This study examines substances from plant leaves of Azadirachta indica and Melia azedarach extracted with methanol (80%) and then successively fractionated with increasing gradient polarity solvents. The methanol extract from the two plant leaves was selected to be incorporated with nanocomposites because of their high antimicrobial activities. HPLC analysis was performed for the determination of total phenolics and avonoids. LC-ESI-MS positive ion acquisition mode revealed the presence of four main chemical classes; limonoids, triterpenes, fatty acids, and phenolics. Sol-gel processes were adapted to prepare CaO/chitosan composite loaded with the methanol extract of the two plant leaves, acting as innovative antibacterial agents. The fabricated nanocomposites were characterized by XRD, TEM, SEM, and FT-IR methods. Minimal bactericidal concentrations (MBC) were established by agar plating using bacteria treated with MIC and at least 2 concentrations double-higher than the MIC. Bio lm was cultivated in the presence of sub-MICs of the extracts and the nanocomposites, followed by quanti cation with the crystal violet assay. The examined chitosan-CaO-based hybrid nanocomposites loaded with the methanol fractions from the leaves of A. indica and M. azedarach had an excellent performance as bio lm inhibitors. This indicates their good potential for biomedical applications.
In the new antibiotic era, the exponential increase in multiresistant bacterial strains has become the main global health problem. Many researchers have focused their efforts on exploring novel or combined strategies for combating bacterial resistance. Good knowledge of the molecular mechanisms of resistance and bacterial virulence factors as key targets provides us with a good basis for resolving the problem. One particularly attractive and promising strategy is to attack the main regulatory “network” of bacterial virulence determinants known as quorum sensing (QS). The inhibition of QS signals will be a novel means of screening more effective quorum-sensing inhibitors (QSIs) and will play a key role in the use of next-generation antimicrobials in the battle against resistance. This motivated the present review to provide a comprehensive clarification of the regulatory mechanisms of quorum-sensing signaling pathways in Chromobacterium violaceum and the discovery of potential plant quorum-sensing inhibitors.
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