A novel procedure to measure the antioxidant capacity of Yerba maté extracts

Yerba maté extracts have in vitro antioxidant capacity attributed to the presence of polyphenolic compounds, mainly chlorogenic acids and dicaffeoylquinic acid derivatives. DPPH is one of the most used assays to measure the antioxidant capacity of pure compounds and plant extracts. It is difficult to compare the results between studies because this assay is applied in too many different conditions by the different research groups. Thus, in order to assess the antioxidant capacity of yerba maté extracts, the following procedure is proposed: 100 µL of an aqueous dilution of the extracts is mixed in duplicate with 3.0 mL of a DPPH 'work solution in absolute methanol (100 µM.L-1), with an incubation time of 120 minutes in darkness at 37 ± 1 °C, and then absorbance is read at 517 nm against absolute methanol. The results should be expressed as ascorbic acid equivalents or Trolox equivalents in mass percentage (g% dm, dry matter) in order to facilitate comparisons. The AOC of the ethanolic extracts ranged between 12.8 and 23.1 g TE % dm and from 9.1 to 16.4 g AAE % dm. The AOC determined by the DPPH assay proposed in the present study can be related to the total polyphenolic content determined by the Folin-Ciocalteu assay

Calcium-controlled peroxidase secretion by sugarbeet cell suspensions in relation to habituation

peer reviewedSugarbeet cells from normal and habituated callus released peroxidases in liquid cultures, in proportion to their endogenous level. Calcium promoted this release more in the normal than in the habituated line. Treatment of the cells with sodium azide, sodium hydrogenarsenate or phenothiazine inhibited the calcium effect, which indicated a dependence on metabolic energy and on calmodulin regulation. The Ca ionophore Ro (bromolasalocid ethanolate) restricted peroxidase release. © 1982 Martinus Nijhoff/Dr W. Junk Publishers

Classification supervisée hybride par motifs lexicaux étendus et classificateurs SVM

International audienceWe present the comparison and combination of two different semi automatic classification methods: an original linguistic based analysis, named extended lexical patterns (motifs lexicaux étendus, MLE) and a machine learning approach (SVM). Classification is supervised because of the use of a thesaurus containing the definition of categories. First, both systems are used and evaluated separately on the same real dataset: law and parliament documents in French. Quite unexpectedly, MLE performs as well as a state-of-the-art method such as SVM. During the second step, the combined method gave a performance improvement which underlines the complementarities of both basis methods.Dans le contexte de l'indexation semi-automatique de textes, nous présentons la comparaison et la combinaison de deux méthodes de classification mettant en oeuvre des approches différentes : analyse par une méthode originale à forte composante linguistique que nous nommons motifs lexicaux étendus (MLE) d'une part et apprentissage artificiel SVM d'autre part. La classification est de type supervisée car elle exploite un ensemble de catégories définies par un thésaurus documentaire. Dans un premier temps, les deux systèmes sont appliqués et évalués séparément sur un même jeu de données réelles, des textes de type législatif et parlementaire en français. De manière quelque peu inattendue, la méthode MLE permet d'atteindre des performances tout à fait compétitives par rapport à la technique state-of-the-art que constitue SVM. Les méthodes sont ensuite combinées dans le but d'obtenir une performance finale supérieure aux performances individuelles. Le gain obtenu indique une complémentarité entre les deux méthodes