Bacteria are social organisms able to build complex structures, such as biofilms, that are highly organized surface-associated communities of microorganisms, encased within a self- produced extracellular matrix. Biofilm is commonly associated with many health problems since its formation increases resistance to antibiotics and antimicrobial agents, as in the case of Pseudomonas aeruginosa and Staphylococcus aureus, two human pathogens causing major concern. P. aeruginosa is responsible for severe nosocomial infections, the most frequent of which is ventilator-associated pneumonia, while S. aureus causes several problems, like skin infections, septic arthritis, and endocarditis, to name just a few. Literature data suggest that natural products from plants, bacteria, fungi, and marine organisms have proven to be effective as anti-biofilm agents, inhibiting the formation of the polymer matrix, suppressing cell adhesion and attachment, and decreasing the virulence factors’ production, thereby blocking the quorum sensing network. Here, we focus on plant derived chemicals, and provide an updated literature review on the anti-biofilm properties of terpenes, flavonoids, alkaloids, and phenolic compounds. Moreover, whenever information is available, we also report the mechanisms of action.

It is known that plant-based ethnomedicine represented the foundation of modern pharmacology and that many pharmaceuticals are derived from compounds occurring in plant extracts. This track still stimulates a worldwide investigational activity aimed at identifying novel bioactive products of plant origin. However, the discovery that endophytic fungi are able to produce many plant-derived drugs has disclosed new horizons for their availability and production on a large scale by the pharmaceutical industry. In fact, following the path traced by the blockbuster drug taxol, an increasing number of valuable compounds originally characterized as secondary metabolites of plant species belonging to the Spermatophyta have been reported as fermentation products of endophytic fungal strains. Aspects concerning sources and bioactive properties of these compounds are reviewed in this paper.