Calycopterin is produced by plants of the genera Dracocephalum[47], Herissantia [48], Calycopteris and Digitalis [49] and its anticancer[50], anti-angiogenic [51], immunoinhibitory [47], antiproliferative[49] and antibacterial [52] properties have already been described.However, this is the first time that calycopterin's effect on PYO production is reported. Flavonoid derivatives, such as naringenin andtaxifolin, decrease PYO production, although at a 100-fold higherconcentration (4 mM) than calycopterin, due to negative modulation ofQS gene expression levels [53]. As these compounds share high chemical similarity to calycopterin, they might share the same mechanismof action (QS modulation). Considering that a functional QS cascade iscrucial for P. aeruginosa swarming and biofilm formation [54], weevaluated calycopterin's effect on biofilm formation and P. aeruginosaswarming motility (Fig. 3) and then compared them to the profile ofother flavonoids that have already been reported in the literature