Lignans in flower buds of Magnolia fargesii

Four lignans were isolated from the flower buds of Magnolia fargesii Cheng, two of which were known lignans, pinoresinol dimethyl ether and lirioresinol-B dimethyl ether; the other two were new lignans, magnolin and fargesin, and their structures have been determined by spectroscopic studies.     

Cytotoxic lignans from Larrea tridentata

Six lignans, including the cyclolignan 3,4'-dihydroxy-3',4'-dimethoxy-6,7'-cyclolignan, were isolated from the flowering tops of Larrea tridentata. Additionally the flavanone, (S)-4',5-dihydroxy-7-methoxyflavanone, was isolated for the first time from L. tridentata or any member of the family Zygophyllaceae. All of the compounds were assessed for their growth inhibitory activity against human breast cancer, human colon cancer and human melanoma cell lines. The lignans had IC50 values of 5-60 microM with the linear butane-type lignans being the most potent, and it was found that colon cancer cells were the least sensitive cell type tested. The relative potency of linear butane type lignans against human breast cancer appears to correlate positively with the number of O-methyl groups present on the molecule.     

Two highly oxygenated eudesmanes and 10 lignans from Achillea holosericea

Two new highly oxygenated eudesmanes and 10 known lignans were isolated from the aerial parts of Achillea holosericea. Their structures were elucidated by extensive application of one- and two-dimensional 1H and 13C NMR spectroscopy.     

Aryltetralol and aryltetralone lignans from Holostylis reniformis

Aryltetralol and aryltetralone lignans were isolated from the hexane extracts of the roots of Holostylis reniformis. Their structures were determined by spectroscopic methods and chemical transformations.     

Aryltetralone lignans and 7,8-seco-lignans from Holostylis reniformis

Aryltetralone lignans and two 7,8-seco-lignans were isolated from the acetone and hexane extracts of the roots of Holostylis reniformis, together with (-)-galbacin. Their structures were determined by spectroscopic methods.     

Immunosuppressive flavones and lignans from Bupleurum scorzonerifolium

Two lignans, isochaihulactone and chaihunaphthone, together with eleven known compounds were isolated from the root of Bupleurum scorzonerifolium. Their structures were established on the basis of spectral evidence. In biological testing, eugenin and saikochromone potently inhibited CD28-costimulated activation of human peripheral blood T cells.     

Dibenzylbutane and aryltetralone lignans from seeds of Virola sebifera

Two lignans rel-(8R, 8'R)-3,4:3',4'-bis-(methylenedioxy)-7.7'-dioxo-lignan and (7'R,8'S,8S)-2'-hydroxy-3,4:4',5'-bis-(methylenedioxy)-7-oxo-2,7'-cyclolignan were isolated from seeds of Virola sebifera. The cyclolignan showed two atropisomers as determined by 1H NMR spectroscopy at low temperature.     

Unusual cyclolanostanes from leaves of Pandanus boninensis

Two unusual triterpenoids, (24S)-24-methyl-25,32-cyclo-5alpha-lanosta-9(11)-en-3beta-ol and (24S)-24-methyl-25,32-cyclo-cycloartane-3beta-ol, were isolated from leaves of Pandanus boninensis along with known triterpenoids and lignans. Their structures were established on the basis of spectroscopic methods and X-ray analysis.     

Constituents from the stems of Actinodaphne lancifolia

Two C(16)-lactonic compounds, actinolides A-B (1-2), were isolated from the stems of Actinodaphne lancifolia, together with five known lactones (3-7) and three known lignans (8-10). Their structures were determined spectroscopically, which included 2D NMR spectroscopic analysis.     

Naphthohydroquinones and lignans from the roots of Plocama pendula, a Canary Island paleoendemism

Two naphthohydroquinones, mollugin 6-methyl ether and plocanaphthin, have been obtained from the roots of Plocama pendula (Rubiaceae), a paleoendemism of the Canary Islands. The former is a new compound, while the latter has now been isolated for the first time from nature. Other compounds obtained from this species were the lignans syringaresinol, pinoresinol and lariciresinol, and the coumarin scopoletin.     

Trypanocidal tetrahydrofuran lignans from inflorescences of Piper solmsianum

In addition to sitosterol, syringaldehyde, 3,4,5-trimethoxybenzoic acid, isoelemicin and grandisin, two new tetrahydrofuran lignans were isolated from Piper solmsianun and characterized as rel-(7R,8R,7'R,8'R)-3',4'-methylenedioxy-3,4,5,5'-tetramethoxy-7,7'-epoxylignan and rel-(7R,8R,7'R,8'R)-3,4,3',4'-dimethylenedioxy-5,5'-dimethoxy-7,7'-epoxylignan on the basis of spectroscopic data, including 2D NMR spectrometric techniques. Their in vitro activity were determined against the trypomastigote form of Trypanossoma cruzi.     

A pinoresinol-lariciresinol reductase homologue from the creosote bush (Larrea tridentata) catalyzes the efficient in vitro conversion of p-coumaryl/coniferyl alcohol esters into the allylphenols chavicol/eugenol, but not the propenylphenols p-anol/isoeugenol

The creosote bush (Larrea tridentata) accumulates a complex mixture of 8-8' regiospecifically linked lignans, of which the potent antioxidant nordihydroguaiaretic acid (NDGA) is the most abundant. Its tetra-O-methyl derivative (M4N) is showing considerable promise in the treatment of refractory (hard-to-treat) brain and central nervous system tumors. NDGA and related 9,9'-deoxygenated lignans are thought to be formed by dimerization of allyl/propenyl phenols, phenylpropanoid compounds that lack C-9 oxygenation, thus differentiating them from the more common monolignol-derived lignans. In our ongoing studies dedicated towards elucidating the biochemical pathway to NDGA and its congeners, a pinoresinol-lariciresinol reductase homologue was isolated from L. tridentata, with the protein obtained in functional recombinant form. This protein efficiently catalyzes the conversion of p-coumaryl and coniferyl alcohol esters into the corresponding allylphenols, chavicol and eugenol; neither of their propenylphenol regioisomers, p-anol and isoeugenol, are formed during this enzyme reaction.     

Synthesis and evaluation of cytotoxic effects of hanultarin and its derivatives

One of the known cytotoxic lignans is (-)-1-O-feruloyl-secoisolariciresinol designated as hanultarin, which was isolated from the seeds of Trichosanthes kirilowii. In this Letter, we described the first synthesis of 1-O-feruloyl-secoisolariciresinol, 1,4-O-diferuloyl-secoisolariceresinol and their analogues. The cytotoxicities of these compounds were evaluated against several cancer cell lines. Interestingly, we found that the feruloyl diester derivative of secoisolariciresinol was the most active cytotoxic compound against all the cancer cells tested in this experiment. The IC(50) values of the1,4-O-diferuloyl-secoisolariceresinol were in the range of 7.1-9.8μM except one cell line. In considering that both ferulic acid and secoisolariciresinol are commonly found in many plants and have no cytotoxicity, this finding is remarkable in that simple covalent bonds between the ferulic acid and secoisolariciresinol cause a cytotoxic effect.     

Lignans from the roots of Echinops giganteus

Two new lignans, (+)-4-(3-methylbutanoyl)-2,6-di(3,4-dimethoxy)phenyl-3,7-dioxabicyclo[3.3.0]octane and (+)-4-hydroxy-2,6-di(3,4-dimethoxy)phenyl-3,7-dioxabicyclo[3.3.0]octane, together with the known lupeol and sitosteryl beta-D-glucopyranoside, have been isolated from the roots of Echinops giganteus var. lelyi C. D. Adams (Compositae). The structures were elucidated on the basis of spectral studies and comparison with published data.     

Antioxidant lignans from Larrea tridentata

Three lignans, (7S,8S,7'S,8'S)-3,3',4'-trihydroxy-4-methoxy-7,7'-epoxylignan, meso-(rel 7S,8S,7'R,8'R)-3,4,3',4'-tetrahydroxy-7,7'-epoxylignan, and (E)-4,4'-dihydroxy-7,7'-dioxolign-8(8')-ene, together with 10 known compounds, were isolated from the leaves of Larrea tridentata. The structures of the new compounds were determined primarily from 1D and 2D NMR spectroscopic analysis. Their antioxidant activities against intracellular reactive oxygen species were evaluated in HL-60 cells.     

DNA strand-scission by phloroglucinols and lignans from heartwood of Garcinia subelliptica Merr. and Justicia plants

Five 2,4,6-prenylated phloroglucinols, garcinielliptones HA (1), HB (2), HC (3), HD (4) and HE (5), were isolated from the heartwood of Garcinia subelliptica Merr. Their structures, including relative configurations, were elucidated by means of spectroscopic data analysis. The ability of phloroglucinols, 1-5 and lignans, tuberculatin (8), justicidin A (9), procumbenoside A (10) and ciliatosides A (11) and B (12), isolated from Justicia ciliata and Justicia procumbens, to induce DNA-cleavage activity was examined using pBR322, a supercoiled, covalently closed circular DNA, and it was analyzed by agarose gel electrophoresis. In the presence of Cu (II), compounds 3, 8, 10 and 11 caused significant breakage of supercoiled plasmid pBR322. The products were relaxed circles with no detectable linear forms. In the Cu(II)-mediated DNA damage of 3 and selective compound 8, Cu(I) was shown not to be an essential intermediate by using the Cu(I)-specific sequestering reagent neocuproine.     

Lignans from Saururus chinensis inhibiting the transcription factor NF-kappaB

The sesquineolignans, saucerneol D and saucerneol E were isolated from the roots of Saururus chinensis together with four known lignans, manassantin A, manassantin B, (-)-saucerneol methyl ether, and (+)-saucernetin. Structure elucidation was based on the analysis of spectroscopic data and anti-inflammatory activity was studied using HeLa cells transfected with NF-kappaB reporter construct. All compounds except for (+)-saucernetin inhibited NF-kappaB dependent reporter gene expression with IC50 values of 2.5-16.9 microM.     

Three new cytotoxic aryltetralin lignans from Sinopodophyllum emodi

Three new aryltetralin lignans, 4-acetyl-4-demethyl-podophyllotoxin (1) and sinolignans A, B (2-3), and two new natural products (4-5), were isolated from the roots and rhizomes of Sinopodophyllum emodi together with twelve known lignans (6-17). Their structures and stereochemistry were elucidated on the basis of spectroscopic evidence, and circular dichroism (CD) method. The cytotoxic activities of all isolated compounds were evaluated against HeLa and KB cell lines. Compared with etoposide, compounds 1, 6-9, and 13 showed more potent cytotoxicities against two tumor cell lines. On the basis of IC₅₀ values, deoxypodophyllotoxin (7) was about 579 and 1123 times more toxic than etoposide in HeLa and KB cell lines, respectively. The preliminary SAR study indicated that an oxygenated group at C-7′ might decrease cytotoxicity against two cell lines, which was different from most previous studies. However, this needs to be systematically verified by extensive pharmacological experiments.     

Lignan profile of Piper cubeba, an Indonesian medicinal plant

The lignan profile of the aerial part of Piper cubeba L. (Piperaceae) was determined using GC, GC–MS and HPLC. The number of lignans found in the leaves was 15, followed by berries and the stalks with respectively 13 and five lignans. This is the first investigation of lignans from the leaves and the stalks of P. cubeba. Cubebin, hinokinin, yatein, isoyatein are common lignans in the genus Piper and appeared as major components in all parts of P. cubeba investigated.     

Lignans causing photodiscoloration of Tsuga heterophylla: 8-hydroxy-oxomatairesinol from sapwood

A lignan, (8S,8'S,)-(+)-8-hydroxy-oxomatairesinol, has been isolated from the sapwood of Tsuga heterophylla (western hemlock, Pinaceae). The known lignans matairesinol, lariciresinol and secoisolariciresinol were also obtained. The structure of the compound was established by 1D and 2D NMR spectroscopy. Results of the light-irradiation test of the lignans from T. heterophylla are also reported.