Étude de l’implication des composés phénoliques des extraits de trois variétés de datte dans son activité antibactérienne | Study of the involvement of the phenolic compounds of extracts from three varieties of date in its antibacterial activity

The date fruit (Phoenix dactylifera L.) possesses a number of therapeutic virtues, and this requires more studies on its components. Phenolics are secondary metabolites of great pharmacological importance because of their several biological activities confirmed in a great number of studies. It’s in this context that we carried out a study with the aim: first, to quantify total phenolics, flavonoids and condensed tannins in organic and aqueous extracts of three Algerian date varieties using Folin-Ciocalteu, aluminum trichloride and vanillin methods respectively. Secondly, to test the sensibility of some bacterial strains (Staphylococcus aureus ATCC 25923, Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 25922, Klebsiella pneumoniae, Streptococcus agalactiae, Bacillus spp.) against our extracts using the diffusion on agar medium method. A linear correlation between phenolic content and the rate of antibacterial activity was also done, in order to highlight the possible involvement of date phenolics in its antibacterial activity. The majority of extracts were active, but with different rates of antibacterial activity following the strain and extraction method, wherein inhibition areas measured between 7.0 ± 0.0 and 30 ± 0.3 mm of diameter. The presence of some phenolic acids and flavonoids was revealed by high-performance liquid chromatography. Quantitative dosage of total phenolics showed rates varying from 74.99 ± 2.70 to 378.64 ± 3.67 gAE/100 g of extract, flavonoids between 1.79 ± 0.12 and 13.01 ± 0.62 QE/100 g of extract and condensed tannins from 34.33 ± 9.15 to 300.18 ± 7.70 CE/100 g of extract. The linear correlation between phenolic content and antibacterial activity was found significant with most extracts, showing, so that, the involvement of a great part of date fruit phenolics in its antibacterial activity.