Sclerocarya birrea (A. Rich.) Hochst. and Sterculia setigera Del. extracts as a potential inhibitor of Pseudomonas aeruginosa PAO1 and Chromobacterium violaceum CV026 virulence factors to combat bacterial pathogenicity

The abuse of antibiotics has led to the widespread development of resistant bacterial strains, there is a need for the development of antimicrobial agents with new properties.
Aim of this study was to determine the anti-quorum sensing potential (expression of virulence factor inhibition) of ethanolic extracts of S. birrea and S. setigera on Chromobacterium violaceum CV026 and Pseudomonas aeruginosa PAO1.
The ability of the extracts to inhibit the production of violacein by C. violaceum and the biofilm formation of Pseudomonas aeruginosa was examined to determine anti-quorum sensing activity. The phytochemical screening and the determination of total polyphenols and total flavonoids were carried out. The antioxidant activity of the extracts was measured using anti-free radical DPPH model and the reducing of the ferric ion capacity.
For the inhibition of the production of violacein, S. setigera presented the best result with an inhibition of 70.19% compared to the negative control which is 1% DMSO. This inhibition is greater than that of ascorbic acid used as a reference. This species was also the most active on biofilm formation with an inhibition of 72.24% compared to the negative control, it thus showed greater activity than that of ascorbic acid used as a positive reference. The phytochemical study revealed the presence of tannin, flavonoids, triterpenes, saponosides, coumarin in our two extracts. S. birrea gave the best total polyphenol content with 326.05 ± 117.90 mg EAG / g of extract and showed the best result on the DPPH radical with an inhibition of 73.33 ± 1.46% which is statistically equal to that of gallic acid used as a reference.
These extracts showed good antibacterial activity by inhibiting the quorum sensing system. Thus, they could therefore be used for the manufacture of anti-quorum sensing phytomedicines without a bactericidal effect.