Panagiotis Kefalas

Instrumental and sensory analysis of Greek wines; implementation of principal component analysis (PCA) for classification according to geographical origin

Wine is one of the most important products of Greece and other Mediterranean countries. Adulteration of wines, either in terms of geographical origin or variety, has been a major topic of debate and extensive research. Various instrumental methods (gas chromatography, high pressure liquid chromatography) and sensory analysis, in conjunction with statistical analysis, were developed and applied in an attempt to provide reliable answers to this issue. This research aimed at classifying 33 greek wines from various regions by employing both instrumental and sensory analysis. Application of principal component analysis (PCA) to our experimental data resulted in satisfactory classifications of only Greek red wines in terms of their geographical origin. Greek wines were effectively distinguished in two or three groups (depending on PCA figure); wines from Aegean/Ionean islands. North Greece and South Greece. However, further work with greater numbers of samples is required in order to draw more valid conclusions and to obtain a detailed map of greek wines according to their geographical origin and variety.

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).

The effect of polyphenolic composition as related to antioxidant capacity in white wines

Abstract Twenty-six white wines of “Appellation of Origin of High Quality”, covering all viticultural areas of Greece were assayed for their polyphenolic content, using high-performance liquid chromatography coupled with diode array detector. Further, the antiradical activity and reducing power of the wines were evaluated. In both cases, the antioxidant potency of the wines was correlated with the total polyphenol concentration, as well as with the concentration of the two major classes of white wine polyphenols, hydroxycinnamates and flavanols. It was found that wines contain in average 324.7 mg l −1 total hydroxycinnamates (THC) and 52.2 mg l −1 total non-hydroxycinnamates (TNHC), (catechin, epicatechin, gallic acid). The antiradical activity was correlated principally with total phenols (THC+TNHC) and with THC, but poorly with TNHC. By contrast, TNHC were found to exert sound reducing effect, as opposed to THC which were weakly correlated with the reducing power.

Improving yeast strains using recyclable integration cassettes, for the production of plant terpenoids

BackgroundTerpenoids constitute a large family of natural products, attracting commercial interest for a variety of uses as flavours, fragrances, drugs and alternative fuels. Saccharomyces cerevisiae offers a versatile cell factory, as the precursors of terpenoid biosynthesis are naturally synthesized by the sterol biosynthetic pathway.ResultsS. cerevisiae wild type yeast cells, selected for their capacity to produce high sterol levels were targeted for improvement aiming to increase production. Recyclable integration cassettes were developed which enable the unlimited sequential integration of desirable genetic elements (promoters, genes, termination sequence) at any desired locus in the yeast genome. The approach was applied on the yeast sterol biosynthetic pathway genes HMG2, ERG20 and IDI1 resulting in several-fold increase in plant monoterpene and sesquiterpene production. The improved strains were robust and could sustain high terpenoid production levels for an extended period. Simultaneous plasmid-driven co-expression of IDI1 and the HMG2 (K6R) variant, in the improved strain background, maximized monoterpene production levels. Expression of two terpene synthase enzymes from the sage species Salvia fruticosa and S. pomifera (SfCinS1, SpP330) in the modified yeast cells identified a range of terpenoids which are also present in the plant essential oils. Co-expression of the putative interacting protein HSP90 with cineole synthase 1 (SfCinS1) also improved production levels, pointing to an additional means to improve production.ConclusionsUsing the developed molecular tools, new yeast strains were generated with increased capacity to produce plant terpenoids. The approach taken and the durability of the strains allow successive rounds of improvement to maximize yields.

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.

The application of an improved method for trans-resveratrol to determine the origin of Greek red wines

Abstract A rapid and sensitive method has been developed for the determination of trans -resveratrol in wine. This method consists of a solid phase extraction step followed by a rapid HPLC quantification step (30 min). The improvement of this method consists of the washing step of the solid phase extraction method carried out at pH 8.0 (12% ethanol in a phosphate buffer solution), thus permitting a more efficient removal of the interfering phenolic compounds in conjunction with the required low volume of tested sample. Trans -resveratrol content was determined for 29 red Greek wines of appellation of origin. The concentrations found varied between 0.550 and 2.534 mg/l. The wines produced by grape varieties grown in the Greek islands (Rhodes, Crete and Paros) were richer in trans -resveratrol. The grape variety Mandilaria, in particular, was the Greek variety with the highest trans -resveratrol content.

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.

Herbal infusions; their phenolic profile, antioxidant and anti-inflammatory effects in HT29 and PC3 cells.

In this survey, we analyzed the phenolic profile of six herbal infusions namely Cretan marjoram, pink savory, oregano, mountain tea, pennyroyal and chamomile by LCDAD-MS and by GC-MS. Further, we investigated their anticarcinogenic effect as to their ability to (a) scavenge free radicals (b) inhibit proliferation (c) decrease IL-8 levels and (d) regulate nuclear factor-kappa B in epithelial colon cancer (HT29) and prostate (PC3) cancer cells. All herbal infusions exhibited antiradical activity correlated positevely with total phenolic content. Further, infusions exhibited the potential to inhibit cell proliferation and to reduce IL-8 levels in HT29 colon and PC3 prostate cancer cells. The molecular target for chamomile in HT29 seemed to be the NF-κB, while for the other herbal infusions needs to be identified. This study is the first to show the potential chemopreventive activity of infusions prepared from the examined herbs.