Anti-quorum sensing and anti-biofilm activities of Hypericum perforatum extracts against Pseudomonas aeruginosa.

Abstract

ETHNOPHARMACOLOGICAL RELEVANCE\nHypericum perforatum L. (Hypericaceae) has been used as a traditional therapeutic for skin wounds, burns, cuts and stomach ailments including stomach ache, ulcers for a long time in many societies. Although many studies about its antibacterial properties can be found, there is a lack of studies about its quorum sensing inhibition properties, which effects bacterial vulnerability directly, on Pseudomonas aeruginosa.\n\n\nAIM OF THE STUDY\nEvaluation of anti-quorum sensing (anti-QS) and anti-biofilm activity of ethanol, methanol, acetone and ultra-sonicated extracts of Hypericum perforatum L. (HP) which is a well-known wound healer, against P. aeruginosa.\n\n\nMATERIALS AND METHODS\nAerial parts of HP were extracted with ethanol, methanol and acetone. In addition, separate extractions with ultrasonication were carried out with same solvents. Anti-QS activity tests with different doses of HP extracts were performed by employing biomonitor strains, of which the promoter of QS regulating and green fluorescent protein (GFP) genes were fusioned. For anti-biofilm activity, HP extracts were applied to wild type PAO1 strains and biofilm inhibition was quantified via crystal violet staining method.\n\n\nRESULTS\nHP s ethanol, methanol and acetone extracts (250\u202fµg/ml doses) inhibited LasIR signalling pathway up to 65.43%, 59.60%, 55.95% and same solvent extracts obtained with ultrasonication inhibited 71.33%, 64.47%, 57.35% respectively. Moreover, inhibition rates of RhlIR pathway were 28.80%, 50.83%, 45.84% for ethanol, methanol, acetone extracts (250\u202fµg/ml doses) and 51.43%, 57.41%, 50.02% for ultrasonication extracts (250\u202fµg/ml doses), compared to untreated controls. In the experiments, ethanol, methanol, acetone and ultra-sonicated extracts of HP did not inhibit biofilm formation.\n\n\nCONCLUSIONS\nThis study shows that HP plant is capable for blocking of las and rhl QS systems of P. aeruginosa. However, it was observed that ethanol, methanol and acetone extract of the plant samples did not show anti-biofilm activity against P. aeruginosa. This led us to thinking that biofilm formation was caused via another pathway such as IQS or PQS. Further studies with isolated active compounds of HP might give a better understanding of the effects on biofilm formation of P. aeruginosa.