Recherche de substances naturelles aux vertus chimioprotectrices : contribution à l'étude ethnobotanique et phytochimique de trois plantes médicinales africaines à profils antiradicalaires

Abstract : In this thesis, three species of African plants belonging to three different families were investigated from a phytochemical and pharmacological point standpoint. These were Anisophyllea dichostyla (Rhizophoraceae) and Annona caneata (Annonaceae) encountered in the democratic Republic of Congo. The isolation of all the compounds was conducted using different chromatographic techniques.The final elucidation of the structures was by spectroscopic means. chemical methods (hydrolysis,d erivatization) were also used to confirm some of the structures. In the essential oil of A, cuneata stem barks, 25 compounds were identified and characterized by their retention times, their masses and their Kovats Index. Z-sabinene is the major component. In addition 13 polyphenolic compounds, mainly simple phenols were identified namely (p-hydroxy benzoic acid, dihydroxybenzoic acid, ferulic acid, vanillic acid along with syringialdehyde, vanillin and vanillic alcohol). The physicochemical index such as the peroxides, p-anisidine and conjugated dienes values were compared according to the time of storage, to measure the rancidity of the argan oils. A study by NMR made it possible to locate the triglyceridic regiospecificity of the profile of oil. Use of HPLC, GC-MS and LC/MS allowed the identification of additional compounds for the first time in the oil of A, spinosa. The phenolic antioxidants ferulic, vanillic, syringicacids along with tyrosol were detected. The major phytosterol detected in argan oil was squalene with lower amounts of schottenol and spinasterol. However the major tocopherol was found to be gamma-tocopherol and not alpha-tocopherol. The unsaponifiable fractions of the oils showed antioxidant activity at 100mg/l. 26 compounds were detected and identified in A. dichostyla, comprising catechin and ellagic acid derivatives respectively. he total methanolic extract showed a very remarkable antioxidant inhibitor of xanthine oxidase in vitro model. A triterpene (bryonolic acid was also isolated and identified in this species. Two dimentional NMR enabled the elucidation of the stereochemistry and configuration of this compound
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Farid Khallouki. Recherche de substances naturelles aux vertus chimioprotectrices : contribution à l'étude ethnobotanique et phytochimique de trois plantes médicinales africaines à profils antiradicalaires. Sciences agricoles. Université Paul Verlaine - Metz, 2003. Français. ⟨NNT : 2003METZ004S⟩. ⟨tel-01749948⟩

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