Charalampos Proestos

Antioxidant Capacity of Selected Plant Extracts and Their Essential Oils.

The main objective of this study was the screening of some selected aromatic plants very popular in Greece, with respect to their total phenolic content, antioxidant capacity, reducing activity, and oxidative stability. All plants were extracted with the conventional method, reflux with methanol. The essential oils of the plants were also analyzed for their antioxidant properties. The total phenolic content was determined by the Folin-Ciocalteu method using gallic acid as the standard, while the phenolic substances were identified and quantified by High Performance Liquid Chromatography (HPLC) coupled with a multi-wavelength ultraviolet-visible (UV-vis) detector. The antioxidant capacity of the plant extracts was measured by their ability to scavenge free radicals such as (a) DPPH (2,2-diphenyl-1-picrylhydrazyl) and, (b) ABTS (2,2′-azinobis-(3-ethylbenzothiaziline-6-sulfonate). The Folin-Ciocalteu method proved the existence of antioxidants in the aromatic plant extracts. Taking into account the results of the DPPH and ABTS methods, the free radical scavenging capacity was confirmed. Eventually, all plants exhibited low but noticeable protection levels against lipid oxidation, as determined by the Rancimat test.

Analysis of Naturally Occurring Phenolic Compounds in Aromatic Plants by RP-HPLC Coupled to Diode Array Detector (DAD) and GC-MS after Silylation

The following aromatic plants of Greek origin, Origanum dictamnus (dictamus), Eucalyptus globulus (eucalyptus), Origanum vulgare L. (oregano), Mellisa officinalis L. (balm mint) and Sideritis cretica (mountain tea), were examined for the content of phenolic substances. Reversed phase HPLC coupled to diode array detector (DAD) was used for the analysis of the plant extracts. The gas chromatography-mass spectrometry method (GC-MS) was also used for identification of phenolic compounds after silylation. The most abundant phenolic acids were: gallic acid (1.5–2.6 mg/100 g dry sample), ferulic acid (0.34–6.9 mg/100 g dry sample) and caffeic acid (1.0–13.8 mg/100 g dry sample). (+)-Catechin and (−)-epicatechin were the main flavonoids identified in oregano and mountain tea. Quercetin was detected only in eucalyptus and mountain tea.

Antiradical–antimicrobial activity and phenolic profile of pomegranate (Punica granatum L.) juices from different cultivars: a comparative study

Pomegranate juice (PJ) constituents have shown to exhibit anticarcinogenic, antimicrobial, antioxidant and antiviral activities. In the present study, the concentration of phenolic compounds and the antiradical activity of PJs from the fruits of the two relatively new Greek cultivars “Persephone” and “Porphiroyeneti” were determined in comparison to the “Wonderful” cultivar. Total phenolic content and antiradical activity of the examined juices were found to vary in the same decreasing manner as follows: “Porphiroyeneti” > “Wonderful” > “Persephone”. The antimicrobial activity of PJs was also determined, showing equal or higher effect than commercial antimicrobial agents (streptomycin, ampicillin, bifonazole and ketoconazole). All tested extracts demonstrated noteworthy antibacterial activity with minimal inhibitory concentration ranging from 0.05 to 0.20 mg mL−1 and minimal bactericidal concentration ranging from 0.10 to 0.40 mg mL−1. Moreover, PJ extracts showed satisfactory fungistatic (0.05–0.2 mg mL−1) and fungicidal (0.1–0.3 mg mL−1) activity against all fungi tested. Among the cultivars tested, “Porphiroyeneti” showed slightly better antiradical and antimicrobial activity. In addition, a GC-MS methodology was developed for the determination of the phenolic profile of the extracts of PJ after different types of chemical hydrolysis. Finally, an HPLC-PDA-ESI-MSn analysis was conducted for the identification of the phenolic compounds in the extracts of PJ. In total, more than 30 non-anthocyanidinic and more than 20 anthocyanidinic compounds were identified. Our results confirm the functionality of pomegranate juices and the potential applications of PJ extracts towards novel products as food additives or preservatives.

On the Combined Application of Iatroscan TLC-FID and GC-FID to Identify Total, Neutral, and Polar Lipids and Their Fatty Acids Extracted from Foods

An efficient separation and quantification of the individual neutral and polar lipid classes and their constituent fatty acids was achieved by the combination of two different detection techniques: Iatroscan TLC-FID and GC-FID. The solvent composition and ratio of development system, the sample size, the fidelity, and precision were tested in order to estimate the effectiveness of separation of individual neutral and polar lipid classes and the quantitative reproducibility of the Iatroscan TLC-FID technique. GC-FID method, with a high-quality capillary column, allowed sensitive and reproducible fatty acid qualitative and quantitative analyses, separation of fatty acid structural isomers (e.g., n-C16:0, iso-C16:0 and anteiso-C16:0), positional isomers (e.g., C18:1ω-9 and C18:1ω-7), geometrical isomers (cis-trans), and homologues (e.g., C16:0, C17:0, C18:0, etc.) in standards and complex lipid samples. Seventeen (17) lipid classes and fifty-two (52) saturated (SFA), monounsaturated (MUFA), and polyunsaturated (PUFA) fatty acids were identified and quantified, respectively, in samples of standard lipid and fatty acid mixtures, simulating the composition of natural lipids and their fatty acid methyl esters in common foods. The wide number of applications establishes this combination of Iatroscan TLC-FID and GC-FID methods as a powerful tool for lipid class and fatty acid analysis of any fat origin.

Phenolic compounds in red wine digested in vitro in the presence of iron and other dietary factors

Quantitative and qualitative changes in the phenolic composition of red wine may occur during digestion in the lumen, particularly when other dietary components are present. In this study, mixtures of red wine, iron, and ascorbic acid, meat or casein were subjected to a simulated gastrointestinal digestion. This process involves incubation of samples for 4.5 h at 37°C, at different pH values, in the presence of peptic enzymes and fractionation of digests through a dialysis membrane with a molecular weight cut-off of 6000–8000. Selected phenolic compounds were determined in undigested samples and in their dialysable digests by reversed-phase high-performance liquid chromatography. A dramatic decrease in the concentration of the selected phenolic compounds was observed in all samples after they were digested in vitro. Moreover, when iron and/or protein were added to red wine samples, changes in the phenolic profile of the undigested and of the in vitro digested samples were detected. These results suggest that interactions between red wine phenolic compounds and iron, protein and/or digestion components are important determinants of the physicochemical properties and the concentration of these phenolic compounds in the lumen. The in vitro methodology employed herein offers a tool for the study of phenolic compounds under conditions of simulated gastrointestinal digestion, incorporating lumenal events that may affect phenolic compounds.

Αntioxidant activity of Cynara scolymus L. and Cynara cardunculus L. extracts obtained by different extraction techniques

Abstract Extracts of different parts (heads, bracts and stems) of Cynara cardunculus L. (cardoon) and Cynara scolymus L. (globe artichoke), obtained by two different extraction techniques (Ultrasound-Assisted Extraction (UAE) and classical extraction (CE)) were examined and compared for their total phenolic content (TPC) and their antioxidant activity. Moreover, infusions of the plant’s parts were also analysed and compared to aforementioned samples. Results showed that cardoon’s heads extract (obtained by Ultrasound-Assisted Extraction) displayed the highest TPC values (1.57 mg Gallic Acid Equivalents (GAE) g−1 fresh weight (fw)), the highest DPPH• scavenging activity (IC50; 0.91 mg ml−1) and the highest ABTS•+ radical scavenging capacity (2.08 mg Trolox Equivalents (TE) g−1 fw) compared to infusions and other extracts studied. Moreover, Ultrasound-Assisted Extraction technique proved to be more appropriate and effective for the extraction of antiradical and phenolic compounds. Graphical Abstract

Total phenolic content, antioxidant capacity and phytochemical profiling of grape and pomegranate wines

The object of this study was to determine the phenolic profile, the total phenolic content and antioxidant capacity of pomegranate wine and compare to multi-varietal red wine using different spectrophotometric and spectrometric techniques. Total phenolic content was determined by the Folin–Ciocalteu assay. The antioxidant capacity was measured by the DPPH and the ABTS radical scavenging assays. The radical-scavenging capacity was higher for pomegranate wine (statistically significant difference was observed for the DPPH assay) in agreement with its higher total phenolic content (383.19 ± 18.22 and 296.57 ± 25.23 mg gallic acid equivalents/100 mL for pomegranate and grape wine respectively). Customized HPLC-PDA-ESI-MSn and GC-MS methods were applied for the identification and chemical characterization of the phenolic compounds for both wines. Identification using LC-MS was based on their λmax (nm) and the characteristic fragments which derived from the sequential fragmentation in MS while GC-MS was based on commercial libraries and mass spectra of authentic standards. Eighty one different phenolic compounds were characterised by LC-MS and one hundred eight compounds by GC-MS after different chemical hydrolysis regimes. The study signifies the prior treatment with alkaline hydrolysis which had a considerable effect on the detection of phenolic compounds. The results showed that the combination of LC-MS and GC-MS methods allowed the detection of different compounds while results from both techniques are complementary and may confirm each other. Phytochemicals with proven biological activities including antimicrobial, antiviral and chemoprotective, have been identified mainly in pomegranate wines. Furthermore, a significant diversity between pomegranate and grape wines was observed, in terms of their phenolic content and antioxidant profiles indicating the-nutritive and health-promoting effects of pomegranate wine.

Lipid and fatty acid profile of the edible fungus Laetiporus sulphurous. Antifungal and antibacterial properties

Laetiporus sulphureus is a saprophyte belonging to a specific group of wood-decomposing Basidiomycetes growing on deciduous trees. This fungus has been characterized as a herbal medicine and is also known for its antimicrobial properties. In the present study, high energy extraction techniques using different solvents were compared to obtain maximum yield of the edible fungus Laetiporus sulphureus total lipids. The lipid classes and fatty acid composition of the fruiting bodies’ total lipids has been studied using GC-FID and Iatroscan TLC-FID analysis. Among the lipids, the neutral lipids predominated followed by phospholipids and glycolipids. Triglycerides were the most abundant in the neutral lipid fraction, whereas phosphatidylcholine in phospholipids. The existence of relatively high amount of sterols may be correlated to fungus pharmaceutical properties. Total lipids were found to contain high unsaturated degree fatty acids (UFA/SFA>3.4) and dominated of C18:2ω-6, C18:1ω-9 and C16:0 fatty acids. Antibacterial and antifungal properties of mushrooms’ lipid extracts from two different solvents were also examined. Results indicated that hexane extracts possessed better antifungal and slightly better antibacterial activity compared to chloroform extracts though both were less active than the commercial antimicrobial agents.

Study of the migration phenomena of specific metals in canned tomato paste before and after opening. Validation of a new quality indicator for opened cans

A method for the simultaneous determination of Cd-Pb, As-Cu, Cr-Ni and Fe-Mn in canned tomato paste samples by Electrothermal Atomic Absorption Spectrometry was developed and validated. The validation procedure was conducted according to the terms of the European regulation for the official control of contaminants in foods. The validated method was applied for the determination of these metals and metalloids in 13 different tomato paste samples and the results showed that Cd content was higher than the maximum permissible value of 0.050 mg kg(-1) as proposed in European Regulation (EC) No 1881/2006 concerning fresh fruits and vegetables. Furthermore, a new quality indicator was evaluated in order to provide information about tomato paste quality and the appropriate storage time of an opened canned tomato paste. Finally, a migration test was accomplished based on the calculation of mass balance and the comparison of the elemental content in canned tomato paste samples and in aseptic paper pack and it was proved that Fe and Pb were the main metals migrating in tomato paste samples.

Development and Validation of an ETAAS Method for the Determination of Tin in Canned Tomato Paste Samples

The determination of tin in canned food became very important in the last few years since it gives information about the contamination process helping to increase canned food quality and safety. The present work describes the development of a method for the determination of tin in canned tomato paste by electrothermal atomic absorption spectrometry in order to investigate the influents of (1) the industrial sample pretreatment procedure of canned tomato paste and (2) the type of materials used in packaging, on the total concentration of tin in canned tomato paste samples. For method validation, precision (repeatability and reproducibility) and accuracy (by recovery tests) have been assessed as performance criteria. The calculated recoveries ranged between 87.9% and 91.9%. The calculated expanded uncertainties based on the EURACHEM/CITAC Guidelines achieved from three different concentration levels were also calculated. The obtained results indicated that the method is efficiently and properly implemented. The validated method was applied for tin concentration determination in canned tomato paste purchased from the local market. In all analyzed samples, tin concentrations levels were lower than the maximum permissible value recommended by the European Regulation.