Lignans.

The 13 research articles/communications, six reviews, and one perspective that comprise this Special Issue on Lignans, highlight the most recent research and investigations into this diverse and important class of bioactive natural products [...].

Chemotypification of Astrantia major L. (Apiaceae): essential-oil and lignan profiles of fruits.

The fruit essential oils of two populations of Astrantia major L. (Apiaceae, subfamily Saniculoideae) were analyzed in detail by GC and GC/MS analyses. Seventy-six constituents identified accounted for 92.7-94.0% of the oils. The two oils differed significantly: the wild-growing population from Serbia contained zingiberene (47.9%), ß-bisabolene (9.7%), and ß-sesquiphellandrene (7.9%), while the one from Poland (botanical gardens) was sesquiterpene-poor with the major contributors oleic acid (38.6%), nonacosane (15.4%), and linoleic acid (5.1%). Motivated by the unresolved taxonomical relations between the Saniculoideae and Apioideae subfamilies, we performed multivariate statistical analyses on the compositional data of these A. major samples, and additional 14 Saniculoideae and 31 Apioideae taxa. This allowed us to assess the chemotaxonomical usefulness of such chemical data in differentiating taxa from these two Apiaceae subfamilies and to corroborate the existence of at least two A. major chemotypes. Diethyl ether extracts of the two samples of A. major fruits yielded seven diaryltetrahydrofurofurano lignans. Except for eudesmin that has been found for the first time in a Saniculoideae taxon, all other lignans (magnolin, epimagnolins A and B, epieudesmin, yangambin, and epiyangambin) are new for the entire plant family Apiaceae. The lignan profiles also supported the existence of two separate A. major chemotypes.

Compounds with neuroprotective activity from the medicinal plant Machilus thunbergii.

The dichloromethane fraction of the bark of Machilus thunbergii Sieb. et Zucc. (Lauraceae) significantly protected primary cultures of rat cortical cells exposed to the excitotoxic amino acid, L-glutamate. Through the activity-guided isolation from the CH(2)Cl(2) fraction, (+)-9'-hydroxygalbelgin (1), isogalcatin B (2), (7S,8S,8'R)-3',4'-dimethoxy-3,4,-methylenedioxylignan-7-ol (3), 1-hydroxy-7-hydroxymethyl-6-methoxyxanthone (4), 5,7-dimethoxy-3',4'-methylenedioxyflavan-3-ol (5), (+)-(3S,4S,6R)-3,6-dihydroxypiperitone (6), protocatechuic acid methyl ester (7) and tyrosol (8) were obtained. All of them had significant neuroprotective activities against glutamate-induced neurotoxicity in primary cultures of rat cortical cells at concentrations ranging from 0.1 microM to 10.0 microM and were comparable to MK-801, a well-known inhibitor of glutamate receptor.

Machilin G and four neolignans from young fruits of Magnolia denudata show various degrees of inhibitory activity on nitric oxide (NO) production.

Denudatin A and B, denudadione B, fargesone A and machilin G were isolated from Magnolia denudata. These compounds showed inhibitory effects on nitric oxide (NO) production in the lipopolysaccharide plus interferon-gamma activated-murine macrophage cell line, J774.1. Some but not all of the inhibition of NO production by machilin G, and denudatin A and B was apparently through the decreased expression of the inducible NO synthase (iNOS) gene.

Lignanos (1): estructura y funciones en las plantas / No disponible

Los lignanos constituyen un grupo de productos naturales ampliamente distribuido en el reino vegetal, cuyas unidades estructurales son biosintetizadas a través de la ruta del ácido sikímico. Pese a la elevada diversidad de estructuras que presentan, poseen la característica común de estar formados por dos unidades de fenilpropano enlazadas por el átomo central de sus cadenas laterales. Estos compuestos están presentes en desde briófitos y helechos hasta plantas superiores, donde desempeñan importantes funciones fisiológicas, principalmente de tipo defensivo

Lignans are a group of natural products widely distributed within the plant kingdom. The structural units of these compounds are biosynthesized via shikimic acid pathway. Although their structures can be very different, they have in common two units of phenylpropane bound by the central atom of their side chains. These compounds can be found in Bryophytes, ferns as well as in superior plants, in which they are responsible for important physiological functions, mostly of defensive kind

Polyphenols from plants used in traditional Indonesian medicine (Jamu): uptake and antioxidative effects in rat H4IIE hepatoma cells.

Phytochemical investigation of plants used in traditional Indonesian medicine (Jamu) yielded lignans (pinoresinol, 9 alpha-hydroxypinoresinol and salicifoliol), flavonoids (3-O-beta-(D)-glucopyranosyl-(1-->6)-beta-(D)-glucopyranosylkaempferol, luteolin and apigenin) and coumarins (coumarin, 8-hydroxycoumarin and 5-hydroxycoumarin). The beneficial effects of the respective plants for human health are thought to be associated with antioxidative activity. In the present study, the antioxidative capacity of the isolated compounds was determined in an in-vitro assay. Luteolin and kaempferol (cleavage product of 3-O-beta-(D)-glucopyranosyl-(1-->6)-beta-(D)-glucopyranosylkaempferol, which is thought to be formed in the intestine) showed strong antioxidant activity; pinoresinol and 9 alpha-hydroxypinoresinol showed only minor antioxidative effects. The coumarins, as well as apigenin and 3-O-beta-(D)-glucopyranosyl-(1-->6)-beta-(D)-glucopyranosylkaempferol were inactive. The antioxidative effects of luteolin, kaempferol and pinoresinol were further investigated in H4IIE rat hepatoma cells. A strong protective effect of kaempferol and luteolin was found against H2O2-mediated intracellular reactive oxygen species formation measured using the dichlorofluorescein assay and H2O2-mediated DNA strand breaks. Pinoresinol did not have a protective effect against H2O2-mediated DNA-damage, but in the dichlorofluorescein assay, an antioxidative effect was detectable. During studies with H4IIE cells, kaempferol, luteolin and pinoresinol were taken up by the cells within 60 min. The flavonoids were found to be relatively toxic at higher concentrations, while pinoresinol was less cytotoxic. In conclusion, kaempferol and luteolin, at low concentrations (< or = 50 microM), protect H4IIE cells against oxidative stress but are cytotoxic at higher concentrations; the biological effects of pinoresinol are less prominent in comparison. These results are important for the identification of pharmacologically active substances from traditional Indonesian medicinal plants.

Phytoestrogens.

Collectively, plants contain several different families of natural products among which are compounds with weak estrogenic or antiestrogenic activity toward mammals. These compounds, termed phytoestrogens, include certain isoflavonoids, flavonoids, stilbenes, and lignans. The best-studied dietary phytoestrogens are the soy isoflavones and the flaxseed lignans. Their perceived health beneficial properties extend beyond hormone-dependent breast and prostate cancers and osteoporosis to include cognitive function, cardiovascular disease, immunity and inflammation, and reproduction and fertility. In the future, metabolic engineering of plants could generate novel and exquisitely controlled dietary sources with which to better assess the potential health beneficial effects of phytoestrogens.

Podophyllotoxin: distribution, sources, applications and new cytotoxic derivatives.

Several podophyllotoxin derivatives modified in the A, B, C, D and E rings were prepared from podophyllotoxin and methyl isoxazopodophyllic acid and evaluated for their cytotoxicity on several neoplastic cell lines. Chemical transformations performed on these compounds have yielded derivatives more potent and more selective that the parent compound. Most of the compounds maintained their cytotoxicity at the microM level. Distribution, biosynthesis, production, biotechnology, applications and synthesis have also been reviewed.

[Studies on the lignan chemical constituents from pine needles of Pinus massoniana Lamb].

AIM: To study the chemical constituents of the pine needles from Pinus massoniana Lamb.. METHODS: Various chromatographic techniques were used for the separation and purification. The physicochemical properties and spectral data were used to elucidate the structures. RESULTS: Three compounds were isolated from the n-BuOH fraction of water-extracts. The structures were identified as (7S,8R)-4,9'-dihydroxyl-3, 3'-dimethyoxyl-7, 8-dihydrobenzofunan-1'-propanolneolignan-9-O-alpha- L-rhamnopyranoside (massonianoside D, 7), 4,4',9,9'-tetrahydroxyl-3,3'-dimethyoxyl-tetrahydrocyclolignan ((+)-isolariciresinol, 8) and 4,4',9'-trihydroxyl-3,3'-dimethyoxyl-tetrahydrocyclolignan-9-O-beta-D- xylopyranoside (isolariciresinol-9-O-xyloside, 9) on the basis of spectral data (ORD, UV, IR, MS, 1HNMR, 13CNMR, 1H-1HCOSY, HMQC and HMBC etc.). CONCLUSION: Compound 7 is a new compound, while compounds 8 and 9 were isolated from this plant for the first time.

Isolation and characterization of novel benzoates, cinnamates, flavonoids, and lignans from Riesling wine and screening for antioxidant activity.

A German Riesling wine has been fractionated with the aid of countercurrent chromatography. After purification by HPLC, the structures of 101 compounds were established by mass spectrometry and NMR spectroscopy. Seventy-three of the isolated compounds exhibited a phenolic or benzylic structure. Fifty-four compounds were reported for the first time as Riesling wine constituents. New compounds identified in this work included twelve benzoic and cinnamic acid derivatives. In addition to two isomeric (E)-caffeoyl ethyl tartrates, the glucose esters of (E)-cinnamic, (E)-p-coumaric, and (E)-ferulic acid, as well as the 4-O-glucosides of (E)- and (Z)-ferulic acid, have been identified for the first time in Riesling wine. The structures of two additional phenylpropanoids were elucidated as 3-hydroxy-1-(4-hydroxy-3-methoxyphenyl)-propan-1-one and 2,3-dihydroxy-1-(4-hydroxy-3-methoxyphenyl)-propan-1-one. Moreover, two ethyl esters, i.e., ethyl protocatechuate and ethyl gallate, as well as the glucose ester of vanillic acid, were newly detected in Riesling wine. Novel representatives in the flavonoid group were dihydrokaempferol, dihydroquercetin, and four dihydroflavonol glycoconjugates, i.e., the 3-O-glucosides of dihydrokaempferol and dihydroquercetin, as well as the 3-O-xyloside and the 3'-O-glucoside of dihydroquercetin. Additionally, six novel lignans, i.e., lariciresinol 4-O-glucoside, three isolariciresinol derivatives, and two secoisolariciresinols, as well as three neolignans were isolated. Structural elucidation of the newly isolated wine constituents is reported together with the determination of their antioxidant activity.

Fecal lignan and isoflavonoid excretion in premenopausal women consuming flaxseed powder.

Lignans and isoflavonoids are diphenolic compounds found in plant foods, particularly whole grains and legumes. They have been shown to have anticarcinogenic properties in animal and cell studies, and have been associated with reduced cancer risk in epidemiological studies. In order to perform further epidemiological and metabolic studies on these compounds, it is necessary to be able to monitor concentrations in biological samples. In this study, we examined the effects of consumption of flaxseed, a concentrated source of lignans, on fecal lignan excretion and evaluated the effect of high lignan consumption on fecal excretion of isoflavonoids. Thirteen women were studied for two diet periods of three menstrual cycles each in a cross-over design. During the control period, they consumed their usual diets; during the treatment period they consumed their usual diets supplemented with 10 g/day ground flaxseed. Feces were collected on days 7-11 of the last menstrual cycle in each diet period. Five-day fecal composites were analyzed for lignans and isoflavonoids by isotope dilution gas chromatography-mass spectrometry. Fecal excretion of the lignans enterodiol, enterolactone, and matairesinol increased significantly with flax consumption, from 80.0 +/- 80.0 (SD) to 2560 +/- 3100; 640 +/- 480 to 10,300 +/- 7580; and 7.33 +/- 10.0 to 11.9 +/- 8.06 nmol/day, respectively. There were no differences in fecal excretion of the isoflavonoids, daidzein, equol, genistein, and O-demethylangolensin.