Studies on lignan constituents from Schisandra chinensis (Turcz.) Baill. fruits using high-performance liquid chromatography/electrospray ionization multiple-stage tandem mass spectrometry

A reversed-phase high-performance liquid chromatography-diode array detector-electrospray ionization multiple-stage tandem mass spectrometry (RP-HPLC-DAD-ESI-MS(n)) method has been developed for the detection and analysis of lignan constituents in the methanol extract from the fruits of Schisandra chinensis (Turcz.) Baill. RP-HPLC-DAD-ESI-MS(n) and electrospray ionization Fourier transform ion cyclotron resonance multiple-stage tandem mass spectrometry (ESI-FT-ICR-MS(n)) have been applied to investigate the characteristic product ions of four lignan reference compounds. Then, the logical fragmentation pathways of the lignans have been proposed. By comparing the retention time (t(R)) of HPLC, the ESI-MS(n) data and the structures of analyzed compounds with the data of reference compounds and in the literature, 11 peaks in HPLC have been unambiguously identified and another 5 peaks have been tentatively identified or deduced. Also, in the present paper, the extracted ion chromatograms (EIC) have been used to analyze the lignan isomers. The experimental results demonstrate that RP-HPLC-DAD-ESI-MS(n) is a specific and useful method for the identification of the lignan constituents and their isomers.     

Biosynthesis of yatein in Anthriscus sylvestris

Little is known about the biosynthesis of yatein, in spite of its importance as a typical heartwood lignan and a key biosynthetic intermediate of the antitumor lignan podophyllotoxin. The present study, based on individual administration of [13C]phenylalanine and deuterium labelled lignans and simultaneous administration of two distinct lignans labelled with deuterium atoms to Anthriscus sylvestris, established the two independent branch pathways from matairesinol, one to afford yatein via thujaplicatin, 5-methylthujaplicatin, and 4,5-dimethylthujaplicatin and the other to bursehernin via pluviatolide. The latter pathway did not lead to yatein, eliminating the presence of a metabolic grid from matairesinol to yatein.     

Analysis of lignans using micellar electrokinetic chromatography

Micellar electrokinetic chromatography (MEKC) was used to separate twelve lignan compounds originating from Phyllanthus plants. To increase the reliability of peak identification, two micellar systems, the sodium dodecyl sulfate (SDS) and sodium deoxycholate (SDC) systems, were investigated. Because of the high lipophilicity of the lignan analytes, tetrahydrofuran was added to the SDS micellar system to increase its separating ability. In contrast to SDS system, no organic solvent was needed with SDC micelles. Both micellar systems gave a satisfactory separation within a reasonable analysis time. On considering accuracy for quantitation, the SDS method was validated and then used to determine the content of the lignans in two Phyllanthus plants. The selectivity (elution order of the lignans) was significantly different between the SDS and SDC micellar systems. Retention in SDC-MEKC seemed to be dominated by the hydrophobicity of the lignan solutes, while in SDS-MEKC, retention was greatly influenced by hydrogen bonding interactions.     

Saracoside: a new lignan glycoside from Saraca indica, a potential inhibitor of DNA topoisomerase IB

Chemical investigation of the stem bark of Saraca indica has resulted in the isolation of a new lignan glycoside, saracoside, along with four known lignan glycosides lyoniside, icariside E3, (+)5'-methoxyisolarciresinol-9'-O-beta-D-glucopyranoside and nudiposide, and a phenolic glucopyranoside, 3,4,5-trimethoxyphenyl-beta-D-glucopyranoside, which has been isolated for the first time from this species. The isolated lignan glycosides exhibit potent DNA topoisomerase IB inhibitory activity.     

A New Geranylated Lignan from Oenanthe javanica and Anti-Inflammatory Activity

Chemistry of Natural Compounds - A new geranylated lignan, named 8′-geranylated lignan A (1), and a known lignan (2) were isolated from Oenanthe javanica (Blume) DC., to our knowledge, for...     

C?H Bond Arylation in the Synthesis of Aryltetralin Lignans: A Short Total Synthesis of Podophyllotoxin

A short total synthesis of podophyllotoxin, the prototypical aryltetralin lignan natural product, is reported. Key to the success of this synthetic pathway is a Pd‐catalyzed C(sp³)–H arylation reaction enabled by a conformational biasing element to promote C–C reductive elimination over an alternative C N bond‐forming pathway. This strategy allows for access to the natural product in five steps from commercially available bromopiperonal, and sheds light on subtle conformational effects governing reductive elimination pathways from high‐valent palladium centers.     

Process research on arylnaphthalene lignan aza-analogues: a new palladium-catalyzed benzannulation of α,β-bisbenzylidenesuccinic acid derivatives

The discovery of a new Pd-catalyzed benzannulation reaction of bisbenzylidenesuccinimide during process research on arylnaphthalene lignan aza-analogues is described. An extension of the Pd-catalyzed benzannulation to the regiospecific synthesis of various arylnaphthalene lignan aza-analogues utilizing classical Stobbe condensation is included.     

CH Bond Arylation in the Synthesis of Aryltetralin Lignans: A Short Total Synthesis of Podophyllotoxin

A short total synthesis of podophyllotoxin, the prototypical aryltetralin lignan natural product, is reported. Key to the success of this synthetic pathway is a Pd‐catalyzed C(sp³)–H arylation reaction enabled by a conformational biasing element to promote C–C reductive elimination over an alternative C? N bond‐forming pathway. This strategy allows for access to the natural product in five steps from commercially available bromopiperonal, and sheds light on subtle conformational effects governing reductive elimination pathways from high‐valent palladium centers.     

Systematik und nomenklatur der lignane

A system of notation for the lignans and isolignans is proposed. The name cyclolignans instead of isolignans has been suggested. The notation is based on the oxygen equivalents in the benzene rings and side chains. The basic hydrocarbons are designated as lignan and cyclolignan.     

Regiochemical control of monolignol radical coupling: a new paradigm for lignin and lignan biosynthesis

BACKGROUND: Although the lignins and lignans, both monolignol-derived coupling products, account for nearly 30% of the organic carbon circulating in the biosphere, the biosynthetic mechanism of their formation has been poorly understood. The prevailing view has been that lignins and lignans are produced by random free-radical polymerization and coupling, respectively. This view is challenged, mechanistically, by the recent discovery of dirigent proteins that precisely determine both the regiochemical and stereoselective outcome of monolignol radical coupling. RESULTS: To understand further the regulation and control of monolignol coupling, leading to both lignan and lignin formation, we sought to clone the first genes encoding dirigent proteins from several species. The encoding genes, described here, have no sequence homology with any other protein of known function. When expressed in a heterologous system, the recombinant protein was able to confer strict regiochemical and stereochemical control on monolignol free-radical coupling. The expression in plants of dirigent proteins and proposed dirigent protein arrays in developing xylem and in other lignified tissues indicates roles for these proteins in both lignan formation and lignification. CONCLUSIONS: The first understanding of regiochemical and stereochemical control of monolignol coupling in lignan biosynthesis has been established via the participation of a new class of dirigent proteins. Immunological studies have also implicated the involvement of potential corresponding arrays of dirigent protein sites in controlling lignin biopolymer assembly.     

Isolation of the lignan secoisolariciresinol diglucoside from flaxseed (Linum usitatissimum L.) by high-speed counter-current chromatography

High-speed counter-current chromatography was successfully used for the isolation and purification of secoisolariciresinol diglucoside, a bioactive lignan from flaxseed (Linum usitatissimum L.). The solvent system consisted of tert.-butylmethyl ether-n-butanol-acetonitrile-water (1:3:1:5). The purity and identity of the isolated compound was checked by high-performance liquid chromatography analysis in combination with mass spectrometry and NMR measurements.     

Stannyl ester cyclizations

Alpha halo stannyl esters react with alkenes to afford lactones. The reaction is catalyzed by AIBN. The reaction proceeds best with electron rich alkenes. The mechanistic aspects of this novel reaction are discussed. This reaction can also be conducted intramolecularly to produce bicyclic lactones. An approach to the lignan system is presented.     

A novel podophyllotoxin lignan from Justicia heterocarpa

Chromatographic separation of the extract of Justicia heterocarpa T. ANDERS. afforded, in addition to known fatty acids, terpenoids and steroids, a new podophyllotoxin lignan. Structures were elucidated by spectroscopic methods, and the structure of the new lignan was confirmed by single crystal X-ray diffraction studies, which have shown that there is a H-bonding stabilized dimer.     

Asymmetric synthesis of (+)-galbelgin, (-)-kadangustin J, (-)-cyclogalgravin and (-)-pycnanthulignenes A and B, three structurally distinct lignan classes, using a common chiral precursor

The enantioselective synthesis of three structurally distinct classes of lignan from a single, aza-Claisen-derived, chiral morpholine amide is reported. The class of lignan formed is dependent on the substitution pattern in the aryl rings and choice of protecting group on a key benzylic hydroxyl group. The methodology has been used to asymmetrically synthesize and determine the absolute stereochemistry of lignans (+)-cyclogalgravin 3, (-)-pycnanthulignene A 4, (-)-pycnanthulignene B 5, and (-)-kadangustin J 8.     

New Lignan Detetrahydroconidendrin from Juniperus Formosana Hayata

Six crystalline compounds, isocedrolic acid, δ-cadinol, emodin, sugiol, Δ⁵-dehydrosugiol, and a new lignan phenol were isolated from the acetone extractive of wood of Juniperus formosana Hayata. The new lignan phenol was established as detetrahydro-conidendrin by chemical and physical evidence.     

Reactions of the natural lignan hydroxymatairesinol in basic and acidic nucleophilic media: formation and reactivity of a quinone methide intermediate

The chemical properties and synthetic modifications of the natural lignan hydroxymatairesinol in basic and acidic nucleophilic media were studied. Hydroxymatairesinol presumably reacts via a quinone methide and a carbonium ion mechanism under basic and acidic conditions, respectively. In these conditions the benzylic hydroxyl group was displaced by nucleophiles yielding new 7-substituted butyrolactone lignans. Reactions in alcoholic basic solutions yielded the 7-alkoxy ethers diastereoselectively. Several previously known lignans as well as new lignans and lignan derivatives were synthesised. The transformations were monitored and the products identified by HPLC-MS and NMR.     

The isolation and structure of 6″-bromo-isoarboreol - the first bromine containing lignan

A new lignan from $\text{Gmelina arborea}$ is shown to be 1, 2a-dihydroxy-2e-piperonyl-6e-(6″-bromopiperonyl)-3, 7-dioxabicyclo-[3,3,0]-octane, the first example of a bromine containing lignan.     

Ellagitannins and lignan glycosides from Balanophora japonica (Balanophoraceae)

Three new ellagitannins named balanophotannins A-C having a 1,1'-(3,3',4,4'-tetrahydroxy)dibenzofurandicarboxyl group in their molecules and four known lignan glycosides were isolated from the extracts of fresh aboveground and underground parts of a medicinal parasitic plant Balanophora japonica (Balanophoraceae). Their structures were elucidated on the basis of spectral and chemical evidence. Chemotaxonomic significance of the known lignan glycosides in Balanophora japonica was discussed.     

A new and known cytotoxic aryltetralin-type lignans from stems of Bursera graveolens

A new 4alpha-aryltetralin-type lignan called burseranin (1) and a known analogous lignan picropolygamain (2) were isolated along with known triterpenes, lupeol and epi-lupeol from the methanol extract of stems of Bursera graveolens, which showed a remarkable inhibitory activity against human HT1080 fibrosarcoma cells. The whole structure of 1 was established based on combined spectral studies and the absolute structure for 2 was first confirmed by CD spectral evidence. In addition, cytotoxic activities of the stem (methanol) extract and its components are evaluated in this paper.     

Larrealignans A and B, novel lignan glycosides from the aerial parts of Larrea tridentata

Two new lignan glycosides, named larrealignans A (1) and B (2), and a known lignan (3) were isolated from the aerial parts of Larrea tridentata (Zygophyllaceae). The structures of 1 and 2 were determined on the basis of spectroscopic analysis and the results of hydrolytic cleavage. The isolated compounds (1-3) and aglycones (1a, 2a) of 1 and 2 were evaluated for their cytotoxic activities against HL-60 human leukemia cells.