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Prooxidative Potential of Photo-Irradiated Aqueous Extracts of Grape Pomace, a Recyclable Resource from Winemaking Process.

Tsukada M, Nakashima T, Kamachi T, Niwano Y - PLoS ONE (2016)

Bottom Line: That is, reduction of dissolved oxygen by proton-coupled electron transferred from the photo-oxidized phenolic hydroxyl group would form H2O2.The resultant H2O2 was then photolyzed to generate hydroxyl radical (•OH).The prooxidant activity of the photo-irradiated extract indicated by •OH yield was more potent than that of the photo-irradiated GSE and (+)-catechin, and this was well reflected in their bactericidal activity in which the photo-irradiated extract could kill the bacteria more efficiently than did the photo-irradiated GSE and (+)-catechin.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 2-12-1-M6-7 Ookayama, Meguro-ku, Tokyo, 152-8250, Japan.

ABSTRACT
Our previous study revealed that aqueous extract of grape pomace obtained from a winemaking process could exert bactericidal action upon photo-irradiation via reactive oxygen species (ROS) formation. In the present study, we focused on chemical composition and prooxidative profile of the extract. Liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) analysis showed that polyphenolic compounds including catechin monomers, dimers, trimers, and polyphenolic glucosides were contained. The polyphenol rich fraction used for the LC-ESI-MS analysis generated hydrogen peroxide (H2O2) upon photo-irradiation possibly initiated by photo-oxidation of phenolic hydroxyl group. That is, reduction of dissolved oxygen by proton-coupled electron transferred from the photo-oxidized phenolic hydroxyl group would form H2O2. The resultant H2O2 was then photolyzed to generate hydroxyl radical (•OH). The prooxidative profile of the extract in terms of •OH generation pattern upon photo-irradiation was similar to that of grape seed extract (GSE) as an authentic polyphenol product and (+)-catechin as a pure polyphenolic compound, and in all the three samples •OH generation could be retained during photo-irradiation for at least a couple of hours. The prooxidant activity of the photo-irradiated extract indicated by •OH yield was more potent than that of the photo-irradiated GSE and (+)-catechin, and this was well reflected in their bactericidal activity in which the photo-irradiated extract could kill the bacteria more efficiently than did the photo-irradiated GSE and (+)-catechin.

No MeSH data available.


LC-ESI-MS analyses of standard reagents (A) and representative LC chromatogram with estimated chemical structural formulas obtained from MeOH soluble fraction of GPE (B).
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pone.0158197.g001: LC-ESI-MS analyses of standard reagents (A) and representative LC chromatogram with estimated chemical structural formulas obtained from MeOH soluble fraction of GPE (B).

Mentions: The MS and UV spectra of each peak were compared with those of known compounds using existing databases, the Dictionary of Natural Products (http://dnp.chemnetbase.com/). A representative LC chromatogram with estimated chemical structural formulas obtained from MeOH soluble fraction of GPE is shown in Fig 1. The fraction contained phenolic compounds including (+)-catechin, (-)-epicatechin, catechin dimers, and polyphenolic glucosides. Fig 2 shows extracted ion chromatograms of m/z 291, 579, and 867, obtained from MeOH fraction of GPE, indicating that the fraction contained catechin monomers, dimers, and trimmers. Based on the assumption that catechin monomers would not be contained in MeOH insoluble fraction, the calculated concentrations of (+)-catechin and (–)-epicatechin in GPE with 0.5 mg/ml total polyphenol were approximately 20 and 8 μg/ml, respectively.


Prooxidative Potential of Photo-Irradiated Aqueous Extracts of Grape Pomace, a Recyclable Resource from Winemaking Process.

Tsukada M, Nakashima T, Kamachi T, Niwano Y - PLoS ONE (2016)

LC-ESI-MS analyses of standard reagents (A) and representative LC chromatogram with estimated chemical structural formulas obtained from MeOH soluble fraction of GPE (B).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4920348&req=5

pone.0158197.g001: LC-ESI-MS analyses of standard reagents (A) and representative LC chromatogram with estimated chemical structural formulas obtained from MeOH soluble fraction of GPE (B).
Mentions: The MS and UV spectra of each peak were compared with those of known compounds using existing databases, the Dictionary of Natural Products (http://dnp.chemnetbase.com/). A representative LC chromatogram with estimated chemical structural formulas obtained from MeOH soluble fraction of GPE is shown in Fig 1. The fraction contained phenolic compounds including (+)-catechin, (-)-epicatechin, catechin dimers, and polyphenolic glucosides. Fig 2 shows extracted ion chromatograms of m/z 291, 579, and 867, obtained from MeOH fraction of GPE, indicating that the fraction contained catechin monomers, dimers, and trimmers. Based on the assumption that catechin monomers would not be contained in MeOH insoluble fraction, the calculated concentrations of (+)-catechin and (–)-epicatechin in GPE with 0.5 mg/ml total polyphenol were approximately 20 and 8 μg/ml, respectively.

Bottom Line: That is, reduction of dissolved oxygen by proton-coupled electron transferred from the photo-oxidized phenolic hydroxyl group would form H2O2.The resultant H2O2 was then photolyzed to generate hydroxyl radical (•OH).The prooxidant activity of the photo-irradiated extract indicated by •OH yield was more potent than that of the photo-irradiated GSE and (+)-catechin, and this was well reflected in their bactericidal activity in which the photo-irradiated extract could kill the bacteria more efficiently than did the photo-irradiated GSE and (+)-catechin.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 2-12-1-M6-7 Ookayama, Meguro-ku, Tokyo, 152-8250, Japan.

ABSTRACT
Our previous study revealed that aqueous extract of grape pomace obtained from a winemaking process could exert bactericidal action upon photo-irradiation via reactive oxygen species (ROS) formation. In the present study, we focused on chemical composition and prooxidative profile of the extract. Liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) analysis showed that polyphenolic compounds including catechin monomers, dimers, trimers, and polyphenolic glucosides were contained. The polyphenol rich fraction used for the LC-ESI-MS analysis generated hydrogen peroxide (H2O2) upon photo-irradiation possibly initiated by photo-oxidation of phenolic hydroxyl group. That is, reduction of dissolved oxygen by proton-coupled electron transferred from the photo-oxidized phenolic hydroxyl group would form H2O2. The resultant H2O2 was then photolyzed to generate hydroxyl radical (•OH). The prooxidative profile of the extract in terms of •OH generation pattern upon photo-irradiation was similar to that of grape seed extract (GSE) as an authentic polyphenol product and (+)-catechin as a pure polyphenolic compound, and in all the three samples •OH generation could be retained during photo-irradiation for at least a couple of hours. The prooxidant activity of the photo-irradiated extract indicated by •OH yield was more potent than that of the photo-irradiated GSE and (+)-catechin, and this was well reflected in their bactericidal activity in which the photo-irradiated extract could kill the bacteria more efficiently than did the photo-irradiated GSE and (+)-catechin.

No MeSH data available.