Anti-quorum sensing potential of <i>Ocimum basilicum</i> as a culinary herb

Abstract

Bacteria undergo special communication pattern called quorum-sensing (QS) before they can exhibit any detrimental or beneficial effect to man and the environment. This QS phenomenon necessitates the process of biofilm formation leading to medical and environmental consequences. Interrupting QS using natural products may address membrane biofouling and prevent biofilm-related diseases, while reducing the chances of bacterial resistance. In this study, leaves of Ocimum basilicum were extracted in n-hexane, acetone, ethyl acetate, methanol and distilled water. Anti-quorum sensing (AQS) activities of the extracts were investigated at both qualitative and quantitative levels against a locally isolated Chromobacterium violaceum, using solid and liquid media bioassays. Plant compounds with peak AQS activities were characterized and identified using various chromatographic techniques. The aqueous extract recorded the highest yield (4.67 %), which indicates the potential of distilled water to recover appreciable extract quantity from the leaves of Ocimum basilicum. Widest zone of AQS activity (10.00 mm) and peak violacein inhibition rate (37.65 %) were also revealed from the aqueous extract. These further signify that the polar extracts possess compound(s) with better features of AQS activities. Gas chromatography–mass spectrometry (GC-MS) identified p-xylene (23.64 %), hemimellitene (1.68 %) and Benzene, 1-ethyl-4-methyl (1.42 %) as the most active compounds, whose AQS features might be enhanced in combination with other compounds. This research identified (but recommends further scientific investigation on) the potential use of O. basilicum as AQS agent.