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See detailBilberry extract (Antho 50) selectively induces redox-sensitive caspase 3-related apoptosis in chronic lymphocytic leukemia cells by targeting the Bcl-2/Bad pathway
Alhosin, Mahmoud; León-González1, Antonio J.; Dandache et al

in Scientific Reports (2015), 5

Defect in apoptosis has been implicated as a major cause of resistance to chemotherapy observed in B cell chronic lymphocytic leukaemia (B CLL). This study evaluated the pro-apoptotic effect of an ... [more ▼]

Defect in apoptosis has been implicated as a major cause of resistance to chemotherapy observed in B cell chronic lymphocytic leukaemia (B CLL). This study evaluated the pro-apoptotic effect of an anthocyanin-rich dietary bilberry extract (Antho 50) on B CLL cells from 30 patients and on peripheral blood mononuclear cells (PBMCs) from healthy subjects, and determined the underlying mechanism. Antho 50 induced concentration- and time-dependent pro-apoptotic effects in B CLL cells isolated from patients but little or no effect in PBMCs. Among the main phenolic compounds present in this bilberry extract, delphinidin-3-O-glucoside and delphinidin-3-O-rutinoside showed the highest apoptotic effect on B CLL cells, suggesting that anthocyanins play a main role in the cytotoxic activity. Antho 50-induced apoptosis is associated with activation of caspase 3 and down-regulation of the anti-apoptotic protein UHRF1. Antho 50 induced also rapid dephosphorylation of Akt and Bad, and down-regulation of Bcl-2 resulting in reduced cell viability. Antho 50 significantly induced PEG-catalase-sensitive formation of reactive oxygen species in B CLL cells. PEG-catalase prevented the Antho 50-induced reduced cell viability, induction of apoptosis, up-regulation of caspase 3, down-regulation of UHRF1 and Bcl-2, and dephosphorylation of Bad. The present findings indicate that Antho 50 exhibits strong pro-apoptotic activity through redox-sensitive caspase 3 activation-related mechanism in B CLL cells involving dysregulation of Bad/Bcl-2 pathway. This activity is due, at least in part, to a composition rich on glucoside and rutinoside derivatives of delphinidin. They further suggest that Antho 50 has chemotherapeutic potential by targeting selectively B CLL cells. [less ▲]

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See detailAdventitious organogenesis induced in sweet orange (Citrus sinensis L.) var. "half-blood" maltese: morphogenetic and histological study
Benmahmoud, Kaouther; Jedidi, Zmna; Najar, Asma et al

in International Journal of Agronomy and Agricultural Research (2015), 6(2), 1-7

Tunisian citrus crops are faced to several abiotic and biotic constraints among which virus and virus-like diseases are incurable. The production of virus-free plants systematically needs the use of in ... [more ▼]

Tunisian citrus crops are faced to several abiotic and biotic constraints among which virus and virus-like diseases are incurable. The production of virus-free plants systematically needs the use of in vitro techniques. In this context, somatic embryogenesis and further plantlet regeneration of the Tunisian “half-blood” Maltese orange were obtained using explants consisting in style/stigma collected from unopened flowers. Somatic embryos were induced on Murashige and Skoog medium containing 13.3 µM 6-benzylaminopurine and 500 mg.l-1 malt extract, but their germination was obtained on hormone free-medium. Somatic embryogenesis was induced indirectly from intermediate friable callus initiated at the basal part of the style. Somatic embryos exhibited central procambial cells and were surrounded by a protoderm isolating them from the callus. These embryos had bipolar structure confirmed by the presence of shoot and root apices at cotyledonary stage. The use of cotyledon excised from those embryos failed to regenerate somatic embryos, but gave rise to direct organogenesis in two forms, true buds and protuberances both evolved in shoots after transfer in hormone-free medium. According to histological observations, protuberances are induced from epidermal and subepidermal cells of the cotyledon explant and remain closely attached to their mother tissue even at the shoot stage. [less ▲]

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See detailEffects of 2,4-dichlorophenoxyacetic acid combined to 6-Benzylaminopurine on callus induction, total phenolic and ascorbic acid production, and antioxidant activities in leaf tissue cultures of Crataegus azarolus L. var. aronia
Chaabani, Ghaya; Tabart, Jessica; Kevers, Claire ULg et al

in Acta Physiologiae Plantarum (2015), 37

The present research work describes the effects of 2,4-dichlorophenoxyacetic acid (2,4-D)/6-Benzylamino-purine (BAP) ratio on callus induction, total phenols and ascorbic acid production and antioxidant ... [more ▼]

The present research work describes the effects of 2,4-dichlorophenoxyacetic acid (2,4-D)/6-Benzylamino-purine (BAP) ratio on callus induction, total phenols and ascorbic acid production and antioxidant activities in leaf-derived calli of Crataegus azarolus (hawthorn). The supplementation of 1.0 mg/L 2,4-D and 1.0 mg/L BAP to MS medium was found to be the most efficient for callus induction (as percentage and fresh weigh). The results of biochemical analysis showed that the highest total phenols contents were obtained in callus cultured on MS medium supplemented with 2.0 mg/L 2,4-D and 1.0 mg/L BAP (52 ± 0.56 mg GAE/g DM) and were significantly lower than those of intact leaves (76 ± 1.72 mg GAE/g DM). However, the highest ascorbic acid contents were found in callus cultured on MS supplemented with 1.0 mg/L 2,4-D and 0.5 mg/L BAP (0.96 ± 0.13 mg AAE/g DM) and these amounts were statistically similar to those found in leaves tissues (0.74 ± 0.07 mg AAE/g DM). Antioxidant activities of callus extracts were determined using two TEAC assays and results showed that extract of callus cultured on MS medium supplemented with 2.0 mg/L 2,4-D and 1.0 mg/L BAP have the greatest antiradical activities against DPPH (124 ± 2.92 mg TE/g DM) and ABTS (0.19 ± 0.02 mg TE/g DM) compared to the leaves of field-grown plant. Thus, the use of high level of 2,4-D over BAP can be suitable to enhance the quality more than the quantity of bioactive compounds in leaf callus culture of hawthorn. [less ▲]

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See detailAntioxidant capacity and phenolic composition of red wines from various grape varieties : specificity of pinot noir.
degives, Julien; Kevers, Claire ULg; DEFRAIGNE, Jean ULg et al

in Giuseppe Viali (Ed.) 3rd international conference on cellular environmental stressors in biology and medicine : focus on redox reactions (2014, June 25)

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See detailAntioxidant fractions and phenolic constituents from leaves of Pluchea carolinensis and Pluchea rosea
Perera Cordoba, Wilmer Hervet; Wauters, Jean-Noël ULg; Kevers, Claire ULg et al

in Free Radicals and Antioxidants (2014), 4(2), 1-7

Abstract: Objective: To evaluated the antioxidant potential of several polar fractions of P. carolinensis and P. rosea as well as pure chemicals, some of them quantified in both species by HPLC. Methods ... [more ▼]

Abstract: Objective: To evaluated the antioxidant potential of several polar fractions of P. carolinensis and P. rosea as well as pure chemicals, some of them quantified in both species by HPLC. Methods: The antioxidant potential of polar fractions and pure chemicals were assayed by 2,2-diphenyl-1-picrylhydrazyl and oxygen radical potential methods. The phenolic content was performed by using Folin–Ciocalteu’s reagent. Specific phenolic acids and flavonoids were quantified by DAD-RP-HPLC. Results: The highest DPPH antioxidant potential expressed in mg TE/gDE were frequently measured in fractions from n-butyl alcohol i.e 2 (192.1 ± 0.3); 6 (181.0 ± 0.1) of P. carolinensis and in fraction 7 (188.1 ± 5.5) of P. rosea while for ORAC (mg TE/gDE) assay fraction 2 (543.0 ± 64.6) and 4 (501.4 ± 49.7) of P. carolinensis and 3 (401.3 ± 16.1) and 6 (401.3 ± 16.1) of P. rosea showed the best results. Some flavonoids and phenolic acids were also assayed; all of them showed highest Oxygen radical absorbance capacity values. Conclusion: We report the antioxidant potential of polar fractions, as well as of some pure phenolics responsible of the antioxidant potential. Some phenolics were identified and quantified for the first time in both species. Apparently, caffeoylquinic acid derivatives contribute more significant to the total antioxidant potential of the extracts. [less ▲]

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See detailAntioxidant capacity of small dark fruits. Influence of cultivars and harvest time
Kevers, Claire ULg; PINCEMAIL, Joël ULg; Defraigne, Jean-Olivier ULg et al

in Journal of Berry Research (2014), 4

BACKGROUND: Small dark fruits represent one of the most important sources of bioactive compounds with antioxidant capacity in the human diet. The content of health-promoting antioxidants in these fruits ... [more ▼]

BACKGROUND: Small dark fruits represent one of the most important sources of bioactive compounds with antioxidant capacity in the human diet. The content of health-promoting antioxidants in these fruits may be important information to take into account when a fruit producer has to choose which cultivar to grow. OBJECTIVE: It is important to know how antioxidant capacity and antioxidant compounds as total phenolics and ascorbic acid vary between 9 small dark fruit species and for each species among cultivars (2 to 10 per species). METHODS: The antioxidant capacity (ORAC assay), total phenolic (Folin-Ciocalteu) and ascorbic acid content were measured in 9 fruits (plums, blackcurrants, blackberries, blueberries, cherries, redcurrants, raspberries, white currants and gooseberries) / 42 cultivars harvested at maturity during their high production period. RESULTS: The comparison of the average of the various cultivars of each small fruits showed that blackcurrants had the best antioxidant capacity (with plums), the highest ascorbic acid content and the highest total phenolic content (with blackberries). The present study shows that total phenolic compounds, ascorbic acid and antioxidant capacity strongly differed between genotypes of each small dark fruits. Other parameters as harvest time, culture conditions and maturity degree at the harvest may also influence the antioxidant capacity of small fruits. CONCLUSION: Among small dark fruits, blackcurrants have high qualities. Choices of variety, harvest time and maturity degree are important for all fruits. [less ▲]

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See detailAntioxidant capacity and phenolic composition of red wines from various grape varieties: Specificity of Pinot Noir.
Van Leeuw, Robin; Kevers, Claire ULg; PINCEMAIL, Joël ULg et al

in Journal of Food Composition and Analysis (2014), 36

Wines produced from various grape varieties present different properties affecting taste and color. The hypothesis was that grape genotype could have a deep impact on wine antioxidant properties and ... [more ▼]

Wines produced from various grape varieties present different properties affecting taste and color. The hypothesis was that grape genotype could have a deep impact on wine antioxidant properties and phenolic composition. But in this study on 38 different wines of 4 main grape varieties, large variability in the levels of individual phenolic compounds as well as in antioxidant capacity was observed in each grape variety. Comparisons of the wine varieties based on their individual phenolic profile (flavonols, anthocyanidins, flavan-3-ols, phenolic acids, resveratrol…) and antioxidant capacities (ORAC, DPPH, hemolysis, ESR, total phenolics) showed limited differences. An exception was the group of wines made from the grape variety Pinot Noir, in which the range of phenolic compounds was different from the other wines: anthocyanidins (87 mg L-1, 119 to 206 mg L-1 in other grape varieties) and flavonols (17 mg L-1, 20 to 57 mg L-1in others except Primitivo) showed lower levels while flavanols (327 mg L-1, 152 to 244 mg L-1 in others) and phenolic acids (161 mg L-1, 103 to 152 mg L-1 in others) showed levels higher than in the other wines. This different profile was associated with a lower antioxidant capacity (i.e. mean ORAC value: 20988 for Pinot Noir, 27820 to 33651 for others). [less ▲]

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See detailEffect of polyamines or precursors on the hyperhydricity process in micropropagated apple trees.
Tabart; Franck, Thierry ULg; Kevers, Claire ULg et al

in Plant Cell, Tissue & Organ Culture (2014)

Hyperhydricity is a physiological disorder affecting tissue-culture-generated plants. It is associated with excessive hydration and poor lignification. The effects of exogenous polyamines (spermidine and ... [more ▼]

Hyperhydricity is a physiological disorder affecting tissue-culture-generated plants. It is associated with excessive hydration and poor lignification. The effects of exogenous polyamines (spermidine and putrescine) and polyamine precursors (arginine and ornithine) were studied on ‘Jonagold’ apple shoots subjected to hyperhydric conditions for one in vitro multiplication cycle (28 days) on a culture medium containing gelrite as gelling agent. Supplementation of the gelrite-containing medium with 10-5 M spermidine, ornithine, or arginine reduced the percentage of hyperhydricity by at least 50%. Exogenous supplementation with spermidine or a polyamine precursor also caused total phenolics and the antioxidant capacity (measured by ORAC and DPPH assays) to decrease in shoots during the first two weeks. These results suggest an important role of spermidine and its precursor ornithine in countering hyperhydricity. Supplementation could help to maintain high endogenous levels of polyamines and phenolamides necessary for cell osmoregulation, antioxidant protection, cell wall cross-linking, and plant growth regulation. [less ▲]

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See detailRelationship between vasodilation capacity, antioxidant activity and phenolic content of different types of wine aging in oak barrels
Degives, Julien; Kevers, Claire ULg; PINCEMAIL, Joël ULg et al

in International Conference Wine Active Compounds 2014 (2014)

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See detailEtude de la dynamique des populations d'insectes sur la culture du riz NERICA dans les conditions du Masuku, Sud-Est du Gabon (Franceville)
ONDO OVONO, Paul; GATARASI, Thaddée; OBAME MINKO, Daniel et al

in International Journal of Biological and Chemical Sciences (2014)

La dynamique des populations d’insectes sur la culture du riz a été étudiée durant toutes les phases de croissance. L’essai a été installé sur les parcelles pédagogiques de l’Institut National Supérieur ... [more ▼]

La dynamique des populations d’insectes sur la culture du riz a été étudiée durant toutes les phases de croissance. L’essai a été installé sur les parcelles pédagogiques de l’Institut National Supérieur d’Agronomie et de Biotechnologies à Franceville. Il s’inscrit dans le cadre de la poursuite des travaux d’évaluation de l’adaptabilité de nouvelles variétés de riz de type NERICA, introduites dans la province du Haut –Ogooué au Sud-Est du Gabon. L’objectif de la présente étude est de collecter des informations concernant les insectes susceptibles de s’attaquer au riz et de sélectionner les variétés NERICA qui résistent le mieux aux attaques. Chacune des six variétés de type NERICA (1, 4, 11, 12, 14 et 17) a été semée en utilisant un dispositif en blocs complètement randomisés avec trois répétitions, en 2010 et 2011. La collecte des insectes volants a été effectuée au moyen de pièges aériens et du filet entomologique. Au sol, la capture s’est faite au moyen de pièges. Les larves d’insectes foreurs des tiges, les chenilles et les pucerons des racines ont été capturés à la main. Au total, 46 familles appartenant à 9 ordres ont été recensées donc 29 renferment des espèces nuisibles et définies comme ravageuses du riz. Les 17 autres familles sont classées comme insectes utiles. Les stades de tallage, d’initiation paniculaire et d’épiaison ont été en général les plus visités par les différentes familles d’insectes. Les variétés NERICA 1 et NERICA 11 ont présenté les plus faibles taux d’infestation et de dégâts. Par ailleurs, la perte en biomasse a été considérable chez toutes les variétés. [less ▲]

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See detailAntioxidant capacity of hydrophilic food matrices: optimization and validation of ORAC assay.
Kevers, Claire ULg; Sipel, Arnaud; PINCEMAIL, Joël ULg et al

in Food Analytical Methods (2014), 7

It is widely accepted that ORAC is a useful method for assessing food extracts that contain various antioxidants. The principal aim of this study was to validate the ORAC assay. We first identified ... [more ▼]

It is widely accepted that ORAC is a useful method for assessing food extracts that contain various antioxidants. The principal aim of this study was to validate the ORAC assay. We first identified parameters that can interfere with the ORAC assay and we optimized it. Then, experiments were conducted to determine the limits of linearity and response function, to determine the accuracy profiles to circumvent some of the drawbacks of traditional validation procedures. Trueness, selectivity and limits of quantification of the method were also determined. Our objective of ORAC method validation is thus to give guarantees that most of the results generated during use of this method will be close enough to unknown true value of antioxidant capacity of food matrices. The validation results indicate that the described method will give accurate and reliable results for Trolox equivalent values ranging from 50 to 200 µmol/L. [less ▲]

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See detailDeriving a global antioxidant score for commercial juices by multivariate graphical and scoring techniques: applications to blackcurrant juice
Tabart, Jessica; Kevers, Claire ULg; Dardenne, Nadia ULg et al

in Preedy (Ed.) Processing and Impact on Antioxidants in Beverages (2014)

Blackcurrants constitute an important source of potential health promoting phytochemicals (e.g. phenolic compounds, ascorbic acid) due to their antioxidant properties. Only small portions of berries are ... [more ▼]

Blackcurrants constitute an important source of potential health promoting phytochemicals (e.g. phenolic compounds, ascorbic acid) due to their antioxidant properties. Only small portions of berries are consumed fresh, most of their intake coming from processed foods, such as juices. Seven techniques were used to measure antioxidant capacity and antioxidant compounds of 10 juices. This yielded a large disparity of results. No single test, even the most popular ORAC assay, is able to compare the antioxidant capacity of similar food matrix such as blackcurrant juices. By combining tests from a large battery of « antioxidant » assays, it is possible to improve the discrimination of a food matrix by establishing a Global Antioxidant Score (GAS) which correlates well with graphical representations like Chernoff faces or stars. The latter approaches may help food industry managers and authorities to compare their « antioxidant » products with those existing on the market. [less ▲]

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See detailOn the Potential Effect of Increased Dietary Intake of Fruits and Vegetables on Biomarkers of Lipid Peroxidation in Type 2 Diabetes Patients
PINCEMAIL, Joël ULg; PAQUOT, Nicolas ULg; Cillard, J et al

in Journal of Pharmacy & Nutrition Sciences (2013), 3(3),

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See detailImproving micropropagation of Dioscorea cayenensis – D. rotundata complex by the use of nodal cuttings and microtubers
Ondo Ovono, Paul; Kevers, Claire ULg; Dommes, Jacques ULg

in Acta Agriculturae Scandinavica : Section B - Soil & Plant Science (2013), 63(7), 653-656

Yams (Dioscorea spp) are tuber crops used as staple food in Africa because of their nutritional value. In contrast to the inefficiency of traditional method of planting, micropropagation by nodal cuttings ... [more ▼]

Yams (Dioscorea spp) are tuber crops used as staple food in Africa because of their nutritional value. In contrast to the inefficiency of traditional method of planting, micropropagation by nodal cuttings allows to increase the multiplication and the rapid production of pathogen free plant material. The first aim ofIn this work was to show tha,t micropropagation of yam from both nodal cuttings and microtubers was first possible tested both from nodal cuttings and from microtubersand compared. It appears that microtubers rapidly develop shoots, more rapidly than nodal cuttings. Respectively 16 and 28 weeks are needed to obtain 10 cm high shoots. In a second time, the two techniques of multiplication were used in parallel to improve the multiplication rate. So, one nodal cutting after 28 weeks of culture can be subcultured as nodal cuttings (for 28 other weeks) and as microtuber parts (for 16 weeks). At the end of each subculture of nodes or microtubers, nodal cuttings and microtubers were cut and subcultured. This technique allowed obtaining more rapidly a lot of microtubers. The use of nodal cuttings allowed obtaining about 3 104 cuttings in 2 years. The additional use of the formed microtubers and the division of the microtubers at the subculture in three parts increased this multiplication rate by 15. The importance of this work was to consider microtubers not only as final planting product, but also to include them in the in vitro multiplication protocol to drastically increase the production of cuttings and finally of microtubers. [less ▲]

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See detailAntioxidant potential of different plum cultivars during storage
MIHALACHE ARION, Cristina; TABART, Jessica; Kevers, Claire ULg et al

in Food Chemistry (2013), 146

Plums, the most commonly consumed fruits from Romania, are fruit rich in bioactive compounds like antioxidants. This research work was carried out to investigate the antioxidant potential of twelve plum ... [more ▼]

Plums, the most commonly consumed fruits from Romania, are fruit rich in bioactive compounds like antioxidants. This research work was carried out to investigate the antioxidant potential of twelve plum cultivars, fresh and stored during 10 days at 4°C by using different methods (DPPH, ORAC and erythrocyte resistance to haemolysis). The contents of total phenolic compounds and total anthocyanins were also determined by specific spectrometric methods. Significant differences between fresh and stored plum cultivars (p < 0.05) were found. Storage at 4°C resulted in an increase in antioxidant potential and anthocyanins content of the autumn plum varieties. Autumn plum varieties showed also a higher antioxidant capacity than summer varieties, as assessed by the ORAC and the haemolysis resistance assays. Our results suggest that even after storage plums could be a good source of antioxidants, which may provides health-promoting effects for humans. [less ▲]

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See detailEvaluation au champ des caractéristiques agromorphologiques de certaines variétés de riz NERICA testées au sud-est du Gabon
Ondo Ovono, Paul; Maganga-Louembe, Mariette; Kevers, Claire ULg et al

in Agronomie africaine (2013), 25

The intensified cultivation of the rice crop constitutes an important challenge for Gabon in its strategy for food security of the populations. For this purpose, six NERICA rice varieties were selected by ... [more ▼]

The intensified cultivation of the rice crop constitutes an important challenge for Gabon in its strategy for food security of the populations. For this purpose, six NERICA rice varieties were selected by farmers from the PVS (Participatory Varietal Selection) trials that were conducted MASUKU in High-Ogooué sine 2009. The agromorphological characteristics like tillering and plant height and yield components (number of panicles/m2, number of grains/panicle, 1000 grain weight, sterility rate) were tested during the vegetative phase. The results were exciting. The six new varieties revealed the following good characteristics: - a good aptitude for high tillering (more than 350 tillers per m2 ); - a good height (more than 120 cm per plant); - a high number of panicles per m2(more than 220 panicles per m2); - the good weight of 1000 grains (more than 25 g). In general, the yield per hectare was very good varying between 4200 kg/ha for NERICA 11 and 7150 kg/ha for the NERICA 14. Consequently, the six newNERICA rice varieties are well adapted to the agroecological conditions of MASUKU and can be diffused in the rice plains of the locality. [less ▲]

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See detailVariation in phenolic constituents and antioxidant capacities of plant organs of three Cuban species of Pluchea Cass. (Asteraceae) under ex vitro and in vitro growth conditions.
Perera, Wilmer; Kevers, Claire ULg; Michiels, Jean-Albert ULg et al

in Journal of Medicinal Plants Research (2013)

The phenolic content and antioxidant capacity of Cuban Pluchea species extracts were measured by polar extraction technique with the aim to optimize antioxidant-rich extracts. Our results highlighted the ... [more ▼]

The phenolic content and antioxidant capacity of Cuban Pluchea species extracts were measured by polar extraction technique with the aim to optimize antioxidant-rich extracts. Our results highlighted the variability of the phenolic content and antioxidant potential in the genus Pluchea according to the species and plant organs. The antioxidant capacity and phenolics were additionally examined in P. carolinensis under various growth conditions, ex vitro (location, age, and harvest time) and in vitro (amount of added cytokinin). Some specific phenolic compounds were monitored during the harvest time. Leaves proved to be richest in antioxidants, followed by inflorescences. The antioxidant capacity of P. carolinensis (DPPH: 103.2 ±1.3 mg TE/g DW; ORAC: 254.4 ±14.2 mg TE/g DW) and P. rosea (DPPH: 97.2 ±5.9 mg TE/g DW ORAC: 286.7 ±23.7 mg TE/g DW) leaf extracts were higher than that measured in material from various plant species, including fruits, vegetables and condiments. adult P. carolinensis grown in a natural environment and harvested in winter showed the highest phenolic content and antioxidant activity. A micropropagation protocol was developed for P. carolinensis. The presence of cytokinin in the in vitro culture medium increased the antioxidant capacity in leaves, but the level remained lower than in natural plants. [less ▲]

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See detailSample dilution influences the determination of antioxidant capacity in food. How to minimize it?
Sipel, Arnaud; Kevers, Claire ULg; PINCEMAIL, Joël ULg et al

in Food Analytical Methods (2013), 6(5), 1485-1491

The influence of sample dilution on the measurement of antioxidant capacity was analyzed. To ensure the reproducibility of results it is necessary to realize such scarce investigations. This study focuses ... [more ▼]

The influence of sample dilution on the measurement of antioxidant capacity was analyzed. To ensure the reproducibility of results it is necessary to realize such scarce investigations. This study focuses on different antioxidant capacity assays, commonly used for the analysis of pure substances and food extracts. For all compounds and foods tested in most of the four assays (TEAC, DPPH and ORAC), effects of sample dilution on the measured (and recalculated) antioxidant capacity were observed, differences up to 28% between dilutions. An extrapolation method was proposed to obtain a “real value” thus to minimize the effects of the sample dilution. This extrapolation method is relatively simple, based on a linear regression of 4 or 5 appropriate dilutions of the sample and applicable to the various assays. The use of such a method will improve the consistency of inter-laboratory antioxidant capacity data and thus permit better comparisons. In contrast, there was no dilution problem with FRAP assays. [less ▲]

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See detailExtraction conditions can greatly influence antioxidant capacity assays in plant food matrices
Michiels, Jean-Albert ULg; Kevers, Claire ULg; Pincemail, Joël ULg et al

in Food Chemistry (2012), 130

The estimated antioxidant capacity of different matrices can vary considerably between research reports. Besides intrinsic factors (not studied here), our work showed that may have various causes. Firstly ... [more ▼]

The estimated antioxidant capacity of different matrices can vary considerably between research reports. Besides intrinsic factors (not studied here), our work showed that may have various causes. Firstly, different methods are used to measure antioxidant capacity. Secondly, the results obtained for a single matrix by one method (such as ORAC) can vary with the extraction conditions. Parameters having a great impact on the amount and composition of antioxidants in extracts, and thus on the measured antioxidant capacity, notably include the extraction solvent composition, temperature, extraction time (duration), solvent-to-solid ratio, and storage conditions. Standardization of the extraction procedure is thus necessary for accurate and reproducible determination of the antioxidant capacity and phenolics in different food matrices by different laboratories. In this study we optimised such a procedure for four fresh plant matrices (orange, apple, leek, and broccoli). The optimised procedure requires extraction in a mixture of acetone/water/acetic acid (70/28/2, v/v/v) for 1 h at 4°C, with a solvent-to-solid ratio of 20 mL per 1 g. Fresh material should be used, but if this is not possible, one may lyophilise the plant matrices or store the extracts for a few days at -20°C before analysis. [less ▲]

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