Antioxidant properties of tea investigated by EPR spectroscopy

Polovka, Martin; Brezová, Vlasta; Staško, Andrej

doi:10.1016/s0301-4622(03)00159-5

Cited by 132 publications

(89 citation statements)

References 65 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Oregano is of plant origin, consequently, this line was attributed to paramagnetic Mn(II) ions as previously mentioned by Morsy andKhaled (2001, 2002); Lozak et al (2002); Morsy (2002); Polat and Korkmaz (2003); Polovka et al (2003Polovka et al ( , 2006 and Suhaj et al (2006).…”

Section: Epr Investigationmentioning

confidence: 55%

“…As we suggest, the same phenomenon influence the shape of EPR spectra of solid oregano samples. Additionally, a characteristic narrow EPR signal (g = 2.0022, ∆B pp ~ 1 mT), assigned to stable radical structures (Morsy & Khaled 2001Morsy 2002;Polovka et al 2003Suhaj et al 2006) (* in Figure 1) is superimposed on this broad line. The relative EPR intensity of this sharp signal is significantly dependent on the absorbed gamma-radiation dose.…”

Section: Epr Investigationmentioning

confidence: 95%

“…We have previously proved (Polovka et al 2003) that relatively undisturbed bonding of Mn(II) in the protein complex is responsible for the less resoluted EPR spectrum of solid tea samples. As we suggest, the same phenomenon influence the shape of EPR spectra of solid oregano samples.…”

Section: Epr Investigationmentioning

confidence: 97%

“…Additionally, DPPH acts as an acceptor of electrons from antioxidants; several electron transfer reactions of DPPH with phenols, amines and other compounds were described in literature (Yordanov 1996;Staško et al 2002). The depletion of DPPH after the addition of antioxidants can be measured by UV-VIS spectroscopy (λ max = 520 nm), EPR spectroscopy, as well as by other techniques (Polovka et al 2003). It was previously successfully applied e.g.…”

Section: Antioxidant Ability Assaysmentioning

confidence: 99%

“…It was previously successfully applied e.g. to characterise the antioxidant activities of oregano and black pepper extracts (Schwarz et al 2001;Exarchou et al 2002;Polovka et al 2006;Suhaj et al 2006) or for the test of radical-scavenging ability of several commercial teas and wines (Staško et al 2002Polovka et al 2003).…”

Section: Antioxidant Ability Assaysmentioning

confidence: 99%

See 4 more Smart Citations

The influence of gamma-irradiation on the formation of free radicals and antioxidant status of oregano (Origanum vulgare L.)

Horváthová¹,

Suhaj²,

Polovka³

et al. 2007

Czech J. Food Sci.

View full text Add to dashboard Cite

The influence of various gamma-radiation dose absorptions on oregano (<i>Origanum vulgare</i> L.) solid samples was monitored by means of electron paramagnetic resonance (EPR) spectroscopy. Further, the antioxidant activity of oregano methanol/water extracts was characterised using DPPH (1,1-diphenyl-2-picrylhydrazyl free radical); thiobarbituric acid reactive substances (TBARS); ferric reducing power (FRP); and total content of phenolic compounds (TPC) assays. EPR spectroscopy was used for the investigation of the influence of the absorbed dose on the character of the paramagnetic structures formed, as well as for their thermal stability and life-time characterisation. EPR spectrum of the reference (non-irradiated) sample represents a broad singlet line with unresolved hyperfine splitting, attributable to Mn(II) ions, upon which the additional sharp EPR signal (g = 2.0022, ΔB<sub>pp</sub> ≈ 1 mT) is superimposed, assigned to stable semiquinone radicals produced by the oxidation of polyphenolic compounds present in plants. The additional paramagnetic structures of different origin (mostly of cellulose and carbohydrate), possessing diverse thermal stability and life-time, were identified in the gamma-irradiated samples. Immediately after irradiation, a statistically significant increase was observed of the TBARS values and the total content of phenolic compounds in methanol/water oregano extract. The alterations of the antioxidant properties of oregano extracts with the time after the radiation treatment were also monitored. A substantial time-dependent decrease of antioxidant activity was observed, probably as a result of storage, with both irradiated and non-irradiated oregano samples, as obvious from the ferric reducing power test and the content of total phenolic substances. The influence of irradiation and subsequent storage of oregano samples on the DPPH radical-scavenging ability was only negligible.

show abstract