Separation and NMR studies on lignans of Raulinoa echinata

Bromination of eudesmin isolated from araucaria araucana induces epimerization and give bromine derivatives with loss of anti-Candida activity

Furofuran lignanes show important biological activities for the treatment of infectious diseases, inflammatory and metabolic pathologies. They have been isolated from leaves and barks of many plants. In Chile the native conifer Araucaria araucana produces eudesmin, matairesinol, secoisolariciresinol and lariciresinol in stemwood, branchwood and knotwood. These compounds were previously isolated by laborious flash chromatography on silica gel. Here we report the easy isolation of eudesmin by soxhlet extraction from milled knots of Araucaria araucana with hexane, followed by cryo-crystallization at -20 °C. Upon bromination of the isolated eudesmin epimerization at one benzylic position occurs, giving epieudesmin and the corresponding mono and di-brominated derivatives. The structures were determined by 1D, 2D NMR and X-ray diffraction. The analysis of products against Candida yeast showed that eudesmin has a moderate activity against different strains of Candida from 62.5 to 500 µg/mL. This activity decreases for epieudesmin, while bromine derivatives are not active.

Larvicidal activity of lignans and alkaloid identified in Zanthoxylum piperitum bark toward insecticide-susceptible and wild Culex pipiens pallens and Aedes aegypti

BACKGROUND

The yellow fever mosquito, Aedes aegypti, and the common house mosquito, Culex pipiens pallens, transmit dengue fever and West Nile virus diseases, respectively. This study was conducted to determine the toxicity of the three lignans (-)-asarinin, sesamin and (+)-xanthoxylol-γ,γ-dimethylallylether (XDA), and the alkaloid pellitorine from Zanthoxylum piperitum (Rutaceae) bark to third-instar larvae from insecticide-susceptible C. pipiens pallens and Ae. aegypti as well as wild C. pipiens pallens resistant to deltamethrin, cyfluthrin, fenthion, and temephos.

METHODS

The toxicities of all isolates were compared with those of mosquito larvicide temephos. LC50 values for each species and their treatments were significantly different from one another when their 95% confidence intervals did not overlap.

RESULTS

XDA was isolated from Z. piperitum as a new larvicidal principle. XDA (LC50, 0.27 and 0.24 mg/l) was 4, 53, and 144 times and 4, 100, and 117 times more toxic than pellitorine, sesamin, and asarinin toward larvae from susceptible C. pipiens pallens and Ae. aegypti, respectively. Overall, all the isolates were less toxic than temephos (LC50, 0.006 and 0.009 mg/l). These constituents did not differ in toxicity to larvae from the two Culex strains. The present finding indicates that the lignans and alkaloid and the insecticides do not share a common mode of larvicidal action or elicit cross-resistance.

CONCLUSION

Naturally occurring Z. piperitum bark-derived compounds, particularly XDA, merit further study as potential mosquito larval control agents or as lead compounds for the control of insecticide-resistant mosquito populations.

A New Lignan from the Leaves of Zanthoxylum armatum

A new furofuran lignan, zanthonin (1) together with 13 known compounds including seven furofuran lignans (2–8), one isobutyl amide (9), a furanocoumarin (10) and four flavonoids (11–14) have been isolated from the leaves of Zanthoxylum armatum. The chemical structures of these compounds were elucidated mainly on the basis of NMR (1D and 2D) and MS data. This is the first report on the isolation of methylxanthoxylol (4) from Z. armatum.

Fargesin, a component of Flos Magnoliae, stimulates glucose uptake in L6 myotubes

Flos Magnoliae (FM) is a commonly used Chinese medicinal herb for symptomatic relief of allergic rhinitis, sinusitis and headache. Although several FM species have been used as substitutes or adulterants for clinical use, possible differences in their pharmacological actions have not been reported. To confirm the effects of FM on skeletal muscle glucose metabolism, we tested the effects of several compounds isolated from FM on glucose uptake by L6 myotubes. We found that fargesin, a component of FM, dose-dependently stimulated glucose consumption in L6 myotubes, which was accompanied by enhanced glucose transporter (GLUT)-4 translocation to the cell surface. Fargesin-stimulated glucose uptake was blocked by wortmannin, a phosphatidylinositol-3 kinase (PI3 K) inhibitor. Fargesin stimulated Akt phosphorylation, a key component in the insulin signaling pathway, which was completely inhibited by wortmannin. Here, we demonstrated that fargesin, a bioactive component of Flos Magnoliae, increases basal glucose uptake and GLUT4 translocation in L6 myotubes by activating the PI3 K-Akt pathway.

Suppression of inducible nitric oxide synthase expression by furfuran lignans from flower buds of Magnolia fargesii in BV-2 microglial cells

Activated microglia produces diverse neurotoxic factors such as nitric oxide (NO) and tumor necrosis factor-alpha that serve as apoptotic inducers resulting in various neurodegenerative diseases. The inhibition of microglia-derived NO production by inducible nitric oxide synthase (iNOS) has been reported to be beneficial in retarding neurodegenerative disorders. Three active lignans have been isolated from the flower buds of Magnolia fargesii by the bioassay-guided fractionation using lipopolysaccharide (LPS)-activated BV-2 microglial cell culture system. The structures of them were identified as kobusin (1), aschantin (2) and fargesin (3) by the analyses of spectroscopic data. They inhibited the production of NO by activated microglia. Their IC(50) values were 21.8 +/- 3.7, 14.8 +/- 2.5 and 10.4 +/- 2.8 microg/mL, respectively. They suppressed LPS-induced NF-kappaB activation and the expression of iNOS protein and mRNA. Furthermore, they showed scavenging activity of neurotoxic peroxynitrite that can be produced by NO and superoxide anion. These results imply that lignans from Magnolia fargesii might be beneficial for the treatment of neuro-inflammatory diseases through the inhibition of iNOS expression and peroxynitrite scavenging potential.

The lignan eudesmin extracted from Piper truncatum induced vascular relaxation via activation of endothelial histamine H1 receptors

In Brazilian folk medicine, extracts from Piper species are used to reduce blood pressure. Previously, we demonstrated the vasodilatory activity of crude extracts from leaves of Piper truncatum explaining their possible use in the treatment of hypertension in traditional medicine. In the present study, we investigated the effects of eudesmin, a lignan isolated from hexane extract of leaves from Piper truncatum, on the contractility of rat aortas and the possible mechanisms involved in its vascular action. Eudesmin induced an intense concentration-dependent relaxation of aortic rings precontracted with phenylephrine. The concentration of eudesmin necessary to reduce phenylephrine-induced aortic contraction by 50% (IC(50)) was 10.69+/-0.67 microg/ml. Eudesmin-induced vasodilation required an intact endothelium since vascular relaxation was inhibited by mechanic removal of endothelium, and by pretreatment with nitric oxide synthase inhibitor and soluble guanylate cyclase inhibitor. Relaxation induced by eudesmin was also impaired in the presence of indomethacin and diphenhydramine, a cyclooxygenase inhibitor and an antagonist of type 1 histamine receptor (H(1)), respectively. IC(50) was increased to 18.1+/-1.8 and 18.1+/-2.6 microg/ml (P<0.05; n=6) after exposure to indomethacin and diphenhydramine, respectively. Atropine (muscarinic receptor antagonist), propranolol (beta-adrenoceptor antagonist) and glibenclamide (ATP-sensitive K(+) channel blocker) did not alter the effect of eudesmin. These results indicate that eudesmin-induced vascular relaxation in rat aorta is mediated by release of nitric oxide and prostanoid through the involvement of histamine receptor present in the endothelial cells.

Evaluation of insecticidal activity of diterpenes and lignans from Aristolochia malmeana against Anticarsia gemmatalis

The insecticidal activity of hexane extracts from the roots and leaves of Aristolochia malmeana was evaluated against Anticarsia gemmatalis larvae by topical application. Extract from the roots was the most active and caused 50% mortality in larvae at 308.4 microg/microL. From this extract, a clerodane diterpene, (-)-kolavenic acid, and three lignans, (-)-kusunokinin, (-)-hinokinin, and (8 S,8' R,9 S)-cubebin, were isolated by chromatography and partition procedures and then evaluated for their insecticidal activities either individually or in pairs. (-)-Kusunokinin showed higher activity against A. gemmatalis (LD10=9.3, LD50=230.1 microg/microL) than the crude extract, and its activity was dose-dependent, whereas the other constituents did not exhibit any significant activity. Together with (-)-kusunokinin and (-)-hinokinin, (-)-copalic acid, (-)-2-oxokolavenic acid, (-)- ent-6-beta-hydroxy-copalic acid, (8 R,8' R,9 R)- and (8 R,8' R,9 S)-cubebins, (-)-fargesin, and (-)-phillygenin were isolated from the hexane extract of the leaves. The compounds were identified on the basis of spectroscopic analysis.

A new lignan glycoside from the stem bark of styrax japonica s. et Z

A new lignan glycoside was isolated from the stem bark of Styrax japonica (Styracaceae). This lignan glycoside, named styraxjaponoside C (1), was identified by spectroscopic methods. In addition, six known compounds, arctiin (2), pinoresinol-4-O-beta-D-glucopyranoside (3), matairesinoside (4), methylsyringin (5), syringin (6), and egonol (7) were isolated from this plant. The structures of 1-7 were determined on the basis of spectroscopic and physicochemical data. Compounds 2 and 5 were isolated from this plant for the first time.

Calmodulin inhibitors from Leucophyllum ambiguum

Activity-directed fractionation of a CH(2)Cl(2)-MeOH (1:1) extract of Leucophyllum ambiguum led to the isolation of two new lignans designated with the trivial names of 2'-methoxykobusin (1) and 2'-methoxy-4' '-hydroxydemethoxykobusin (2). In addition, the known compounds kobusin (3), 2',2' '-dimethoxysesamin (4), trans-cinnamic acid, apigenin, and apigetrin were obtained. The identification of the novel analogues 1 and 2 was accomplished by spectral methods. The structure of 1 was unequivocally confirmed by X-ray analysis. Compounds 1-4 interacted with bovine-brain calmodulin and inhibited the activation of the calmodulin-dependent enzyme cAMP phosphodiesterase.

Triterpenoid constituents of Raulinoa echinata

A phytochemical investigation of the stems of the South Brazilian endemic species Raulinoa echinata has led to the isolation of two new methoxylated protolimonoid epimers (1 and 2) together with the known melianone and melianodiol. The leaves afforded three glabretal-type triterpene derivatives esterified by N-methylanthranilic acid (3-5). Compounds 1 and 2 displayed weak inhibitory activity when assayed in vitro against trypomastigote forms of Trypanosoma cruzi. Compounds 1-5 were inactive in a brine shrimp (Artemia salina) lethality test.