@article{RohnRawelKroll2004, author = {Rohn, Sascha and Rawel, Harshadrai Manilal and Kroll, J{\"u}rgen}, title = {Antioxidant activity of protein-bound quercetin}, year = {2004}, abstract = {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.}, language = {en} } @article{RawelRantersRohnetal.2004, author = {Rawel, Harshadrai Manilal and Ranters, Holger and Rohn, Sascha and Kroll, J{\"u}rgen}, title = {Assessment of the reactivity of selected isoflavones against proteins in comparison to quercetin}, year = {2004}, abstract = {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.}, language = {en} } @article{HernandezTrianaKrollProlletal.1996, author = {Hernandez-Triana, Manuel and Kroll, J{\"u}rgen and Proll, J{\"u}rgen and Noack, Jutta and Petzke, Klaus-J{\"u}rgen}, title = {Benzyl-isothiocyanate (BITC) decreases quality of egg white proteins in rats}, year = {1996}, language = {en} } @article{RawelMeidtnerKroll2005, author = {Rawel, Harshadrai Manilal and Meidtner, Karina and Kroll, J{\"u}rgen}, title = {Binding of selected phenolic compounds to proteins}, issn = {0021-8561}, year = {2005}, abstract = {In the context of this study, the noncovalent binding of selected phenolic compounds (chlorogenic, ferulic, and gallic acids, quercetin, rutin, and isocluercetin) to different proteins (human serum albumin, bovine serum albumin, soy glycinin, and lysozyme) was studied with direct (Hummel- Dreyer/size exclusion chromatography) and/or indirect methods (fluorescence absorbance properties of the binding components). In the latter case, the measurement of the phenol binding was achieved by exploiting the intrinsic fluorescence emission properties of cluercetin as a probe. From the data obtained, the binding constants and the number of binding sites were calculated. The binding parameters were influenced by different factors, where, e.g., increasing temperature and ionic strength as well as decreasing pH cause a diminished binding. The structures of the proteins as determined by circular dichroism indicate changes in the tertiary structure with the secondary structure remaining intact}, language = {en} } @article{RawelKrollRieseSchneideretal.1998, author = {Rawel, Harshadrai Manilal and Kroll, J{\"u}rgen and Riese-Schneider, Brigitte and Haebel, Sophie}, title = {Changes in physico-chemical and enzymatic properties of benzyl isothiocyanate derivatized proteinases}, year = {1998}, language = {en} } @article{KrollRawelCzajka2002, author = {Kroll, J{\"u}rgen and Rawel, Harshadrai Manilal and Czajka, D{\"o}rte}, title = {Changes induced in properties of food proteins by apigenin and quercetin}, year = {2002}, abstract = {Selected food proteins (myoglobin and soy glycinin) were caused to react with flavonoids (apigenin and quercetin) to estimate the influence of the number and the position of hydroxy substituents. The protein derivatives formed have been charcterized in terms of their properties where they showed changes in the content of free amino groups, tryptophan, and thiol groups. The myoglobin derivatives have also been characterized in terms of their solubility at different pH-values to document the influence on the functional properties. The influence of myoglobin derivatives on the in vitro digestibility with trypsin was also demonstrated, with the digestion of the derivatized myoglobin being favored.}, language = {en} } @article{RawelRohnKroll2005, author = {Rawel, Harshadrai Manilal and Rohn, Sascha and Kroll, J{\"u}rgen}, title = {Characterisation of 11S protein fractions and phenolic compounds from green coffee beans under special consideration of their interactions - A review}, issn = {0012-0413}, year = {2005}, abstract = {The intention of this study was to increase the knowledge on the composition and structure of coffee bean proteins and the changes induced in them especially with regard to their interactions with the phenolic compounds also present. For this purpose green coffee beans were extracted by means of standard methanol extraction to quantify the chlorogenic acid content. Different solubilisation buffers were applied to extract the protein fractions with or without prior fat removal. The protein samples thus obtained were analysed by different methods (RP-HPLC, SDS-PAGE and SELDI-TOF- MS). Preliminary model studies were performed to characterize the interactions between the isolated green coffee protein fractions and chlorogenic acid (the major phenolic compound in coffee beans) with the intention of fulfilling the ultimate goal of characterizing such reactions in roasted coffee. The results show that the content of chlorogenic bound covalently to the protein increases. A reaction with the nucleophilic protein side chains (tryptophan, cystein and lysine) was recorded. Cross-inked protein polymers were also detected, whereby the a-chain was found to be more reactive. These reactions effect the solubility of the coffee bean proteins, the latter in turn becoming more acidic in nature. The secondary structure was affected only slightly as determined by circular dichroism. The in-vitro tryptic digestibility was also influenced, where again the cc-chain seems to be more susceptible. The observed polymerisation due to derivatisation by chorogenic acid declines the digestion. Similar digestion behaviour was also observed during tryptic hydrolysis of roasted coffee compared to that of green coffee, roasting allowing more stronger denaturation caused by the accompanying Maillard reaction. The derivatised green coffee bean proteins were found to have moderate antioxidative capacity}, language = {en} } @article{KrollNoackRaweletal.1994, author = {Kroll, J{\"u}rgen and Noack, Jutta and Rawel, Harshadrai Manilal and Kr{\"o}ck, Regina and Proll, J{\"u}rgen}, title = {Chemical reactions of benzyl isothio cyanate with egg-white protein fractions}, year = {1994}, language = {en} } @article{KrollRawel1996, author = {Kroll, J{\"u}rgen and Rawel, Harshadrai Manilal}, title = {Chemical reactions of benzyl isothiocyanate with myoglobin}, year = {1996}, language = {en} } @article{PetzkeSchuppeRohnetal.2005, author = {Petzke, Klaus-J{\"u}rgen and Schuppe, S. and Rohn, Sascha and Rawel, Harshadrai Manilal and Kroll, J{\"u}rgen}, title = {Chlorogenic acid moderately decreases the quality of whey proteins in rats}, issn = {0021-8561}, year = {2005}, abstract = {During processing and storage, phenolic compounds (PCs) may react with food protein bound amino acids (AAs). Such reactions have been reported to change physicochemical and to decrease in vitro digestion properties of proteins. A rat growth and nitrogen (N) balance study was conducted to prove whether derivatization with chlorogenic acid (CA) affects the nutritional quality of beta-lactoglobulin (beta-LG). Test diets (10\% protein level) contained nonderivatized beta-LG (LG, treated under omission of CA), low derivatization level beta-LG (LGL), high derivatization level beta-LG (LGH), or casein supplemented with L-methionine (0.3\% of diet; C+met) as an internal standard. An additional group received untreated beta-LG supplemented with pure CA (1.03\% of diet; LG+CA). The AA composition of test proteins, plasma AAs, and liver glutathione (GSH) concentrations were determined. Protein digestibility-corrected amino acid score (PDCAAS) was calculated using human or rat AA requirement patterns and rat fecal digestibility values. N excretion was significantly higher in feces and lower in urine of rats fed with LGH as compared to LG and LGL. Consequently, true N digestibility (TND) was significantly lower with LGH as compared to LG and LGL. The lower content of methionine, cysteine, lysine, and tryptophan in LGH corresponded to a reduced TND. Net protein utilization (NPU) was not different between treated beta-LG fed diet groups but was lower than in LG+CA and C+met fed groups. Only at a relatively high level of derivatization with CA, the otherwise good nutritional quality of beta-LG is affected so that TND is reduced, while NPU still remains unaffected. Derivatization of beta-LG with CA does not seem to lead to an additional deficiency in a specific indispensable AA in growing rats fed with 10\% protein}, language = {en} } @article{WalzelOzierenskiStarketal.1996, author = {Walzel, Erwin and Ozierenski, B{\"a}rbel and Stark, Claudia and Kroll, J{\"u}rgen}, title = {Der Einfluß von niederverestertem Pektin und Pektinabbauprodukten auf die Inkorporation von Blei bei konventionalisierten und keimfreien Ratten}, year = {1996}, language = {de} } @article{RawelFreyMeidtneretal.2006, author = {Rawel, Harshadrai Manilal and Frey, Simone K. and Meidtner, Karina and Kroll, J{\"u}rgen and Schweigert, Florian J.}, title = {Determining the binding affinities of phenolic compounds to proteins by quenching of the intrinsic tryptophan fluorescence}, series = {Molecular nutrition \& food research : bioactivity, chemistry, immunology, microbiology, safety, technology}, volume = {50}, journal = {Molecular nutrition \& food research : bioactivity, chemistry, immunology, microbiology, safety, technology}, number = {8}, publisher = {Wiley}, address = {Weinheim}, issn = {1613-4125}, doi = {10.1002/mnfr.200600013}, pages = {705 -- 713}, year = {2006}, abstract = {The noncovalent binding of selected phenolic compounds (chlorogenic-, ferutic-, gallic acid, quercetin, rutin, and isoquercetin) to proteins (HSA, BSA, soy glycinin, and lysozyme) was studied by an indirect method applying the quenching of intrinsic tryptophan fluorescence. From the data obtained, the binding constants were calculated by nonlinear regression (one site binding; y = Bx/k + x). It has been reported that tannins inhibit human salivary amylase and that these complexes may reduce the development of cariogenic plaques. Further, amylase contains two tryptophan residues in its active site. Therefore, in a second part of the study involving 31 human subjects, evidence was sought for noncovalent interactions between the phenols of green tea and saliva proteins as measured by the fluorescence intensity. Amylase activity was determined before and after the addition of green tea to saliva of 31 subjects. Forty percent of the subjects showed an increase in amylase activity contrary to studies reporting only a decrease in activity. The interactions of tannin with amylase result in a decrease of its activity. It still remains to be elucidated why amylase does not react uniformly under conditions of applying green tea to saliva. Further, in terms of using phenols as caries inhibitors this finding should be of importance.}, language = {en} } @article{RawelKroll2003, author = {Rawel, Harshadrai Manilal and Kroll, J{\"u}rgen}, title = {Die Bedeutung von Cassava (Manihot esculenta Crantz) als Hauptnahrungsmittel in tropischen L{\"a}ndern}, year = {2003}, language = {de} } @article{KrollRawel2006, author = {Kroll, J{\"u}rgen and Rawel, Harshadrai Manilal}, title = {Die Sojabohne : Inhalsstoffe und deren Lebensmittelchemische und ern{\"a}hrungsphysiologische Bedeutung}, issn = {0012-0431}, year = {2006}, abstract = {The soy bean contains besides comparatively large amounts of nutritionally and physiologically valuable proteins and lipids, also a series of other minor components termed as secondary plant metabolites. In this respect most of the research focus has been directed to the group of isoflavones. Epidemiological studies as well as model and animal experiments document that the consumption of soy products/-components is accompanied by many postive physiological effects, which are discussed shortly in this paper}, language = {de} } @article{StarkWalzelOzierenskietal.1995, author = {Stark, Claudia and Walzel, Erwin and Ozierenski, B{\"a}rbel and Kroll, J{\"u}rgen}, title = {Die Wirkung von Pektin bei aktueller Bleiexposition}, year = {1995}, language = {de} } @article{KrollRohnRawel2004, author = {Kroll, J{\"u}rgen and Rohn, Sascha and Rawel, Harshadrai Manilal}, title = {Einsatz von MALDI- und SELDI-Massenspectrometrie zur Charakterisierung ausgew{\"a}hlten Nahrungsproteine und Proteinmodifikationen}, issn = {0250-1554}, year = {2004}, abstract = {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.}, language = {de} } @article{RohnRawelWollenbergeretal.2003, author = {Rohn, Sascha and Rawel, Harshadrai Manilal and Wollenberger, Ursula and Kroll, J{\"u}rgen}, title = {Enzyme acitivity of alpha-chymotrypsin after derivatization with phenolic compounds}, year = {2003}, language = {en} } @book{JohnsenKrollLange1993, author = {Johnsen, Dieter and Kroll, J{\"u}rgen and Lange, Reinhard}, title = {Ern{\"a}hrung - Umwelt - Gesundheit : Teil 1}, series = {Studienmaterialien des Weiterbildenden Studiums Umweltschutz f{\"u}r Bildung und Hauswirtschaft}, journal = {Studienmaterialien des Weiterbildenden Studiums Umweltschutz f{\"u}r Bildung und Hauswirtschaft}, editor = {Berndt, Klaus-Peter and Sch{\"a}fer, Erich}, publisher = {Univ. Potsdam}, address = {Potsdam}, isbn = {3-929757-17-6}, pages = {72 S.}, year = {1993}, language = {de} } @article{KruseKroll1995, author = {Kruse, Hans-Peter and Kroll, J{\"u}rgen}, title = {Fettaustauscher : lebensmittelchemische und ern{\"a}hrungsphysiologische Aspekte}, year = {1995}, language = {de} } @article{RawelKrollSchroeder1998, author = {Rawel, Harshadrai Manilal and Kroll, J{\"u}rgen and Schr{\"o}der, Insa Sigrid}, title = {In vitro enzymatic digestion of benzyl- and phenylisothiocyanate derivatized food proteins}, year = {1998}, language = {en} }