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

Abstract

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.

Effect of electron beam irradiation on proximate, microbiological and sensory characteristics of chyavanaprash — Ayurvedic poly herbal formulation

“…TBARS values were significantly increased after irradiation in irradiated coconut cream powder (Yusof, Ahmad Ramli, & Ali, 2007). The irradiation caused a considerable increase of TBARS values of oregano extract prepared from the sample irradiated at 30 kGy, no significant change was observed in irradiated oregano samples (Horvathova et al, 2007). FRP was significantly reduced in irradiated pepper (Suhaj et al, 2006).…”

“…Fat content and gallic acid were analyzed by the methods followed by Mazumdar and Majumder (2003) and Jeganathan and Kannan (2008), respectively. Total phenolics and ferrous reducing power (FRP) were determined according to the method followed by Horvathova, Suhaj, Polovka, Brezova, and Simko (2007).…”

Influence of ionizing irradiation on the antioxidant enzymes of <i>Vicia faba</i> L.

“…In this concern, Štajner et al (2007) stated that the use of γ-irradiation at a dose up to 10 kGy did not provoke significant changes in lipid peroxidation and caused a slight increase which could be the consequence of the appropriate antioxidant response. Also Horvathova et al (2007) reported that irradiation cased a considerable increase in the TBAS values of oregano extract prepared from the increase in the activity of POD, which uses H 2 O 2 as substrate.…”

Effect of low doses γ-irradiation on oxidative stress and secondary metabolites production of rosemary (Rosmarinus officinalis L.) callus culture

“…Moreover, a significant (po0.05) increase in the production rate of O 2 À was observed in irradiated samples and this increase was more pronounced at dose level 20 Gy (1.8770.11 nmol/min g FW) compared to the control (0.5270.02 nmol/min g FW). Horvathova et al (2007) reported that irradiation caused a considerable increase in the TBAS values of oregano extract prepared from the sample irradiated by gamma irradiation. Gamma irradiation could lead to an accumulation of free radicals such as O 2 À and H 2 O 2 , which unbalances the system of free radical elimination and thus induces lipid peroxidation.…”