Relative assessment of anti-quorum sensing in Piper betle leaves extract via pyoverdin assay

Abstract

Anti-quorum sensing property has been a popular alternative approach over bactericidal/bacteriostatic property in combating bacterial infection while simultaneously tackling the dilemma of antibiotic resistance. We presented pyoverdin assay as an initial screening to qualitatively determine the anti-quorum sensing activity in Piper betle by measuring the loss of absorbance at wavelength 630 nm. Growth of Pseudomonas aeruginosa was proven to be unaffected by the presence of the P. betle leaves extract. The regression value (R2) of the quorum sensing (QS) activity in untreated supernatant of P. aeruginosa was 0.9636 and we presented the QS activity in fold-change, normalized to untreated sample for a fair comparison between batch of assays. We further assessed the QS activity in the extracts of P. betle leaves and found the QS activity of P. aeruginosa grown in the presence of ethyl acetate extract at 200 μg/ml was reduced to 0.6-fold. As the concentrations went lower, higher fold of QS activity was observed, suggesting that P. betle leaves extract is demonstrating anti-QS activity at a higher concentration. Further fractionate of ethyl acetate crude extracts resulted in three fractionates with high anti-QS activity with >50% reduction in QS activity and five fractionates with intermediate anti-QS activity. The use of pyoverdin assay to qualitatively portray the anti-QS activity could shorten the lengthiness of extracting and measuring the signaling molecule yet, produces reliable information to screen for anti-QS activity and guide for further fractionation and purification of bioactive compound.