Studies of the metal ion-catalysed oxidation of heterocyclic sulfur compounds.

Chemical oxidation by hydrogen peroxide is used for the treatment of hazardous organic materials present at low concentrations in contaminated soil and water. A knowledge of the oxidation of thiophene and its derivatives, with particular reference to oxidative destruction and the identification of intermediate oxidation products would be useful for a deeper understanding of reaction mechanisms in waste treatment and the optimization of conditions. In this thesis, the oxidation of thiophenes, namely thiophene and 2- and 3-methylthiophene, with hydrogen peroxide and catalyst systems, e.g. Fenton's reagent, Gif systems and titanium dioxide-assisted photocatalytic oxidations, all of which may involve the formation of free radicals, e.g. the hydroxyl radical (HO-), has been studied. Fenton-related catalyst systems, mixtures of iron salts (and sometimes also with copper salts) and hydrogen peroxide, have been suggested in the literature and their reactions with thiophenes have been investigated. Additionally, other catalytic systems that have also been suggested in the literature as having potential have been studied. The oxidation of thiophene derivatives with Fenton-like reagents involving a combinations of hydrogen peroxide with other metal salts including vanadium(IV), titanium(III), copper(I) and copper(II) have been explored, since all of these systems appear to form hydroxyl radicals. Further Fenton-related oxidations of reaction intermediates have been carried out in order to help understand whether the oxidation products described are derived directly from the original compound or from further oxidation of a reaction intermediate. The progress of the oxidation reactions was followed by chromatographic analysis, using Gas Chromatography-Mass Spectrometry and High Performance Liquid Chromatography, so as to establish the nature of the oxidation products and the possible reaction pathways. Components of the mixtures were identified by comparison with commercially available products or synthetic standards. Oxidation reactions were monitored over set time intervals and the amounts of residual thiophenes were determined. In all of the oxidation reactions investigated, Fenton-related and Fenton-like, heteroaromatic ring destruction was observed, together with the formation of small amounts of hydroxylated ring products and dimeric structures. The oxidative destruction of thiophenes was successfully achieved with the above catalyst systems in the presence of excess hydrogen peroxide.Recent literature has questioned the formation of hydroxyl radicals in Fenton-related systems, and in order to contribute to the debate regarding the oxidizing species responsible for the destruction of each of the thiophenes, the oxidation reactions have been carried out in the presence of a complexing agent such as ethylenediaminetetraacetic acid (EDTA), and a radical trapping reagent 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), respectively. Evidence of radical trapping was observed. Gif chemistry may involve the formation of high oxidation state iron complexes rather than free radicals. The oxidation of thiophenes was carried out using Fenton's reagent under Gif conditions and the results were compared with those from conventional Fenton and related conditions, to determine whether free radical species are involved in the latter. Radical derived products were again observed.Titanium-catalysed photooxidation has also formed part of this study to determine the nature of intermediate products which might be similar to those from Fenton-catalysed systems. For these reasons, the photocatalytic oxidation of 2-methylthiophene was studied in aqueous solution and the reaction was conducted in the presence and absence of titanium dioxide under an oxygen atmosphere. A similar range of radical derived products was found as in the conventional Fenton and related systems

Phenolic Contents and Antioxidant Potential of Crataegus Fruits Grown in Tunisia as Determined by DPPH, FRAP, and -Carotene/Linoleic Acid Assay

Crataegus fruit is one of most important fruits in Tunisian flora. Some fruits of this genus are edible. This study was undertaken in order to examine the benefits of these fruits in human health and their composition of antioxidants including total polyphenol, flavonoids, proanthocyanidins content, and total anthocyanins. The antioxidative properties of the ultrasonic methanolic extract were assessed by different in vitro methods such as the FRAP, DPPH, and -carotene/linoleic acid assay. We concluded that peel fraction of red fruits possessed relatively high antioxidant activity and might be a rich source of natural antioxidants in comparison with the pulp and seed fruit extract. The results also showed that hawthorn yellow fruit presents lower amounts of phenolic content, absence of anthocyanins, and less antioxidant capacity. Most of peel and seed fractions were stronger than the pulp fractions in antioxidant activity based on their DPPH IC 50 , FRAP values, and results of -carotene/linoleic acid. The total phenolic compounds contents were also highly correlated with the DPPH method and the FRAP assay

Screening of the antioxidant activity of essential oil and various extracts of Origanum rotundifolium Boiss. from Turkey

This study is designed to examine the chemical composition and in vitro antioxidant activity of the essential oil and various extracts of Origanum rotundifolium Boiss. from Turkey. The total of the 40 identified components accounted for 97.23% (GC) and 95.10% (FID) of the total oil. Major components of the oil were borneol, terpinen-4-ol, and spathulenol. To determine the presence of well known and widespread phenolic compounds, water-soluble extract of O. rotundifolium was analyzed by HPLC. In the methanol-soluble extract, caffeic acid, p-coumaric acid, (+)-catechin, and ferulic acid were found in several quantities. Antioxidant activity of the essential oil and extracts of O. rotundifolium has been determined by four different test systems namely DPPH, β β β β-carotene/linoleic acid, chelating effect and reducing power. A strong correlation was observed between the radical scavenging capacity and polarity of the extracts. The methanol-soluble extract which contains the most polar phytochemicals showed the strongest antioxidant effect in all test systems. As expected, amount of the total phenolics and flavonoids was very high in methanol-soluble extract

Biological Activities of Extracts and Essential Oil of Thymus transcaucasicus Ronniger

WOS: 000373724000021Hexane, chloroform, water extracts and essential oil obtained from flowering aerial parts of Thymus transcaucasicus Ronniger were screened for potential in vitro antioxidant, antimicrobial and antiviral activities. Chemical composition of essential oil was determined by employing GC-MS analysis; thymol being the main component in 55%. The essential oil and extracts were screened for their possible antioxidant activities by two complementary test systems, namely DPPH free radical scavenging and beta-Carotene color bleaching test-a spectrophotometric method. The highest free radical scavenging activity was observed in the essential oil (IC50: 20 mu g/ml) whilst, in beta-Carotene color bleaching test, hexane extract showed superiority, with an inhibition rate at 72.3%. Antibacterial and antifungal activities of the extracts were also evaluated and among which the essential oil exerted better activity against all microorganisms tested except for Pseudomonas aeruginosa. Nevertheless, none was effective against test viruses, namely HSV and Influenza.Karadeniz Technical University (BAP)Karadeniz Teknik University [2007.111.004.4]The authors appreciate for the financial support of Karadeniz Technical University (BAP Project No. 2007.111.004.4)

Phenolic Contents and Antioxidant Potential of Crataegus Fruits Grown in Tunisia as Determined by DPPH, FRAP, and β-Carotene/Linoleic Acid Assay

Crataegus fruit is one of most important fruits in Tunisian flora. Some fruits of this genus are edible. This study was undertaken in order to examine the benefits of these fruits in human health and their composition of antioxidants including total polyphenol, flavonoids, proanthocyanidins content, and total anthocyanins. The antioxidative properties of the ultrasonic methanolic extract were assessed by different in vitro methods such as the FRAP, DPPH, and β-carotene/linoleic acid assay. We concluded that peel fraction of red fruits possessed relatively high antioxidant activity and might be a rich source of natural antioxidants in comparison with the pulp and seed fruit extract. The results also showed that hawthorn yellow fruit presents lower amounts of phenolic content, absence of anthocyanins, and less antioxidant capacity. Most of peel and seed fractions were stronger than the pulp fractions in antioxidant activity based on their DPPH IC50, FRAP values, and results of β-carotene/linoleic acid. The total phenolic compounds contents were also highly correlated with the DPPH method and the FRAP assay

In vitro antimicrobial, antioxidant, and antiviral activities of the essential oil and various extracts from Thymus nummularis M. Bieb.

WOS: 000379195200007This study is designed to determine the in vitro antioxidant, antimicrobial and antiviral activities of hexane, chloroform, water extracts and essential oils of Thymus nummularis M. Bieb. Chemical composition of essential oil was determined by employing GC-MS and GC-FID analyses; thymol being the main component in 58 %. The oil and extracts were screened for their possible antioxidant activities by two complementary test systems, namely DPPH free radical scavenging and Carotene color bleaching test a spectrophotometric method. The highest free radical scavenging activity was observed in the essential oil (IC50: 2.3 mu g/ml) whilst, in beta-Carotene color bleaching test, chloroform extract showed superiority, with an inhibition rate at 79.95 %. Antibacterial and antifungal activities of the extracts were also evaluated and among which the essential oil exerted better activity against all microorganisms tested except for Pseudomonas aeruginosa. Nevertheless, none was effective against test viruses, namely HSV and Influenza

Antioxidant phenolic constituents, antimicrobial and cytotoxic properties of Stachys annua L. from both natural resources and micropropagated plantlets

An efficient micropropagation protocol was developed to produce Stachys annua plantlets and the extracts obtained from both micropropagated and naturally growing individuals were evaluated for their possible antimicrobial, antioxidant and cytotoxic activities. Mean number of shoot (4.5 +/- 0.54 per explant) and node number (4.56 +/- 0.5 per explant) as well as biomass yield based on fresh (0.29 +/- 0.02 gm per explant) and dry weight (0.029 +/- 0.003 gm per explant) were found to be the highest on MS medium with 6-BA, whilst the highest mean shoot length (36.65 +/- 1.58 mm) was obtained from MS medium containing 2iP. Hexane extracts from both sources showed activity against Staphylococcus aureus whilst methanol extracts of micropropagated plantlets exerted activity on Pseudomonas aeruginosa. In antioxidant activity assays, the best antioxidant activity was up to IC50 9.41 mg/mL in DPPH and 1409.5 (mg/100 gm trolox equivalent) was found in FRAP. Extracts from natural plantlets showed higher cytotoxic activity micropropagated ones, with IC50 of 0.099 mu g/mL and IC(50)of 0.211 mu g/mL on HeLa cells, respectively. Total phenolics ranged from 87.47 to 605.12 in micropropagated samples while 771.46 (mg/100 gm gallic acid equivalent) in natural resources

The effect of microporous vanadosilicate AM-6 thin films as photocatalysts for the degradation of methylene blue

In the current study, a new photocatalyst in thin film form exhibiting photocatalytic activity under visible light range was introduced. For that purpose, microporous vanadosilicate (AM-6, (Na,K)(2)VSi5O13) and silver nanoparticle (Ag-0) incorporated vanadosilicate AM-6 thin films were investigated as photocatalysts for the photocatalytic decomposition of methylene blue (MB). To create different oxidation states of vanadium cation present in the center dot center dot center dot V-o-V-o-V center dot center dot center dot quantum wires within the framework of AM-6, two different molar compositions were used for thin film formation of vanadosilicate AM-6. The vanadosilicate AM-6 thin films demonstrated photocatalytic activity under ultraviolet (UV) and visible light irradiation. The microporous titanosilicate (ETS-10, (Na.K)(2)TiSi5O13) thin films, isomorph of vanadosilicate AM-6, were also used as photocatalysts for the degradation of MB for the comparison of photocatalytic effectiveness. When visible light irradiation is used for the photocatalytic decomposition of MB, the photocatalytic activity of AM-6 was significantly different with respect to ETS-10. The narrower band gap of AM-6 with respect to the band gap of ETS-10 and the presence of V5+ cations in the structure of AM-6 provided photocatalytic activity under visible light irradiation. It was found that, vanadosilicate AM-6 films with higher amount of V5+ ions possess better photocatalytic activity under visible light irradiation for the degradation of MB, which can be attributed to the presence of V5+ cations within the framework of AM-6. The presence of both V4+ and V5+ cations was characterized by XPS and Raman spectroscopy in the vanadosilicate AM-6 thin films. To enhance the photocatalytic activity of AM 6 thin films, Na+ and K+ ions of the as-synthesized AM-6 thin films were ion-exchanged with Ag+ ions and then reduced to Ag-0 nanoparticles (NP) by using sodium borohydride (NaBH4) solution. The results showed that Ag-0 NP incorporated AM-6 thin films showed an increased photocatalytic activity due to various reasons such as the role of metal nanoparticles as electron traps, surface plasmon resonance effect, and band-gap narrowing

Phenolic Profiles, Antimicrobial and Cytotoxic Properties of Both Micropropagated and Naturally Growing Plantlets of Calamintha sylvatica subsp. sylvatica Bromf.

UCAR, Evren ONAY/0000-0003-1152-4881WOS: 000508003800016A rapid micropropagation protocol was designed to produce Calamintha sylvatica plantlets by using nodal segments as explants for the shoot formation. 6-BA favored the highest shoot formation and biomass yield, whilst kinetin was found superior for the highest shoot length (38.97 +/- 2.85 mm) and node numbers (2.89 +/- 0.63). Rosmarinic acid was detected as major phenolic acid, ranging from 7.59 mg/100 g to 81.44 mg/100 g. Hexane extracts from natural and in vitro propagated plantlets showed activity only against Staphylococcus aureus ATCC 25923 with MIC values at 6.25 and 3.33 m/mL, respectively while in the latter case, extracts from natural plantlets exerted higher cytotoxic activity than those of micropropagated ones (IC50 values were 83 mu g/mL and 98 mu g/mL on HeLa cells, respectively). C. sylvatica showed high micropropagation performance and produced remarkable amount of rosmarinic acid in vitro as well as antimicrobial and cytotoxic effect.KTU-BAP (The Scientific Research Commitee of Karadeniz Technical University); King Saud UniversityDeanship of Scientific Research at King Saud UniversityThe study was carried out with the financial support of KTU-BAP (The Scientific Research Commitee of Karadeniz Technical University, Project No. KTU-BAP.1064). Authors are thankful to King Saud University for financial support under the issue of Distinguished Scientist Research Fellowship Program (DSFP)

Antioxidant phenolic constituents, antimicrobial and cytotoxic properties of Stachys annua L. from both natural resources and micropropagated plantlets

UCAR, Evren ONAY/0000-0003-1152-4881; Ucar, Evren Onay/0000-0003-1152-4881WOS: 000407987700007An efficient micropropagation protocol was developed to produce Stachys annua plantlets and the extracts obtained from both micropropagated and naturally growing individuals were evaluated for their possible antimicrobial, antioxidant and cytotoxic activities. Mean number of shoot (4.5 +/- 0.54 per explant) and node number (4.56 +/- 0.5 per explant) as well as biomass yield based on fresh (0.29 +/- 0.02 gm per explant) and dry weight (0.029 +/- 0.003 gm per explant) were found to be the highest on MS medium with 6-BA, whilst the highest mean shoot length (36.65 +/- 1.58 mm) was obtained from MS medium containing 2iP. Hexane extracts from both sources showed activity against Staphylococcus aureus whilst methanol extracts of micropropagated plantlets exerted activity on Pseudomonas aeruginosa. In antioxidant activity assays, the best antioxidant activity was up to IC50 9.41 mg/mL in DPPH and 1409.5 (mg/100 gm trolox equivalent) was found in FRAP. Extracts from natural plantlets showed higher cytotoxic activity micropropagated ones, with IC50 of 0.099 mu g/mL and IC(50)of 0.211 mu g/mL on HeLa cells, respectively. Total phenolics ranged from 87.47 to 605.12 in micropropagated samples while 771.46 (mg/100 gm gallic acid equivalent) in natural resources.KTU-BAP (The Scientific Research Commitee of Karadeniz Technical University) [KTU-BAP.1064. 2216]The authors deeply appreciate the financial support of KTU-BAP (The Scientific Research Commitee of Karadeniz Technical University) for the project KTU-BAP.1064. 2216 Research FellowshipProgramme For ForeignCitizens(TUBITAK) is acknowledged for funding author A. H. Laghari for post doctorate studies in Karadeniz Technical University