Saponinas de quinua (Chenopodium quinoa Willd.): un subproducto con alto potencial biológico / Saponins of Quinoa (Chenopodium quinoa Willd.): a by-product with high biological potential

Las saponinas son un tipo de metabolito secundario ampliamente estudiado por sus reconocidas propiedades biológicas. Gran parte de las investigaciones en fitoquímica están dirigidas a encontrar nuevas fuentes naturales de saponinas con aplicación medicinal. La quinua (Chenopodium quinoa Willd.) es una planta que ha alcanzado un valioso reconocimiento por ser una fuente de alimentos altamente nutritivos, así como una especie rica en saponinas triterpénicas contenidas, principalmente, en la cáscara de las semillas. A la fecha, se han identificado alrededor de 30 saponinas derivadas de la hederagenina y de los ácidos oleanólico, fitolacagénico y serjanico en la planta. El consumo del grano de quinua implica la remoción de la cáscara a fin de reducir su sabor amargo, la ingesta de niveles residuales de saponinas y la obtención de un subproducto rico en las mismas. Esta revisión, inicialmente, ofrece una contex-tualización general de las saponinas; posteriormente, recopila las características estructurales de las saponinas identificadas en la quinua, describe el efecto del procesamiento del grano en su contenido de saponinas y, finalmente, expone los efectos biológicos explorados con extractos de saponinas de quinua, los cuales pueden ser considerados como punto de partida en investigaciones futuras dirigidas al fortalecimiento de su uso en el campo farmacéutico y/o nutracéutico.

Saponins are a type of secondary metabolite that have been widely studied due to their recognized biological properties. Most research into phytochemical has focused on finding new natural sources of saponins with medicinal interest. Quinoa ( Chenopodium quinoa) is a plant that has attained importance as a valuable source of food highly nutritious and rich in triterpenes saponins which are mainly in the outer husks of the seeds. Up to date, about 30 saponins derived from hederagenin, oleanolic acid, phytolaccagenic acid, and serjanic acid have been identified in the plant. Quinoa consumption involves removal of the husk to reduce its bitter taste, the ingestion of residual levels of saponins and obtaining a product rich in saponins. This revision, initially, offers a general contextualization of saponins, then, gathers the structural features of identified saponins in quinoa, describes the effect of the processing of the grain on its saponins content, and finally, exposes the biological properties explored with quinoa saponins extracts which might be considered as a starting point for future investigations aimed at strengthening of their use in the pharmaceutical and/or nutraceutical field.

Determination of the complexing capacity of wine for Zn using the absence of gradients and nernstian equilibrium stripping technique.

The complexing capacity of synthetic (0.011 M tartrate in 13.5% ethanol) and real wine (Raimat Abadia) in titrations with added total Zn concentrations up to 0.03 M has been determined following the free Zn concentrations with AGNES (absence of gradients and Nernstian equilibrium stripping) technique. A correction to find the preconcentration factor or gain (Y(1)) really applied at each one of the ionic strengths reached due to Zn additions along the titration has been applied. The standard implementation of AGNES to real wine led to the observation of two anomalous behaviors: (a) an increasingly negative current in the deposition stage (labeled as "HER" effect) and (b) a minimum in the currents of the stripping stage plot (labeled as the "dip" effect). A practical strategy to apply AGNES avoiding the dip effect has been developed to quantify properly free Zn concentrations. The van den Berg-Ruzic-Lee linearization method (assuming the existence of just 1:1 complexes) has been adapted to consider the dilution effect and the ionic strength changes. Aggregated stability constants and total ligand concentrations have been calculated from synthetic and wine titration data. The found complexing capacity in the studied wine (c(T,L) = 0.0179 ± 0.0007 M) indicates the contribution of ligands other than tartrate (which is confirmed to be the main one).

Determination of free Zn2+ concentration in synthetic and natural samples with AGNES (Absence of Gradients and Nernstian Equilibrium Stripping) and DMT (Donnan Membrane Technique).

The determination of free Zn(2+) ion concentration is a key in the study of environmental systems like river water and soils, due to its impact on bioavailability and toxicity. AGNES (Absence of Gradients and Nernstian Equilibrium Stripping) and DMT (Donnan Membrane Technique) are emerging techniques suited for the determination of free heavy metal concentrations, especially in the case of Zn(2+), given that there is no commercial Ion Selective Electrode. In this work, both techniques have been applied to synthetic samples (containing Zn and NTA) and natural samples (Rhine river water and soils), showing good agreement. pH fluctuations in DMT and N(2)/CO(2) purging system used in AGNES did not affect considerably the measurements done in Rhine river water and soil samples. Results of DMT in situ of Rhine river water are comparable to those of AGNES in the lab. The comparison of this work provides a cross-validation for both techniques.