Christos Petrakis

Evaluation of scavenging activity assessed by Co(II)/EDTA-induced luminol chemiluminescence and DPPH* (2,2-diphenyl-1-picrylhydrazyl) free radical assay.

The scavenging activities of three standard antioxidants, quercetin, ascorbic acid, and trolox, were evaluated by Co(II)/ethylenediamine-tetraacetic acid (EDTA)-induced luminol chemiluminescence and the 2,2-diphenyl-1-picrylhydrazyl (DPPH*) free radical assay. Therefore, the aim of this study was to characterise an enzyme-free and time-independent chemiluminescence method for the assessment of the scavenging profile of compounds in a cell-free system using the Co(II)/EDTA-luminol-peroxide system. These results showed that the three standards were efficient and effective in inhibiting both Co(II)/EDTA-induced luminol chemiluminescence and the free radical DPPH*. For all the data obtained in this work, the scavenging activity for the standards tested decreased in the following order: quercetin > trolox > ascorbic acid. The present study has applied a simple and precise procedure for the study of hydroxyl radical scavenging activity by Co(II)/EDTA-induced luminol chemiluminescence, and this was assessed by DPPH* free radical scavenging.

Nutrient antioxidants in some herbs and Mediterranean plant leaves

Abstract Hexane extracts obtained by percolation from the leaves of nine Mediterranean plants ( Daphne oleoides , Myrtus communis , Pelargonium zonale , Phillyrea latifolia , Pistacia terebinthus , Quercus pubescens , Rhamnus lucioides , Sideritis syriaca , Smilax aspera ) and from five leaf spices ( Rosmarinum officinalis , Coridothymus capitatus , Laurus nobilis , Salvia fruticosa , Salvia pomifera ) were examined for the presence of tocopherols by thin layer chromatography, gas chromatography, high performance liquid chromatography and combined gas chromatography–mass spectrometry. With the exception of Sideritis syriaca , in all the plants and spices examined α-tocopherol was found to be present. The β - and γ -homologues were detected only in the extracts of Pelargonium zonale and Smilax aspera . Quantitative analysis by HPLC gave values ranging from 250 to 1325 ppm total tocopherols (on a dry leaf basis). These values are higher than those reported for oil seeds (sunflower seed, cottonseed, rapeseed, sesame seed) or other oil sources (peanut, soybean, maize).

Sonochemical degradation of triclosan in water and wastewater

The sonochemical degradation of 5 microg l(-1) triclosan, a priority micro-pollutant, in various environmental samples (seawater, urban runoff and influent domestic wastewater) as well as in model solutions (pure and saline water) was investigated. Experiments were conducted with a horn-type sonicator operating at 80 kHz frequency and a nominal applied power of 135 W, while solid-phase microextraction coupled with gas chromatography-electron capture detector (SPME/GC-ECD) was employed to monitor triclosan degradation. The latter followed pseudo-first order kinetics with the rate constant being (min(-1)): 0.2284 for seawater>0.1051 for 3.5% NaCl in deionised water>0.0597 for centrifuged urban runoff approximately 0.0523 for untreated urban runoff >0.0272 for deionised water >0.0063 for wastewater influent. SPME/GC-ECD and SPME coupled with gas chromatography-mass spectrometry (SPME/GC-MS) were also used to check for the formation of chlorinated and other toxic by-products; at the conditions in question, the presence of such compounds was not confirmed.

A transition metal enhanced luminol chemiluminescence in the presence of a chelator.

We have investigated the chemiluminescence signal of luminol and hydrogen peroxide in the presence of a transition metal (Co(II), Cu(I), Fe(II), Fe(III)) and of a chelator (EDTA, citric acid) in pH 8.5, 9 and 10 borate buffer solutions. We observed that the chemiluminescence intensities of these systems reached a plateau, where they remained stable for a period of 2-30 s. We also observed linearity between the intensity of chemiluminescence and the hydrogen peroxide concentration. The combination of Co(II) and EDTA at pH 9 was found to give the optimum signal with reference to time stability, intensity and reproducibility. Thus, compared to previous chemiluminescence applications, the present results permit us to propose a simple, enzyme-free and time-independent technique for the detection and quantification of hydrogen peroxide.

Irrigation and harvest time affect almond kernel quality and composition

Abstract The effect of irrigation and harvest time was studied with respect to almond kernel quality with two almond cultivars. Kernel quality analyses included kernel weight, moisture content, kernel oil quality and composition, and sugar content and composition. ‘Ferragnes’ kernels had similar oil content and quality but higher oleic acid content than ‘Texas’ almonds. Various differences were also found in sugar content and composition between the two cultivars. Irrigation delayed almond maturation, had no effect on oil and sugar content, but improved oil composition with higher oleic acid content and sugar composition with higher sucrose content compared to dry-grown almonds. Late harvested almonds contained more dry matter per kernel, higher oil content but of lower quality, based on the UV absorption coefficients and oil composition, and higher sugar content mainly due to further sucrose accumulation compared to early harvested almonds.

A peroxyoxalate chemiluminescence-based assay for the evaluation of hydrogen peroxide scavenging activity employing 9,10-diphenylanthracene as the fluorophore

INTRODUCTION A simple, rapid, sensitive, and enzyme-free analytical method for estimating scavenging of hydrogen peroxide (H2O2) was developed. METHODS Peroxyoxalate chemiluminescence (POCL) was measured, using 9,10-diphenylanthracene as fluorophore. RESULTS The chemiluminescence signal was found to be linear in response to increasing amounts of H2O2 in ethyl acetate/acetonitrile (9:1) (r2 = .9990), within a range of concentrations varying from 9.0 to 72.0 microM. In contrast, acetonitrile was highly unsuitable because of poor linearity (r2 = .3736) and poor signal stability. The linearity of POCL inhibition, as a measure of H2O2 scavenging, was tested employing well-known, lipid-soluble antioxidants, including beta-carotene, butylated hydroxytoluene (BHT) and alpha-tocopherol, and also the more polar flavonol quercetin, and the water-soluble L-ascorbic acid (AA). Under the experimental conditions, the corresponding values of H2O2 scavenging activity (SA(HP)) for quercetin, beta-carotene, alpha-tocopherol, and L-AA were 19.1 +/- 0.4, 70.9 +/- 20.1, 8.4 +/- 0.4, and 44.8 +/- 5.6 x 10(-3) microM(-1) DISCUSSION The data establish the assay as a method for assessing the H2O2 quenching activity of lipid-soluble antioxidants.

Chemiluminescent evaluation of peroxide value in olive oil.

A method is described for the evaluation of the peroxide value (PV, meq. O(2) kg(-1)) in olive oil. The method is based on the chemiluminogenic energy-transfer reaction of bis(2,4,6-(trichlorophenyl)oxalate (TCPO) with hydrogen peroxide or total peroxides in the presence of Mn(II) as catalyst and 9,10-dimethylanthracene as fluorophore. The procedure developed allows the evaluation of PV within the range of 0.6-100meq. O(2) kg(-1) (CL intensity = 1.76 x PV (meq. O(2) kg(-1)) + 23.2, r(2) = 0.994, n = 9) and relative standard deviation within the range 1-5% by using a simple manual measurement.

Olive Oil Extraction

Publisher Summary This chapter presents that olive oil is the oily juice of the olive, separated from the other components of the fruit. Properly extracted from fresh, mature fruit of good quality, the oil has a characteristic sensory profile. Its fatty acid composition is characterized by a good balance between saturated, monounsaturated, and polyunsaturated acids. It is also unique among common vegetable oils in that it can be consumed in the crude form, thus conserving vitamin content and phenolic compounds of nutritional importance. The flow sheet of the recently used extraction plants comprises four main operations that are explained in the chapter and they are fruit cleaning (defoliation, olive washing), preparation of the paste (crushing, malaxation), separation of the solid (pomace) and liquid phases (oily must and wastewater) and separation of the liquid phases (oil/wastewater). Currently, main manufactures of olive oil extraction plants are Alpha Laval, Amenduni and Flottweg GmbH. Quality and origin certificates should be based on quality assurance systems. These entail process control. An effective process control is based on standardized operating conditions and procedures. The GMP represents a set of minimum standard conditions that should be followed throughout the whole production chain, from cultural operations in the olive grove to the shelves of the supermarket. In addition, Hazard Analysis Critical Point Control (HACCP) is necessary for the consumers protection.