A chromene and prenylated benzoic acid from Piper aduncum

In addition to nerolidol, 2',6'-dihydroxy-4'-methoxydihydrochalcone, methyl 2,2-dimethyl-8-(3'-methyl-2'-butenyl)-2H-1-chromene-6-carboxylate, methyl 2,2-dimethyl-2H-1-chromene-6-carboxylate and methyl 8-hydroxy-2,2-dimethyl-2H-1-chromene-6-carboxylate, two new natural products were isolated from the leaves of Piper aduncum, 2,2-dimethyl-2H-1-chromene-6-carboxylic acid and 3-(3',7'-dimethyl-2',6 '-octadienyl)-4-methoxybenzoic acid. The structures of the isolates were established based on analysis of spectroscopic data, including ES-MS. The DNA-damaging activity of the isolated compounds was also investigated against mutant strains of Saccharomyces cerevisiae. (C) 1999 Elsevier B.V. Ltd. All rights reserved.

Further bioactive piperidine alkaloids from the flowers and green fruits of Cassia spectabilis

The flowers of Cassia spectabilis yielded three new piperidine alkaloids, (-)-3-O-acetylspectaline (1), (-)-7-hydroxyspectaline (2), and iso-6-spectaline (3), together with the known (-)-spectaline (4). The green fruits of this plant were also investigated, resulting in the isolation of 1 and 4. Their structures were elucidated using a combination of multidimensional NMR and MS techniques, and relative stereochemistries were established by NOESY correlations and analysis of coupling constants. The DNA-damaging activity of these compounds was evaluated using a mutant yeast, Saccharomyces cerevisiae, assay.

The absolute configuration of 1-(3 ',4 '-dihydroxycinnamoyl)cyclopentane-2,3-diol from the Amazonian tree Chimarrhis turbinata

An antioxidant, 1-(3',4'-dihydroxycinnamoyl) cyclopentane-2,3-diol [ or ( E)-2,3-dihydroxycyclopentyl-3-(3',4'-dihydroxyphenyl) acrylate ( 1)], and two known trans- and cis-chlorogenic acid methyl esters were isolated from the ethanolic extract of the leaves of Chimarrhis turbinata. The relative configuration of 1 was determined by NMR and by comparison of the circular dichroic spectrum ( CD) with those of the enantiomers of synthetic 3', 4'-dimethoxycinnamoyl analogues. The absolute configuration of one of the synthetic enantiomers was determined using the CD exciton chirality method. This established the structure of naturally occurring 1 as (E)- 2,3-dihydroxycyclopentyl- 3-(3', 4'-dihydroxyphenyl) acrylate.

Quantitative determination of maitenin and 22 beta-hydroxymaitenin in callus of Maytenus aquifolium (Celastraceae) by reverse phase high performance liquid chromatography

Explants of Maytenus aquifolium were induced to form callus and, subsequently, suspension cultures. The isolation of natural products from callus led to the identification of the cytotoxic triterpene quinonemethides, maitenin (1) and 22 beta-hydroxymaitenin (2), A rapid, sensitive and reliable reversed-phase high-performance liquid chromatography method was developed using a Cls column and isocratic elution for the determination of 1 and 2, the elaborated method gave well-resolved peaks for these compounds with good detection response and linearity in the range of 0.08-72.0 mu g. The quantification of 1 and 2 was performed by an external standard method. (C) 1998 John Wiley & Sons, Ltd.

Turbinatine, a potential key intermediate in the biosynthesis of corynanthean-type indole alkaloids

Extraction of the leaves of Chimarrhis turbinata has led to the isolation of turbinatine (1), a new corynanthean-type indole alkaloid, besides four known indole alkaloids, strictosidine, 5alpha-carboxystrictosidine, vallesiachotamine, and isovallesiachotamine. The structural determination of 1 was based on 1D and 2D spectroscopic data. An evaluation of the DNA-damaging activities of the isolates was performed by means of a bioassay using mutant strains of Saccharomyces cerevisiae, which indicated these compounds were weakly active.

Anxiolytic effects of erythrinian alkaloids from Erythrina mulungu

One new erythrinian alkaloid derivative, (+)-11 alpha-hydroxyerythravine (1), and the known (+)-erythravine (2) and (+)-alpha-hydroxyerysotrine (3) were isolated from the flowers of Erythrina mulungu. Their structures were determined by spectroscopic/spectrometric data interpretation of H-1, C-13, and 2D NMR and MS experiments. The relative configuration was established by NOESY analysis, while the conformation adopted by these molecules was evaluated through molecular modeling studies and coupling constants obtained by NMR analysis. Furthermore, the anxiolytic effects of the E. mulungu aqueous alcoholic crude extract and of the purified alkaloids were evaluated using the elevated T-maze test.

New naphthopyranone glycosides from Paepalanthus vellozioides and Paepalanthus latipes

Three new compounds-3,4-dihydro-10-hydroxy-7-methoxy-3-(R)-methyl-1H-3,4-dihydronaphtho-]2,3c]pyran-1-one-9-O-beta-D-glucopy ranoside (1), 3,4-dihydro-10-hydroxy-7-methoxy-3-(R)-methyl-1H-3,4-dihydronaphtho-[2,3c]-pyran-1-one-9-O-beta-D-glucopyranosyl-(1-->6)-glucopyranoside (2), and 3,4-dihydro-10-dihydroxy-7-methoxy-3-(R)-methyl-1H-3,4-dihydronaphtho-[2,3c]-pyran-1-one-9-O-beta-D-allopyranosyl (1-->6)-glucopyranoside (3)-were isolated from the leaves of Paepalanthus vellozioides and Paepalanthus latipes and characterized by spectrometric methods, mainly electrospray mass spectrometry and 1D and 2D NMR experiments. These unusual glycosylated dihydronaphthopyranones may serve as taxonomic markers of the genus Paepalanthus, since these compounds were not detected in other genera belonging to the Eriocaulaceae family.

APPLICATIONS OF ARTIFICIAL-INTELLIGENCE IN ORGANIC-CHEMISTRY .17. NEW PROGRAMS IN THE SISTEMAT PROJECT

This work describes the new improvements of the SISTEMAT project, one system for structural elucidation mainly in the field of Natural Products Chemistry. Some examples of the resolution of problems using C-13 Nuclear Magnetic Resonance and Mass Spectroscopy are given. Programs to discover new heuristic rules for structure generation are discussed. The data base contains about 10000 C-13 NMR spectra.

Determination of absolute configuration of 1,3-diols by the modified Mosher's method using their di-MTPA esters

1,3-Diols are frequently involved in biologically important compounds and, therefore, determination of the stereochemistry of these structural elements, in particular those in acyclic systems, has been one of the focuses of attention in natural products chemistry. The modified Mosher's method, commonly used for the determination of the absolute configuration of secondary alcohols, was applied to determine the absolute configuration of 1,3-diols with their di-MTPA esters. Several epimeric pairs of syn- and anti-1,3-diols with known absolute configurations were converted to the corresponding di-MTPA esters and the Delta delta values were then calculated. For the acyclic syn-1,3-diols, the Delta delta values were systematically arranged as predicted from the basic concept of the modified Mosher's method, demonstrating that the method is valid for these compounds. In contrast, the Delta delta values were irregularly arranged for the acyclic anti-1,3-diols and, accordingly, this method is not valid for these cases. These results are complementary to those of the previously reported CD exciton chirality method and, hence, the combined use of the modified Mosher's method and the CD exciton chirality method can determine the absolute configuration of the acyclic 1,3-diols. Also, this method is successfully applicable to cyclic 1,3-diols irrespective of their relative stereochemistry. (C) 2002 Wiley-lass, Inc.

A general survey and some taxonomic implications of diterpenes in the Asteraceae

This paper provides a general survey of the occurrence of diterpenes in the Asteraceae. Data on 4351 botanical occurrences were obtained from the literature. These were grouped by skeleton for each genus. Then, the genera were grouped by subtribes, which, in turn, were gathered in tribes, followed by subfamilies. In spite of the low number of species containing diterpenes, it was possible to describe some structural features of these compounds, i.e. The skeletal types in various taxa and the positions in some skeletons that are always oxidized or never undergo oxidation in some genera. Thus, it was verified that: in the subfamily Cichorioideae, only a few of the studied species possess diterpenes, wherein kaurane is the most frequent diterpene skeleton. In the Asteroideae, the presence of diterpenes is much greater than that in the Cichorioideae and Carduoideae. At tribal taxonomic level, for example, the Astereae produce labdanes and clerodanes; Heliantheae and Eupatorieae produce kauranes and labdanes, respectively; and Calenduleae produce pimaranes. Some taxonomic implications are presented. (c) 2005 the Linnean Society of London.

Limonoids showing selective toxicity to DNA repair-deficient yeast and other constituents of Trichilia emetica

Bioactivity-directed fractionation of the MeCOEt extract of Trichilia emetica (Meliaceae) resulted in the isolation of the limonoids nymania 1 (1), drageana 4 (3), trichilin A (4), rohituka 3 (5),and Tr-B (7) and the novel seco-A protolimonoid 8. of these, nymania 1 and Tr-B showed selective inhibitory activity toward DNA repair-deficient yeast mutants. The isolation, structure elucidation, C-13 NMR spectral assignments, and biological activities of:these compounds are reported.

Dihydrochalcones and flavonolignans from Iryanthera lancifolia

An extract from the pericarps of I. lancifolia afforded two dihydrochalcones (1 and 2) and two flavonolignans (3 and 4), with compounds 2-4 being of novel structure. The antioxidant activities of compounds 1-4 were evaluated through the measurement of malondialdehyde production, and Q(1/2) (concentration necessary far 50% inhibition of autoxidation) data were calculated. The Q(1/2) values obtained for 1-4 and the standard compounds a-tocopherol and quercetin were 6.9, 4.7, 5.5, 4.8, 12.1, and 7.6 mu g/mL, respectively.

Antifungal constituents from roots of Virola surinamensis

Chromatographic fractionation of the dichloromethane extract from roots of Virola surinamensis yielded two new natural products, 3-epi-juruenolide C and 2'-hydroxy-7,4'-dimethoxyisoflavone, as well as various known steroids, lignans, isoflavones, flavonoids and diarylpropanes. of these, alpha,2'-dihydroxy-4,3'-dimethoxydihydrochal biochanin A and 2'-hydroxy-7,4'-dimethoxyisoflavone displayed antifungal activity against Cladosporium cladosporioides at a minimum amount of 5 mu g, whereas 7-hydroxyflavanone and 7-hydroxy-4'-methoxyisoflavone exhibited an antifungal activity 10-fold higher than the positive control Nystatin. (C) 1999 Elsevier B.V. Ltd. All rights reserved.

Preparative isolation of a novel flavonoid from an infusion of Byrsonima basiloba leaves by high-speed counter-current chromatography

A method for the isolation of three compounds from the infusion of leaves of Byrsonima basiloba A. Juss. by high-speed counter-current chromatography (HSCCC) was developed. This technique led to the separation of a novel compound, quercetin 3-O-alpha-L-rhamnopyranosyl-(1 -> 3)-O-[alpha-L-rhamnopyranosyl-(1 -> 6)]-beta-D-allopyranoside, and two known compounds quercetin3-O-(X-L-rhamnopyranosyl-(1 -> 6)-beta-D-galactopyranoside and (+)-catechin in 4 h with purities of over 92%. The structures of the compounds were determined by one- and two-dimensional NMR spectroscopy and HPLC.

Indole glucoalkaloids from Chimarrhis turbinata and their evaluation as antioxidant agents and acetylcholinesterase inhibitors

As part of our study on bioactive agents from Brazilian rainforest plants, two new glucoalkaloids, 3,4-dehydro-strictosidine (1) and 3,4-dehydro-strictosidinic acid (2), were isolated from Chimarrhis turbinata, along with seven known glucoalkaloids, cordifoline (3), strictosidinic acid (4), strictosidine (5), 5alpha-carboxystrictosidine (6), turbinatine (7), desoxycordifoline (8), and harman-3-carboxylic acid (9). The structures of the new alkaloids were established on the basis of comprehensive spectral analysis, mainly 1D and 2D NMR experiments, as well as high-resolution HRESIMS. Alkaloid 3 showed strong free-radical scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) as well as pronounced antioxidant activity evidenced by redox properties measured by ElCD-HPLC. Additionally, alkaloids 1-9 were submitted to TLC screening for acetylcholinesterase inhibitors. Both 7 and 8 were shown to be moderate acetylcholinesterase inhibitors at a concentration of 0.1 and 1.0 muM, respectively. In an in vitro rat brain assay, 7 showed moderate activity (IC50 1.86 muM), compared to the standard compound, galanthamine (IC50 0.92 muM).