial resistance to antibiotics, immune defenses, and environmental stresses. In this review, we have categorized xanthones, both of biological origin and synthesized, based on their structure and summarized the recent studies on their ability to inhibit Gram-positive and -negative bacteria as well as the various underlying mechanisms that contribute to their microbicidal activity. These mechanisms include inhibition of virulence factors and biofilm formation, interaction with cell membranes, and interference with cell wall synthesis and DNA replication. In addition, we have listed the various methods involved in biofilm inhibition and the structure-activity relationship of various xanthone molecules, highlighting how xanthone derivatives exhibit increased antibacterial activity. With the growing concern of antibiotic resistance, exploring natural compounds like xanthones to study their interaction with bacterial cells is crucial for identifying new treatment options.