References of "Michiels, Jean-Albert"
     in
Bookmark and Share    
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 29 (2 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 189 (16 ULg)
Full Text
See detailConcentrations of pepsinogens A and C in peripheral blood of cattle at different developmental stages.
Melo de Sousa, Noelita ULg; Michiels, Jean-Albert ULg; Terroni, D. et al

in Proceedings of the 6th European Congress of Bovine Health and Management (ECBHM) (2011, September 07)

Measurements of global proteolytic activity of pepsinogens are successfully used for diagnosis of gastric nematode parasitism in cattle. Higher pepsinogen concentrations detected in peripheral circulation ... [more ▼]

Measurements of global proteolytic activity of pepsinogens are successfully used for diagnosis of gastric nematode parasitism in cattle. Higher pepsinogen concentrations detected in peripheral circulation were found to be associated with damage in gastric mucosa The aim of the present study was to investigate the ontogenesis of PgnA and PgnC in cattle. Bovine PgnA and PgnC were isolated in our laboratory. Both antigens were labeled to 125I by using chloramine T method. Standard curves ranged from 125 to 1.0 ng/mL. Antisera were raised in rabbits: AS866 (anti-PgnA) and AS869 (anti-PgnC). The optimal dilutions for primary antisera were 1:15,000 and 1:20,000 for AS866 and AS869, respectively. In order to establish the ontogenesis of both PgnA and PgnC, samples were collected from 50 bovine fetuses (3rd to the 9th month), 18 calves and 57 adult cattle. Mean(±SEM) concentrations of PgnA were 4.6±0.7 ng/mL, 78.9±6.7 ng/mL and 133.2±17.6 ng/mL in fetuses, calves and mature cows, respectively. Concentrations of PgnC were <0.9 ng/mL, 13.5±1.1 ng/ml and 201.5±26.5 ng/ml in fetuses, calves and mature cows, respectively. The ratio PgnA/PgnC concentrations decrease from fetal age (maximal ratio due to undetectable PgnC concentrations), being 5.8 in young calves and lowest (0.7) in mature cows. In conclusion, PgnA and PgnC concentrations can be distinctly measured by specific RIA systems. Ratio PgnA/PgnC concentrations can be useful to better understand the ontogenesis of gastric aspartic proteinases in cattle. It is expected that clinical application of these assays will help vet practitioners to establish diagnosis of gastric nematode parasitism in dairy and beef herds taking into account the age of the animal. [less ▲]

Detailed reference viewed: 56 (7 ULg)