This study was carried out to evaluate the overall antioxidant capacity of the essential oils of the leaves of Clausena anisata (Rutaceae) and Plectranthus glandulosus (Labiateae), commonly used in the traditional method of grain storage in the northern part of Cameroon. Towards this objective, the co-oxidation of βcarotene as well as the reducing power, the radical scavenging capacity and the conjugated dienes profile of the essential oils during storage for a period of 10 days at 28 ± 2.2 °C and 65±5.7% RH were determined. The least concentration necessary to prevent 50% oxidation (EC 50 ) of β-carotene was found to be 6.53 mg/l, 5.84 mg/l and 524 µg/l respectively for C. anisata, P. glandulosus and butylated hydroxytoluene (BHT) which was the control. On the other hand, the reducing power of the different oils in a decreasing order was found to be P. glandulosus (EC 50 =2.41) > C. anisata (EC 50 =1.77 mg/l) while the EC 50 of Scavenging abilities were 2.66 and 3.02 mg/l for C. anisata and P. glandulosus respectively. Based on the conjugated dienes profile, the essential oils showed higher antioxidant activity compared to Butylated hydroxytoluene (BHT) activity. The effective time (ET 50 ) of the formulation ranging from 300 to 1000 ppm varied from 2 to 8 days for C. anisata and from 3 to 11 days for P. glandulosus. For the control (BHT), the effect varied from 5 to 15 days at an exposition temperature of 50 °C.
Leafy vegetables form part of the diet of most people of tropical Africa. The contribution of these leafy vegetables to their mineral needs has not been well elaborated. The aim of this study was to determine the effects of different processing methods on the mineral composition and anti-nutritional components of some tropical leafy vegetables. Twenty-one species of different vegetables locally grown and consumed in the northern region of Cameroon were collected and analyzed for their iron, copper, manganese, zinc, magnesium, calcium, sodium and potassium content. The levels of anti-nutrients like phytates, oxalates, tannins and saponins that are likely to affect the bioavailability of these minerals were also determined. The effects of processing methods on the mineral composition and anti-nutritional components of these leafy vegetables were also determined. Amongst these species, Moringa oleifera, Hibiscus canabinum, Solanum nigrum, Cucurbita maxima and Vernonia calvoana that are used for soup, and found in relative abundance in the region were subjected to two cooking methods (boiling plus squeeze-washing and a combination of boiling in alkaline salt (kanwa) plus squeeze-washing). The levels of iron, zinc, manganese, copper, magnesium, calcium, sodium and potassium varied in the different vegetables. In all vegetables studied, magnesium was the most abundant mineral. The iron levels ranged from 14.99±2.00mg/100g dry weight (DW) in M. oleifera to 167.42 ± 18.63mg/100g DW in H. sabdariffa. Boiling and squeezewashing led to significant losses of minerals with sodium being the most affected. On the contrary, higher values of iron, calcium and sodium were found in samples that were boiled in alkaline salt and squeeze-washed. The levels of antinutrients were also reduced as a consequence of processing. Percentage losses during boiling with or without alkaline salt were between 25.4 and 55.5% for phytates, 11.1 and 80% for oxalates, 16.4 and 68.5% for saponins and 25 and 26.44% for tannins. Boiling, therefore, with or without alkaline salt is an effective means of reducing the levels of these antinutrients in vegetables to tolerable levels.
Maize occupies an important place in the resolution of food insecurity problems in the sub-Saharan region of Africa. However due to poor post-harvest technologies, more than 35% of annual crop yield is often lost during storage as a consequence of insect attack. While chemical pesticides constitute an efficient tool for reducing these losses, current excessive usage runs the risk of modifying the quality and safety of foods produced from these grains. The use of essential oils of plant origin for grain storage has been advocated as a non invasive method with limited or no effect on the quality and safety of the grains or their products. This study was carried out as an evidence of bioactivity of two essential oils of Clausena anisata (Willd.) Hook and Plectranthus glandulosus Hook F. against adults of Tribolium castaneum Herbst and Sitophilus zeamais Motschulsky, which are two important stored product insect pests in Northern Cameroon. Because of the low persistence of the insecticidal activities of these plants, their essential oils to achieve a complete protection of the stored products must be applied at frequent delays. The present investigation focuses on the occurrence of residues of these oils on treated maize grain and flour. The doses of crude essential oils used to treat adults of S. zeamais and T. castaneum in a contact and inhalation process were their LD 99 s. After the evaluation of their insecticidal activity the persistence of each essential oil was observed every 2 days till 14 days. After the disappearance of their insecticidal activities, essential oil was re-extracted and their residual compounds were identified from treated grain and flour. The major compounds of C. anisata are, estragole, α-humulene, germacrene D and (E)-nerolidol. In P. glandulosus they are: fenchone, α-terpinolene and piperitenone oxide. After 14 days, only 64.24% of compounds of C. anisata were recovered on treated flour and 55.16% on grains. Concerning P. glandulosus, 48.94% was recovered on grains and 61.23% on flour.
Les fleuves Logone et Chari qui se jettent dans le Lac Tchad, sont exposés à toute forme de pollution. Le but de ce travail est d'évaluer la contamination par les métaux lourds des eaux, des sédiments et des poissons du Lac Tchad. Trois espèces de poissons: Tilapia nilotica, Lates niloticus et Arius latiscutatus ont été obtenues au Lac Tchad et transportées sous glace au laboratoire. Le Cd, le Pb et le Cr ont été dosés dans la tête, le foie, la chair et les os de ces poissons, dans les sédiments et l'eau au spectrophotomètre d'absorption atomique. Le Cd et le Pb n'étaient pas détectés dans les eaux et les sédiments. En comparant nos résultats obtenus dans la chair des poissons, à la grille de qualité de Mersch, la pollution des eaux du Lac Tchad va d'une situation intermédiaire (Cd) à une pollution importante (Cr). Les sédiments étaient plus contaminés que les eaux. Toutes ces valeurs sont au-delà des normes existantes. L'analyse des variances (ANOVA) inter espèces, au seuil de 95% entre les organes, montre qu'il y a une corrélation positive (r = 0,74) et très significative (p = 0,02) entre la chair et les os des différentes espèces.
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