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Contribution à l’étude phytochimique d’espèces végétales de la flore tunisienne (Aristolochia longa L. et Bryonia dioïca Jacq.) : évaluation des activités antioxydante et antimicrobienne

Abstract : Composition of essential oil is known to depend on intrinsic and extrinsic factors. Experiments were conducted to study the variation in the essential oil composition of Aristolochia longa (Aristolacheae) harvested at different period (August, 2009; September, 2011; March, 2012; and April, 2013). The essential oil composition was assessed by GC–FID and GC–MS analyses. Hence, oxygenated sesquiterpenes (50.2–81.1%) and oxygenated monoterpenes (5.9–28.0%) are the major chemical groups. The antimicrobial properties of essential oils were evaluated against six microorganisms by the disc diffusion method. Increasingly, the essential oil isolated from roots collected in September (2011), exhibited the highest antimicrobial activity against Streptococcus agalactiae (G+) and Enterococcus faecium (G+). The composition of the fatty acids of the roots and aerial parts of A. longa and Bryonia dioïca (Cucurbutaceae) was analyzed by GC-FID and GC-MS. The oils extracted from the aerial parts of both species were rich in polyunsaturated fatty acids with the essential linolenic and linoleic acids being the most prominent compounds. Oleic and linoleic acids were the majors fatty acids in the roots of both species. The antibacterial activity, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the lipid extracts were determined against a panel of five bacterial strains. The antibacterial activity of the root lipid extracts was particularly important against Enterococcus feacium (G+) (CMI value of 125 μg/mL; CMB values > 250 μg/mL) and Streptococcus agalactiae (G+) (CMI value of 125 μg/mL; CMB values 250 μg/mL for A. longa roots). These results indicate that A. longa and B. dioïca could be considered as good sources of essential fatty acids which can act as natural antibacterial agents. An experimental design is an experimental set-up to simultaneously evaluate several factors at given numbers of levels in a predefined number of experiments, and also to provide maximum chemical information by analysing chemical data. So, Plackett–Burman (PB) experimental was used to appreciate the stability of DPPH and to estimate antioxidant activity of ferulic acid and the plant extracts. Hence, to increase DPPH absorbance at 190μM the buffer type, pH medium, solvent type and reaction time should be maintained at its lower level while buffer concentration, temperature, buffer ratio should be kept at its high level. While, to increase DPPH absorbance at 50 μM is obtained with buffer acetate, lower temperature and short reaction time. Further, the radical scavenging activity of the plant extracts and ferulic acid as a pure compound is examined in the selected conditions by PB design
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Mouna Dhouioui. Contribution à l’étude phytochimique d’espèces végétales de la flore tunisienne (Aristolochia longa L. et Bryonia dioïca Jacq.) : évaluation des activités antioxydante et antimicrobienne. Chimie analytique. Université de Lyon; Université de Tunis El-Manar. Faculté des Sciences de Tunis (Tunisie), 2016. Français. ⟨NNT : 2016LYSE1212⟩. ⟨tel-03008819⟩

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