|
|
Determination of selected chemical parameters of fruits of modern gooseberry varieties
Javorská, Kateřina ; Vítová, Eva (referee) ; Vespalcová, Milena (advisor)
Diploma thesis deals with determination of individual chemical parameters contained in modern varietes of gooseberries (Grossularia uva-crispa). The theoretical part is focused on the botanical characteristics of the plant, a description of selected varietes, chemical composition and food utilization fruits. The second half of the theoretical part is devoted to the characterization of selected nutritional parameters and methods for determination of total anthocyanins, phenolic compounds, vitamin C and antioxidant activity. Total of 17 varietes of gooseberries, which come from growers Vondráček and the Research and Breeding Institute of Pomology Holovousy Ltd. were analyzed in the experimental part. pH differential method was used to determination total monomeric anthocyanins. Total content of polyphenols were determined by using the Folin-Ciocalteu reagent. Next was determined content of vitamin C in all varieties by HPLC and was evaluated the total antioxidant aktivity using radical DPPH. In conclusion, individual varieties of gooseberries were compared by the contents of the determined chemical parameters.
|
|
|
Characterisation of chokeberry and saskatoon berry fruits
Burdějová, Lenka ; Omelka, Ladislav (referee) ; Vítová, Eva (advisor)
Diploma thesis deals with the characterization of chokeberry (Aronia melanocarpa) and saskatoon berry (Amelanchier alnifolia) fruits. The theoretical part focuses on the botanical classification, chemical composition, curative effects and the use of chokeberry and saskatoon berry in the food industry. Further, the attention is also devoted to a review of methods for the determination of important antioxidants, specialized on the determination of polyphenols, anthocyanins, ascorbic acid and total antioxidant activity. The experimental part of the work deals with the determination of selected parameters in different varieties of chokeberry and serviceberry, harvested in 2012 and 2013 using spectroscopic and chromatographic techniques with an emphasis on effect of solvent (50% ethanol, destilled water, DMSO). Specifically total content of polyphenols and anthocyanins, color characteristics using the CIE L*a*b* system and the ability of the sample to reduce the iron are determined using the UV-VIS-NIR spectroscopy. Further ascorbic acid concentration in individual extracts is quantified by High performance liquid chromatography coupled with a diode array detector and the total antioxidant activity is characterized by electron paramagnetic resonance involving •DPPH and ABTS•+ assays.
|
|
|
Pressurized solvent extraction of plant material for food industry use
Holasová, Petra ; Vítová, Eva (referee) ; Vespalcová, Milena (advisor)
Flavonoids were identified and quantified in samples of dry leaves of plant Stevia rebaudiana Bertoni. Content of flavonols (kaempherol, quercetin, myricetin, rutin) and flavons (apigenin, luteolin) were compared in three samples (standard leaves of Stevia rebaudiana Bertoni, Stevia rebaudiana Bertoni origin from Ukraine and from Czech republic), that were extracted by three extraction methods (PSE, ultrasonic extraction, Soxhlet extraction) with two polar solvents, methanol and ethanol, in combination with non-polar hexane. Extracts were analyzed by HPLC with detection UV-VIS. Antioxidant activity and total content of flavonoids in extracts were measured by spectrometry. Stable free radical DPPH. was used for determination of scavenging effect in extracts. PSE was the most effective extraction method with this conditions – 120 °C, dynamic mode and with methanol like solvent.
|
|
|
Antimicrobial effect of plant extracts
Konderla, Patrik ; Vespalcová, Milena (referee) ; Veselá, Mária (advisor)
The purpose of this bachelor thesis was to research the possible antimicrobial activity of various extracts of rosehip tea and also determine the antioxidant activity and the concentration of biologically active compounds (polyphenols and flavonoids) in these tea. Teoretical part describes basic information about plant Rosa canina and chemical composition of rosehips, summary of the natural biologically active compounds and general classification of tea. The practical part is focused on detection of antimicrobial activity of tea extracts against bacterial strains Serratia marcescens and Bacillus subtilis as well as spectrophotometrical determination of concentration polyphenols, flavonoids and overall antioxidant activity of these extracts. From the results flow the testing aqueous extracts rosehips tea analysed antimicrobial effects. Also was found, that these extracts has high content of polyphenols and flavonoids.
|
|
|
Study of antioxidants in dried fruits.
Barošová, Michaela ; Drábková,, Michaela (referee) ; Márová, Ivana (advisor)
Presented diploma work is focused on study of antioxidants in different kinds of dried fruits. Analyses of ascorbate, tocopherols, carotenoids and flavonoids were performed using RP-HPLC with spectrophotometric detection. Analysis of dried fruits showed high level of vitamins and phenolocs mainly in berries. High level of carotenoids was observed in dried apricots and plums. Further, antioxidant activity of dried fruit extracts was tested by ABTS method. High antioxidant activity was found mainly in dried apples, cranberries and blueberries. The biological test with yeast Sascharomyces cerevisiae D7 was used for the analysis of antimutagenic efects of dried fruits. High antimutagenic activity exhibited dried cranberries and blueberries. Most of tested dried fruits with high antimutagenic effect exhibited also high antioxidant activity as well as high content of some antioxidants. No direct correlation was found among these parameters. Last part of this work was focused on study of influence of drying on antioxidant content in two types of apples. Drying at mild controlled conditions exhibited no significant negative effect on active substance content; in some samples their concentration was observed.
|
|
|
Antioxidative substances in selected fruit and herbal teas
Tomková, Martina ; Buňková, Radka (referee) ; Márová, Ivana (advisor)
This diploma project deals with antioxidant and antimutagenic properties of selected herbal and fruit teas commonly used in Czech population. Influence of different tea packaging (bag teas and loose leaf teas) on bioactive compound content was compared. Further, effect of long-term storage in common household conditions was studied. Antioxidant properties of teas were characterized using some group parameters - total antioxidant activity ("Randox Total Antioxidant Status Kit"), total phenolics and total flavonoids - as well as some individual representatives of low molecular weight antioxidants. Higher antixidant content was found in herbal teas than in fruit teas. Comparing bag teas with loose leaf teas higher antioxidant activity was shown in loose leaf teas. Individual antioxidants were analyzed using HPLC method with spectrophotometric detection and verified by on-line LC/MS. IN all tea samples catechins - catechin, epicatechin, epicatechin gallate and other flavonoids - rutin, morin, quercetin, kaempferol, myricetin and luteolin were determined. In most of teas high level of catechin and rutin was detected. The highest level of flavonoids was determined in herbal poured teas. Ascorbic acid content was also determined by HPLC method. Higher vitamine C level was found in most of fruit teas and in rose hip tea. Antimutagenicity of tea extracts was tested by in vitro test using Saccharomyces cerevisiae D7 yeast. High antimutagenic activity showed mainly nettle tea, tutsan tea and most of fruit teas. During long-term storage (1 year, 20°C, darkness) a significant decrease of all analyzed antioxidant parameters was followed. Higher lost of antioxidants was found in fruit teas when compared with the herbal ones.
|
|
|
In vitro study of antioxidant activity of food supplements
Vopelková, Dominika ; Pořízka, Jaromír (referee) ; Omelka, Ladislav (advisor)
Bachelor thesis deals with the determination of antioxidant activity of food supplements in vitro. The theoretical part focuses on legislative requirements of food supplements, their characteristic and classification. Further, the attention is also devoted to antioxidants, their properties, effects, importance and utilization. Separate chapter describes herbs, which are an essential component of researched supplements, their effects and properties. For experimental part several food supplements in various forms (capsule, tea, juice, dried fruits) were chosen and total content of polyphenols was determined using the UV-VIS spectroscopy. Further, the total antioxidant activity is characterized by electron paramagnetic resonance involving DPPH method.
|
|
|
Biologically significant substances in cereal products
Vondráčková, Hedvika ; Halienová, Andrea (referee) ; Márová, Ivana (advisor)
Presented work was focused on study of biologically significant substances in cereal products. In experimental part selected active substances in cereal bars were analyzed. The highest content of total phenolics, total flavonoids, total antioxidant capacity, procyanidin B2 and chlorogenic acid was measured in plums and blueberry bars. The highest level of reduced saccharides was evaluated in raspberry and cereal bars. Presence of main simple sugars - maltose, glucose and fructose was detected in all bar samples.
|
|
|
The Methods for the Detection of Antioxidant Substances
TURKOVÁ, Kateřina
Antioxidants and free radicals are widely discussed in the clinical and nutritional literature. Various reactive oxygen species (ROS) may be produced from normal biochemical, essential metabolic processes or from external sources as exposure to a variety of agents presented in the environment. Lipids, proteins, carbohydrates and DNA are all capable of reacting with ROS and can be implicated in etiology of various human disorders. The antioxidant system protects the organism from the effects of free radicals by scavenging them and thus preventing structural damage of cells. Measuring the individual components of the antioxidant system has provided important information about the defences against free radical effect. During the last decade, many analytical methods have been developed to determine the antioxidant activity of natural compounds and their mixtures in vitro. Some procedures involve the methods based on the generation of various radical species and their elimination by treatment with potential antioxidant compounds. The tests used for the evalution of total antioxidant activity are: Trolox equivalent antioxidant capacity-TEAC, diphenylpicrylhydrazil - DPPH, oxygen radical absorbance capacity-ORAC and the methods testing the ability to prevent lipid peroxidation. The other group includes the procedures that are based on measurement of redox properties of compouds (ferric reducing antioxidant potential assay-FRAP, cyclic voltammetry, HPLC).
|
|
| |
guest ::
