Anti-quorum sensing, antibiofilm, and antibacterial activities of extracts of <i>Centella asiatica</i> L. leaves, and <i>in vitro</i> derived leaves-calli through tissue culture: a potential for biofouling-prevention

Abstract

Extracts of <i>Centella asiatica</i> leaves (LEs), and <i>in-vitro</i> leaf-calli (CEs), were investigated for antibacterial, antibiofilm, and anti-quorum sensing activities. Ethyl acetate extracts from leaves (EALE), leaf-calli (EACE), methanolic extracts from leaves (MELE), and leaf-calli (MECE) showed antibacterial activity; the minimum inhibitory concentrations (MICs) of LEs and CEs ranged from 0.312-2.50 mg ml^-1 and 0.625 - 2.50 mg ml^-1, respectively. The MICs of EALE and EACE were 2.50 mg ml^-1, each, for <i>C. violaceum</i> 12742, and <i>P. aeruginosa</i> PAO1. At sub-MIC levels, EALE and EACE showed anti-quorum sensing (anti-QS) activity, demonstrated by concentration dependent pigment inhibition of <i>C. violaceum</i> 12742. Similarly, EALE and EACE inhibited QS-controlled virulence factors in <i>P. aeruginosa</i> PAO1 (biofilm, pyocyanin, and pyoverdin); again, the inhibition was concentration-dependent. The best effect was at immediate sub-MIC concentration i.e. 1250 µg ml^-1. GC-MS analyses revealed the presence of compound 9,12-Octadecadienoic acid, and in silico docking study suggested interactions with QS-receptors CviR', LasI, and LasR proteins for anti-QS activity.