Response Surface Modelling through Box-Behnken approach to optimize bacterial quorum sensing inhibitory action of Tribulus terrestris root extract

Certain root extracts have quorum quenching property that interfere with biofilm formation by rhizobacteria. We studied the medicinal plant Tribulus terrestris L. (Zygophyllaceae) and modeled its root extract inhibitory action against rhizosphere associated bacteria Chromobacterium violaceum. A wild type strain and a non-chromogenic mutant strain were grown on agar supplemented with N-3-oxohexanoyl-homoserine lactone quorum-sensing signal molecule. The root extract did not show bactericidal property, but interfered with quorum sensing. Quorum quenching was affected by bacterial population density, rate of root extract addition, and its concentration. Results indicate the quorum quenching activity of the root extract varied with each of these variables. Maximum quenching activity required 300 µg ml-1 extract thrice daily. Response surface modelling of factors by Box-Behnken approach was used for optimizing the quorum quenching activity of the extract. The accuracy of the mathematical model was verified by ANOVA and Cook's distance table. The results can be further used in quorum quenching studies as the extract reduces bacteria infectivity. This strategy offers options to overcome multidrug resistance and assist the host immune response.