TY - JOUR A1 - Zala, Eva A1 - Struszczyk, Marcin Henryk A1 - Peter, Martin G. T1 - Effects of preparation methods for chitosan films on their properties Y1 - 2001 ER - TY - JOUR A1 - Yenesew, Abiy A1 - Twinomuhwezi, Hannington A1 - Kiremire, Bernard T. A1 - Mbugua, Martin N. A1 - Gitu, Peter M. A1 - Heydenreich, Matthias A1 - Peter, Martin G. T1 - 8-Methoxyneorautenol and radical scavenging flavonoids from Erythrina abyssinica N2 - A new pterocarpan (named 8-methoxyneorautenol) was isolated from the acetone ext. of the root bark of Erythrina abyssinica. In addn., the known isoflavonoid derivs. eryvarin L, erycristagallin and shinpterocarpin were identified for the first time from the roots of this plant. The structures were detd. on the basis of spectroscopic evidence. The new compd. showed selective antimicrobial activity against Trichophyton mentagrophytes. The acetone ext. of the root bark of E. abyssinica showed radical scavenging activity towards 2,2-diphenyl-1-picrylhydrazyl radical (DPPH). The pterocarpenes, 3-hydroxy-9-methoxy-10-(3,3-dimethylallyl)pterocarpene and erycristagallin, were the most active constituents of the roots of this plant and showing dose-dependent activities similar to that of the std. quercetin. [on SciFinder (R)] Y1 - 2009 UR - http://www.ajol.info/journal_index.php?jid=120&ab=bcse SN - 1011-3924 ER - TY - JOUR A1 - Yenesew, Abiy A1 - Mushibe, E. K. A1 - Induli, M. A1 - Derese, Solomon A1 - Midiwo, Jacob O. A1 - Kabaru, Jacques M. A1 - Heydenreich, Matthias A1 - Koch, Andreas A1 - Peter, Martin G. T1 - 7a-O-methyldeguelol, a modified rotenoid with an open ring-C, from the roots of Derris trifoloata N2 - From the acetone extract of the roots of Derris trifoliata an isollavonoid derivative, named 7a-O- methyldeguelol, a modified rotenoid with an open ring-C, representing a new sub-class of isollavonoids (the sub-class is here named as rotenoloid), was isolated and characterised. In addition, the known rotenoids, rotenone, deguelin and alpha-toxicarol, were identified. The structures were determined on the basis of spectroscopic evidence. Rotenone and deguelin were identified as the larvicidal principles of the acetone extract of the roots of Derris trifoliata. (c) 2005 Elsevier Ltd. All rights reserved Y1 - 2005 SN - 0031-9422 ER - TY - JOUR A1 - Yenesew, Abiy A1 - Midiwo, Jacob O. A1 - Meisner, M. A1 - Heydenreich, Matthias A1 - Peter, Martin G. T1 - Two prenylated flavanones from stem bark of erythrina burttii Y1 - 1998 ER - TY - JOUR A1 - Yenesew, Abiy A1 - Midiwo, Jacob O. A1 - Heydenreich, Matthias A1 - Schanzenbach, Dirk A1 - Peter, Martin G. T1 - Two Isoflavanones from the Stem Bark of Erythrina sacleuxii N2 - From the stem bark of Erythrina sacleuxii two new isoflavanones, (R)-5,7-dihydroxy-2',4',5'- trimethoxyisoflavanone (trivial name, (R)-2,3-dihydro-7-demethylrobustigenin) and (R)-5-hydroxy- 2',4',5'-trimethoxy-2'',2''- dimethylpyrano[5'',6'':6,7]isoflavanone (trivial name, (R)-saclenone) were isolated. In addition the known compounds shinpterocarpin, 2,3-dehydrokievitone, abyssinone V, abyssinone V-4'-methyl ether, erythrinasinate and 4'-O-methylsigmoidin B were isolated. The structures were determined on the basis of spectroscopic evidence. Y1 - 2000 ER - TY - JOUR A1 - Yenesew, Abiy A1 - Midiwo, Jacob O. A1 - Heydenreich, Matthias A1 - Peter, Martin G. T1 - Four isoflavanones from stem bark of erythrina sacleuxii Y1 - 1998 ER - TY - JOUR A1 - Yenesew, Abiy A1 - Midiwo, Jacob O. A1 - Guchu, S. M. A1 - Heydenreich, Matthias A1 - Peter, Martin G. T1 - Three iosoflav-3-enes and a 2-arylbenzofuran from the root bark of Erythrina burttii N2 - From the root bark of Erythrina burttii three new isoflav-3-enes, 7,4'-dihydroxy-2'-methoxy-6- (1'',1''-dimethylallyl)isoflav-3-ene (trivial name, burttinol-A), 4'-hydroxy-2'- methoxy-(2'',2''-dimethylpyrano[5'',6'':8,7]isoflav-3-ene (trivial name, burttinol-B), 7,4'-dihydroxy-2'-methoxy-8-(3'',3''-dimethylallyl)isoflav-3-ene (trivial name, burttinol-C), and a new 2-arylbenzofuran, 6,4'-dihydroxy-2'-methoxy-5- (1'',1''-dimethylallyl)-2-arylbenzofuran (trivial name, burttinol-D) were isolated. In addition, the known compounds, abyssinone V-4'-methyl ether, bidwillol A, calopocarpin, erybraedin A, erythrabyssin II, isobavachalcone, phaseollidin and phaseollin were identified. The structures were determined on the basis of spectroscopic evidence. Y1 - 2002 ER - TY - JOUR A1 - Yenesew, Abiy A1 - Kiplagat, John T. A1 - Derese, Solomon A1 - Midiwo, Jacob O. A1 - Kabaru, Jacques M. A1 - Heydenreich, Matthias A1 - Peter, Martin G. T1 - Two unusual rotenoid derivatives, 7a-O-methyl-12a-hydroxydeguelol and spiro-13-homo-13-oxaelliptone, from the seeds of Derris trifoliata N2 - The crude methanol extract of the seeds of Derris trifoliata showed potent and dose dependent larvicidal activity against the 2nd instar larvae of Aedes aegypti. From this extract two unusual rotenoid derivatives, a rotenoloid (named 7a-O-methyl-12a-hydroxydeguelol) and a spirohomooxarotenoid (named spiro-13-homo-13-oxaelliptone), were isolated and characterised. In addition a rare natural chromanone (6,7-dimethoxy-4-chromanone) and the known rotenoids rotenone, tephrosin and dehydrodeguelin were identified. The structures were assigned on the basis of spectroscopic evidence. The larvicidal activity of the crude extract is mainly due to rotenone. (c) 2006 Elsevier Ltd. All rights reserved Y1 - 2006 UR - http://www.sciencedirect.com/science/article/pii/S0031942206000045 U6 - https://doi.org/10.1016/j.phytochem.2006.01.002 ER - TY - JOUR A1 - Yenesew, Abiy A1 - Irungu, Beatrice A1 - Derese, Solomon A1 - Midiwo, Jacob O. A1 - Heydenreich, Matthias A1 - Peter, Martin G. T1 - Two prenylated flavonoids from the stem bark of Erythrina burttii N2 - From the stem bark of Erythrina burttii, a new isoflavone, 5,2',4'-trihydroxy-7-methoxy-6-(3- methylbut-2-enyl)isoflavone (trivial name, 7-O-methylluteone) and a new flavanone, 5,7-dihydroxy-4'-methoxy- 3'-(3-methylbutadienyl)-5'-(3-methylbut-2-enyl)flavanone (trivial name, burttinonedehydrate) along with three known isoflavonoids (8-prenylluteone, 3-O-methylcalopocarpin and genistein) were isolated. The structures were detd. on the basis of spectroscopic evidence. Y1 - 2003 ER - TY - JOUR A1 - Yenesew, Abiy A1 - Induli, M. A1 - Derese, Solomon A1 - Midiwo, Jacob O. A1 - Heydenreich, Matthias A1 - Peter, Martin G. A1 - Akala, Hoseah M. A1 - Wangui, Julia A1 - Liyala, Pamela A1 - Waters, Norman C. T1 - Anti-plasmodial flavonoids from the stem bark of Erythrina abyssinica N2 - The ethyl acetate extract of the stem bark of Erythrina abyssinica showed anti-plasmodial activity against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum with IC50 values of 7.9 +/- 1.1 and 5.3 +/- 0.7 mug/ml, respectively. From this extract, a new chalcone, 2,3,4,4'-tetrahydroxy-5- prenylchalcone (trivial name 5-prenylbutein) and a new flavanone, 4',7-dihydroxy-3'-methoxy-5'- prenylflavanone (trivial name, 5-deoxyabyssinin II) along with known flavonoids have been isolated as the anti- plasmodial principles. The structures were determined on the basis of spectroscopic evidence. (C) 2004 Elsevier Ltd. All rights reserved Y1 - 2004 SN - 0031-9422 ER - TY - JOUR A1 - Yenesew, Abiy A1 - Derese, Solomon A1 - Midiwo, Jacob O. A1 - Bii, Christine C. A1 - Heydenreich, Matthias A1 - Peter, Martin G. T1 - Antimicrobial flavonoids from the stem bark of Erythrina burttii N2 - The chloroform extract of the stem bark of Erythrina burttii showed antifungal and antibacterial activities using the disk diffusion method. Flavonoids were identified as the active principles. Activities were observed against fungi and Gram(+) bacteria, but the Gram(-) bacteria Escherichia coli was resistant. (c) 2005 Elsevier B.V. All rights reserved Y1 - 2005 SN - 0367-326X ER - TY - JOUR A1 - Wanjohi, John M. A1 - Yenesew, Abiy A1 - Midiwo, Jacob O. A1 - Heydenreich, Matthias A1 - Peter, Martin G. A1 - Dreyer, M. A1 - Reichert, M. A1 - Bringmann, Gerhard T1 - Three dimeric anthracene derivatives from the fruits of Bulbine abyssinica N2 - From the fruits of Bulbine abyssinica three new dimeric anthracene derivatives, (P)-8,9,1',8'- tetrahydroxy-3,3'-dimethyl[10,7'-bianthracene]-1,4,9',10'- tetraone (trivial name abyquinone A), (10R)-1,4,8,1',8-pentahydroxy-3,3'-dimethyl-[10,7'-bianthracene]9,9',10' (10H)-trione (trivial name abyquinone B), and (10R)-3,4'-dihydro-1,4,8,3',8',9'-hexahydroxy-3,3'- dimethyl-[10,7'-biant hracene]9,1'(10H,2'H)-dione (trivial name abyquinone Q were isolated. Despite their structural differences, these three compounds are connected to each other by the apparently biomimetic conversion of abyquinone C (a preanthraquinonylanthrone with two stereogenic centers) into B (an anthraquinonylanthrone with one stereogenic center) and finally into A (an axially chiral bianthraquinone) under mild conditions, involving a highly efficient center-to-axis chirality transfer. In addition, the known anthraquinones islandicin and chrysophanol were identified. The structures were determined on the basis of spectroscopical evidences, chemical transformations, and quantum chemical CD calculations. (C) 2005 Elsevier Ltd. All rights reserved Y1 - 2005 SN - 0040-4020 ER - TY - JOUR A1 - Vijayakrishnan, Balakumar A1 - Issaree, Arisara A1 - Corilo, Yuri E. A1 - Ferreira, Christina Ramires A1 - Eberlin, Marcos N. A1 - Peter, Martin G. T1 - MSn of the six isomers of (GlcN)(2)(GlcNAc)(2) aminoglucan tetrasaccharides (diacetylchitotetraoses) rules of fragmentation for the sodiated molecules and application to sequence analysis of hetero-chitooligosaccharides JF - Carbohydrate polymers : an international journal devoted to scientific and technological aspects of industrially important polysaccharides N2 - The six possible isomers of di-N-acetylchitotetraoses [AADD, ADDA, ADAD, DADA, DAAD, and DDAA, where D stands for 2-amino-2-deoxy-3-D-glucose (GlcN) and A for 2-acetamido-2-deoxy-beta-D-glucose (GlcNAc)] were analyzed by ESI(+)-MSn. Collision induced dissociation via MSn experiments were performed for the sodiated molecules of m/z 769 [M+Na](+) for each isomer, and fragments were generated mainly by glycosidic bond and cross-ring cleavages. Rules of fragmentation were then established. A reducing end D residue yields the (O.2)A(4) cross-ring [M-59+Na](+) fragment of m/z 710 as the most abundant, whereas isomers containing a reducing end A prefer to lose water to form the [M-18+Na](+) ion of m/z 751, as well as abundant (O.2)A(4) cross-ring [M-101+Na](+) fragments of m/z 668 and B-3 [M-221+Na](+) ions of m/z 548. MS3 of C- and Y-type ions shows analogous fragmentation behaviour that allows identification of the reducing end next-neighbour residue. Due to gas-phase anchimeric assistance, B-type cleavage between the glycosidic oxygen and the anomeric carbon atom is favoured when the glycon is an A residue. Relative ion abundances are generally in the order B >> C > Y, but may vary depending on the next neighbour towards the non-reducing end. These fragmentation rules were used for partial sequence analysis of hetero-chitooligosaccharides of the composition D(2)A(3), D(3)A(3), D(2)A(4), D(4)A(3), and D(3)A(4). KW - Chitosan KW - Fragmentation KW - Oligosaccharides KW - Sequence analysis KW - Tandem mass spectrometry Y1 - 2011 U6 - https://doi.org/10.1016/j.carbpol.2010.04.041 SN - 0144-8617 VL - 84 IS - 2 SP - 713 EP - 726 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - van Aalten, Daan M. F. A1 - Komander, David A1 - Synstad, Bjoenar A1 - Gaseidnes, Sigrid A1 - Peter, Martin G. A1 - Eijsink, Vincent G. H. T1 - Structural Insights into the catalytic mechanism of a family 18 exochitinase N2 - Chitinase B (ChiB) from Serratia marcescens is a family 18 exochitinase whose catalytic domain has a TIM-barrel fold with a tunnel-shaped active site. We have solved structures of three ChiB complexes that reveal details of substrate binding, substrateassisted catalysis, and product displacement. The structure of an inactive ChiB mutant (E144Q) complexed with a pentameric substrate (binding in subsites 22 to 13) shows closure of the ''roof'' of the active site tunnel. It also shows that the sugar in the 21 position is distorted to a boat conformation, thus providing structural evidence in support of a previously proposed catalytic mechanism. The structures of the active enzyme complexed to Allosamidin (an analogue of a proposed reaction intermediate) and of the active enzyme soaked with pentameric substrate show events after cleavage of the glycosidic bond. The latter structure shows reopening of the roof of the active site tunnel and enzyme-assisted product displacement in the 11 and 12 sites, allowing a water molecule to approach the reaction center. Catalysis is accompanied by correlated structural changes in the core of the TIM barrel that involve conserved polar residues whose functions were hitherto unknown. These changes simultaneously contribute to stabilization of the reaction intermediate and alternation of the pKa of the catalytic acid during the catalytic cycle. Y1 - 2002 ER - TY - JOUR A1 - Vaaje-Kolstad, G. A1 - Vasella, A. A1 - Peter, Martin G. A1 - Netter, C. A1 - Houston, Douglas R. A1 - Westereng, B. A1 - Synstad, Bjoenar A1 - Eijsink, Vincent G. H. A1 - van Aalten, Daan M. F. T1 - Interactions of a family 18 chitinase with the designed inhibitor HM508 and its degradation product, chitobiono- delta-lactone N2 - We describe enzymological and structural analyses of the interaction between the family 18 chitinase ChiB from Serratia marcescens and the designed inhibitor N,N'-diacetylchitobionoxime-N-phenylcarbamate (HM508). HM508 acts as a competitive inhibitor of this enzyme with a K-i in the 50 muM range. Active site mutants of ChiB show K-i values ranging from 1 to 200 muM, providing insight into some of the interactions that determine inhibitor affinity. Interestingly, the wild type enzyme slowly degrades HM508, but the inhibitor is essentially stable in the presence of the moderately active D142N mutant of ChiB. The crystal structure of the D142N-HM508 complex revealed that the two sugar moieties bind to the -2 and -1 subsites, whereas the phenyl group interacts with aromatic side chains that line the +1 and +2 subsites. Enzymatic degradation of HM508, as well as a Trp-->Ala mutation in the +2 subsite of ChiB, led to reduced affinity for the inhibitor, showing that interactions between the phenyl group and the enzyme contribute to binding. Interestingly, a complex of enzymatically degraded HM508 with the wild type enzyme showed a chitobiono-delta- lactone bound in the -2 and -1 subsites, despite the fact that the equilibrium between the lactone and the hydroxy acid forms in solution lies far toward the latter. This shows that the active site preferentially binds the E-4 conformation of the -1 sugar, which resembles the proposed transition state of the reaction Y1 - 2004 SN - 0021-9258 ER - TY - JOUR A1 - Tsukamoto, Junko A1 - Haebel, Sophie A1 - Valenca, Gustavo P. A1 - Peter, Martin G. A1 - FRanco, Telma T. T1 - Enzymatic direct synthesis of acrylic acid esters of mono- and disaccharides N2 - Background: There is an increased need to replace materials derived from fossil sources by renewables. Sugar- cane derived carbohydrates are very abundant in Brazil and are the cheapest sugars available in the market, with more than 400 million tons of sugarcane processed in the year 2007. The objective of this work was to study the prepn. of sugar acrylates from free sugars and free acrylic acid, thus avoiding the previous prepn. of protected sugar derivs., such as glycosides, or activated acrylates, such as vinyl acrylate. Results: Lipase catalyzed esterification of three mono- and two disaccharides with acrylic acid, in the presence or absence of mol. sieves was investigated. The reactions were monitored by high-performance liq. chromatog. (HPLC) and the products were analyzed by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry. The main products are mono- and diacrylates, while higher esters are formed as minor products. The highest conversion to sugar acrylates was obsd. for the D-glucose and D- fructose, followed by D-xylose and D-maltose. Mol. sieves had no pronounced effect on the conversion. Conclusions: A feasible method is described to produce and to characterize sugar acrylates, including those contg. more than two acrylate groups. The process for prodn. of these higher esters could potentially be optimized further to produce mols. for crosslinking in acrylate polymn. and other applications. The direct enzymic esterification of free carbohydrates with acrylic acid is unprecedented. [on SciFinder (R)]. Y1 - 2008 UR - http://www3.interscience.wiley.com/journal/117946200/grouphome/home.html SN - 0268-2575 ER - TY - JOUR A1 - Thiele, Gabriela A1 - Rottmann, Antje A1 - Germer, Antje A1 - Kleinpeter, Erich A1 - Spindler, Klaus-Dieter A1 - Synstad, Bjoenar A1 - Eijsink, Vincent G. H. A1 - Peter, Martin G. T1 - Synthesis and conformational analysis of pseudosugar analogues of chitotriose N2 - In this article, the synthesis of analogs of N,N',N''-triacetylchitotriose in which the central sugar residue was replaced by a succinic acid is presented. Mol. modeling calcns. revealed that the pseudotrisaccharides exist in low energy extended conformations which show similar space filling as N,N',N''-triacetylchitotriose. Of the N,N',N''-triacetylchitotriose pseudosugar analogs tested as chitinase inhibitors, none showed any appreciable competition (numerical data not presented). The conformational anal. along with further synthetic efforts will hopefully lead to more efficient pseudosaccharides as chitinase inhibitors. Y1 - 2002 ER - TY - JOUR A1 - Struszczyk, Marcin Henryk A1 - Ratajska, M. A1 - Boryniec, Stefan A1 - Peter, Martin G. A1 - Loth, Fritz T1 - The determination of the degree of N-acetylation of chitosan Y1 - 1997 ER - TY - JOUR A1 - Struszczyk, Marcin Henryk A1 - Pospieszny, Henryk A1 - Schanzenbach, Dirk A1 - Peter, Martin G. T1 - Biodegradation of various chitosans using Aspergillus fumigatus Y1 - 2001 ER - TY - JOUR A1 - Struszczyk, Marcin Henryk A1 - Loth, Fritz A1 - Pospieszny, Henryk A1 - Peter, Martin G. T1 - Biodegradation of films and paper sheets containing chitosan Y1 - 2001 ER -