116 research outputs found
Dosage des polyphĂ©nols et activitĂ© anti-oxydante de feuilles et dâinflorescences mĂąles de Borassus aethiopum, Mart. (Arecaceae)
Borassus aethiopum est une plante de la famille des ArĂ©cacĂ©es. Câest un gĂ©ant palmier qui prĂ©sente un tronc dur appelĂ© stipe, des racines fasciculĂ©es et des feuilles longues en forme dâĂ©ventail. Elle est presque cosmopolite et ses diffĂ©rentes parties sont utilisĂ©es dans nombreux domaines : Ă©conomiques, Ă©cologiques, alimentaires et sanitaire. En effet, sur le plan sanitaire, la pharmacopĂ©e utilise lâalcinĂąt des feuilles en boisson dans lâeau pour traiter la bilharziose viscĂ©rale (Sakande, 2004). Lâobjet de notre Ă©tude est de dĂ©terminer la teneur en polyphĂ©nols et de tester lâactivitĂ© antioxydante dâextraits de feuilles en comparaison avec ceux des inflorescences mĂąles. Ainsi, la mĂ©thode colorimĂ©trique de Folin Denis, dĂ©crite par BassĂšne (2012) a Ă©tĂ© utilisĂ©e pour le dosage des polyphĂ©nols. LâactivitĂ© antioxydante a Ă©tĂ© dĂ©terminĂ©e par les mĂ©thodes chromatographique sur couche mince selon Takao et al. (1994) et colorimĂ©trique dĂ©crite par Sakande (2004). Les teneurs en polyphĂ©nols totaux obtenues sont 13,56% et 5,6% Eq dâacide tannique respectivement dans les feuilles et les inflorescences mĂąles. Les teneurs respectives en tanins dans les feuilles et les inflorescences mĂąles ont Ă©tĂ© Ă©valuĂ©es Ă 13,46% et 5,47% Eq dâacide tannique. La chromatographie sur couche mince a rĂ©vĂ©lĂ© une activitĂ© antioxydante dans les extraits de feuilles et dâinflorescences mĂąles. Par la mĂ©thode colorimĂ©trique utilisant le DPPH, les rĂ©sultats obtenus en mg Eq dâacide ascorbique sont 4 et 5 mg Eq respectivement dans les extraits dâacĂ©tate Ă©thyle et butanolique de feuilles ; les extraits dâacĂ©tate dâĂ©thyle et butanolique dâinflorescences mĂąles respectifs ont une activitĂ© antioxydante Ă©valuĂ©e Ă 10 et 20 mgEq dâacide ascorbique. Les rĂ©sultats obtenus de cette Ă©tude montre que les extraits de feuilles ont des teneurs en polyphĂ©nols et en tanins supĂ©rieures Ă celles des extraits dâinflorescences mĂąles. LâactivitĂ© antioxydante a Ă©tĂ© deux fois plus importante dans les extraits de feuilles que dans les extraits dâinflorescences mĂąles. Cependant, dans les feuilles lâextrait dâacĂ©tate dâĂ©thyle renferme deux fois plus de polyphĂ©nols et de tanins que lâextrait butanolique ; lâactivitĂ© antioxydante est aussi plus Ă©levĂ©e dans ce premier extrait.Mots clĂ©s : Borassus aethiopum, feuilles, inflorescences mĂąles, polyphĂ©nols, tanins, activitĂ© antioxydante
Activité anti-inflammatoire des feuilles dBorassus aethiopum Mart. (Arecaceae)
Le rĂŽnier est un palmier trĂšs utilisĂ© dans la pharmacopĂ©e traditionnelle ; Le calcinĂąt des feuilles est utilisĂ© en boisson dans lâeau pour traiter la bilharziose viscĂ©rale. La tigelle de la noix germĂ©e en dĂ©coction lutte contre lâimpuissance sexuelle, une activitĂ© anti-inflammatoire avec une inhibition de 70% de lâoedĂšme induite par la carragĂ©nine a Ă©tĂ© rĂ©vĂ©lĂ©e dans les extraits dâinflorescences mĂąles. La mĂ©thode de lâoedĂšme induit par la carragĂ©nine de Winter a Ă©tĂ© utilisĂ©e sur des rats de souche Wistar pour mettre en Ă©vidence lâactivitĂ© antiinflammatoire des feuilles de Borassus aethiopum. Lâextrait dâacĂ©tate dâĂ©thyle et sa fraction F1 Ă la dose 30 mg/kg ont une activitĂ© anti-inflammatoire voisine de celle de lâaspirine Ă 30 mg/kg; cette activitĂ© (exprimĂ©e en pourcentage dâinhibition) est respectivement de 79,21%, 73,16 et 92,53% Ă la premiĂšre heure. Ainsi Ă la cinquiĂšme heure ces pourcentages sont 69,18%, 54,59% et 58,75% respectivement pour la rĂ©fĂ©rence, lâextrait dâacĂ©tate dâĂ©thyle et la fraction F1.Mots clĂ©s: Borassus aethiopum Mart, feuilles et activitĂ© anti-inflammatoire
Etude de la variation de la végétation en milieux salé et acide au Sénégal
Lâobjectif de lâĂ©tude Ă©tait de comprendre la variation de la vĂ©gĂ©tation en milieux acide et salĂ©. LarĂ©partition de la vĂ©gĂ©tation des sols sulfatĂ©s acides salĂ©s en fonction de certains paramĂštres (pH, conductivitĂ© Ă©lectrique ou CE, humiditĂ© du sol et texture des sols) a ainsi Ă©tĂ© Ă©tudiĂ©e dans les secteurs situĂ©s au Sud et au Nord du fleuve Saloum (SĂ©nĂ©gal). Des relevĂ©s ont Ă©tĂ© effectuĂ©s sur les diffĂ©rentes unitĂ©s gĂ©omorphologiques (terrasses et dunes) suivant la mĂ©thode des grappes de superficies graduelles. Au niveau de chaque surface de collecte, des Ă©chantillons de sol ont Ă©tĂ© prĂ©levĂ©s Ă 6 cm de profondeur pour dĂ©terminer leur CE, pH, teneur en eau et texture. LâĂ©tude a mis en Ă©vidence la distribution de la vĂ©gĂ©tation en fonction des unitĂ©s gĂ©omorphologiques et des types de faciĂšs ainsi que les changements des faciĂšs Ă©cologiques Ă travers les distributions aires-espĂšces. Lâanalyse en composantes principales a montrĂ© le rĂŽle important de la texture du sol sur le regroupement de la vĂ©gĂ©tation en fonction des gammes de salinitĂ©, dâaciditĂ© et du taux dâhumiditĂ©. La connaissance du mode de regroupement de la vĂ©gĂ©tation en milieux acide et salĂ© pourrait aider dans le choix du type dâamĂ©nagement pour rĂ©gĂ©nĂ©rer les potentialitĂ©s agronomiques de ces sols et leur rĂ©intĂ©gration dans le systĂšme productif national.Mots clĂ©s: AciditĂ© des sols, diversitĂ© biologique, humiditĂ©, salinitĂ© des sols, texture
Etude de lâactivitĂ© antioxydante des extraits des feuilles de Vitex doniana (Verbenacea)
Lâobjectif de la prĂ©sente Ă©tude Ă©tait dâĂ©valuer lâactivitĂ© antioxydante des extraits des feuilles de Vitex doniana par spectrophotomĂ©trie en utilisant les mĂ©thodes de piĂ©geage des radicaux libres 2,2-diphĂ©nyl-1- picryl-hydrazyle (DPPHâą) et acide 2,2â-azino-bis-(3-Ă©thylbenzothiazoline-6-sulfonique) (ABTS+âą). Une extraction Ă©thanolique des feuilles de Vitex doniana a Ă©tĂ© effectuĂ©e au Soxhlet. Lâextrait sec recueilli a Ă©tĂ©Â redissout dans de lâeau puis fractionnĂ© en utilisant successivement de lâhexane, du dichloromĂ©thane et de lâacĂ©tate dâĂ©thyle. Les propriĂ©tĂ©s antioxydantes de lâextrait Ă©thanolique et celles de ses diffĂ©rentes fractions ont étĂ© Ă©valuĂ©es aux concentrations de 2,5 ; 10 ; 100 et 200 ÎŒg/mL. Les pourcentages dâinhibition (PI) expriment lâeffet antioxydant mesurĂ©. Lâextrait Ă©thanolique et ses diffĂ©rentes fractions ont prĂ©sentĂ© une activitĂ© de piĂ©geage des deux radicaux libres. Lors des tests dâinhibition de lâabsorbance du radical DPPHâą, les PI ont variĂ© de (18,15±0,01)% pour la fraction hexanique (2,5 ÎŒg/mL) Ă (92,45±0,01)% pour la fraction dâacĂ©tate dâĂ©thyle (100 ÎŒg/mL). Avec le radical ABTS+âą, les PI ont variĂ© de (52,76±0,05)% pour la fraction hexanique (2,5 ÎŒg/mL) Ă (98,27±0,12)% pour la fraction dâacĂ©tate dâĂ©thyle (100 ÎŒg/mL). Ainsi, lâextrait Ă©thanolique des feuilles de Vitex doniana et ses diffĂ©rentes fractions possĂšdent un pouvoir antioxydant significatif.Mots clĂ©s : ActivitĂ© antioxydante, DPPH, ABTS, Vitex doniana
Extractable phosphorus and rice yield in an ultisol of the humid forest zone in West Africa
Little attention has been devoted to calibrating soil tests for phosphorus (P) in the field for upland rice in West Africa. The information is needed to improve fertilizer P recommendations. A field experiment was conducted in the rainy season of 1994 to establish the relationship between extractable P by Bray 1 and grain yield of four upland rice cultivars grown on an Ultisol in the forest zone of Ivory Coast. The critical limit of Bray 1 P in the soil at 90% relative rice grain yield varied from 12.5 to 15.0 mg P/kg of soil for the four cultivars tested. The P critical limit in the soil tended to be lower for the cultivars of rice earlier found to be efficient at converting applied P into grain yield
Plant phosphorus and rice yield in an Ultisol of the humid forest zone in West Africa
Little attention has been devoted to calibrating plant tissue tests for phosphorus (P) in the field for upland rice in West Africa, although information is needed for improving crop production through efficient P nutrition. A field experiment was conducted under rainfed conditions in the 1994 season to establish the relationships between plant P content and grain yield of upland rice grown on an Ultisol, having a range in extractable P, in the humid forest zone of Ivory Coast. The critical limit of P content in the whole rice plant tops at the tillering stage, at 90% relative grain yield, was found to be 2 g kgâ1 P for the four upland rice cultivars tested. Total P uptake in the biomass was significantly correlated with rice grain (r=0.81, n=20) and straw (r=0.79) yields of the cultivars
Nutrient application reduces iron toxicity in lowland rice in West Africa
Iron toxicity is a widespread nutrient disorder that affects rice growing in inland swamps and on irrigated lowland soils throughout the humid forest and savanna zones of West Africa. It has been reported to reduce lowland
rice yields in West Africa by 12â100%, depending on the intensity of the toxicity and the tolerance of the rice cultivar (Sahrawat et al 1996)
Direct and residual fertilizer phosphorus effects on yield and phosphorus efficiency of upland rice in an Ultisol
Phosphorus (P) deficiency is one of the major limiting factors for crop production in highly weathered soils in the humid zone of West Africa. Very few studies have evaluated the residual value of fertilizer P to rice in these soils. Field experiments were conducted for three years (1993â1995) to determine the response of four upland rice cultivars to fertilizer P applied at 0, 45, 90, 145 and 180 kg P ha-1 only once in 1993, and to fertilizer P residues in 1994 and 1995. The soil at the experimental site, in the humid forest zone of Ivory Coast (West Africa), was an Ultisol, low in available P.
Grain yields of the rice cultivars were significantly increased by fertilizer P in 1993, and by the fertilizer P residues in 1994 and 1995 although the magnitude of response decreased with time since the fertilizer was applied. The cultivars differed in cumulative agronomic and physiological efficiencies, and the efficiencies were higher at the lower rates of P. The amounts of total P removed in three successive crops were similar for all the four rice cultivars although P harvest index was 10â12% higher in the P efficient than inefficient cultivars. The results suggest that the differences observed in the P efficiency of rice cultivars are due to differences in the internal efficiency of P
Response of upland rice to phosphorus in an ultisol in the humid forest zone of West Africa
Phosphorus (P) deficiency is one of the major limiting factor for crop production in highly weathered soils in the
humid tropics. Field experiments were conducted for two years (1992 and 1993) to determine P response and
efficiencies of upland rice cultivars in an Ultisol, low in available P, in the forest zone of Cote d'Ivoire. The rice
cultivars tested were selected from a large number of entries tested earlier for acidity tolerance.
Grain yields of the cultivars were significantly increased by P application. There was little further response
in grain yield at higher rates than 60 kg P ha -1. The rice cultivars differed in agronomic and physiological P
efficiencies and the efficiencies were higher at lower rates of R The rooting depths of the cultivars were increased by application of P at the lowest application rate (30 kg P ha-1).The results suggest that P fertilization of soil acidity-tolerant upland rice cultivars can significantly improve the productivity of the ultisols
Long-Term Phosphorus Fertilizer Effects on Phosphorus Uptake, Efficiency, and Recovery by Upland Rice on an Ultisol
Phosphorus (P) deficiency is a major constraint to upland rice production on highly weathered, low activity clay soils in the humid zone of West Africa. There is a paucity of information on the long-term fertilizer P effects on rice on these soils. A field experiment was conducted for six years (1993â1998) to determine the response of four upland rice cultivars to fertilizer P applied at 0, 45, 90, 135, and 180 kg P haâ1 only once in 1993, and to residual P in 1994, 1995, 1996, and 1998. The experimental site was located on an Ultisol, low in available P, in the humid forest zone of CĂŽte d'Ivoire, West Africa. This paper discusses long-term P effects on P uptake and efficiency of upland rice cultivars. The cultivars evaluated differed in cumulative agronomic and physiological P efficiencies, and the efficiencies were higher at lower P rates for the P-efficient cultivars. The P uptake response and P harvest index were affected by P rate and its residual effect, which decreased with time after P was applied. The mean cumulative recovery of applied P in five crops of four rice cultivars varied from 5.5 to 9.4%. The results suggest that the variation in P efficiency of the cultivars is due to differences in the efficiency of utilization of P for grain production
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