Refine
Has Fulltext
- no (36) (remove)
Year of publication
- 2004 (36) (remove)
Document Type
- Article (33)
- Doctoral Thesis (3)
Is part of the Bibliography
- yes (36)
Institute
- Institut für Ernährungswissenschaft (36) (remove)
Isoflavones as constituents of plant foods : Isoflavone als Bestandteile pflanzlicher Lebensmittel
(2004)
Vor dem Hintergrund der Diskussion über die ernährungsphysiologische Bedeutung von Isoflavonen befasst sich die vorliegende Übersichtsarbeit auf der Basis von 186 Literaturquellen mit der Struktur, dem Vorkommen, der Aufnahme, der Biosynthese, der Resorption, dem Metabolismus und der biologischen Wirkung dieser Untergruppen der Pflanzenphenole. Diskutiert werden sowohl positive als auch negative biologische Wirkungen dieser Verbindungen. Strukturabhängig können die Isoflavone mit anderen Lebensmittelinhaltsstoffen in Wechselwirkung treten. With the background of the actual ongoing discussion on the nutritional
Bovine serum albumin (BSA) was derivatized by covalent attachment of different amounts of quercetin (ratios of BSA : quercetin were 20:1, 10:1, 7:1, 5:1, 2:1 (w/w)). The antioxidant activity of the protein-phenol derivatives was investigated using a modified TEAC assay. The results show that the covalent attachment of quercetin to BSA decreases the total antioxidant activity in comparison to an equivalent amount of free quercetin depending on the degree of derivatization. The derivative with the highest amount of covalently bound quercetin (2:1 derivative) showed an antioxidant activity of only 79% compared to an equivalent amount of free quercetin. After the enzymatic proteolysis of the BSA quercetin derivatives with trypsin, the total antioxidant activity of the degradation products increases in comparison to the respective undigested derivatives, but does not reach the activity of an equivalent amount of free quercetin. Even after 240 minutes of tryptic degradation there is still a lack in antioxidant activity (for the 7:1 derivative nearly 33%) as compared to free quercetin.
Assessment of the reactivity of selected isoflavones against proteins in comparison to quercetin
(2004)
Selected isoflavones (genistein, daidzein, formononetin, prunetin, biochanin A and two synthetic isoflavones) were allowed to interact with soy and whey proteins. The reaction products were analyzed in terms of covalent binding at the nucleophilic side chains of proteins. Changes in molecular properties of the proteins derivatives were documented by SDS-PAGE, IEF and SELDI-TOF-MS. The structural changes induced were studied using circular dichroism (CD). The in vitro digestibility was assessed with trypsin. The results show that the occurrence of the catechol moiety, i.e. the two adjacent (ortho) aromatic hydroxyl groups on ring B of the flavonoid structural skeleton appears to be perquisite condition for covalent binding to proteins. The catechol moiety on ring A was less reactive. Its absence lead to a slight or no significant reaction, although non-covalent interactions may still be possible even when lacking this structural element. A comparison of the data is also made with quercetin representing the flavonols.
The application of mass spectrometry for the characterization of food proteins represents one of the most important tools in food chemistry and nutritional science. In the last few years there has been a tremendous development in the classical questions with regard to determination of molecular mass, identification amino acid sequence and structure of proteins. With these technical improvements, it is becoming more and more interesting to characterize the changes involved in proteins embedded in the food matrix as a result of their technological processing, especially in terms of the influence on their functional, nutritional and phsiological properties. Many such posttransational protein modifications occuring due to reactions with other food constituents (e.g. secondary plant metabolites) provide a series of possible fields for application of a sample preparation with a soft ionisation technique using mass spectrometry. The matrix assisted laser desorptions/ionisation ? time of flight ? mass spectrometry (MALDI-TOF-MS) and the surface enhanced laser desorptions/ionisation ? time of flight ? mass spectrometry (SELDI-TOF-MS) have become since than two of the most important methods of choice for solving of such questions and these both techniques have been described here with correponding examples.
Background: Patients with severe forms of cancer are reported to have reduced concentrations of micronutrients in plasma due to the chronic reduction of food intake and an increased metabolism of these components. The purpose of this study was to evaluate if an accumulation of carotenoids, alpha-tocopherol and retinol in malignant ascitic fluid in women with ovarian cancer might contribute to a loss of these components from plasma. Methods: Blood and ascitic fluid samples obtained from 21 women with ovarian carcinomas and 17 healthy controls were analyzed for retinol, retinol- binding protein (RBP), alpha-tocopherol and carotenoids. Results: Plasma concentrations of all micronutrients were lower in cancer patients compared to controls. Ascitic fluid concentration of all investigated components was comparable (73- 110%) to plasma. While the mean concentration of retinol in malignant ascites represented 73% of that in plasma, the concentration of RBP was less than 10% resulting in an increased mean molar ratio of retinol to RBP from 1.18 to 10.5. Conclusions: The results suggest that lower plasma concentrations of micronutrients in women suffering from ovarian carcinoma are not only caused by a cachexia-induced decrease of food intake and a higher rate of metabolic utilization, but also by a substantial yet not considered transfer from plasma into ascitic fluid possibly associated with plasma lipoproteins. This raises questions with regard to the protective function of these plasma components in ascitic fluid, the consequences of paracentesis on an additional supplementation and finally the possibility to use one or a combination of these components as an additional marker to discriminate between benign and malignant ascites. Copyright (C) 2004 S. Karger AG, Basel
There is increasing evidence that reactive oxygen species (ROS) are mediators in growth factor and cytokine signaling pathways. Mechanisms by which ROS can interfere with signaling cascades may include regulation of protein activities by the modification of essential cysteines. Modification can be performed chemically or enzyme-catalyzed. Enzymes catalyzing a reversible thiol modification within proteins are to be able to react with both, ROS and protein thiols. If hydroperoxides are involved, promising candidates are peroxiredoxins and glutathione peroxidases (GPx), especially the phospholipid hydroperoxide GPx. Interleukin-1, one of the key players in inflammatory response, stimulates the production of ROS itself, but its signaling cascade can also be influenced by ROS and by thiol modifying agents. Targets are located in early, intermediate, and late events in the signaling cascade. We here summarize what is known about the effects of thiol modifying agents, selenium and glutathione peroxidases, on the assembly of the IL-1 receptor signaling complex as an early event, on the activation of NF-kappaB as an intermediate event, and on the expression of cell adhesion molecules as a late event in IL-1 signaling. (C) 2003 Elsevier Inc. All rights reserved
Measurement of total urinary proteins in individuals that tested positive by urinary dipstick is a typical method for assessing the presence of potentially serious renal disorders. In the absence of such overt proteinuria, however, measurement of specific urinary proteins may be useful in the diagnosis of nephropathies and may provide greater insight into the pathogenesis. The urine of 28 dogs (16 with renal disease and 12 healthy) was evaluated to determine whether specific low-molecular-weight proteins or the pattern of protein excretion could also be used as a marker of tubular dysfunction in dogs. Specific proteins were assessed by immunological methods, whereas protein profiles were determined by surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (MS). In particular, changes in the excretion of retinol-binding protein (RBP) and Tamm-Horsfall protein (THP) appear to be of clinical relevance in the diagnosis of canine kidney diseases. The pattern of urinary protein and peptides revealed specific changes in abundance in dogs with renal disease at molecular masses (kD) of 11.58, 12.41, 12.60, 14.58, 20.95 (RBP), 27.85, and 65.69 (albumin). In conclusion, comparable proteins as in humans might be used as urinary markers for proximal (RBP) and distal (THP) tubular dysfunction in dogs. Surface-enhanced laser desorption/ionization time-of-flight MS is a promising tool for the study of kidney physiology and pathophysiology and might aid in the discovery of new biomarkers of renal disease
Objective: To determine whether the cholesterol-lowering effect of a plant-based low-fat diet can be improved by a flexible control design that controls the extent of fat reduction based on the individual response of blood cholesterol. Design: Randomized, double-blind intervention study. Setting: A hotel in Prerow, Germany. Subjects: A total of 32 participants ( 21 female and 11 male participants) with total cholesterol level >5.7 mmol/l. Intervention: The control group consumed a plant-based low-fat diet with constantly 20% of energy as fat; the intervention group received a diet with either 20 or 15% of energy as fat, depending on the serum cholesterol response of the preceding week. A flexible control design based on the individual cholesterol response during a run-in period of 1 week was used within a low-fat intervention. Results: During the run-in period, the consumption of a plant-based low-fat diet led to a reduction in total cholesterol by 18 +/- 6 mmol/l ( P<0.001), in LDL cholesterol by 19 +/- 9 mmol/l ( P<0.001) and triglycerides by 13 +/- 3 mmol/l ( P<0.001). During the feedback control period, an additional reduction in total cholesterol by 13 +/- 8 ( P<0.001) and in LDL cholesterol by 17 +/- 11 (P<0.001) was observed compared to 15715 and 7718 in the control group. The effect of an additional feedback control was only marginal and not statistically significant compared to the effect of the low-fat diet alone. Conclusions: On a level of fat intake already reduced to 20% of energy, the use of a feedback control to adapt the fat content of the diet depending on the individual serum cholesterol response was not more effective in reducing blood cholesterol levels than a plant-based low-fat diet alone. Sponsorship: Institute of Micro-Ecology, Herborn; the Stoll VITA Foundation, Waldshut; ALBAT+WIRSAM Software, Linden; Reformhaus Technical College, Oberstedten; Kolln Flocken Werke, Elmshorn, all in Germany
Soluble, viscous, but not insoluble dietary fibre has been shown to lower serum cholesterol. Due to the high content of polyphenols, however, insoluble dietary fibre from carob pods may have physiological benefits beyond those of the usual insoluble dietary fibre preparations. Insoluble polyphenol-rich fibre preparations from carob pods have also been shown to significantly lower serum total and LDL cholesterol in cholesterol-fed rodents (hamsters, rats), while HDL and triglycerides remained unchanged. An increased fecal excretion of bile acids caused by binding to the fibre constituents is supposed to be responsible for this effect. In human studies, consumption of 15 g/d of a carob fibre preparation over 6 weeks lowered LDL cholesterol by 11.0% in hypercholesterolemic subjects. This suggests that carob fibre may be effective in the dietary treatment of hypercholesterolernia. Recent studies have also shown that dietary fiber rich in polyphenols may (1) lower the glycemic index of food and (2) have anti-inflammatory effect. If carob fibre shows similar effects, it may be of special interest in the treatment of the metabolic syndrome
In mammals the composition of milk changes during early lactation, with a rapid decline of fat-soluble vitamins and a continuous increase in total lipids. The mechanisms underlying this phenomenon are not well understood, but might involve selective mechanisms related to mammary uptake or secretion into the milk. Since carotenoids are specifically distributed among the lipoprotein fractions in plasma, the simultaneous determination of carotenoids in plasma, lipoprotein fractions and milk might offer an opportunity to gain insight into this phenomenon. In 21 healthy mothers carotenoids in plasma and lipoprotein fractions were investigated at day 2 and 19 and milk on day 4 and 19 after delivery. Plasma levels of alpha-tocopherol and cholesterol as well as lutein, zeaxanthin and cryptoxanthin were significantly lower later in lactation (day 19) than shortly after birth (P < 0.01). The stage of lactation had no effect on the distribution of carotenoids and -tocopherol among the plasma lipoprotein fractions. In milk, triacylglycerol increased (P < 0.01). In contrast, levels of carotenoids, alpha- tocopherol and vitamin A were highest in colostrum and declined (P < 0.01). Because the magnitude of decrease was not the same in all carotenoids, the carotenoid pattern changed substantially. In colostrum the carotenoid pattern resembled those of plasma and the low- density lipoprotein fraction. In mature milk it was similar to the pattern found in the high density lipoprotein fraction. Based on these observations a selective mechanism might be responsible for the transfer of these components in milk involving different lipoprotein fractions at specific times of lactation