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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.


Effect of photo-irradiation time on the yield of H2O2 in MeOH soluble and insoluble fractions.Each value represents the mean with standard deviation (n = 3). Significant differences (p<0.05) are denoted by different alphabetical letters. ND: not detected.
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pone.0158197.g004: Effect of photo-irradiation time on the yield of H2O2 in MeOH soluble and insoluble fractions.Each value represents the mean with standard deviation (n = 3). Significant differences (p<0.05) are denoted by different alphabetical letters. ND: not detected.

Mentions: Total polyphenol contents of MeOH soluble and insoluble fractions are summarized in Fig 3. Total polyphenol content of MeOH soluble fraction was approximately 3.5 times higher than that of MeOH insoluble fraction (p<0.01). Fig 4 shows H2O2 concentrations in photo-irradiated MeOH soluble and insoluble fractions. Although H2O2 formation increased with irradiation time in the both fractions, the resultant H2O2 concentrations in MeOH fraction were much higher than those in corresponding MeOH insoluble fractions (p<0.05). Fig 5 summarizes the effect of photo-irradiation time on •OH generation in MeOH soluble and insoluble fractions. As was the case with H2O2, •OH generation as expressed as DMPO-OH concentration increased with irradiation time in the both fractions, and the resultant DMPO-OH concentrations in MeOH soluble fraction were much higher than those in corresponding MeOH insoluble fractions (p<0.05). DMPO-OH levels in the negative controls (kept under a light-shielding condition for 60 s) were trace levels in the both fractions.


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)

Effect of photo-irradiation time on the yield of H2O2 in MeOH soluble and insoluble fractions.Each value represents the mean with standard deviation (n = 3). Significant differences (p<0.05) are denoted by different alphabetical letters. ND: not detected.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0158197.g004: Effect of photo-irradiation time on the yield of H2O2 in MeOH soluble and insoluble fractions.Each value represents the mean with standard deviation (n = 3). Significant differences (p<0.05) are denoted by different alphabetical letters. ND: not detected.
Mentions: Total polyphenol contents of MeOH soluble and insoluble fractions are summarized in Fig 3. Total polyphenol content of MeOH soluble fraction was approximately 3.5 times higher than that of MeOH insoluble fraction (p<0.01). Fig 4 shows H2O2 concentrations in photo-irradiated MeOH soluble and insoluble fractions. Although H2O2 formation increased with irradiation time in the both fractions, the resultant H2O2 concentrations in MeOH fraction were much higher than those in corresponding MeOH insoluble fractions (p<0.05). Fig 5 summarizes the effect of photo-irradiation time on •OH generation in MeOH soluble and insoluble fractions. As was the case with H2O2, •OH generation as expressed as DMPO-OH concentration increased with irradiation time in the both fractions, and the resultant DMPO-OH concentrations in MeOH soluble fraction were much higher than those in corresponding MeOH insoluble fractions (p<0.05). DMPO-OH levels in the negative controls (kept under a light-shielding condition for 60 s) were trace levels in the both fractions.

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.