Counterion Condensation on Spheres in the Salt-free Limit

A highly-charged spherical colloid in a salt-free environment exerts such a powerful attraction on its counterions that a certain fraction condenses onto the surface of a particle. The degree of condensation depends on the curvature of the surface. So, for instance, condensation is triggered on a highly-charged sphere only if the radius exceeds a certain critical radius \collrad^{*}. \collrad^{*} is expected to be a simple function of the volume fraction of particles. To test these predictions, we prepare spherical particles which contain a covalently-bound ionic liquid, which is engineered to dissociate efficiently in a low-dielectric medium. By varying the proportion of ionic liquid to monomer we synthesise nonpolar dispersions of highly-charged spheres which contain essentially no free co-ions. The only ions in the system are counterions generated by the dissociation of surface-bound groups. We study the electrophoretic mobility of this salt-free system as a function of the colloid volume fraction, the particle radius, and the bare charge density and find evidence for extensive counterion condensation. At low electric fields, we observe excellent agreement with Poisson-Boltzmann predictions for counterion condensation on spheres. At high electric fields however, where ion advection is dominant, the electrophoretic mobility is enhanced significantly which we attribute to hydrodynamic stripping of the condensed layer of counterions from the surface of the particle.Comment: 13 pages, 9 figures and two table

Potential Phytopharmacy and Food Applications of Capsicum spp.: A Comprehensive Review

Capsicum genus (Solanaceae) is native to the Americas. Today, it is an important agricultural crop cultivated around the world, not only due to its economic importance, but also for the nutritional value of the fruits. Among their phytochemical constituents, capsaicinoids are characteristic and responsible of the pungency of sharp-tasting cultivars. Moreover, Capsicum and capsaicinoids (mainly, capsaicin) have been largely studied because of their health benefits. Thus, this study reviews the scientific knowledge about Capsicum spp. and their phytochemicals against cancer, diabetes, gastrointestinal diseases, pain, and metabolic syndrome, as well as their antioxidant and antimicrobial activity. These bioactivities can be the basis of the formulation of functional ingredients and natural preservatives containing Capsicum extracts or isolated compounds

Antisickling properties of divanilloylquinic acids isolated from Fagara zanthoxyloides Lam. (Rutaceae)

Fagara zanthoxyloides Lam. (syn. Zanthoxylum zanthoxyloides) (Rutaceae) is the most cited Fagara species for the treatment and the prevention of sickle cell disease crisis. Sickle cell anemia (SCA) is a public health problem in many countries particularly in Africa. The present study was designed to evaluate the antisickling properties of three isomeric divanilloylquinic acids (3,4-O-divanilloylquinic acid or burkinabin A; 3,5-O-divanilloylquinic acid or burkinabin B and 4,5-O-divanilloylquinic acid or burkinabin C) identified previously by LC/MS/NMR analysis in the root bark of F. zanthoxyloides [Ouattara et al. 2004. LC/MS/NMR analysis of isomeric divanilloylquinic acids from the root bark of Fagara zanthoxyloides Lam. Phytochemistry 65, 1145-1151]. The three isomers showed interesting antisickling properties which increased from burkinabins A to C. © 2008 Elsevier GmbH. All rights reserved.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

TRADITIONAL MEDICINE DEVELOPMENT FOR MEDICAL AND DENTAL PRIMARY HEALTH CARE DELIVERY SYSTEM IN AFRICA.

Traditional African Medicine (TAM) is our socio-economic and socio-cultural heritage, servicing over 80% of the populations in Africa. Although, it has come a long way from the times of our ancestors, not much significant progress on its development and utilization had taken place due to colonial suppression on one hand, foreign religions in particular, absolute lack of patriotism and political will of our Governments, and then on the other hand, the carefree attitudes of most African medical scientists of all categories. It is incontrovertible that TAM exhibits far more merits than demerits and its values can be exploited provided the Africans themselves can approach it with an open mind and scientific mentality. The degree of sensitization and mobilization by the World Health Organization (WHO) has encouraged some African countries to commence serious development on TAM. The African Regional Director of the WHO has outlined a few guidelines on the responsibilities of all African nations for the realistic development of TAM, in order to sustain our health agenda and perpetuate our culture. The gradual extinction of the forests and the inevitable disappearance of the aged Traditional Medical Practitioner should pose an impending deadline for us to learn, acquire and document our medical cultural endowment for the benefit of all Africans and indeed the entire mankind

TOXICITY POTENTIALS OF SENNA PODOCARPA (GUILL.ET PERR.) LOCK PODS IN RODENTS

The effects of acute (LD50) and sub-chronic doses of the aqueous infusion of Senna podocarpa (Guill. et Perr.) Lock pod on the liver, kidney, brain and testis of mice and rats were studied, respectively. The acute toxicity studies did not produce any observable lethal effects and the calculated LD50 was 6.6 g/kg. The histopathological analysis of the liver, kidney, brain and testis showed no adverse effect. Behavioral observations and the histopathological findings did not show significant differences between the control and the treated groups. There were no marked adverse alterations or degeneration of tissues since these vital organs showed normal architectures suggesting no morphological disturbances as compared with the control group. The findings indicated that the aqueous infusion of S. podocarpa pod was devoid of overt acute and sub-chronic toxic effects in mice and rats

TOXICITY POTENTIALS OF SENNA PODOCARPA (GUILL.ET PERR.) LOCK PODS IN RODENTS

The effects of acute (LD50) and sub-chronic doses of the aqueous infusion of Senna podocarpa (Guill. et Perr.) Lock pod on the liver, kidney, brain and testis of mice and rats were studied, respectively. The acute toxicity studies did not produce any observable lethal effects and the calculated LD50 was 6.6 g/kg. The histopathological analysis of the liver, kidney, brain and testis showed no adverse effect. Behavioral observations and the histopathological findings did not show significant differences between the control and the treated groups. There were no marked adverse alterations or degeneration of tissues since these vital organs showed normal architectures suggesting no morphological disturbances as compared with the control group. The findings indicated that the aqueous infusion of S. podocarpa pod was devoid of overt acute and sub-chronic toxic effects in mice and rats

Full length Research Article - TOXICITY POTENTIALS OF CASSIA FISTULA FRUITS AS LAXATIVE WITH REFERENCE TO SENNA

The aqueous extract of the pods of Cassia fistula Linn (Leguminosae - Caesalpinoideae), cultivated in Ile-Ife, Nigeria were investigated for pharmacological and toxicological properties. The in-vitro effect of Cassia fistula infusion on isolated guinea-pig ileum was examined. The acute and sub-chronic toxicity of the infusion of C. fistula and Cassia acutifolia Del. Pod-(Senokot tablet) as the reference drug were also determined. The results obtained for C .fistula infusion when compared with senokot tablet showed that the infusion of Cassia fistula pods possessed very low levels of toxicity, having the LD50 of 6600mg/kg and also without any pathological effects on the organs examined microscopically. It is therefore concluded from the study that C. fistula pod infusion could be safely utilized as laxative drugs and as a substitute for the official Senna

Counterion condensation on spheres in the salt-free limit

A highly-charged spherical colloid in a salt-free environment exerts such a powerful attraction on its counterions that a certain fraction condenses onto the surface of a particle. The degree of condensation depends on the curvature of the surface. So, for instance, condensation is triggered on a highly-charged sphere only if the radius exceeds a certain critical radius R*. R* is expected to be a simple function of the volume fraction of particles. To test these predictions, we prepare spherical particles which contain a covalently-bound ionic liquid, which is engineered to dissociate efficiently in a low-dielectric medium. By varying the proportion of ionic liquid to monomer we synthesise nonpolar dispersions of highly-charged spheres which contain essentially no free co-ions. The only ions in the system are counterions generated by the dissociation of surface-bound groups. We study the electrophoretic mobility of this salt-free system as a function of the colloid volume fraction, the particle radius, and the bare charge density and find evidence for extensive counterion condensation. At low electric fields, we observe excellent agreement with Poisson–Boltzmann predictions for counterion condensation on spheres. At high electric fields however, where ion advection is dominant, the electrophoretic mobility is enhanced significantly which we attribute to hydrodynamic stripping of the condensed layer of counterions from the surface of the particle