Perfect 1JCH-resolved HSQC: Efficient measurement of one-bond proton-carbon coupling constants along the indirect dimension.

A versatile 1JCH-resolved HSQC pulse scheme for the speedy, accurate and automated determination of one-bond proton-carbon coupling constants is reported. The implementation of a perfectBIRD element allows a straightforward measurement from the clean doublets obtained along the highly resolved F1 dimension, even for each individual 1JCHa and 1JCHb in diastereotopic HaCHb methylene groups. Real-time homodecoupling during acquisition and other alternatives to minimize accidental signal overlapping in overcrowded spectra are also discussed.

Alkaloids in bufonid toads (melanophryniscus): temporal and geographic determinants for two argentinian species.

Bufonid toads of the genus Melanophryniscus represent one of several lineages of anurans with the ability to sequester alkaloids from dietary arthropods for chemical defense. The alkaloid profile for Melanophryniscus stelzneri from a location in the province of Córdoba, Argentina, changed significantly over a 10-year period, probably indicating changes in availability of alkaloid-containing arthropods. A total of 29 alkaloids were identified in two collections of this population. Eight alkaloids were identified in M. stelzneri from another location in the province of Córdoba. The alkaloid profiles of Melanophryniscus rubriventris collected from four locations in the provinces of Salta and Jujuy, Argentina, contained 44 compounds and differed considerably between locations. Furthermore, alkaloid profiles of M. stelzneri and M. rubriventris strongly differed, probably reflecting differences in the ecosystem and hence in availability of alkaloid-containing arthropods.

Profisetinidin type tannins responsible for antioxidant activity in Copaifera reticulata.

The in vitro antioxidant and free radical scavenging properties in bark extracts of South American tree Copaifera reticulata Ducke. (Caesalpinaceae) were studied using different bioassays. Lipid peroxidation was assessed by means of the production of thiobarbituric acid reactive substances (TBARS) in rat liver homogenate. All the extracts tested were effective in this method. The highest activity was observed in the aqueous extract, showing an IC50 of 30 micrograms/ml. DNA sugar damage induced by Fe (II) salts was also used to determine the capacity of the samples to suppress hydroxyl radical-mediated degradation of DNA. Although all the extracts tested were effective in reducing oxidation of DNA, the highest activity was observed in the methanol extract, showing an IC50 of 2 micrograms/ml. Bioassay-guided fractionation of a total methanol extract monitored by luminol-enhanced chemiluminescence, together with structural elucidation using 13C NMR and FABMS, led to the identification of profisetinidin type tannins in a semi-pure fraction. The fraction containing the active compounds also reduced the production of TBARS in rat liver homogenates (IC50 = 530 micrograms/ml) and DNA damage (IC50 = 1 microgram/ml), suggesting that profisetinidins could be responsible for the free radical scavenging and antioxidant activities observed in the extracts.

Aromatase inhibition by an 11,13-dihydroderivative of a sesquiterpene lactone.

Compounds that inhibit aromatase activity are used for the treatment of breast cancer. A group of sesquiterpene lactones inhibit aromatase activity and also exert cytotoxicity through their reactive alpha-methylene-gamma-lactone group. To synthesize sesquiterpene lactones with greater specificity for aromatase inhibition and lower cytotoxicity, we chemically reduced the alpha-methylene-gamma-lactone group in the active aromatase inhibitor 10-epi-8-deoxycumambrin B (compound 1), to obtain the new compound 11betaH,13-dihydro-10-epi-8-deoxycumambrin B (compound 2). Reduction of the alpha-methylene-gamma-lactone group abrogated the cytotoxic activity of compound 1 against the JEG-3, HeLa, and COS-7 cell lines. Compound 2 had higher aromatase inhibitory activity than compound 1 (IC(50) = 2 +/- 0.5 microM versus 7 +/- 0.5 microM, K(i) = 1.5 microM versus 4.0 microM) and was a more potent type II ligand to the heme iron present in the cytochrome P450(arom) active site. Compound 2 inhibited aromatase activity in JEG-3 cells in a comparable manner to the inhibitor aminoglutethimide (AG) used clinically for the treatment of breast cancer. Additionally, compound 2 inhibited androstenedione-induced uterine hypertrophy in sexually immature mice (41% of uterine weight suppression for compound 2 versus 51% for AG). We conclude that the anti-aromatase activity of sesquiterpene lactones does not depend on the presence of the highly reactive alpha-methylene-gamma-lactone group, whereas their cytotoxicity does. These findings may facilitate the development of safer agents for breast cancer therapy.

Withanolides from Vassobia lorentzii.

Eight new withanolides were isolated from the aerial parts of Vassobia lorentzii and characterized by spectroscopic methods and with the aid of molecular modeling. The compounds were identified as (17S,20R,22R)-5beta,6beta:18,20-diepoxy-18-hydro xy-1-oxowitha-2,5, 24-trienolide (1); (17S,20R,22R)-18,20-epoxy-4beta, 18-dihydroxy-1-oxowitha-2,5,24-trienolide (2); (17S,18R,20R, 22R)-4beta-hydroxy-18,20-epoxy-18-methoxy-1-oxowitha-2,5, 24-trienolide (3); (17S,18S,20R,22R)-4beta-hydroxy-18, 20-epoxy-18-methoxy-1-oxowitha-2,5,24-trienolide (4); (17S,20R, 22R)-4beta-hydroxy-18,20-epoxy-1,18-dioxowitha-2,5,24-tri enolide (5); (17S,18R,20R,22R)-18,20-epoxy-18-methoxy-1,4-dioxowitha++ +-2,5, 24-trienolide (6); (17S,18S,20R,22R)-18,20-epoxy-18-methoxy-1, 4-dioxowitha-2,5,24-trienolide (7); and (17S,20R,22R)-5beta, 6beta-epoxy-4beta,18,20-trihydroxy-1-oxowitha-2,24-die nolide (8). Compounds 1 and 2 were obtained as epimeric mixtures at C-18.

A novel activity for a group of sesquiterpene lactones: inhibition of aromatase.

A group of eleven sesquiterpene lactones isolated from different Asteraceae species from north-western Argentina were investigated for their inhibitory action on the estrogen biosynthesis. Seven of them, of different skeleton types, were found to inhibit the aromatase enzyme activity in human placental microsomes, showing IC50 values ranging from 7 to 110 microM. The most active were the guaianolides 10-epi-8-deoxycumambrin B (compound 1), dehydroleucodin (compound 2) and ludartin (compound 3). These compounds were competitive inhibitors with an apparent Ki = 4 microM, Ki = 21 microM and Ki = 23 microM, respectively. Compounds 1 and 2 acted as type II ligands to the heme iron present in the active site of aromatase cytochrome P450 (P450arom). Besides, all of them failed to affect the cholesterol side-chain cleavage enzyme activity on human placental mitochondrias. This is the first report on the aromatase inhibitory activity of this group of natural compounds.

Lupane derivatives from Lophopetalum wallichii with farnesyl protein transferase inhibitory activity.

Chloroform-soluble extracts of the stems and of the mixed stems and stem bark of Lophopetalum wallichii were found to be inhibitory in a farnesyl protein transferase (FPTase) bioassay system. During the course of activity-guided fractionation, the known lupane-type triterpenes, ochraceolide A (1), ochraceolide B (2), betulin, and lupeol and the new lupane lactone, dihydro ochraceolide A (4), were isolated. The stereochemistry of the epoxide group of ochraceolide B (2) was determined by preparation of both epoxide isomers [2, and the new semisynthetic derivative, 20-epi-ochraceolide B (3)] from 1. The structure of 4 was established by reduction of 1 with sodium borohydride. Compounds 1 and 2 exhibited significant inhibitory activity in the FPTase assay (IC50 values of 1.0 and 0.7 microgram/mL, respectively). Lupeol was found to be weakly active (IC50 65.0 micrograms/mL) in this test system, whereas no significant inhibition was detected for betulin or compounds 3 or 4. When evaluated against a panel of human cancer cells in culture, compounds 1 and 4 were modestly cytotoxic. Compounds 2 and 3 were not active in the panel.

Aleppicatines A and B from Euphorbia aleppica.

Two new pentacyclic diterpene polyesters, aleppicatine A and B, have been isolated from the acetone extract of the whole plant of Euphorbia aleppica, in addition to five known cycloartane-type triterpenes (24-methylenecycloartanol, cyclolaudenol cycloart-25-en-3 beta-ol-24-one, cycloart-22-en-3 beta,25-diol and cycloart-25-en-3 beta,24-diol), scopoletin, kaempferol and 4-hydroxybenzoic acid and its methyl ether. The structures of the new compounds and their hydrolysis products have been extensively characterized by high-field NMR spectroscopic methods, including 2D NMR techniques.

Cytotoxicity and NMR spectral assignments of ergolide and bigelovin.

Two potent cytotoxic sesquiterpene lactones, ergolide (1) and bigelovin (2) were isolated from Inula hupehensis I. helianthus-aquatica and their structures and NMR data were assignment unambiguously by using a combination of one-and two-dimensional NMR techniques and computer modeling calculations.

Amarogentin, a naturally occurring secoiridoid glycoside and a newly recognized inhibitor of topoisomerase I from Leishmania donovani.

A MeOH extract of Swertia chirata found to inhibit the catalytic activity of topoisomerase I of Leishmania donovani was subjected to fractionation to yield three secoiridoid glycosides: amarogentin (1), amaroswerin (2), and sweroside (3). Amarogentin is a potent inhibitor of type I DNA topoisomerase from Leishmania and exerts its effect by interaction with the enzyme, preventing binary complex formation.

Cardenolides from Nierembergia aristata.

The EtOAc extract of the whole plant of the Argentinian species Nierembergia aristata showed significant cytotoxicity against eleven different cancer cell lines. In addition to several known compounds, bioassay-guided fractionation led to the isolation of three new cardenolides, 17-epi-11 alpha-hydroxy-6, 7-dehydrostrophanthidin-3-O-beta-boivinopyranoside[1],6, 7-dehydrostrophanthidin-3-O-beta-boivinopyranoside [2], and 6,7-dehydrostrophanthidin-3-O-beta-oleandropyranoside[3], of which the latter demonstrated activity against all the cell lines tested. To our knowledge, this is the first report of the isolation of cardiac glycosides from a species in the Solanaceae.

Anacardoside from the seeds of Semecarpus anacardium.

From the seeds of Semecarpus anacardium, a new phenolic glucoside, anacardoside, was isolated, and its structure and configuration were elucidated by a combination of NMR techniques as 1-O-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyloxy-3-hydro xy-5-methylbenzene.

Four diterpene esters from Euphorbia myrsinites.

The Turkish species Euphorbia myrsinites has yielded four new tetracyclic diterpene tetraesters from a cytotoxic acetone extract, in addition to the known cycloartane-type triterpenoids and betulin. The new compounds and their hydrolysis product have been extensively characterized by high field spectroscopic techniques, and were shown to be four new tetraesters of the parent alcohol, myrsinol.

Swertifrancheside, an HIV-reverse transcriptase inhibitor and the first flavone-xanthone dimer, from Swertia franchetiana.

The first flavone-xanthone C-glucoside, swertifrancheside, was isolated from Swertia franchetiana, and its structure was elucidated on the basis of spectroscopic analysis as 1,5,8-trihydroxy-3-methoxy-7-(5',7',3'',4''- tetrahydroxy-6'-C-beta-D-glucopyranosyl-4'-oxy-8'-flavyl)-xanthone . This compound was a moderately potent inhibitor of HIV reverse transcriptase.