Abstract
Plants are known for their widespread biological activities with special reference to the use in folkloric medicines for the treatment of several diseases and metabolic disorders from ancient times. The presence of bioactive phytochemicals especially phenolic compounds, tocopherol, phytol etc. are responsible for the potential bioactivities of plants. In the present study, the radical scavenging potential of ethanolic extract of Camellia kissi wall. was evaluated. In addition, the effect of C. kissi wall. on quorum sensing (QS) associated virulence and biofilm formation in Pseudomonas aeruginosa PAO1 was also investigated. The crude extract of C. kissi wall exhibited a significant antioxidant activity against DPPH and hydroxyl radicals with a scavenging percentage of 73.77 ± 3.58 and 75.3 ± 4.45 % respectively. The plant extract also significantly inhibited the QS regulated pyocyanin production, bacterial motility and recalcitrant biofilm formation in P. aeruginosa PAO1. The anti-biofilm activity was confirmed by confocal laser scanning microscopic (CLSM) analysis. The in vitro anti QS activity of C. kissi wall. was further confirmed by molecular docking studies specifically targeting the QS transcriptional regulatory protein, LasR. The present result will provide ample avenues to exploit medicinal plants in attenuating the QS regulated microbial infections and oxidative stress in the post-antibiotic era.
Highlights
In the metabolic process of living organisms, oxidation reactions represent an intermediate step and produce free radicals
Imbalance in the production and subsequent discharge of free radicals during the oxidation steps facilitate the production of strong reactive oxygen species (ROS) that plays an significant role in damage of the biological macromolecules such as nucleic acids, carbohydrates, proteins and lipids (Meena et al, 2012; Subhaswaraj et al, 2017a; Rajkumari et al, 2018)
The presence of phytol in the ethanolic leaf extract of C. kissi wall., as identified from Gas Chromatography-Mass Spectrometric (GC-MS) elucidated the efficacy of plant extract in scavenging free radicals and combating quorum sensing (QS) regulated virulence and biofilm formation in P. aeruginosa PAO1 (Santos et al, 2013; Pejin et al, 2015)
Summary
In the metabolic process of living organisms, oxidation reactions represent an intermediate step and produce free radicals. The generation of free radicals or ROS is dute to the metabolic imbalance and elevate during environmental stress and chronic bacterial infections (Cap et al, 2012). When the generation of ROS exceeds certain limit, the integral antioxidant machinery fails to scavenge the highly reactive free radicals wher exogenous supply of antioxidant is necessary to neutralize the ROS mediated oxidative stress. In this context, plant derived phytochemicals especially polyphenolic group of compounds reported for radical scavenging activity and neutralization of oxidative stress (Luis et al, 2016). Antioxidant, anti QS and anti-biofilm potential of ethanolic extract of C. kissi wall. The in vitro anti QS activity was further corroborated by molecular docking analysis that provided valuable information about the mechanism of QS inhibition
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