Antioxidant phenolics of different barley (Hordeum vulgarae L.) cultivars
Notice bibliographique
Résumé
The extracts from six barley cultivars (Hordeum vulgarae L.) grown in the Canadian prairies, namely AC Metcalfe, Falcon, Phoenix, Tercel, Tyto, and Peregrine, were evaluated for their potential antioxidant, antiradical, and antiproliferative efficacies by various chemical and biological methods. Antioxidative compounds were solvent-extracted after optimizing extraction parameters (solvent composition, extraction temperature, and time) using response surface methodology (RSM). In addition, the distribution of antioxidative constituents in the barley grain was investigated by separately pearling two barley cultivars (Falcon and AC Metcalfe) into seven fractions (F1-F7) in a layer-wise fashion up to 50% of the kernel weight. Antioxidative efficacy of the layers and the remaining kernel (pearled grain) was evaluated using chemical and biological methods. Furthermore, phenolic compounds present in the six barley samples were separated into free, soluble conjugates, and insoluble-bound fractions using alkaline hydrolysis and the antioxidative potential of each of the fractions was also investigated. -- The optimum conditions for extraction of antioxidative components from barley extracts were 80% aqueous methanol, 60°C, and 40 min as determined by RSM. Total phenolic content (TPC) of whole kernel extracts ranged from 13.58 to 22.93 and 0.81 to 1.38 mg ferulic acid equivalents per gram lyophilizate and defatted material, respectively. The order of TPC was Peregrine > AC Metcalfe > Falcon > Tyto > Phoenix > Tercel. Total antioxidant capacity (TAC), as measured by Trolox equivalent antioxidant capacity (TEAC), ranged from 3.74 to 6.82 μmol Trolox equivalents per gram defatted material. Antioxidant and antiradical efficacies of barley extracts were evaluated using different assays including 2,2-diphenyl-1-picrylhydrazyl (DPPH), superoxide, oxygen radical absorbance capacity (ORACFL), hydroxyl radical averting capacity (HORACFL), and photochemiluminescence (PCL). All six barley extracts showed significant antioxidant and antiradical activities although the order of their activity changed from assay to assay. Barley extracts exhibited substantial metal chelation activity as measured by 2,2 '- bipyridyl competition assay. Evaluating the whole barley extracts using a number of model systems such as β-carotene/linoleate, bulk stripped corn oil as well as accelerated oxidation study, using Rancimat®, further revealed that the whole barley extract possessed strong antioxidant activity. Whole grain extracts exhibited strong inhibitory effects against copper-induced human LDL cholesterol oxidation as well as peroxyl and hydroxyl radical-induced DNA double strand scission. Barley extracts also exhibited substantial antiproliferative effect against growth of Caco-2 human colorectal adenocarcinoma cells in a concentration-dependent manner. -- In the second phase of the study involving fractionation, it was revealed that anti oxidative constituents were mainly located in the outer 9% (w/w) of the kernel. TPC of Falcon and AC Metcalfe fractions ranged from 0.51 to 6.26 and 0.17 to 4.16 as ferulic acid equivalents per gram defatted material. TAC, as measured by TEAC, varied from 0.45 to 60 and 0.69 to 56 μmol Trolox equivalents per gram defatted material, respectively. Antioxidant efficacy gradually diminished from the outer layers to the inner layers. In general, antioxidant efficacy determined by other methods followed a similar trend to that of TAC. -- In the last phase of the study involving hydrolysis of phenolic compounds, it was revealed that a greater proportion of antioxidative compounds were present in insoluble-bound form followed by soluble conjugate form. It was further revealed that the antioxidant and antiradical efficacies of insoluble bound phenolic compounds were the highest followed by soluble conjugates and free phenolic. The predominant phenolic acid detected in barley extracts was ferulic acid. The other phenolic acids detected were vanillic, caffeic, p-coumaric and sinapic acids.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».