Maria Z. Tsimidou

Composition and antioxidant activity of essential oils from Oregano plants grown wild in Greece

ZusammenfassungBei dieser Arbeit wurden vier Proben etherischer Öle aus Pflanzen gewonnen, die weit verbreitet in Griechenland sind und von ökonomischer Wichtigkeit in der ganzen Welt am Gewürzmarkt sind. Es wurden Carvacrol und Thymol auf ihre wahrscheinliche antioxidative Aktivität getestet. Die vier Pflanzenarten sindOriganum vulgare hirtum, Origanum onites, Coridothymus capitatus und Satureja thymbra. Die etherischen Öle wurden mit Hilfe der Gaschromatographie-Massenspektroskopie charakterisiert. Sowohl die untersuchten etherischen Öle als auch Carvacrol und Thymol wurden durch TLC und auch durch Messung der Peroxid-Werte eines bei 35°C aufbewahrten Schweinefettes getestet. Die Ergebnisse zeigen, daß der antioxidative Effekt auf die Anwesenheit von Carvacrol und Thymol im etherischen Öl zurückgeführt werden kann.AbstractIn this study, four samples of essential oils obtained from plant species with a wide distribution in Greece and economic importance for the world-wide spice market and also carvacrol and thymol were tested for their possible antioxidant activity. The four plant species wereOriganum vulgare subsp.hirtum, O. onites, Coridothymus capitatus andSatureja thymbra. The essential oils were chemically characterised by gas chromatography-ion trap detection. All the essential oils examined and also carvacrol and thymol were found to have antioxidant activity when tested on TLC plates and by measuring peroxide values of lard stored at 35° C. The results indicate that the antioxidant effect may be related to the presence of carvacrol and thymol in essential oils.

Phenolic compounds and stability of virgin olive oil—Part I

Abstract The stability of 24 samples of Greek virgin olive oil was examined in relation to total polyphenol content, and individual phenols were determined by reversed-phase HPLC. Tyrosol, the major olive-oil phenol, is not correlated with the shelf-life of the oil. Total polyphenol content and hydroxytyrosol-to-tyrosol ratio have a significant linear correlation with the resistance of the oil to autoxidation.

Contribution of α-tocopherol to olive oil stability

Abstract The effect of 100, 500 and 1000 ppm of α-tocopherol on the oxidative stability of purified olive oil kept in the dark at 40 °C was studied. Purified olive oil was prepared by liquid column chromatography and was practically devoid of minor constituents with possible pro-oxidant or antioxidant activity. α-Tocopherol acted as antioxidant at all levels of addition, although the antioxidant effect was greater at 100 ppm than at higher concentrations. In the initial stage of autoxidation a slightly pro-oxidant effect was observed. In the presence of strong antioxidants naturally occurring in olive oil, such as ortho-diphenols, α-tocopherol did not show any significant additional antioxidant effect during the period of low peroxide accumulation.

Determination of phenolic compounds in virgin olive oil by reversed-phase HPLC with emphasis on UV detection

Abstract A method is described for the chromatographic separation and quantitative determination of phenolic compounds in virgin olive oil by high-performance liquid chromatography (HPLC) using gradient elution. For the determination of individual compounds molar absorptivities at 280 nm are calculated. A technique based on the use of four external standards (tyrosol, vanillic acid, syringic acid, o -coumaric acid) is applied in order to minimize errors due to different λ max and ϵ 280 . The method was applied successfully to olive oil samples.

Kinetic studies of degradation of saffron carotenoids encapsulated in amorphous polymer matrices

Kinetic studies on degradation of saffron water soluble carotenoids (mainly crocins) encapsulated in three different amorphous matrices (pullulan and two polyvinylpyrrolidone, PVP, samples differing in their molecular weight) were carried out at different water activity (aw) conditions (0.43, 0.53, 0.64 and 0.75) in the dark at 35°C. Degradation of the polar pigments was monitored by periodic measurements of the coloring strength. Among the polymeric matrices used as wall materials, which largely decreased the oxidation rates of crocetin glycosides, PVP 40 was the most effective carrier under all storage conditions. In the vicinity of the glass transition temperature (Tg) zone, where pullulan and PVP360 undergo state transformations, there was a change in the reaction rate. The lower degradation rates were observed for PVP40 under conditions where this matrix was fully plasticized (i.e. rubbery) and “collapsed”, implying that the degradation kinetics are not governed by factors related to the physical state and molecular mobility of the inert matrix. Carotenoid losses have been observed even at temperatures below the Tg of the polymeric matrices.

Phenolic Compounds in Virgin Olive Oils: Fractionation by Solid Phase Extraction and Antioxidant Activity Assessment

The polar fraction of virgin olive oil was separated into two main parts (A and B) using solid phase extraction. Analysis of individual components by RP-HPLC indicated that the part (A) contained only simple phenols and phenolic acids. Part (B) had a complex nature. The two parts tested for their antioxidant activity showed relatively high protection factors in safflower oil stored at 80°C. Part B was found to contribute more than part A to the stability of the oil. The antioxidant activity of both fractions was related to their content of total polyphenols and o-diphenols. Acidic and alkaline hydrolysis showed significant quantitative changes in the HPLC profiles indicating the presence of ether and ester bonds while high-performance anion exchange chromatography of sugars after hydrolysis gave evidence for the presence of only traces of glycosides. A first attempt to identify a characteristic chromatographic peak of part B by HPLC fractionation and mass spectrometry showed the presence of an ester of tyrosol most probably with a dicarboxylic acid.

Olive Oil Composition

Publisher Summary The composition of olive oil is primarily triacylglycerols (~99%) and secondarily free fatty acids, mono- and diacylglycerols, and an array of lipids such as hydrocarbons, sterols, aliphatic alcohols, tocopherols, and pigments. A plethora of phenolic and volatile compounds are also present. Some of these compounds contribute to the unique character of the oil. Fatty acids present in olive oil are palmitic (C16:0), palmitoleic (C16:1), stearic (C18:0), oleic (C18:1), linoleic (C18:2), and linolenic (C18:3). Myristic (C14:0), heptadecanoic, and eicosanoic acids are found in trace amounts. This chapter discusses some classes of minor constituents that are present only in the crude oil. Filtration reduces the initial levels to a great extent whereas refining results in their removal.

Evaluation of oregano antioxidant activity in mackerel oil

Abstract Dry oregano was tested for its antioxidant activity in mackerel oil stored at 40 °C in the dark. Its effectiveness at 0.5% level was comparable to that of 200 ppm BHA and 0.5% (w/w) dry rosemary and stronger to that of red chillies and bay leaf which did not improve the stability of the fish oil. Oregano at 1% (w/w) level had a similar effect to that of 200 ppm TBHQ.

Ab initio and density functional theory studies for the explanation of the antioxidant activity of certain phenolic acids.

Ab initio and density functional theory molecular orbital calculations were carried out at both the HF/6-31+G(d) and B3LYP/6-31+G(d) levels for the four antioxidants, p-hydroxycinnamic acid derivatives, namely, the p-coumaric, caffeic, ferulic, and sinapinic acid and the corresponding radicals, in an attempt to explain the structural dependency of the antioxidant activity of these compounds. Optimized resulting geometries, vibrational frequencies, absolute infrared intensities, and electron-donating ability are discussed. Both the high degree of conjugation and the extended spin delocalization in the phenoxyl radicals offer explanation for the scavenging activity of the four acids. In structurally related compounds, the calculated heat of formation value in radical formation appears as a meaningful molecular descriptor of antioxidant activity in accordance with experimental data. This becomes more clear at the B3LYP level.

Industrial Glycerol as a Supplementary Carbon Source in the Production of β-Carotene by Blakeslea trispora

The dynamics of industrial types of glycerol as a supplementary carbon source to glucose for beta-carotene production by Blakeslea trispora was investigated in batch cultures. The growth kinetics, cellular lipid accumulation-degradation, substrate assimilation, and beta-carotene production were clearly dependent on the level of addition of pure glycerol. The highest beta-carotene production (15.0 mg/g of dry biomass) was obtained at an initial glycerol concentration of 60.0 g/L. Substitution of pure glycerol by the nonpurified soap byproduct did not inhibit cell growth. Conversely, partial purification of the biodiesel byproduct by removing methanol and fatty acids was unavoidable for cell growth. Both types of industrial glycerol stimulated beta-carotene synthesis more than 10 (soap byproduct) and 8 times (biodiesel byproduct) compared to control medium. The maximum beta-carotene contents were 10 and 8 mg/g of dry biomass, respectively, and its relative content in the carotenoid fraction was 86-88%.