Ramón Fernando García de la Cruz

Synthesis and studies of the antifungal activity of 2-anilino-/2,3-dianilino-/2-phenoxy- and 2,3-diphenoxy-1,4-naphthoquinones

Several synthetic and natural naphthoquinone derivatives have been associated with antifungal activity. Candida albicans is a fungus that is known to exist in the normal human flora, but under certain conditions it can cause mild to fatal infections. Its pathogenicity has been associated with fungus conversion from cellular yeast to filamentous form Y–M. Inhibition of this process by several anilino-, dianilino-, phenoxy-, and diphenoxy-1,4-naphthoquinones was investigated in order to find some correlation between structure, redox properties and biological activity.

Inhibition of polyamine oxidase activity affects tumor development during the maize-Ustilago maydis interaction

Ustilago maydis is a biotrophic plant pathogenic fungus that leads to tumor development in the aerial tissues of its host, Zea mays. These tumors are the result of cell hypertrophy and hyperplasia, and are accompanied by the reprograming of primary and secondary metabolism of infected plants. Up to now, little is known regarding key plant actors and their role in tumor development during the interaction with U. maydis. Polyamines are small aliphatic amines that regulate plant growth, development and stress responses. In a previous study, we found substantial increases of polyamine levels in tumors. In the present work, we describe the maize polyamine oxidase (PAO) gene family, its contribution to hydrogen peroxide (H2O2) production and its possible role in tumor development induced by U. maydis. Histochemical analysis revealed that chlorotic lesions and maize tumors induced by U. maydis accumulate H2O2 to significant levels. Maize plants inoculated with U. maydis and treated with the PAO inhibitor 1,8-diaminooctane exhibit a notable reduction of H2O2 accumulation in infected tissues and a significant drop in PAO activity. This treatment also reduced disease symptoms in infected plants. Finally, among six maize PAO genes only the ZmPAO1, which encodes an extracellular enzyme, is up-regulated in tumors. Our data suggest that H2O2 produced through PA catabolism by ZmPAO1 plays an important role in tumor development during the maize-U. maydis interaction.

Kinetic modeling of the biosorption of Cd2+ ions from aqueous solutions onto Eichhornia crassipes roots using potentiometry: low-cost alternative to conventional methods

This work presents the use of potentiometric measurements for kinetic studies of biosorption of Cd2+ ions from aqueous solutions on Eichhornia crassipes roots. The open circuit potential of the Cd/Cd2+ electrode of the first kind was measured during the bioadsorption process. The amount of Cd2+ ions accumulated was determined in real time. The data were fit to different models, with the pseudo-second-order model proving to be the best in describing the data. The advantages and limitations of the methodology proposed relative to the traditional method are discussed.

A Kinetic, Equilibrium, and Thermodynamic Study on the Biosorption of Tl + and Cd 2+ by Eichhornia crassipes Roots Using Carbon Paste Electrode

In this work, Eichhornia crassipes roots were used as a modifier for carbon paste electrode in a biosorption study of thallium (Tl+) and cadmium (Cd2+) ions. The ions were accumulated on modified electrode surfaces at open circuit potential and analyzed by square wave anodic stripping voltammetry. Before the biosorption study, the effect of ratio of biomass and binder in uptake metal was evaluated. The biosorption study shows that adsorption of ions was dependent on pH. The kinetic study showed that, for both ions, experimental data were well described by the pseudo-second order model (R2 > 0.99) and the equilibrium was better described by the Langmuir model. The value of dimensionless equilibrium parameter (RL) obtained in the equilibrium study showed that Eichhornia crassipes can be considered an effective biomaterial for Tl+ and Cd2+ removal from an aqueous solution. The thermodynamic parameters calculated, enthalpy (ΔHo), entropy (ΔSo) and Gibbs energy (ΔGo), indicated that the biosorption process was spontaneous and endothermic.