Conditions. -The effect of the N-halosuccinimides, the influence of the catalyst, the reaction te... more Conditions. -The effect of the N-halosuccinimides, the influence of the catalyst, the reaction temperature, and the aggregate state of the substrates (1,3-diketones, a β-ketoamide, aryl-substituted ketones, and cyclic ketones) on the course of the halogenation is investigated. Diketones and the ketoamide are halogenated in the solid state and without a catalyst. The generally applied aqueous work-up affords in the case of diketones (I) stable hydrated derivatives. The halogenation of the other ketones proceeds in the presence of catalytic amounts of TosOH in molten mixtures, at room temperature in most cases or at 80°C. -(PRAVST, I.; ZUPAN, M.; STAVBER*, S.; Tetrahedron 64
Coenzyme Q10 (CoQ10), also known as Ubiquinone, is a natural antioxidant with a fundamental role ... more Coenzyme Q10 (CoQ10), also known as Ubiquinone, is a natural antioxidant with a fundamental role in cellular bioener- getics. Endogenous tissue levels drop progressively with increasing age and a deficiency has also been observed in va- rious medical conditions and lifestyles. The limited supply to the organism by foods has been further reduced by food processing as it is known that processed products and foods with a lower amount of fat usually have smaller amounts of CoQ10. This and the numerous health benefits of its supplementation are the main reason triggering the interest of the food industry which has started to use this compound to fortify food products. Due to its lipophilicity, until recently this goal was not easily achievable with most products. Forms of CoQ10 with increased water-solubility or dispersibility ha- ve been developed for this purpose, allowing the fortification of aqueous products. We studied the stability of Coenzy- me Q10 in some fortified products that ...
Halogenation O 0235 Directed Regioselectivity of Bromination of Ketones with NBS: Solvent-Free Co... more Halogenation O 0235 Directed Regioselectivity of Bromination of Ketones with NBS: Solvent-Free Conditions versus Water. -Bromination of aryl alkyl ketones or dialkyl ketones with NBS under solvent-free conditions in the presence of acid results in a highly selective α-bromination. In water, a benzene ring bromination is observed in the case of methoxy-substituted aromatic ketones. -(PRAVST, I.; ZUPAN, M.; STAVBER*, S.; Tetrahedron Lett. 47 (2006) 27, 4707-4710; Lab. Org. Bioorg. Chem., Fac. Chem. Chem. Technol., Stefan Inst., Univ.
The effect of steric interactions on the regioselectivity of fluorination of para alkyl substitut... more The effect of steric interactions on the regioselectivity of fluorination of para alkyl substituted phenols was investigated and the strong effect of size of the alkyl substituent, the structure of the F-N reagent and the solvent on the site of fluorination was established. The course of reaction obeyed a second order rate equation, while the fluorination process required higher DH s activation than oxidation or oxidative demethylation. Solvent polarity variations had a small effect on the rate of functionalisation, while an excellent Hammett correlation with r C ZK2.3 was determined. q
Several aryl substituted ketones, cyclic ketones, 1,3-diketones and a b-ketoamide were halogenate... more Several aryl substituted ketones, cyclic ketones, 1,3-diketones and a b-ketoamide were halogenated with N-halosuccinimides under solvent-free reaction conditions (SFRC) at various temperatures (20-80 C), whereas less enolized ketones required the presence of an acid catalyst (p-toluenesulfonic acid, PTSA). Bromination of substituted acetophenones obeys first order kinetics v¼k Br [ketone] and the following correlation with the keto-enol equilibrium constant: log k Br ¼0.3pK E þC 1 , less enolized substrates being more reactive; the moderate positive charge developed in the rate determining step was confirmed by the Hammett correlation (r¼À0.5). On the other hand, in cyclic ketones an opposite relation was observed: log k Br ¼À0.6pK E þC 2 , indicating higher reactivity of substrates with higher enolization constant (K E ). The important role of the nature of the solvent (MeCN, MeOH) in preorganization of the ketone-NBS-PTSA mixture prior to SFRC bromination was found.
The health effects of olive oil are attributed to its high content of oleic acid and other consti... more The health effects of olive oil are attributed to its high content of oleic acid and other constituents, particularly its phenolic fraction. Olive oil also contains other substances with potential health effects such as coenzyme Q10 (CoQ10) and coenzyme Q9 (CoQ9). The objective of our study was to investigate some factors that could influence the quantity of coenzyme Q (CoQ) in olive oils. We analyzed almost 100 samples of commercial oil blends and fresh extra virgin olive oils of various cultivars using high-performance liquid chromatography. With the investigation of various monocultivar samples we determined that genetic parameters (cultivars) have an important influence on the composition of olive oils, particularly the content of CoQ10. Possible effects of the degree of ripeness were also studied for the cultivars Istrska belica and Leccino. We determined that the highest levels of both CoQ10 and CoQ9 can be found in early maturation stages.
Journal für Verbraucherschutz und Lebensmittelsicherheit, 2011
In the European Union (EU), food supplements are regulated as food and their use is expanding rap... more In the European Union (EU), food supplements are regulated as food and their use is expanding rapidly. There is no enforcement to ensure that good manufacturing practices (GMPs) are followed during production but manufacturers are fully responsible for their products. Recently, the safety and quality of supplements available in the market has come into question. In our surveillance, we examined
Avoiding volatile and toxic organic solvents during each particular phase of synthetic protocols ... more Avoiding volatile and toxic organic solvents during each particular phase of synthetic protocols should become important goal of chemical synthesis designers in academia and particularly in the industrial research community. Solvent-free reaction conditions (SFRC) are becoming a widely used experimental technique for the selective and efficient introduction of halogen atoms into organic compounds. The different approaches to the preparation of halosubstituted organic molecules using equimolar amount of the substrate and reagent under SFRC are reviewed and evaluated. Fluorination of various types of organic compounds under SFRC using fluorine gas, N-F reagents, and hydrogen or metal fluorides is compiled. Chloro-, bromo-or iodofunctionalisation under SFRC using molecular halogens, N-halosuccinimides, hydrogen or others halides is reviewed. Oxidative halogenations of comprehensive types of organic compounds under SFRC are evaluated.
120 and 79% increases over the reference were calculated for the Q10Vital liquid and powder, resp... more 120 and 79% increases over the reference were calculated for the Q10Vital liquid and powder, respectively. Conclusions:
The use of health claims on foods with a poor nutritional composition could pose a risk of mislea... more The use of health claims on foods with a poor nutritional composition could pose a risk of misleading some groups of consumers in their food choices. This study aimed to explore the influence of the use of claims on consumers' preferences for yoghurts with a different nutritional composition and the influence of more and less familiar claims on food choices. The study was conducted on 371 consumers using conjoint methodology and further cluster analysis. Fruit yoghurt was used as a base product. We investigated the impact of the following product attributes on consumers' preferences: presence/absence of a probiotic and fat metabolism claim; sugar content; and fat content. The results suggest that, while consumers generally consider the nutritional composition of yoghurt to be more important than the tested claims, some groups of consumers are more sensitive to the use of health-related statements. We observed the consumers' generally positive preference for a familiar probiotic claim, and their negative preference for a non-familiar fat metabolism claim. Overall, these results indicate that some groups of consumers are more sensitive to the use of health-related communications and are therefore more exposed to the risk of being misled if the composition of the yoghurt they buy is in fact less favourable. It would be beneficial if nutrient profiles were introduced to limit the use of claims on foods.
Conditions. -The effect of the N-halosuccinimides, the influence of the catalyst, the reaction te... more Conditions. -The effect of the N-halosuccinimides, the influence of the catalyst, the reaction temperature, and the aggregate state of the substrates (1,3-diketones, a β-ketoamide, aryl-substituted ketones, and cyclic ketones) on the course of the halogenation is investigated. Diketones and the ketoamide are halogenated in the solid state and without a catalyst. The generally applied aqueous work-up affords in the case of diketones (I) stable hydrated derivatives. The halogenation of the other ketones proceeds in the presence of catalytic amounts of TosOH in molten mixtures, at room temperature in most cases or at 80°C. -(PRAVST, I.; ZUPAN, M.; STAVBER*, S.; Tetrahedron 64
Coenzyme Q10 (CoQ10), also known as Ubiquinone, is a natural antioxidant with a fundamental role ... more Coenzyme Q10 (CoQ10), also known as Ubiquinone, is a natural antioxidant with a fundamental role in cellular bioener- getics. Endogenous tissue levels drop progressively with increasing age and a deficiency has also been observed in va- rious medical conditions and lifestyles. The limited supply to the organism by foods has been further reduced by food processing as it is known that processed products and foods with a lower amount of fat usually have smaller amounts of CoQ10. This and the numerous health benefits of its supplementation are the main reason triggering the interest of the food industry which has started to use this compound to fortify food products. Due to its lipophilicity, until recently this goal was not easily achievable with most products. Forms of CoQ10 with increased water-solubility or dispersibility ha- ve been developed for this purpose, allowing the fortification of aqueous products. We studied the stability of Coenzy- me Q10 in some fortified products that ...
Halogenation O 0235 Directed Regioselectivity of Bromination of Ketones with NBS: Solvent-Free Co... more Halogenation O 0235 Directed Regioselectivity of Bromination of Ketones with NBS: Solvent-Free Conditions versus Water. -Bromination of aryl alkyl ketones or dialkyl ketones with NBS under solvent-free conditions in the presence of acid results in a highly selective α-bromination. In water, a benzene ring bromination is observed in the case of methoxy-substituted aromatic ketones. -(PRAVST, I.; ZUPAN, M.; STAVBER*, S.; Tetrahedron Lett. 47 (2006) 27, 4707-4710; Lab. Org. Bioorg. Chem., Fac. Chem. Chem. Technol., Stefan Inst., Univ.
The effect of steric interactions on the regioselectivity of fluorination of para alkyl substitut... more The effect of steric interactions on the regioselectivity of fluorination of para alkyl substituted phenols was investigated and the strong effect of size of the alkyl substituent, the structure of the F-N reagent and the solvent on the site of fluorination was established. The course of reaction obeyed a second order rate equation, while the fluorination process required higher DH s activation than oxidation or oxidative demethylation. Solvent polarity variations had a small effect on the rate of functionalisation, while an excellent Hammett correlation with r C ZK2.3 was determined. q
Several aryl substituted ketones, cyclic ketones, 1,3-diketones and a b-ketoamide were halogenate... more Several aryl substituted ketones, cyclic ketones, 1,3-diketones and a b-ketoamide were halogenated with N-halosuccinimides under solvent-free reaction conditions (SFRC) at various temperatures (20-80 C), whereas less enolized ketones required the presence of an acid catalyst (p-toluenesulfonic acid, PTSA). Bromination of substituted acetophenones obeys first order kinetics v¼k Br [ketone] and the following correlation with the keto-enol equilibrium constant: log k Br ¼0.3pK E þC 1 , less enolized substrates being more reactive; the moderate positive charge developed in the rate determining step was confirmed by the Hammett correlation (r¼À0.5). On the other hand, in cyclic ketones an opposite relation was observed: log k Br ¼À0.6pK E þC 2 , indicating higher reactivity of substrates with higher enolization constant (K E ). The important role of the nature of the solvent (MeCN, MeOH) in preorganization of the ketone-NBS-PTSA mixture prior to SFRC bromination was found.
The health effects of olive oil are attributed to its high content of oleic acid and other consti... more The health effects of olive oil are attributed to its high content of oleic acid and other constituents, particularly its phenolic fraction. Olive oil also contains other substances with potential health effects such as coenzyme Q10 (CoQ10) and coenzyme Q9 (CoQ9). The objective of our study was to investigate some factors that could influence the quantity of coenzyme Q (CoQ) in olive oils. We analyzed almost 100 samples of commercial oil blends and fresh extra virgin olive oils of various cultivars using high-performance liquid chromatography. With the investigation of various monocultivar samples we determined that genetic parameters (cultivars) have an important influence on the composition of olive oils, particularly the content of CoQ10. Possible effects of the degree of ripeness were also studied for the cultivars Istrska belica and Leccino. We determined that the highest levels of both CoQ10 and CoQ9 can be found in early maturation stages.
Journal für Verbraucherschutz und Lebensmittelsicherheit, 2011
In the European Union (EU), food supplements are regulated as food and their use is expanding rap... more In the European Union (EU), food supplements are regulated as food and their use is expanding rapidly. There is no enforcement to ensure that good manufacturing practices (GMPs) are followed during production but manufacturers are fully responsible for their products. Recently, the safety and quality of supplements available in the market has come into question. In our surveillance, we examined
Avoiding volatile and toxic organic solvents during each particular phase of synthetic protocols ... more Avoiding volatile and toxic organic solvents during each particular phase of synthetic protocols should become important goal of chemical synthesis designers in academia and particularly in the industrial research community. Solvent-free reaction conditions (SFRC) are becoming a widely used experimental technique for the selective and efficient introduction of halogen atoms into organic compounds. The different approaches to the preparation of halosubstituted organic molecules using equimolar amount of the substrate and reagent under SFRC are reviewed and evaluated. Fluorination of various types of organic compounds under SFRC using fluorine gas, N-F reagents, and hydrogen or metal fluorides is compiled. Chloro-, bromo-or iodofunctionalisation under SFRC using molecular halogens, N-halosuccinimides, hydrogen or others halides is reviewed. Oxidative halogenations of comprehensive types of organic compounds under SFRC are evaluated.
120 and 79% increases over the reference were calculated for the Q10Vital liquid and powder, resp... more 120 and 79% increases over the reference were calculated for the Q10Vital liquid and powder, respectively. Conclusions:
The use of health claims on foods with a poor nutritional composition could pose a risk of mislea... more The use of health claims on foods with a poor nutritional composition could pose a risk of misleading some groups of consumers in their food choices. This study aimed to explore the influence of the use of claims on consumers' preferences for yoghurts with a different nutritional composition and the influence of more and less familiar claims on food choices. The study was conducted on 371 consumers using conjoint methodology and further cluster analysis. Fruit yoghurt was used as a base product. We investigated the impact of the following product attributes on consumers' preferences: presence/absence of a probiotic and fat metabolism claim; sugar content; and fat content. The results suggest that, while consumers generally consider the nutritional composition of yoghurt to be more important than the tested claims, some groups of consumers are more sensitive to the use of health-related statements. We observed the consumers' generally positive preference for a familiar probiotic claim, and their negative preference for a non-familiar fat metabolism claim. Overall, these results indicate that some groups of consumers are more sensitive to the use of health-related communications and are therefore more exposed to the risk of being misled if the composition of the yoghurt they buy is in fact less favourable. It would be beneficial if nutrient profiles were introduced to limit the use of claims on foods.
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Papers by Igor Pravst