Actividad antioxidante y polifenoles de las algas marinas halimeda opuntia y halimeda monile

En este trabajo se estudió la actividad antioxidante de dos especies de algas marinas (H. opuntia y H. monile) mediante el ensayo de atrapamiento de radicales DPPH• y el sistema β-Caroteno-acido linoleico. Adicionalmente a las fracciones de ácidos fenolicos libres, ésteres solubles y ésteres insolubles de ácidos fenólicos se les determinó el contenido en fenoles totales mediante la técnica de Folin-Ciocalteu y posteriormente se identificaron y cuantificaron 8 ácidos fenólicos y cinámicos, resultando el componente mayoritario el ácido salicílico. En los ensayos utilizados se obtuvieron valores altos de actividad antioxidante para las diferentes fracciones. A partir de estos resultados se puede postular que la actividad antioxidante de los extractos polares de estas algas pudiera ser explicada, al menos parcialmente, por la presencia de los ácidos fenólicos y cinámicos. En el caso del alga Halimeda monile, de acuerdo con la literatura consultada, es el primer reporte de la actividad antioxidante.In this paper, the antioxidant activity displayed by two different green seaweed species (H. opuntia y H. monile) was studied using the β- carotene/ linoleic acid and the DPPH• scavenging.systems as different experimental in vitro antioxidant assessment models. Polar seaweed fractions containing free phenolic acids, soluble esters and insoluble esters of phenolic acids were chemically characterized in terms of their phenolic content and composition. In that direction, 8 phenolic acids were identified and quantified, and salycilic acid was shown to be the majoritary compound on the fractions from both species. In addition, the polar fractions were proved to exert antioxidant activity in the two used experimental systems with considerably low values of CI50. Thus, in view of these findings, the antioxidant activity of these polar Halimeda spp. extracts could be supported and at least partially related to the presence of phenolic acids. In case of Halimeda monile this is, at least to the extend of our knowledge, the first report of such biological activity

Lower bounds for measurable chromatic numbers

The Lovasz theta function provides a lower bound for the chromatic number of finite graphs based on the solution of a semidefinite program. In this paper we generalize it so that it gives a lower bound for the measurable chromatic number of distance graphs on compact metric spaces. In particular we consider distance graphs on the unit sphere. There we transform the original infinite semidefinite program into an infinite linear program which then turns out to be an extremal question about Jacobi polynomials which we solve explicitly in the limit. As an application we derive new lower bounds for the measurable chromatic number of the Euclidean space in dimensions 10,..., 24, and we give a new proof that it grows exponentially with the dimension.Comment: 18 pages, (v3) Section 8 revised and some corrections, to appear in Geometric and Functional Analysi

Soil cover plants on water erosion control in the South of Minas Gerais

Water erosion is responsible for soil, water, carbon and nutrient losses, turning into the most important type of degradation of Brazilian soils. This study aimed to evaluate the influence of three cover plants under two tillage systems on water erosion control in an Argisol at south of Minas Gerais state, Brazil. The cover plants utilized in the study were pigeon pea, jack bean and millet, under contour seeding and downslope tillage. Experimental plots of 4 x 12 m, with 9% slope, under natural rainfall were used for the quantification of losses of soil, water, nutrients, and organic matter. One experimental plot was kept without plant cover (reference). Higher erosivity was observed in December and January, although a great quantity of erosive rainfall was detected during the whole raining period. Contour seeding provided a greater reduction of water erosion than downslope tillage, as expected. The jack bean under contour seeding revealed the lowest values of soil, water, nutrients and organic matter losses

Feeding strategies and energy to protein ratio on tambaqui performance and physiology

The objective of this work was to evaluate the effect of feed deprivation and refeeding with diets containing different energy to protein ratios (E/P) on the performance and physiology of juvenile tambaqui (Colossoma macropomum). A 4x2 factorial arrangement with three replicates was used, with four E/P ratios (11.5, 10.5, 9.5, and 8.5 kcal g-1 digestible energy per protein) and two feeding regimens (with and without deprivation), during 60 days. Fish from the food-deprived group were fasted for 14 days and refed from the fifteenth to the sixtieth day, whereas the remaining fish were fed for 60 days. At the end of the experimental period, weight of fish subjected to food deprivation was lower than that of those continuously fed; however, this condition did not influence the physiological parameters analyzed. Tambaqui fed 11.5 kcal g-1 achieved lower final weight than those fed with the other diets, in both regimens. Among the physiological parameters, only plasma protein presented significant increase in fish fed 8.5 kcal g-1, in both feeding regimens, probably due to the higher dietary protein concentration. These results indicate that fish show a partial compensatory growth, and that 10.5 kcal g-1 can be recommended for the diet of juvenile tambaqui