Insights into lignin primary structure and deconstruction from Arabidopsis thaliana COMT (caffeic acid O-methyl transferase) mutant Atomt1
作者:Syed G. A. Moinuddin、Michaël Jourdes、Dhrubojyoti D. Laskar、Chanyoung Ki、Claudia L. Cardenas、Kye-Won Kim、Dianzhong Zhang、Laurence B. Davin、Norman G. Lewis
DOI:10.1039/c004817h
日期:——
The Arabidopsis mutant Atomt1 lignin differs from native lignin in wild type plants, in terms of sinapyl (S) alcohol-derived substructures in fiber cell walls being substituted by 5-hydroxyconiferyl alcohol (5OHG)-derived moieties. During programmed lignin assembly, these engender formation of benzodioxane substructures due to intramolecular cyclization of their quinone methides that are transiently formed following 8-O-4′ radical-radical coupling. Thioacidolytic cleavage of the 8-O-4′ inter-unit linkages in the Atomt1 mutant, relative to the wild type, indicated that cleavable sinapyl (S) and coniferyl (G) alcohol-derived monomeric moieties were stoichiometrically reduced by a circa 2 : 1 ratio. Additionally, lignin degradative analysis resulted in release of a 5OHG–5OHG–G trimer from the Atomt1 mutant, which then underwent further cleavage. Significantly, the trimeric moiety released provides new insight into lignin primary structure: during polymer assembly, the first 5OHG moiety is linked via a C8–O–X inter-unit linkage, whereas subsequent addition of monomers apparently involves sequential addition of 5OHG and G moieties to the growing chain in a 2 : 1 overall stoichiometry. This quantification data thus provides further insight into how inter-unit linkage frequencies in native lignins are apparently conserved (or near conserved) during assembly in both instances, as well as providing additional impetus to resolve how the overall question of lignin macromolecular assembly is controlled in terms of both type of monomer addition and primary sequence.
Regioselective cycloaddition of o-quinone 4 and protected sinapyl alcohol 2 gave 1,4-benzodioxane 5, which was converted to (+/-)-nitidanin (6), an antimalarial compound. Two novel procedures were developed to determine the location of the side chains of the adduct (5) based on partial ring cleavage. (c) 2006 Elsevier Ltd. All rights reserved.
Lignans from Santalum album and Their Cytotoxic Activities
作者:Yukiko Matsuo、Yoshihiro Mimaki
DOI:10.1248/cpb.58.587
日期:——
A new neolignan, (7R,8R)-5-O-demethylbilagrewin (1), together with four known lignans (2—5), were isolated from the heartwood of Santalum album (Santalaceae). The structure of 1 was determined by analysis of extensive spectroscopic data. The isolated compounds and derivatives were evaluated for their cytotoxic activities against HL-60 human promyelocytic leukemia cells and A549 human lung adenocarcinoma cells. Compounds 1 and 2 exhibited cytotoxicity against HL-60 cells with IC50 values of 1.5±0.02 and 4.3±0.13 μM, and against A549 cells with IC50 values of 13.6±0.32 and 19.9±1.27 μM, respectively. The aldehyde group of 1 and 2 was revealed to be a structural requirement for the appearance of cytotoxicity in this type of lignans. These tumor cell deaths were shown to be mediated through induction of apoptosis.
Aromatic Constituents from the Heartwood of Santalum album L.
作者:Tae Hoon Kim、Hideyuki Ito、Kikuyo Hayashi、Toshio Hasegawa、Takahisa Machiguchi、Takashi Yoshida
DOI:10.1248/cpb.53.641
日期:——
A phytochemical investigation of the polar constituents in the heartwood of Indian Santalum album L. resulted in the isolation of three new neolignans (1-3) and a new aromatic ester (4), along with 14 known components. The structures of the new compounds (1-4) were established using spectroscopic methods.