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Dražen Vikić-Topić

Bio: Dražen Vikić-Topić is an academic researcher from Juraj Dobrila University of Pula. The author has contributed to research in topics: Carbon-13 NMR & Chemical shift. The author has an hindex of 17, co-authored 87 publications receiving 1171 citations. Previous affiliations of Dražen Vikić-Topić include University of Rochester & University of Zagreb.


Papers
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TL;DR: The 4,4'-methylenebis(5-isopropyl-2-methyl)phenol derivative of carvacrol showed lower inhibiting capacity also for the HeLa cells, which makes this particular derivative attractive as an efficient antioxidant with negligible cytotoxic effects.
Abstract: Four derivatives of thymol, carvacrol, and eugenol were synthesized: 4-(hydroxymethyl)-5-isopropyl-2-methylphenol, 4,4′-methylenebis(5-isopropyl-2-methyl)phenol, 4-allyl-6-(hydroxymethyl)-2-methoxyphenol, and 4-(hydroxymethyl)-2-isopropyl-5-methylphenol. The obtained derivatives showed remarkably better antioxidative properties according to 1,1-diphenyl-2-picrylhydrazyl assay (50% inhibitory concentrations = 4–156 µg/mL) and Rancimat assay (protection factors = 1.55–5.84) when compared with parent compounds and values similar to or better than those of butylated hydroxytoluene and vitamin C. At concentrations of 10 mM carvacrol derivatives had no toxic effect on viability of Escherichia coli K-12 (determined by minimum inhibitory concentrations). Other phenol derivatives showed reduced cytotoxic effect on E. coli K-12 at concentrations of 2–5 mM on the basis of 50% lethal dose measurements. In comparison with the parent compounds, phenol derivatives showed reduced cytotoxic effect for Saccharomyces cerevi...

255 citations

Journal ArticleDOI
TL;DR: UAE could be used as an efficient technique for the extraction of pectin from tomato waste and by-products with strong emphasis on environmental friendly processing approach, according to obtained results.

209 citations

Journal ArticleDOI
TL;DR: In this article, a series of complexes HgX_2(H_4pymtH)_2 (X = Cl, Br, I, SCN, CN, Hg(CN)&Hg(SCN)+2(HCN+1, HCN+2, H-1, 3) with tetrahedral coordination was obtained by the reaction of HCN with pseudohalides.

75 citations

Journal ArticleDOI
TL;DR: In this article, a series of mercury(II) compounds of the empirical formulae HgX2L, and Hg X2L2 (X=Cl−, Br−, I−, SCN−; L=imtH−, meimt−; imtH2=1,3-imidazole-2-thione, 1-methyl-1-3-IMidazile-2 -thione; meimTH=1-methyl1-dimethyl-1 -dimethyl1 -th

64 citations

Journal Article
TL;DR: In this article, the Koenigs-Knorr-Zemplen method was used to synthesize naturally occurring glucosides of benzyl alcohol, (+/-)-menthol, (+)-borneol, thymol, carvacrol and eugenol.
Abstract: Naturally occurring glucosides of benzyl alcohol, (+/-)-menthol, (+)-borneol, thymol, carvacrol and eugenol were synthesized by the Koenigs-Knorr-Zemplen method (yields 19.5-52.2%). Their beta-D-glucopyranosidic structures were determined by one- and two-dimensional homo- and heteronuclear H-1 and C-13 NMR spectroscopy. The beta-configuration was additionally confirmed by the hydrolysis with P-glucosidase. Tetraacetyl-beta-D-glucopyranosides, as intermediates, were GC-MS analyzed. Diastereomeric beta-glucoside tetraacetates of (+/-)-menthol were well separated on the HP-101 column. The mass spectra of glucopyranoside tetraacetates were mutually compared, as well as with the spectra of their aglycones.

47 citations


Cited by
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[...]

08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

Journal ArticleDOI
TL;DR: The most commonly methods used in vitro determination of antioxidant capacity of food constituents are reviewed and presented, and the general chemistry underlying the assays in the present paper was clarified.
Abstract: Recently, there has been growing interest in research into the role of plant-derived antioxidants in food and human health. The beneficial influence of many foodstuffs and beverages including fruits, vegetables, tea, coffee, and cacao on human health has been recently recognized to originate from their antioxidant activity. For this purpose, the most commonly methods used in vitro determination of antioxidant capacity of food constituents are reviewed and presented. Also, the general chemistry underlying the assays in the present paper was clarified. Hence, this overview provides a basis and rationale for developing standardized antioxidant capacity methods for the food, nutraceutical, and dietary supplement industries. In addition, the most important advantages and shortcomings of each method were detected and highlighted. The chemical principles of these methods are outlined and critically discussed. The chemical principles of methods of 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulphonate) radical (ABTS·+) scavenging, 1,1-diphenyl-2-picrylhydrazyl (DPPH·) radical scavenging, Fe3+–Fe2+ transformation assay, ferric reducing antioxidant power (FRAP) assay, cupric ions (Cu2+) reducing power assay (Cuprac), Folin-Ciocalteu reducing capacity (FCR assay), peroxyl radical scavenging, superoxide anion radical (O 2 ·− ) scavenging, hydrogen peroxide (H2O2) scavenging, hydroxyl radical (OH·) scavenging, singlet oxygen (1O2) quenching assay and nitric oxide radical (NO·) scavenging assay are outlined and critically discussed. Also, the general antioxidant aspects of main food components were discussed by a number of methods which are currently used for detection of antioxidant properties food components. This review consists of two main sections. The first section is devoted to main components in the foodstuffs and beverages. The second general section is some definitions of the main antioxidant methods commonly used for determination of antioxidant activity of components in the foodstuffs and beverages. In addition, there are given some chemical and kinetic basis and technical details of the used methods.

1,278 citations

Journal ArticleDOI
TL;DR: Antioxidants had a growing interest owing to their protective roles in food and pharmaceutical products against oxidative deterioration and in the body and against oxidative stress-mediated pathological processes as discussed by the authors, and many studies evaluating the antioxidant activity of various samples of research interest have been conducted.
Abstract: Antioxidants had a growing interest owing to their protective roles in food and pharmaceutical products against oxidative deterioration and in the body and against oxidative stress-mediated pathological processes. Screening of antioxidant properties of plants and plant-derived compounds requires appropriate methods, which address the mechanism of antioxidant activity and focus on the kinetics of the reactions including the antioxidants. Many studies evaluating the antioxidant activity of various samples of research interest using different methods in food and human health have been conducted. These methods are classified, described, and discussed in this review. Methods based on inhibited autoxidation are the most suited for termination-enhancing antioxidants and for chain-breaking antioxidants, while different specific studies are needed for preventive antioxidants. For this purpose, the most common methods used in vitro determination of antioxidant capacity of food constituents were examined. Also, a selection of chemical testing methods was critically reviewed and highlighted. In addition, their advantages, disadvantages, limitations and usefulness were discussed and investigated for pure molecules and raw extracts. The effect and influence of the reaction medium on the performance of antioxidants are also addressed. Hence, this overview provides a basis and rationale for developing standardized antioxidant methods for the food, nutraceuticals, and dietary supplement industries. In addition, the most important advantages and shortcomings of each method were detected and highlighted. The chemical principles of these methods are outlined and critically discussed. The chemical principles of methods of 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulphonate) radical (ABTS·+) scavenging, 1,1-diphenyl-2-picrylhydrazyl (DPPH·) radical scavenging, Fe3+-Fe2+ transformation assay, ferric reducing antioxidant power (FRAP) assay, cupric ions (Cu2+) reducing power assay (Cuprac), Folin-Ciocalteu reducing capacity (FCR assay), peroxyl radical (ROO·), superoxide radical anion (O2·-), hydrogen peroxide (H2O2) scavenging assay, hydroxyl radical (OH·) scavenging assay, singlet oxygen (1O2) quenching assay, nitric oxide radical (NO·) scavenging assay and chemiluminescence assay are outlined and critically discussed. Also, the general antioxidant aspects of main food components were discussed by a number of methods, which are currently used for the detection of antioxidant properties of food components. This review consists of two main sections. The first section is devoted to the main components in the food and pharmaceutical applications. The second general section comprises some definitions of the main antioxidant methods commonly used for the determination of the antioxidant activity of components. In addition, some chemical, mechanistic and kinetic basis, and technical details of the used methods are given.

677 citations

BookDOI
01 Jan 1973

430 citations

Journal ArticleDOI
TL;DR: In this article, a review of pectin extraction from food waste and by-products is presented, focusing on the conventional and innovative processing techniques (microwave extraction, enzymatic extraction, ultrasound-assisted extraction).
Abstract: Background A large amount of food wastes and by-products are produced from farm to plate. They represent valuable sources for the production of high-added value compounds such as pectin. Pectin is the methylated ester of polygalacturonic acid and presents a wide range of applications in pharmaceutical and cosmetic products as well as in food industry such as gelling agent in fruit-based products, stabilizer in fruit and milk beverages and fruit filling for bakery and confectionary products, among others. Therefore, pectin recovery is of great importance. Scope and Approach The commercially available pectin is almost exclusively derived from citrus peels or apple pomace, by-products from fruit juice manufacturing. But, nowadays the number of novel food waste and by-products sources for pectin extraction are increasing. Moreover, the application of innovative approaches is necessary due to the limitation of conventional processes. The present review will focus on the conventional and innovative processing techniques (microwave extraction, enzymatic extraction, ultrasound-assisted extraction) to extract pectin from different wastes and by-products. Key Findings and Conclusions The pectin extraction differs according to the matrix studied as well as temperature, pH, time, solvents, and solid to liquid ratio. The use of innovative extraction processes such as ultrasound, microwave and enzymes can be a useful tool to increase pectin yield and quality, and reducing extraction time, temperature, use of toxic solvents and strong acidic conditions for pectin recovery. Moreover, the combination of solvent modelling and the use of particular extraction processes can enable the selective recovery of pectin.

377 citations