Inhibitory Effects of <i>Sapindus mukorossi</i> Gaertn. Extract on Biofilm Formation and Quorum Sensing in <i>Pseudomonas aeruginosa</i> : A Natural Alternative to Combat Bacterial Resistance

Developing natural alternatives to antibiotics is an essential aspect for countering bacterial pathogens. This study focused on the influence of plant-derived extracts on biofilm and quorum-sensing (QS) inhibition in Pseudomonas aeruginosa. On screening, the methanolic extract (ME) of Sapindus mukorossi (Sm-ME) effectively inhibited biofilm formation. The major bioactive groups present in Sm-ME were alkaloids, flavonoids, terpenoids, and saponins. These phytochemicals were validated by biochemical, Fourier transform infrared spectroscopy, and gas chromatography-mass spectroscopy analysis. Sm-ME significantly inhibits up to 82.5% of P. aeruginosa biofilm formation and anti-QS activity in a dose-dependent manner. The microscopy analysis and the down-regulation of virulence genes (lasI, lasR, rhII, and rhIIR) validated the effectiveness of Sm-ME in P. aeruginosa inhibition. Additionally, Sm-ME retained good biocatalytic activity on exposure to high temperatures up to 90°C and higher antioxidant activity than ascorbic acid. These findings briefly demonstrated the potential influence of Sm-ME for combating biofilm and QS inhibitions in P. aeruginosa via a natural, sustainable alternative to antibiotics.