Determination of selected elements in plant extracts by atomic absorption spectrometry

Předmětem této bakalářské práce bylo stanovení vybraných prvků (Na, Mg, K, Ca, Zn, Se) v rostlinných extraktech a šťávách rostlin pomocí techniky atomové absorpční spektrometrie s různými způsoby atomizace. Pro stanovení výše uvedených prvků byly optimalizovány jednotlivé metody. Při použití plamene jako atomizačního prostředí byla optimalizována především výška procházejícího paprsku primárního záření výbojky nad hranou hořáku. Zde se výška pohybovala obecně mezi 6,0 - 8,0 mm. Dále byly optimalizovány průtoky jednotlivých složek plamene (acetylen, vzduch, oxid dusný) a byla seřízena poloha výbojky s dutou katodou a pozice plamene. Za optimálních podmínek byly naměřeny základní charakteristiky popisující metodu stanovení uvedených prvků (LOD pro sodík 2,13 µg L-1 , pro hořčík 2,44 µg L-1 , pro draslík 11,3 µg L-1 , pro vápník 15,6 µg L-1 , pro zinek 6,04 µg L-1 , pro selen 0,34 µg L-1 ). V další části práce byly optimalizované metody použity pro měření uvedených prvků v reálných vzorcích. Po prvotní úpravě zahrnující ředění získaných vzorků, přídavky různých reakčních činidel aj., byly vzorky v atomovém absorpčním spektrometru atomizovány plamenem (Na, Mg, K, Ca, Zn) a následně stanoveny, či převedeny na těkavou sloučeninu (Se) a stanoveny pomocí techniky generování těkavých hydridů chemickým...The aim of this bachelor thesis was to determine selected elements (Na, Mg, K, Ca, Zn, Se) in plant extracts and juices by atomic absorption spectrometry using different types of atomization. Each method has been optimized for determination of the mentioned elements. For flame atomization it has been used optimization of height of the primary radiation from the hollow cathode lamp over the edge of the burner. The height was generally between 6.0 and 8.0 mm. Then there have been optimized flow of each component of the flame (acetylene, air, nitrous oxide) and it has been set location of the hollow cathode lamp and the flame. Under the optimized conditions basic characteristics describing the method of the determination of mentioned elements have been measured (LOD for sodium 2.13 µg L-1 , for magnesium 2.44 µg L-1 , for potassium 11.3 µg L-1 , for calcium 15.6 µg L-1 , for zinc 6.04 µg L-1 , for selenium 0.34 µg L-1 ). In the next part of the thesis the optimized methods have been used for measuring concentration of all elements in real samples. After the preparation of the samples including dilution, addition of various reagents etc., they have been atomized by flame in an atomic absorption spectrometer (Na, Mg, K, Ca, Zn) and determined, or converted to a volatile compound (Se) and determined by...Katedra analytické chemieDepartment of Analytical ChemistryPřírodovědecká fakultaFaculty of Scienc

Enzymatic modifications of bioactive flavonoids

Extract from milk thistle (Silybum marianum (L.) Gaertn., synonym Carduus marianus L., Asteraceae) silymarin contains among others primarily bioactive flavonolignans. They have hepatoprotective and antioxidative effects and also anticancer, chemoprotective, dermatoprotective and hypocholesterolemic activity. This thesis focuses on the preparation of metabolites of the second phase of biotransformation unexplored flavonolignans 2,3-dehydrosilybin (DHSB), silychristin (SCH), 2,3-dehydrosilychristin (DHSCH). Pure sulfated derivatives were prepared using aryl sulfotransferase from Desulfitobacterium hafniense and p-nitrophenyl sulfate (p- NPS) as a donor. Flavonolignans yield exclusively monosulfates at the position C- 20 (C-19 in the case of silychristin and 2,3-dehydrosilychristin), except for 2,3- dehydrosilybin that gives also the 7,20-disulfated derivatives. For all samples were made antioxidant tests - DPPH assay (the highest activity had 2,3-dehydrosilychristin sulfate: IC50= 7,87 µM), Folin-Ciocalteau reduction assay (the highest activity had 2,3-dehydrosilychristin: 1,58 ekvivalents of gallic acid), ABTS+ scavenging (the highest activity had silychristin: 1,50 ekvivalents of vitamin C), inhibition of microsomal lipid peroxidation (the highest activity had 2,3-dehydrosilybin: IC50 = 10,6 µM),..

Determination of selected elements in plant extracts by atomic absorption spectrometry

The aim of this bachelor thesis was to determine selected elements (Na, Mg, K, Ca, Zn, Se) in plant extracts and juices by atomic absorption spectrometry using different types of atomization. Each method has been optimized for determination of the mentioned elements. For flame atomization it has been used optimization of height of the primary radiation from the hollow cathode lamp over the edge of the burner. The height was generally between 6.0 and 8.0 mm. Then there have been optimized flow of each component of the flame (acetylene, air, nitrous oxide) and it has been set location of the hollow cathode lamp and the flame. Under the optimized conditions basic characteristics describing the method of the determination of mentioned elements have been measured (LOD for sodium 2.13 µg L-1 , for magnesium 2.44 µg L-1 , for potassium 11.3 µg L-1 , for calcium 15.6 µg L-1 , for zinc 6.04 µg L-1 , for selenium 0.34 µg L-1 ). In the next part of the thesis the optimized methods have been used for measuring concentration of all elements in real samples. After the preparation of the samples including dilution, addition of various reagents etc., they have been atomized by flame in an atomic absorption spectrometer (Na, Mg, K, Ca, Zn) and determined, or converted to a volatile compound (Se) and determined by..

Sulfated Metabolites of Flavonolignans and 2,3-Dehydroflavonolignans: Preparation and Properties

Silymarin, an extract from milk thistle (Silybum marianum) fruits, is consumed in various food supplements. The metabolism of silymarin flavonolignans in mammals is complex, the exact structure of their metabolites still remains partly unclear and standards are not commercially available. This work is focused on the preparation of sulfated metabolites of silymarin flavonolignans. Sulfated flavonolignans were prepared using aryl sulfotransferase from Desulfitobacterium hafniense and p-nitrophenyl sulfate as a sulfate donor and characterized by high-resolution mass spectrometry (HRMS) and nuclear magnetic resonance (NMR). Their 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and N,N-dimethyl-p-phenylenediamine (DMPD) radical scavenging; ferric (FRAP) and Folin–Ciocalteu reagent (FCR) reducing activity; anti-lipoperoxidant potential; and effect on the nuclear erythroid 2-related factor 2 (Nrf2) signaling pathway were examined. Pure silybin A 20-O-sulfate, silybin B 20-O-sulfate, 2,3-dehydrosilybin-20-O-sulfate, 2,3-dehydrosilybin-7,20-di-O-sulfate, silychristin-19-O-sulfate, 2,3-dehydrosilychristin-19-O-sulfate, and silydianin-19-O-sulfate were prepared and fully characterized. Sulfated 2,3-dehydroderivatives were more active in FCR and FRAP assays than the parent compounds, and remaining sulfates were less active chemoprotectants. The sulfated flavonolignans obtained can be now used as authentic standards for in vivo metabolic experiments and for further research on their biological activity

Chemoenzymatic Preparation and Biophysical Properties of Sulfated Quercetin Metabolites

Sulfated quercetin derivatives are important authentic standards for metabolic studies. Quercetin-3′-O-sulfate, quercetin-4′-O-sulfate, and quercetin-3-O-sulfate as well as quercetin-di-O-sulfate mixture (quercetin-7,3′-di-O-sulfate, quercetin-7,4′-di-O-sulfate, and quercetin-3′,4′-di-O-sulfate) were synthetized by arylsulfotransferase from Desulfitobacterium hafniense. Purified monosulfates and disulfates were fully characterized using MS and NMR and tested for their 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS+) and N,N-dimethyl-p-phenylenediamine (DMPD) radical scavenging, Folin-Ciocalteau reduction (FCR), ferric reducing antioxidant power (FRAP), and anti-lipoperoxidant activities in rat liver microsomes damaged by tert-butylhydroperoxide. Although, as expected, the sulfated metabolites were usually less active than quercetin, they remained still effective antiradical and reducing agents. Quercetin-3′-O-sulfate was more efficient than quercetin-4′-O-sulfate in DPPH and FCR assays. In contrast, quercetin-4′-O-sulfate was the best ferric reductant and lipoperoxidation inhibitor. The capacity to scavenge ABTS+• and DMPD was comparable for all substances, except for disulfates, which were the most efficient. Quantum calculations and molecular dynamics simulations on membrane models supported rationalization of free radical scavenging and lipid peroxidation inhibition. These results clearly showed that individual metabolites of food bioactives can markedly differ in their biological activity. Therefore, a systematic and thorough investigation of all bioavailable metabolites with respect to native compounds is needed when evaluating food health benefits