TY - JOUR A1 - Walzel, Erwin A1 - Ozierenski, Bärbel A1 - Stark, Claudia A1 - Kroll, Jürgen T1 - Der Einfluß von niederverestertem Pektin und Pektinabbauprodukten auf die Inkorporation von Blei bei konventionalisierten und keimfreien Ratten Y1 - 1996 ER - TY - JOUR A1 - Walzel, Erwin A1 - Kroll, Jürgen T1 - Kritische Spurenelemente in der Ernährung Y1 - 1995 ER - TY - JOUR A1 - Stark, Claudia A1 - Walzel, Erwin A1 - Ozierenski, Bärbel A1 - Kroll, Jürgen T1 - Die Wirkung von Pektin bei aktueller Bleiexposition Y1 - 1995 ER - TY - JOUR A1 - Rohn, Sascha A1 - Rawel, Harshadrai Manilal A1 - Wollenberger, Ursula A1 - Kroll, Jürgen T1 - Enzyme acitivity of alpha-chymotrypsin after derivatization with phenolic compounds Y1 - 2003 ER - TY - JOUR A1 - Rohn, Sascha A1 - Rawel, Harshadrai Manilal A1 - Rober, M. A1 - Kroll, Jürgen T1 - Reactions with phenolic substances can induce changes in some physico-chemical properties and activities of bromelain - the consequences for supplementary food products N2 - Bromelain was allowed to react with phenolic compounds. The activity and selected physico-chemical properties of the resulting derivatives were characterized. In vitro experiments showed that the proteolytic activity of bromelain was inhibited. Bromelain also serves as a food protein, because food stuffs based on pineapple contain relatively high concentrations of bromelain. In vitro digestion of bromelain derivatives with the main proteolytic enzymes of the gastrointestinal tract was also adversely affected. A covalent attachment of the phenolic compounds was identified at the tryptophan, free amino (lysines and N-terminal) and thiol groups of bromelain. A decrease in solubility of the derivatives was observed. The isoelectric point was shifted to lower pH values and high molecular weight fractions were identified. All effects observed depended on the reactivity of the phenolic substances. Two supplementary food products containing both bromelain and quercetin were also tested in terms of their proteolytic activity and digestibility Y1 - 2005 SN - 0950-5423 ER - TY - JOUR A1 - Rohn, Sascha A1 - Rawel, Harshadrai Manilal A1 - Pietruschinski, Nadine A1 - Kroll, Jürgen T1 - In vitro inhibition of alpha -chymotryptic activity by phenolic compounds N2 - alpha-Chymotrypsin was modified by covalent attachment of selected phenolic and related compounds (caffeic acid, chlorogenic acid, ferulic acid, gallic acid, quinic acid, m-/o-/p-dihydroxybenzene and p-benzoquinone) at pH 9. The derivatives formed were characterised in terms of their activity and selected physicochemical properties. In vitro experiments showed that the proteolytic digestion of food proteins with alpha-chymotrypsin derivatives was adversely affected. This decrease depended on the reactivity of the phenolic and related substances tested as well as on the kind of substrate applied. The derivatisation was accompanied by a reduction in the amount of free lysine and tryptophan residues. Moreover, the solubility of the derivatives decreased over a broad pH range, with a parallel increase in the hydrophobicity. The isoelectric point was shifted to a lower pH value, and formation of high-molecular-weight fractions was documented by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Y1 - 2001 UR - http://www3.interscience.wiley.com/cgi-bin/abstract/86510624 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 - Rohn, Sascha A1 - Rawel, Harshadrai Manilal A1 - Kroll, Jürgen T1 - Inhibitory effects of plant phenols on the activity of selected enzymes N2 - Selected enzymes (alpha-amylase, trypsin, and lysozyme) were allowed to react with some simple phenolic and related compounds (caffeic acid, chlorogenic acid, ferulic acid, gallic acid, m-, o-, and p-dihydroxybenzenes, quinic acid, and p-benzoquinone). The derivatized enzymes obtained were characterized in terms of their activity. In vitro experiments showed that the enzymatic activity of the derivatives was adversely affected. This enzyme inhibition depended on the reactivity of the phenolic and related substances tested as well as on the kind of substrate applied. The decrease in the activity was accompanied by a reduction in the amount of free amino and thiol groups, as well as tryptophan residues, which resulted from the covalent attachment of the phenolic and related compounds to these reactive nucleophilic sites in the enzymes. The enzyme inhibition correlates well with the blocking of the mentioned amino acid side chains. Y1 - 2002 UR - http://pubs.acs.org/journals/jafcau/abstract.cgi/jafcau/2002/50/i12/abs/jf011714b.html ER - TY - JOUR A1 - Rohn, Sascha A1 - Rawel, Harshadrai Manilal A1 - Kroll, Jürgen T1 - Influence of plant phenols on selected enzymes N2 - Secondary plant metabolites are important native food components, which are becoming more and more interesting due to their physiological effects on humans. Some representatives of these compounds are very reactive and can interact with other main food components like proteins resp. enzymes. This work deals with the reactions of selected enzymes (trypsin, alpha-chymotrypsin and alpha-amylase) with simple phenolic and related substances (caffeic acid, chlorogenic acid, ferulic acid, gallic acid, meta-, ortho- and para-dihydroxybenzene, 1,4-benzoquinone, quinic acid). The derivatives formed were characterized in terms of their activity and selected physicochemical properties. In vitro experiments showed that the proteolytic digestion of food proteins with trypsin and alpha-chymotrypsin derivatives was adversely affected. This decrease depends on the reactivity of the phenolic and related substances tested as well as on the kind of substrate applied. Reactions of phenolic compounds with other enzymes (alpha-amylase and lysozyme) showed similar results with regard to physicochemical properties and their activities. Y1 - 2002 ER - TY - JOUR A1 - Rohn, Sascha A1 - Petzke, Klaus-Jürgen A1 - Rawel, Harshadrai Manilal A1 - Kroll, Jürgen T1 - Reactions of chlorogenic acid and quercetin with a soy protein isolate - Influence on the in vivo food protein quality in rats JF - Molecular nutrition & food research : bioactivity, chemistry, immunology, microbiology, safety, technology N2 - Plant phenolic compounds are known to interact with proteins producing changes in the food (e.g., biological value (BV), color, taste). Therefore, the in vivo relevance, especially, of covalent phenolprotein reactions on protein quality was studied in a rat bioassay. The rats were fed protein derivatives at a 10% protein level. Soy proteins were derivatized with chlorogenic acid and quercetin (derivatization levels: 0.056 and 0.28 mmol phenolic compound/gram protein). Analysis of nitrogen in diets, urine, and fecal samples as well as the distribution of amino acids were determined. Depending on the degree of derivatization, the rats fed with soy protein derivatives showed an increased excretion of fecal and urinary nitrogen. As a result, true nitrogen digestibility, BV, and net protein utilization were adversely affected. Protein digestibility corrected amino acid score was decreased for lysine, tryptophan, and sulfur containing amino acids. KW - amino acid score KW - plant phenolic compounds KW - protein derivatization KW - protein digestibility KW - soy protein Y1 - 2006 U6 - https://doi.org/10.1002/mnfr.200600043 SN - 1613-4125 VL - 50 SP - 696 EP - 704 PB - Wiley CY - Weinheim ER -