Furobenzopyrans from Ammi visnaga suppress Pseudomonas aeruginosa virulence

This study investigates the potential of Khellin (KH), a furobenzopyran derived from Ammi visnaga, to inhibit the virulence factors of Pseudomonas aeruginosa. KH was tested at concentrations ranging from 0 μg/ml to 900 μg/ml, with no visible growth inhibition observed at concentrations below 90 μg/ml (sub-minimum inhibitory concentration, MIC). The effects of KH (9 μg/ml), a positive control (ciprofloxacin, 0.1 μg/ml), and a control (0 μg/ml) on virulence factors, including pyocyanin and elastase production, N-3-oxo-dodecanoyl-L-homoserine lactone (3-oxo-C12 HSL) secretion, and lasR gene expression, were assessed. KH treatment resulted in a significant reduction of 47% in pyocyanin levels compared to the control group (p < 0.05) and a significant decrease of 54.8% in elastase activity compared to the control group (p < 0.05). KH also significantly reduced (69%) the secretion of 3-oxo-C12 HSL, correlating with the 45% suppression of lasR gene expression (p < 0.05). These findings suggest that sub-MIC levels of KH reduce P. aeruginosa virulence by suppressing quorum-sensing genes, highlighting its potential for anti-virulence therapy against persistent infections and antibiotic resistance.