Peter Schreier

Publications of Peter Schreier

• Virtuous medicine.

  Authors: Peter Schreier, Hans-Ulrich Humpf

  Molecular nutrition & food research. 01/2012; 56(1):5.

• Bilberries and their anthocyanins ameliorate experimental colitis.

  Authors: Heidi Piberger, Anett Oehme, Claudia Hofmann, Andrea Dreiseitel, Philipp G Sand, Florian Obermeier, Juergen Schoelmerich, Peter Schreier, Gerhard Krammer, Gerhard Rogler

  Molecular nutrition & food research. 09/2011; 55(11):1724-9.

  Bilberries have positive effects in acute and chronic diarrhea. Patients with inflammatory bowel disease (IBD) report on improved symptoms upon ingestion. Bilberries contain approximately 10% ofBilberries have positive effects in acute and chronic diarrhea. Patients with inflammatory bowel disease (IBD) report on improved symptoms upon ingestion. Bilberries contain approximately 10% of anthocyanins (ACs), which have anti-oxidative, anti-carcinogenic, and anti-inflammatory properties. We investigated whether experimental colitis can be ameliorated by dried bilberries or ACs. Acute and chronic dextrane sodium sulphate (DSS) colitis were induced in Balb/c mice by 2.5% DSS in the drinking water. Mice were fed with dried bilberries or ACs, respectively. Cytokines were determined in supernatants from mesenteric lymph nodes (MLNs) by ELISA and apoptosis was investigated by terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling assays. Oral administration of bilberries during acute DSS-induced colitis ameliorated disease severity and reduced secretion of IFN-γ and tumor necrosis factor from mesenteric lymph node cells. Dried bilberries also improved chronic DSS-colitis. Ingestion of ACs reduced intestinal inflammation in acute and chronic DSS-colitis with decreased histological scores and cytokine secretion. Both bilberries and ACs prevented inflammation-induced apoptosis in colonic epithelial cells. Taken together, ingestion of dried bilberries had positive effects on various parameters especially in acute DSS-colitis. Oral administration of ACs resulted in an amelioration of acute colitis as well as chronic colitis. These promising results justify a clinical study on their therapeutic effect in inflammatory bowel disease patients.

• Preparation and characterization of shellac-coated anthocyanin pectin beads as dietary colonic delivery system.

  Authors: Anett Oehme, Anagnostis Valotis, Gerhard Krammer, Ingfried Zimmermann, Peter Schreier

  Molecular nutrition & food research. 05/2011; 55 Suppl 1:S75-85.

  Anthocyanins are connected with various biological activities. A promising way to enhance the availability of anthocyanins for in situ effects in the lower intestine is colon-specificAnthocyanins are connected with various biological activities. A promising way to enhance the availability of anthocyanins for in situ effects in the lower intestine is colon-specific delivery. Shellac and shellac/hydroxypropyl methylcellulose (HPMC) coated anthocyanin amidated pectin beads as dietary colonic delivery systems were successfully prepared by ionotropic gelation and fluid bed Wurster coating with aqueous shellac solution. Release characteristics, studied in vitro and ex vivo using simulated gastric fluid (SGF), ileostomy fluid and colostomy fluid (CF) revealed a retardation of anthocyanins during simulated passage of stomach and ileum as well as the desired release of pigments in the colon. Coating level was identified as an important parameter. By addition of 5 or 15% of the water-soluble polysaccharide HPMC to the shellac film, resistance in SGF was increased due to the plasticizer properties of the polymer. Incorporation of 15% HPMC (w/w based on shellac) into the shellac film additionally led to increased anthocyanin diffusivity and complete release as well as degradation of the formulation in CF. In the used in vitro and ex vivo model system mimicking the human intestinal transit, the potential of shellac and shellac/HPMC coated anthocyanin amidated pectin beads as dietary colon targeting systems was demonstrated.

• Intestinal transit and systemic metabolism of apple polyphenols.

  Authors: Kathrin Kahle, Michael Kempf, Peter Schreier, Wolfgang Scheppach, Dieter Schrenk, Tanja Kautenburger, Dorothée Hecker, Wolfgang Huemmer, Matthias Ackermann, Elke Richling

  European journal of nutrition. 12/2010; 50(7):507-22.

  Apples are the most widely consumed fruits in Germany and various other countries. Positive health effects of apple-derived polyphenols in vivo depend on their absorption, metabolism, distribution,Apples are the most widely consumed fruits in Germany and various other countries. Positive health effects of apple-derived polyphenols in vivo depend on their absorption, metabolism, distribution, and elimination from the body after consumption. Data on the metabolism of these polyphenols in humans are scarce. In order to study the intestinal transit and metabolism of apple polyphenols in humans, a variety of experiments were carried out. Polyphenols were incubated with saliva (for 5 min), simulated gastric or duodenal juice (4 or 10 h, respectively), or rat hepatocytes (4 h) under aerobic conditions, and with ileostomy fluid under aerobic conditions for 10 h. The polyphenol profile in human serum (8 h later) and renal elimination in urine (24 h later) were also investigated after consumption of 1 L apple juice. Polyphenols and their metabolites were identified and quantified by high-performance liquid chromatography with diode array detection (HPLC-DAD), HPLC-electrospray ionization-tandem mass spectrometry (ESI-MS/MS), and gas chromatography (GC)-MS. In the presence of native saliva or ileostomy fluid, β-glycosides of phloretin and quercetin were hydrolyzed, to varying degrees depending on the sugar moiety, and to much lesser degrees in the presence of antibiotics. In the gastric milieu, almost complete degradation of procyanidin B(2) to (-)-epicatechin was observed. In the presence of artificial duodenal juice flavan-3-ol epimerization occurred. Quercetin was completely converted to phloroglucinol, 3,4-dihydroxybenzoic acid, and 2,4,6-trihydroxybenzoic acid. Formation of isomeric products of hydroxycinnamic acid esters and their corresponding methyl esters was also observed, and similar results were obtained after incubation with rat hepatocytes. Products of phase II metabolism, two phloretin O-glucuronides and eight (methyl) quercetin O-glucuronides, were identified in the hepatocyte samples. Following enzymatic hydrolysis, 5-caffeoylquinic acid, 4-p-coumaroylquinic acid, caffeic acid, (-)-epicatechin, phloretin, and quercetin were recovered in both serum and urine (5.3% and 3.5% of the amounts consumed, respectively). In addition, 19.5% of the polyphenols consumed were identified in the urine in the form of hydroxylated phenolic and hippuric acids. The findings relating to the absorption, metabolism, and systemic availability of polyphenols in vivo should contribute to our understanding of their biological effects, and the characterization of newly formed metabolites should facilitate further studies.

• Flavan-3-ol C-glycosides--preparation and model experiments mimicking their human intestinal transit.

  Authors: Iris Hasslauer, Anett Oehme, Sanja Locher, Anagnostis Valotis, Gordon Van't Slot, Hans-Ulrich Humpf, Peter Schreier

  Molecular nutrition & food research. 05/2010; 54(11):1546-55.

  In order to study the human intestinal transit of flavan-3-ol C-glycosides, several C-glycosyl derivatives were prepared by non-enzymatic reaction of (+)-catechin with α-D-glucose, α-D-galactose andIn order to study the human intestinal transit of flavan-3-ol C-glycosides, several C-glycosyl derivatives were prepared by non-enzymatic reaction of (+)-catechin with α-D-glucose, α-D-galactose and α-D-rhamnose, respectively. In contrast to literature data, we propose that the reaction mechanism proceeds in analogy to the rearrangement of flavan-3-ols during epimerization under alkaline conditions. Four of the 12 synthesized flavan-3-ol C-glycosides were incubated under aerobic conditions at 37°C using saliva (2 min) and simulated gastric juice (3 h). To simulate human intestine, the C-glycosides were also incubated under anaerobic conditions at 37°C both in human ileostomy fluid (10 h) and colostomy fluid (24 h), respectively. The flavan-3-ol C-glycosides under study, i.e. (+)-epicatechin 8-C-β-D-glucopyranoside (1a), (+)-epicatechin 6-C-β-D-glucopyranoside (1d), (+)-catechin 6-C-β-D-galactopyranoside (2b), (+)-catechin 6-C-β-D-rhamnopyranoside (3b) were analyzed in the incubation samples by HPLC-DAD and HPLC-DAD-MS/MS. They were found to be stable in the course of incubation in saliva, simulated gastric juice and ileostomy fluid and underwent degradation in colostomy fluid. While the 6-C-β-D-glucopyranoside 1d was completely metabolized between 2 and 4 h, decomposition of the 6-C-β-D-galactopyranoside 2b reached only 16 ± 2% within 4 h of incubation. Linear degradation rates of 1d and 2b in colostomy fluid differed significantly. As microbial metabolism of flavan-3-ols is known not to be influenced by the stereochemistry of the aglycon, varying degradation rates are ascribed to the effect of the sugar moiety. Based on these results we assume that flavan-3-ol C-glycosides pass through the upper gastrointestinal tract (oral cavity, stomach and small intestine) unmodified and are then metabolized by the colonic microflora.

• Biologically relevant flavan-3-ol C-glycosides - preparation and model experiments mimicking their human and intestinal transit

  Authors: Iris Hasslauer, Anett Oehme, Sanja Locher, Anagnostis Valotis, Gordon van 't Slot, Hans-Ulrich Humpf, Peter Schreier

  Molecular Nutrition & Food Research. 01/2010; 54:1546-1555.

• An examination of anthocyanins' and anthocyanidins' affinity for cannabinoid receptors.

  Authors: Gabriele Korte, Andrea Dreiseitel, Peter Schreier, Anett Oehme, Sanja Locher, Goeran Hajak, Philipp G Sand

  Journal of medicinal food. 12/2009; 12(6):1407-10.

  A growing body of evidence suggests that anthocyanins and anthocyanidins may possess analgesic properties in addition to neuroprotective and anti-inflammatory activities. These functionalitiesA growing body of evidence suggests that anthocyanins and anthocyanidins may possess analgesic properties in addition to neuroprotective and anti-inflammatory activities. These functionalities suggest a role for the cannabinoid receptor (CB) in mediating biological effects. Competitive radioligand binding assays identified cyanidin (K(i) = 16.2 microM) and delphinidin (K(i) = 21.3 microM) as ligands with moderate affinity to human CB1. For CB2, similar affinities were achieved by cyanidin (K(i) = 33.5 microM), delphinidin (K(i) = 34.3 microM), and peonidin (K(i) = 46.4 microM). Inhibition constants >50 microM were obtained for pelargonidin, malvidin, cyanidin-3,5-di-O-glucoside, cyanidin-3-O-glucoside, cyanidin-3-O-galactoside, and cyanidin-3-O-rutinoside for both CB subtypes.

• Pyrrolizidine alkaloids in pollen and pollen products.

  Authors: Michael Kempf, Sandra Heil, Iris Haßlauer, Lukas Schmidt, Katharina von der Ohe, Claudine Theuring, Annika Reinhard, Peter Schreier, Till Beuerle

  Molecular nutrition & food research. 12/2009;

  Recently, 1,2-dehydropyrrolizidine alkaloid (PA) ester alkaloids, found predominantly as their N-oxides (PANOs, pyrrolizidine N-oxides), have been reported in both honey and in pollen obtainedRecently, 1,2-dehydropyrrolizidine alkaloid (PA) ester alkaloids, found predominantly as their N-oxides (PANOs, pyrrolizidine N-oxides), have been reported in both honey and in pollen obtained directly from PA plants and pollen loads collected by bees, raising the possibility of health risks for consumers of these products. We confirm these findings in regard to floral pollen, using pollen collected directly from flowers of the known PA plants Senecio jacobaea, S. vernalis, Echium vulgare and pollinia of Phalaenopsis hybrids, and we extend analyses of 1,2-unsaturated PAs and 1,2-unsaturated PANOs to include bee-pollen products currently being sold in supermarkets and on the Internet as food supplements. PA content of floral pollen ranged from 0.5 to 5 mg/g. The highest values were observed in pollen obtained from Senecio species. Up to 95% of the PAs are found as PANOs. Detailed studies with S. vernalis revealed unique PA patterns in pollen and flowers. While seneciphylline was the most prominent PA in S. vernalis pollen, the flowers were dominated by senecionine. To analyze trace amounts of 1,2-unsaturated PAs in pollen products, our previously elaborated method consisting of strong cation exchange-SPE, two reduction steps followed by silylation and subsequent capillary high-resolution GC-MS using SIM mode was applied. In total, 55 commercially available pollen products were analyzed. Seventeen (31%) samples contained 1,2-unsaturated PAs in the range from 1.08 to 16.35 mug/g, calculated as retronecine equivalents. The 1,2-unsaturated PA content of pollen products is expressed in terms of a single sum parameter and no background information such as foraged plants, pollen analysis, etc. was needed to analyze the samples. The detection limit of overall procedure and the reliable quantitation limit were 0.003 and 0.01 mug/g, respectively.

• Feeding Deterrence and Detrimental Effects of Pyrrolizidine Alkaloids Fed to Honey Bees (Apis mellifera).

  Authors: Annika Reinhard, Martina Janke, Werner von der Ohe, Michael Kempf, Claudine Theuring, Thomas Hartmann, Peter Schreier, Till Beuerle

  Journal of chemical ecology. 09/2009;

  Recent studies have shown the occurrence of plant derived pyrrolizidine alkaloids (PAs) in retail honeys and pollen loads, but little is known about how these compounds influence the fitness ofRecent studies have shown the occurrence of plant derived pyrrolizidine alkaloids (PAs) in retail honeys and pollen loads, but little is known about how these compounds influence the fitness of foraging honey bees. In feeding experiments, we tested a mix of tertiary PAs and the corresponding N-oxides from Senecio vernalis, pure monocrotaline, and 1,2-dihydromonocrotaline in 50% (w/w) sucrose solutions. The bees were analyzed chemically to correlate the observed effects to the ingested amount of PAs. PA-N-oxides were deterrent at concentrations >0.2%. 1,2-Unsaturated tertiary PAs were toxic at high concentrations. The observed PAs mortality could be linked directly to the presence of the 1,2-double bond, a well established essential feature of PA cytotoxicity. In contrast, feeding experiments with 1,2-dihydromonocrotaline revealed no toxic effects. Levels of less than 50 mug 1,2-unsaturated tertiary PAs per individual adult bee were tolerated without negative effects. PA-N-oxides fed to bees were reduced partially to the corresponding tertiary PAs. Unlike some specialized insects, bees are not able to actively detoxify PAs through N-oxidation. To gain insight into how PAs are transmitted among bees, we tested for horizontal PA transfer (trophallaxis). Under laboratory conditions, up to 15% of an ingested PA diet was exchanged from bee to bee, disclosing a possible route for incorporation into the honey comb. In the absence of alternative nectar and pollen sources, PA-containing plants might exhibit a threat to vulnerable bee larvae, and this might affect the overall colony fitness.

• sPhospholipase A(2) is inhibited by anthocyanidins.

  Authors: Andrea Dreiseitel, Gabriele Korte, Peter Schreier, Anett Oehme, Sanja Locher, Goeran Hajak, Philipp Sand

  Journal of neural transmission (Vienna, Austria : 1996). 09/2009;

  Epidemiological studies suggest that nutritional antioxidants may reduce the incidence of neurodegenerative disorders and age-related cognitive decline. Specifically, protection against oxidativeEpidemiological studies suggest that nutritional antioxidants may reduce the incidence of neurodegenerative disorders and age-related cognitive decline. Specifically, protection against oxidative stress and inflammation has served as a rationale for promoting diets rich in vegetables and fruits. The present study addresses secretory phospholipase A(2) (sPLA(2)) as a novel candidate effector of neuroprotection conferred by anthocyanins and anthocyanidins. Using a photometric assay, 15 compounds were screened for their ability to inhibit PLA(2). Of these, cyanidin, malvidin, peonidin, petunidin, and delphinidin achieved K (i) values </=18 muM, suggesting a modulatory role for berry polyphenols in phospholipid metabolism.

• Identification of 3-hydroxy-beta-damascone and related carotenoid-derived aroma compounds as novel potent inducers of Nrf2-mediated phase 2 response with concomitant anti-inflammatory activity.

  Authors: Clarissa Gerhäuser, Karin Klimo, Wolfgang Hümmer, Jana Hölzer, Astrid Petermann, Antonio Garreta-Rufas, Frank-D Böhmer, Peter Schreier

  Molecular nutrition & food research. 09/2009;

  Structural comparison of apple constituents with known inducers of phase two cytoprotective enzymes led to the identification of 3-hydroxy-beta-damascone and related carotenoid derived aromaStructural comparison of apple constituents with known inducers of phase two cytoprotective enzymes led to the identification of 3-hydroxy-beta-damascone and related carotenoid derived aroma compounds as potent inducers of NAD(P)H:quinone reductase (QR) activity. Damascone-related compounds were found to be more potent inducers than ionone derivatives, with CD values (concentrations required to double the specific activity of QR in Hepa1c1c7 cell culture) in the range of 1.0-5.7 muM. QR induction by 3-hydroxy-beta-damascone was shown to be mediated via transcription factor Nrf2 signaling in transient transfection experiments. We further identified aroma compounds as potent inhibitors of LPS-induced inducible nitric oxide synthase activity in Raw 264.7 cell culture. Again, damascone derivatives were most potent with half-maximal inhibitory concentration values of 1.8-7.9 muM. These results reveal previously unrecognized cancer chemopreventive potential of aroma compounds such as beta-damascenone, 3-hydroxy-beta-damascone, and related substances, which may contribute to the cancer protective efficacy of apple products and other dietary sources in animal models.

• Cytochrome P450 2C19 inhibitory activity of common berry constituents.

  Authors: Philipp G Sand, Andrea Dreiseitel, Martin Stang, Peter Schreier, Anett Oehme, Sanja Locher, Goeran Hajak

  Phytotherapy research : PTR. 08/2009;

  The cytochrome P450 enzyme CYP2C19 is involved in the metabolism of many commonly prescribed drugs, including proton pump inhibitors, antiepileptics and antidepressants. CYP2C19 inhibitors from foodThe cytochrome P450 enzyme CYP2C19 is involved in the metabolism of many commonly prescribed drugs, including proton pump inhibitors, antiepileptics and antidepressants. CYP2C19 inhibitors from food and food supplements may augment the toxicity of these agents and lead to noncompliance with treatment. The present investigation addresses CYP2C19 inhibition by 18 berry constituents using a chemiluminescent assay. Test compounds displayed inhibitory properties in a concentration-dependent fashion, with IC(50) values ranging from 20.2 microM up to >316 microM. In the order of decreasing effect size, anthocyanidins were followed by anthocyanidin-monoglycosides and procyanidins. Anthocyanidin-diglucosides exhibited weak and biphasic effects. When compared with the CYP2C19 inhibitor fluvoxamine, the flavonoids under study were 50- to 750-fold less potent. It is concluded that the above natural substances are moderate to poor inhibitors of CYP2C19 in vitro. Copyright (c) 2009 John Wiley & Sons, Ltd.

• Online Gas Chromatography Combustion/Pyrolysis-Isotope Ratio Mass Spectrometry (HRGC-C/P-IRMS) of (+/-)-Dihydroactinidiolide from Tea ( Camellia sinensis ) and Rooibos Tea ( Aspalathus linearis ).

  Authors: María Del Mar Caja, Christina Preston, Michael Menzel, Michael Kempf, Peter Schreier

  Journal of agricultural and food chemistry. 07/2009;

  Online capillary gas chromatography-isotope ratio mass spectrometry in both the combustion and the pyrolysis modes (HRGC-C/P-IRMS) was employed to perform authentication studies of the flavoringOnline capillary gas chromatography-isotope ratio mass spectrometry in both the combustion and the pyrolysis modes (HRGC-C/P-IRMS) was employed to perform authentication studies of the flavoring agent (+/-)-dihydroactinidiolide. Thus, the delta(13)C(V-PDB) and delta(2)H(V-SMOW) values of synthetic (ex synthetic beta-ionone and natural beta-carotene) as well as enzymatically (ex synthetic and natural beta-carotene) produced references were studied in comparison with those of the natural substance isolated from black (n = 17) and green teas (n = 6) ( Camellia sinensis ) as well as Rooibos tea ( Aspalathus linearis ) (n = 7). The isotope values determined for both the synthetic and enzymatically produced samples of (+/-)-dihydroactinidiolide reflected the influence of the origin of their educts. Hence, in cases when synthetic educts were used, the delta(13)C(V-PDB) and delta(2)H(V-SMOW) values ranged from -27.0 to -28.4 per thousand and from -28 to -169 per thousand, respectively, whereas the use of natural educts led to ranges from -30.3 to -31.6 per thousand and from -154 to -228 per thousand, respectively. As to the tea samples, delta(13)C(V-PDB) and delta(2)H(V-SMOW) values ranging from -29.0 to -34.1 per thousand and from -153 to -274 per thousand, respectively, were recorded for (+/-)-dihydroactinidiolide from black and green teas, whereas that from Rooibos tea showed (2)H/(1)H ratios ranging from -189 to -210 per thousand as well as slightly enriched values in the (13)C/(12)C ratios ranging from -24.4 to -27.1 per thousand.

• Berry anthocyanins and their aglycons inhibit monoamine oxidases A and B.

  Authors: Andrea Dreiseitel, Gabriele Korte, Peter Schreier, Anett Oehme, Sanja Locher, Martina Domani, Goeran Hajak, Philipp G Sand

  Pharmacological research : the official journal of the Italian Pharmacological Society. 06/2009; 59(5):306-11.

  Monoamine oxidases (MAO) are mitochondrial enzymes that catalyze the oxidation of monoamines in multiple tissues, including the brain. Elevated MAO activity has long been implicated in the etiologyMonoamine oxidases (MAO) are mitochondrial enzymes that catalyze the oxidation of monoamines in multiple tissues, including the brain. Elevated MAO activity has long been implicated in the etiology of depression, anxiety, and neurodegenerative disease, fuelling the search for inhibitors in the prevention and treatment of these disorders. We hypothesized that emerging neuroprotective effects of anthocyanins from berry fruits may be explained by an affinity of these polyphenols for MAO isoforms A or B. Using a luminometric MAO assay, 25 anthocyanidins, anthocyanidin-3-glycosides, anthocyanidin-3,5-diglucosides, proanthocyanidins, and phenolic metabolites were examined. For MAO A and B, IC(50) values in the low micromolar range were reached by anthocyanidins and anthocyanidin-3-glycosides, as opposed to values in the low millimolar range for phenolic acids. Kinetic analyses, performed with cyanidin and cyanidin-3-glucoside, indicated a competitive interaction of cyanidin with MAO A plus a mixed competitive and non-competitive mode of interaction of cyanidin with MAO B and of cyanidin-3-glucoside with both enzyme isoforms. Thus anthocyanins and their aglycons achieve MAO inhibition in vitro that is compatible with central nervous functionalities. For extrapolation of the present findings to in vivo effects, future studies will need to address in more detail the bioavailability of these dietary constituents.

• Molecular nutrition research--a multidisciplinary challenge.

  Authors: Peter Schreier, Hans-Ulrich Humpf

  Molecular nutrition & food research. 02/2009; 53(1):5-6.

• Anthocyanins as lipoxygenase inhibitors.

  Authors: Bastian Knaup, Anett Oehme, Anagnostis Valotis, Peter Schreier

  Molecular nutrition & food research. 01/2009;

  Health benefits associated with diets rich in anthocyanins are ascribed to multilevel biological activities including antioxidative and anti-inflammatory effects. The present study addressesHealth benefits associated with diets rich in anthocyanins are ascribed to multilevel biological activities including antioxidative and anti-inflammatory effects. The present study addresses lipoxygenase inhibition as a mechanism by which anthocyanins may exert health promoting effects. The inhibitory potential of delphinidin (Dp), cyanidin (Cy), peonidin (Pn), and malvidin (Mv) glycosides, i.e., 3-O-glucosides, 3-O-galactosides, and 3-O-arabinosides as well as their aglycons was analyzed by using soybean lipoxygenase-1 and human neutrophil granulocyte 5-lipoxygenase. The determined IC(50) values comprised a wide range, i.e., from the sub-muM level until practically no effect of inhibition (Mv and its glycosides). With IC(50) values of 0.43 and 0.49 muM Dp 3-O-glucoside (Dp3glc) and Dp 3-O-galactoside (Dp3gal) were found to be the most effective soybean lipoxygenase-1 inhibitors; their strong inhibitory potential was also reflected by the IC(50) values determined for these anthocyanins in the 5-lipoxygenase inhibition exhibiting 2.15 and 6.9 muM, respectively. As to the mechanism of inhibition, experiments carried out with lipoxygenase-1 revealed the uncompetitive type. Considering the powerful inhibitory properties of Dp glycosides in relation to their currently known availability in human metabolism, in vivo prevention of inflammatory diseases by these anthocyanins could be envisaged.

• Analysis of proanthocyanidins.

  Authors: Wolfgang Hümmer, Peter Schreier

  Molecular nutrition & food research. 01/2009; 52(12):1381-1398.

• Pyrrolizidine alkaloids in honey: Risk analysis by gas chromatography-mass spectrometry.

  Authors: Michael Kempf, Till Beuerle, Manuela Bühringer, Martina Denner, Daniela Trost, Katharina von der Ohe, Vijaya B R Bhavanam, Peter Schreier

  Molecular nutrition & food research. 10/2008;

  Recently, contamination of honey with pyrrolizidine alkaloids (PA) has been reported as potential health risk. Therefore, it was of interest to develop a reliable tool for selective and quantitativeRecently, contamination of honey with pyrrolizidine alkaloids (PA) has been reported as potential health risk. Therefore, it was of interest to develop a reliable tool for selective and quantitative determination of PA in honey. Sample preparation of the novel method comprises strong cation exchange SPE (SCX-SPE), followed by two reduction steps using zinc and LiAlH(4), as well as subsequent silylation. During this procedure the separated PA are converted into the necin backbone, the common structural feature of PA toxicity, which is analyzed by GC-MS in the SIM mode. The procedure was validated using PA from extracts of Senecio vernalis as well as authentic PA standards including their corresponding N-oxides. The PA content of honey samples was quantified with heliotrine as internal standard. The method was applied to generate a dataset in order to evaluate the potential risk of PA contamination especially for retail honeys available on the German/European market. No selection criteria in terms of floral or geographical origin were applied on the samples before analysis. In total, 216 commercially available floral honey samples were analyzed. Among them 19 samples contained PA, in the range of 0.019-0.120 mug/g, calculated as retronecine equivalents. The reported method facilitates the selective determination of PA without the need to identify each individual PA independently. The PA contamination of honey is expressed in terms of a single sum parameter and no background information such as foraged plants and pollen analysis is necessary. The LOQ is 0.01 ppm with a S/N of 7:1.

• Fatty acid alpha-dioxygenase from Pisum sativum: Temporal and spatial regulation during germination and plant development.

  Authors: Anke K Meisner, Alexander Saffert, Peter Schreier, Astrid Schön

  Journal of plant physiology. 09/2008;

  alpha-Dioxygenases are expressed in plants in response to biotic and abiotic stress. They catalyze the enantioselective 2-hydroperoxidation of long-chain fatty acids, the initial step of thealpha-Dioxygenases are expressed in plants in response to biotic and abiotic stress. They catalyze the enantioselective 2-hydroperoxidation of long-chain fatty acids, the initial step of the alpha-oxidation pathway of fatty acids in plants. In this study, the complete cDNA of an alpha-dioxygenase from germinating pea seeds (Pisum sativum) is presented. The deduced amino acid sequence establishes that the enzyme belongs to the recently characterized family of alpha-dioxygenating enzymes in plants. We also present the first systematic study on the expression of alpha-dioxygenase in germinating and developing pea plants. During germination, alpha-dioxygenase mRNA accumulates in the cotyledons and the embryonic axis of pea seeds de novo. In developing pea plants, the transcript is detected almost exclusively in roots. The accumulation of alpha-dioxygenase protein parallels transcript accumulation in that it is abundant in germinating as well as young plant tissue, and correlates with loss of mRNA during plant maturation. alpha-Dioxygenase enzymatic activity in plant extracts is highest in cotyledons during imbibition. In the embryonic axis and roots of developing plants comparable activity levels are observed, whereas in shoots little alpha-oxidation activity is detected. With this contribution, we present information on the temporal and spatial expression of alpha-dioxygenase during plant germination and development, supporting the hypothesis that the alpha-oxidation pathway of fatty acids plays a role during plant developmental processes.

• Anthocyanins and their metabolites are weak inhibitors of cytochrome P450 3A4.

  Authors: Andrea Dreiseitel, Peter Schreier, Anett Oehme, Sanja Locher, Goeran Hajak, Philipp G Sand

  Molecular nutrition & food research. 09/2008;

  The cytochrome P450 enzyme cytochrome P450 3A4 (CYP3A4) controls the metabolism of about 60% of all drugs, and its inhibition may dramatically affect drug safety. Modulation of cytochrome P450The cytochrome P450 enzyme cytochrome P450 3A4 (CYP3A4) controls the metabolism of about 60% of all drugs, and its inhibition may dramatically affect drug safety. Modulation of cytochrome P450 activity has been observed by constituents of fruit extracts including several flavonoids. The present investigation addresses CYP3A4 inhibition by anthocyanins, their aglycons, proanthocyanidins, and phenolic metabolites using a chemiluminescent assay. Test compounds inhibited CYP3A4 activity in a concentration-dependent manner featuring IC(50) values from 12.2 up to 7,842 muM. In the order of decreasing effect size, anthocyanidins were followed by anthocyanins, proanthocyanidins, and phenolic acids. When compared to earlier data on furanocoumarins from grapefruit extract, the inhibitory activity of tested anthocyanins, and anthocyanidins was shown to be about 10 000-fold weaker, and was negligible for phenolic acids (>100 000-fold weaker). Future studies are invited to address effects of the above flavonoids on other CYP isoforms for more detailed toxicity profiles.