Plant Flavonoids as Reservoirs of Therapeutics against Microbial Virulence Traits: A Comprehensive Review Update

Flavonoids are secondary metabolites abundantly present in plants and, in most cases, essential contributors to plants bioactivity. They have been studied so far for a range of possible health-beneficial effects, including antioxidant, cardioprotective, and cytotoxic. Therefore, there are data on the antimicrobial potential of a significant number of flavonoids. However, less is known regarding their antivirulence traits. Trending antimicrobial research worldwide has pointed out the promising effects of antimicrobial strategies based on the antivirulence principle, so this review aims to present the newest research regarding the antivirulence effects of flavonoids. Articles on antivirulence flavonoids published from 2015 until now were selected. A range of molecules from this class has been studied up to date, with the most abundant data for quercetin and myricetin, while the most studied organism is Pseudomonas aeruginosa. The antivirulence attributes studied included antibiofilm assessment, followed by data on the inhibition of virulence pigments (pyocyanin, violacein, and staphyloxanthin) and virulence enzyme production (such as sortase A and elastase). Less information is collected on the inhibition of morphological transition, motility, and molecular mechanisms underlying the antivirulence properties of flavonoids and in vivo research. Flavonoids are a group of compounds with a wide range of antivirulence traits and might be further developed into essential parts of novel antimicrobial strategies.