TY  - JOUR
A1  - Bringmann, Gerhard
A1  - Mutanyatta-Comar, Joan
A1  - Maksimenka, Katja
A1  - Wanjohi, John M.
A1  - Heydenreich, Matthias
A1  - Brun, Reto
A1  - Müller, Werner E. G.
A1  - Peter, Martin G.
A1  - Midiwo, Jacob O.
A1  - Yenesew, Abiy
T1  - Joziknipholones A and B : the first dimeric phenylanthraquinones, from the roots of Bulbine frutescens
N2  - From the roots of the African plant Bulbine frutescens (Asphodelaceae), two unprecedented novel dimeric phenylanthraquinones, named joziknipholones A and B, possessing axial and centrochirality, were isolated, together with six known compounds. Structural elucidation of the new metabolites was achieved by spectroscopic and chiroptical methods, by reductive cleavage of the central bond between the monomeric phenylanthraquinone and -anthrone portions with sodium dithionite, and by quantum chemical CD calculations. Based on the recently revised absolute axial configuration of the parent phenylanthraquinones, knipholone and knipholone anthrone, the new dimers were attributed to possess the P- configuration (i.e., with the acetyl portions below the anthraquinone plane) at both axes in the case of joziknipholone A, whereas in joziknipholone B, the knipholone part was found to be M-configured. Joziknipholones A and B are active against the chloroquine resistant strain K1 of the malaria pathogen, Plasmodium falciparum, and show moderate activity against murine leukemic lymphoma L5178y cells.
Y1  - 2008
UR  - http://www3.interscience.wiley.com/journal/26293/home?CRETRY=1&SRETRY=0
SN  - 0947-6539
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  - GEN
A1  - Bringmann, Gerhard
A1  - Mutanyatta-Comar, Joan
A1  - Maksimenka, Katja
A1  - Wanjohi, John M.
A1  - Heydenreich, Matthias
A1  - Brun, Reto
A1  - Müller, Werner E. G.
A1  - Peter, Martin
A1  - Midiwo, Jacob O.
A1  - Yenesew, Abiy
T1  - Joziknipholones A and B : the First Dimeric Phenylanthraquinones, from the Roots of Bulbine frutescens
N2  - From the roots of the African plant Bulbine frutescens (Asphodelaceae), two unprecedented novel dimeric phenylanthraquinones, named joziknipholones A and B, possessing axial and centrochirality, were isolated, together with six known compounds. Structural elucidation of the new metabolites was achieved by spectroscopic and chiroptical methods, by reductive cleavage of the central bond between the monomeric phenylanthraquinone and -anthrone portions with sodium dithionite, and by quantum chemical CD calculations. Based on the recently revised absolute axial configuration of the parent phenylanthraquinones, knipholone and knipholone anthrone, the new dimers were attributed to possess the P-configuration (i.e., with the acetyl portions below the anthraquinone plane) at both axes in the case of joziknipholone A, whereas in joziknipholone B, the knipholone part was found to be M-configured. Joziknipholones A and B are active against the chloroquine resistant strain K1 of the malaria pathogen, Plasmodium falciparum, and show moderate activity against murine leukemic lymphoma L5178y cells.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 104 
KW  - antimalarial activity
KW  - chirality
KW  - joziknipholones
KW  - natural products
KW  - structure elucidation
Y1  - 2008
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-42638
ER  -