Antibiofilm properties of Clitoria ternatea flower anthocyanin-rich fraction towards Pseudomonas aeruginosa

Abstract

In Asia, <i>Clitoria ternatea</i> flowers are commonly used as a traditional medicinal herb and as a food colourant. Their bioactive compounds have anti-inflammatory, anti-microbial and anti-biofilm activities. <i>Pseudomonas aeruginosa</i> is one of the major pathogens that cause biofilm-associated infections resulting in an increase in antimicrobial resistance. Hence, the aim of this study was to investigate if the anti-biofilm properties of the anthocyanin-rich fraction of <i>C. ternatea</i> flowers were effective against <i>P. aeruginosa</i> . The effect of the anthocyanin-rich fraction of <i>C. ternatea</i> flowers on <i>P. aeruginosa</i> biofilms formed on a polystyrene surface was determined using the crystal violet assay and scanning electron microscopy (SEM). The anthocyanin-rich fraction reduced biofilm formation by four <i>P. aeruginosa</i> strains with a minimum biofilm inhibitory concentration value ranging between 0.625 and 5.0 mg ml^-1. We further show that the biofilm-inhibiting activity of <i>C. ternatea</i> flowers is not due to the flavonols but is instead attributed to the anthocyanins, which had significant biofilm inhibitory activity (64.0±1.1 %) at 24 h in a time-response study. The anthocyanin-rich fraction also significantly reduced bacterial attachment on the polystyrene by 1.1 log c.f.u. cm^-2 surface based on SEM analysis. Hence, anthocyanins from <i>C. ternatea</i> flowers have potential as an agent to decrease the risk of biofilm-associated infections.