Novel EPR characterization of the antioxidant activity of tea leaves

M. A. Morsy; M. M. Khaled

doi:10.1016/S1386-1425(01)00716-8

Novel EPR characterization of the antioxidant activity of tea leaves

M. A. Morsy^*, M. M. Khaled

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

58 Scopus citations

Abstract

Electron paramagnetic resonance (EPR) spectroscopy is utilized to investigate several categories of green and black tea: Twining green tea (TGT), Chinese green tea (CGT), Red-labels black tea (RBT). Basically, two EPR signals from all the studied samples are observed: One of them is a very weak sharp EPR signal with ΔH_pp≅10 G and g-factor=2.00023 superimposed on the other broad signal with ΔH_pp≅550 G and g-factor=2.02489. The broad signal is a characteristic one of manganese(II) complex, while the sharp signal is related to a stable radical of aromatic origin exist in a powder condition. The feature of the manganese EPR signal is attributed to manganese(II) complex and reflected the molecular behavior of Mn(II) in the protein system of the natural leaves. The sharp signal, which is most probably due to a semiquinones radicals, is observed at room temperature and its intensity is remarkably affected by photo degradation of the studied samples. The intensity of manganese(II) EPR signal is found to be related to ageing and disintegration of the tea leaves. Moreover, direct relation between the relative intensity of the semiquinones radical signal and antioxidant activity of the studied samples was also correlated.

Original language	English
Pages (from-to)	1271-1277
Number of pages	7
Journal	Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy
Volume	58
Issue number	6
DOIs	https://doi.org/10.1016/S1386-1425(01)00716-8
State	Published - 2002

Bibliographical note

Funding Information:
The authors acknowledge the support of King Fahd University of Petroleum and Minerals.

Keywords

Antioxidants
Black tea
EPR
Green tea
Manganese(II)
Quinone-radicals

ASJC Scopus subject areas

Analytical Chemistry
Atomic and Molecular Physics, and Optics
Instrumentation
Spectroscopy

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10.1016/S1386-1425(01)00716-8

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@article{09d71ceb1c4847ddbd3b9bd0f0fb1e51,

title = "Novel EPR characterization of the antioxidant activity of tea leaves",

abstract = "Electron paramagnetic resonance (EPR) spectroscopy is utilized to investigate several categories of green and black tea: Twining green tea (TGT), Chinese green tea (CGT), Red-labels black tea (RBT). Basically, two EPR signals from all the studied samples are observed: One of them is a very weak sharp EPR signal with ΔHpp≅10 G and g-factor=2.00023 superimposed on the other broad signal with ΔHpp≅550 G and g-factor=2.02489. The broad signal is a characteristic one of manganese(II) complex, while the sharp signal is related to a stable radical of aromatic origin exist in a powder condition. The feature of the manganese EPR signal is attributed to manganese(II) complex and reflected the molecular behavior of Mn(II) in the protein system of the natural leaves. The sharp signal, which is most probably due to a semiquinones radicals, is observed at room temperature and its intensity is remarkably affected by photo degradation of the studied samples. The intensity of manganese(II) EPR signal is found to be related to ageing and disintegration of the tea leaves. Moreover, direct relation between the relative intensity of the semiquinones radical signal and antioxidant activity of the studied samples was also correlated.",

keywords = "Antioxidants, Black tea, EPR, Green tea, Manganese(II), Quinone-radicals",

author = "Morsy, \{M. A.\} and Khaled, \{M. M.\}",

note = "Funding Information: The authors acknowledge the support of King Fahd University of Petroleum and Minerals.",

year = "2002",

doi = "10.1016/S1386-1425(01)00716-8",

language = "English",

volume = "58",

pages = "1271--1277",

journal = "Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy",

issn = "1386-1425",

publisher = "Elsevier B.V.",

number = "6",

}

TY - JOUR

T1 - Novel EPR characterization of the antioxidant activity of tea leaves

AU - Morsy, M. A.

AU - Khaled, M. M.

N1 - Funding Information: The authors acknowledge the support of King Fahd University of Petroleum and Minerals.

PY - 2002

Y1 - 2002

N2 - Electron paramagnetic resonance (EPR) spectroscopy is utilized to investigate several categories of green and black tea: Twining green tea (TGT), Chinese green tea (CGT), Red-labels black tea (RBT). Basically, two EPR signals from all the studied samples are observed: One of them is a very weak sharp EPR signal with ΔHpp≅10 G and g-factor=2.00023 superimposed on the other broad signal with ΔHpp≅550 G and g-factor=2.02489. The broad signal is a characteristic one of manganese(II) complex, while the sharp signal is related to a stable radical of aromatic origin exist in a powder condition. The feature of the manganese EPR signal is attributed to manganese(II) complex and reflected the molecular behavior of Mn(II) in the protein system of the natural leaves. The sharp signal, which is most probably due to a semiquinones radicals, is observed at room temperature and its intensity is remarkably affected by photo degradation of the studied samples. The intensity of manganese(II) EPR signal is found to be related to ageing and disintegration of the tea leaves. Moreover, direct relation between the relative intensity of the semiquinones radical signal and antioxidant activity of the studied samples was also correlated.

AB - Electron paramagnetic resonance (EPR) spectroscopy is utilized to investigate several categories of green and black tea: Twining green tea (TGT), Chinese green tea (CGT), Red-labels black tea (RBT). Basically, two EPR signals from all the studied samples are observed: One of them is a very weak sharp EPR signal with ΔHpp≅10 G and g-factor=2.00023 superimposed on the other broad signal with ΔHpp≅550 G and g-factor=2.02489. The broad signal is a characteristic one of manganese(II) complex, while the sharp signal is related to a stable radical of aromatic origin exist in a powder condition. The feature of the manganese EPR signal is attributed to manganese(II) complex and reflected the molecular behavior of Mn(II) in the protein system of the natural leaves. The sharp signal, which is most probably due to a semiquinones radicals, is observed at room temperature and its intensity is remarkably affected by photo degradation of the studied samples. The intensity of manganese(II) EPR signal is found to be related to ageing and disintegration of the tea leaves. Moreover, direct relation between the relative intensity of the semiquinones radical signal and antioxidant activity of the studied samples was also correlated.

KW - Antioxidants

KW - Black tea

KW - EPR

KW - Green tea

KW - Manganese(II)

KW - Quinone-radicals

UR - https://www.scopus.com/pages/publications/0036005835

U2 - 10.1016/S1386-1425(01)00716-8

DO - 10.1016/S1386-1425(01)00716-8

M3 - Article

C2 - 11993474

AN - SCOPUS:0036005835

SN - 1386-1425

VL - 58

SP - 1271

EP - 1277

JO - Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy

JF - Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy

IS - 6

ER -

Novel EPR characterization of the antioxidant activity of tea leaves

Abstract

Bibliographical note

Keywords

ASJC Scopus subject areas

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