TY  - JOUR
A1  - Kroll, Jürgen
A1  - Ranters, Holger
A1  - Rawel, Harshadrai Manilal
A1  - Rohn, Sascha
T1  - Isoflavones as constituents of plant foods : Isoflavone als Bestandteile pflanzlicher Lebensmittel
N2  - 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
Y1  - 2004
ER  - 
TY  - JOUR
A1  - Rohn, Sascha
A1  - Rawel, Harshadrai Manilal
A1  - Kroll, Jürgen
T1  - Antioxidant activity of protein-bound quercetin
N2  - 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.
Y1  - 2004
UR  - http://pubs.acs.org/cgi-bin/article.cgi/jafcau/2004/52/i15/html/jf0496797.html
ER  - 
TY  - JOUR
A1  - Rawel, Harshadrai Manilal
A1  - Ranters, Holger
A1  - Rohn, Sascha
A1  - Kroll, Jürgen
T1  - Assessment of the reactivity of selected isoflavones against proteins in comparison to quercetin
N2  - 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.
Y1  - 2004
UR  - http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=15291506
ER  - 
TY  - JOUR
A1  - Kroll, Jürgen
A1  - Rohn, Sascha
A1  - Rawel, Harshadrai Manilal
T1  - Einsatz von MALDI- und SELDI-Massenspectrometrie zur Charakterisierung ausgewählten Nahrungsproteine und Proteinmodifikationen
N2  - 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.
Y1  - 2004
SN  - 0250-1554
ER  -