The mature biofilm has a complex ar

The mature biofilm has a complex architecture that increases its resistance against the host defence system and conventional antibiotic treatment. The findings of our study revealed that traditionally prepared YaSP could eradicate a preformed biofilm of P. aeruginosa by reducing the number of viable cells and causing cell membrane damage. This corresponds well with the reports of Packiavathy et al. [16], Nguyen et al. [25], and Nguyen et al. [30], who revealed that curcumin extracted from C. longa and α-mangostin extracted from G. mangostana, which are the components of YaSP, can disrupt the structural integrity of S. mutans, S. aureus, E. coli, P. mirabilis, and S. marcescens biofilms. Previous studies have reported the ability of plant-derived compounds with anti-biofilm properties to either enhance their inhibitory effect in combination with antibacterial agents such as zingerone/ciprofloxacin, curcumin/ceftazidime, curcumin/ciprofloxacin, etc. [19,31], or enhance P. aeruginosa immune clearance in in vivo models such as baicalin from Scutellaria baicalensis [32], ellagic acid from Terminalia chebula [33], etc. Therefore, the alteration of preformed biofilms and modulation of biofilm development resulting in thinner biofilms, as observed in the current study, may lead to an increase in susceptibility to conventional antibiotics and host immune clearance. Even though α-mangostin was previously found to be inactive against E. coli and P. aeruginosa [34], the compound exhibits strong antimicrobial activity against S. mutans, S. aureus, and S. epidermidis cells by disrupting the integrity of the cytoplasmic membrane of the pathogens [21,25,30]. Furthermore, α-mangostin was found to strongly reduce cell viability in the preformed biofilm, and the hot oil extractions obtained from both YaSP and G. mangostana caused cytoplasmic membrane damage of P. aeruginosa. It should be noted that the traditional extracting solvent, coconut oil, has also been reported to have inhibitory activity against C. albicans [35], S. mutans [36], and Clostridium difficile [37]. A similar tendency was observed in our study where the preheated virgin coconut oil has found to possess biofilm inhibition property, however, its antibiofilm activity was lower than that of D-YaSP and D-GM which their percentage of biofilm inhibition was up to 97%. Lack of systematic studies on anti-biofilm mechanisms of both active ingredients as well as the traditional extracting solvent of YaSP can be also mentioned as the limitation of this study and are currently being assessed by our research group.