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.

The naphthoquinone structure is found in several natural compounds and is associated with diverse biological properties. In most cases, the biological activity of naphthoquinones has been related to their redox and acid-base properties, which can be modulated by directly adding a substituent to the 1,4-naphthoquinone ring. The synthesis of novel derivatives of 1,4-naphthoquinone is of important interest, since these compounds exhibit strong action as antimalarial, antibacterial, antifungical, and anticancer agents. This review presents a recent overview about compounds with a 1,4-naphthoquinone structure isolated from natural or synthetic sources. The reported biological activities and the proposed action mechanisms for these compounds are also described.

La estructura 1,4-naftoquinona se encuentra en un gran número de compuestos de origen natural y es asociada con diversas propiedades biológicas. En la mayoría de los casos, la actividad biológica de las naftoquinonas se ha relacionado con sus propiedades de oxidación-reducción y ácido-base, las cuales pueden ser moduladas modificando sintéticamente los sustituyentes unidos al anillo 1,4-naftoquinona. La síntesis de nuevos derivados de 1,4-naftoquinona es de particular importancia, ya que estos compuestos muestran importantes actividades como agentes antiparasitarios, antibacterianos, antifúngicos y anticancerígenos. En esta revisión se muestra el panorama actual de los compuestos que contienen la estructura 1,4-naftoquinona tanto aislados de fuentes naturales como de origen sintético. También, se describen las actividades biológicas reportadas y los principales mecanismos de acción que se han propuesto para estos compuestos.