Antisickling properties, thermal and photochemical degradations of anthocyanin extracts from Annona senegalensis (Annonaceae)

Anthocyanin crude extracts and fractions of Annona senegalensis leaves were screened for their antisickling properties using a validated in vitro bioassay model of sickle cell anaemia. Preparative thin layer chromatography of acetylated anthocyanin crude extracts carried out with chloroform as solvent provided two active fractions named Ac1 and Ac2. Fraction Ac2 was  quantitatively isolated and submitted to physicochemical investigations. Thermo-degradation kinetics of the above fraction Ac2 at 80 °C and 100 °C revealed first order reaction with the rate constants k (s-1) of 8.10 10-4 and 11.0 10-4, respectively. Anthocyanin crude extracts and the separated fractions showed in vitro antisickling activity. This activity justifies the use of this plant by congolese traditional healers; thus anthocyanins could be the major active principles. However, these natural pigments are unstable towards UV-vis light irradiations and heat. The conservation of this plant should then be performed in the absence of heat and/or light.Keywords: Sickle cell anemia, Annona senegalensis, anthocyanins, light irradiation, thermodegradatio

Trace metal distribution in the bed, bank and suspended sediment of the Ravensbourne River and its implication for sediment monitoring in an urban river

Purpose This study aims to identify a suitable sediment compartment for sediment quality monitoring by: (a) studying the concentration of trace metals (Cd, Cu, Ni, Pb and Zn) in the bed, bank and suspended sediment compartments of the Ravensbourne River to establish any differences in trace metal concentrations with compartment; (b) determining the influence of sediment particle size fractions ( 0.05) in the concentrations of metals between the suspended sediment and the < 63 μm bed sediment fraction, but there was a significant difference (p < 0.05) between the suspended sediment and the < 63 μm bank sediment fraction. There were also significant differences between the concentrations of metals in the < 63 μm and the 63 μm–2 mm fractions. Generally, the Ravensbourne River did not comply with the draft UK sediment quality guidelines for the metals analysed. Conclusions This study shows the importance of identifying a suitable sediment compartment to sample for compliance with sediment quality standards. The bed and suspended sediments are the most widely used sediment compartments for sediment monitoring, but collecting sufficient mass of the < 63 μm sediment fraction for monitoring presents a challenge for urban gravel bed rivers like the Ravensbourne River. It seems appropriate to establish individual monitoring regimes for different rivers

Activité antidrépanocytaire et thermodégradation des anthocyanes extraits de Sterculia quinqueloba et Ficus capensis

L’activité antifalcémiante de Ficus capensis et Sterculia quinqueloba, deux plantes utilisées en médicine traditionnelle contre la drépanocytose dans la ville de Lubumbashi (RD Congo), a été testée en utilisant le test d’Emmel. Les résultats obtenus ont montré une activité antifalcémiante importante in vitro pour les deux plantes. Cette activité serait due aux anthocyanes. Les concentrations minimales de normalisation desdrépanocytes obtenus sont de 2,5 μg/ml et 3,0 μg/ml pour les anthocyanes de Ficus capensis et de Sterculia quinqueloba respectivement. Le fractionnement de ces anthocyanes par chromatographie sur couche mince utilisant les mélanges des solvants acétate d’éthyle-éthanol 96%-eau distillée-acide acétique 10 :5 :10 :1 pour Ficus capensis et benzène-méthanol-éthanol 96%-acide acétique 2 :4 :1 :1 a montré que ce sont les fractions ayant respectivement les rapports frontaux de 0,49 et 0,66 qui sont les plus actives. Ces anthocyanes ont montré une instabilité vis-à-vis de la chaleur. La cinétique de thermodégradation de la fraction la plus active des anthocyanes de Ficus capensis a donné les valeurs des constantes de vitesse expérimentales de 3,4 10-4 s-1 à 363 K et de 6,2 10-4 s-1 à 393 K.Keywords : Drépanocytose, Test d’Emmel, Concentration Minimale de Normalisation, Taux de normalisation