Lauro Euclides Soares Barata

13C NMR spectral analysis of lignans from Araucaria angustifolia

Abstract Pinoresinol dimethyl ether, secoisolariciresinol, lariciresinol, isolariciresinol and isolariciresinol-4′-methyl ether were isolated from the knots of dead trees of Araucaria angustifolia . The 13 C NMR spectra of these compounds, their methyl and acetyl derivatives, and the corresponding one of matairesinol, have been recorded and the signals assigned. On the basis of these assignments, the structure of the new monomethyl ether of isolariciresinol has been established.

Neolignans of Virola surinamensis

Abstract Elemicin, galbacin, veraguensin and two new neolignans, surinamensin and virolin, were isolated and characterized from the leaves of Virola surinamensis.

Pyrrolizidine alkaloids in the arctiid mothHyalurga syma.

The arctiid mothHyalurga syma (subfamily Pericopinae) sequesters pyrrolizidine alkaloids (PAs) from its larval food plantHeliotropium transalpinum (Boraginaceae). Colorimetric quantification of total PAs in the larvae, pupae, and adults ofHyalurga revealed mean values of about 286–445μg per individual (1.4–2.6% of dry weight). The PA mixtures found in the moth and its larval food plant were evaluated by GC-MS. Food-piant leaves were found to contain the diastereoisomeric retronecine esters indicine (IIIa), intermedine (IIIb), and lycopsamine (IIIc), and the heliotridine ester rinderine (IIId) only as minor constituents, whereas 3′-acetylrinderine (IVc) (68% of total PAs) and the respective 3′-acetyl esters of indicine (IVa) and intermedine (IVb) (both 17%) were the major alkaloids. Supinine (IIa) is detectable in traces only. The PA mixtures in eggs, larvae, pupae, and imagines ofHyalurga were identical: indicine, intermedine, and lycopsamine accompanied by considerable amounts of supinine and amabiline or coromandalinine (IIb/IIc) were the major components. Only larvae were found to store small quantities of a 3′-acetyl derivative. Rinderine and its 3′-acetyl ester were never found in the insects. Low concentrations of the arctiidspecific PA callimorphine (I) were present in larvae, pupae, and imagines. The differences in the PA patterns of the insects and their larval food plant suggest thatHyalurga is capable of modifying plant-derived PAs by inversion of the 7-OH configuration (conversion of the necine base heliotridine into retronecine), and perhaps the inversion of the 3′-OH [conversion of (+)-trachelanthic acid into (−)-viridifloric acid], although the possibility of a selective sequestration of the respective retronecine esters cannot be excluded. Some trials with the orb-weaving spiderNephila clavipes, a common neotropical predator, showed that both freshly emerged and field-caught adults ofHyalurga syma are liberated unharmed by the spider. The liberation could be related to the presence of PAs in the moths.

Cytotoxic withanolides from Acnistus arborescens.

Three cytotoxic withanolides, two with new structures, were isolated from the leaves of Acnistus arborescens and their structures determined by a combination of 1D and 2D NMR, mass spectral, and molecular modeling studies. Dereplication analysis of the ethyl ether extract was useful for evaluating the components showing significant cytotoxic activity.

Qualitative patterns of pyrrolizidine alkaloids in ithomiinae butterflies

Abstract Pynolizidine alkaloids (PAs) were analysed in 40 species (38 genera, all 14 tribes) of the butterfly subfamily Ithomiinae. The principal PAs found were the epimers lycopsamine and intermedine. These results suggest that ithomiines visit mainly PA sources containing moncester lycopsamine-type PAs, and transform various other diastereoisomers into lycopsamine and intermedine, with the 7 R configuration. Other PA-types found in butterflies are probably related to the availability of PA sources. Unknown PAs ([M] + 297), that resemble the arctiid insect-PA callimorphine, were found in small amounts in 10 species.

Stereochemical inversion of pyrrolizidine alkaloids byMechanitis polymnia (Lepidoptera: Nymphalidae: Ithomiinae): Specificity and evolutionary significance

Pyrrolizidine alkaloids (PAs), acquired by adults or larvae of Danainae and Ithomiinae butterflies and Arctiidae moths from plants, protect these lepidopterans against predators and are biosynthetic precursors of male sex pheromones. The investigation of PAs in many species of wild-caught adults of Ithomiinae showed lycopsamine (1) [(7R)-OH, (2′S)-OH, (3′S)-OH] as the main alkaloid. In incorporation experiments, PA-free (freshly emerged) adults of the ithomiineMechanitis polymnia were fed seven PAs: lycopsamine and four of its known natural stereoisomers—indicine (2) [(7R)-OH, (2′R)-OH, (3′S)-OH], intermedine (3) [(7R)-OH, (2′S)-OH, (3′R)-OH], rinderine (4) [(7S)-OH, (2′S)-OH, (3′R)-OH], and echinatine (5) [(7S)-OH, (2′S)-OH, (3′S)-OH], and two PAs without the 7-OH: supinine (6) [(2′S)-OH, (3′R)-OH] and amabiline (7) [(2′S)-OH, (3′S)-OH]. Males epimerized PAs 3, 4, and 5 mainly to lycopsamine (1). Females fed these same three PAs changed a smaller proportion to lycopsamine; their lesser capacity to modify PAs corresponds to their normal acquisition of already transformed PAs from males during mating rather than through visits of adults to plant sources of PAs. The alkaloids1 and2, both 7R and 3′S, were incorporated without or with minimum change by males and females. Feeding experiments with6 and7 (males only) showed an inversion at the 3′ center of6 and no change in7. The inversion from 7S to 7R (probably via oxyreduction) may be closely related to the evolution of acquisition of PAs by butterflies and moths. Two hypotheses are discussed: (1) The ancestral butterflies are probably adapted to tolerate, assimilate, and use (7R)-PAs (most common in plants; all widespread 1,2-unsaturated macrocyclic PA diesters show this configuration). The development of (7R)-PA receptors in the butterflies could lead to a specialization on this configuration in two ways: to help find PA plants and to utilize these components in sexual chemical communication. A later appearance of (7S)-PAs in plants could have selected an enzymatic system for the inversion of this chiral center in order to continue producing (7R)-PA-derived pheromones. (2) The inversion would be due to the evolution of a enzyme system specialized in the transport of (7R)-PAs to the integument; the failure of this system to carry (7S)-PAs led to an enzymatic system to invert them to transportable (7R)-PAs. In this case, the 7R configuration is an effect and not a cause of (7R)-PA-derived pheromones. In both hypotheses, the partial inversion of the 3′-asymmetric center, when the butterfly was fed intermedine (3), rinderine (4), and supinine (6), could be fortuitous due to the conformation of the molecule and/or the enzymatic system.

Classification of Amazonian rosewood essential oil by Raman spectroscopy and PLS-DA with reliability estimation

The Amazon tree Aniba rosaeodora Ducke (rosewood) provides an essential oil valuable for the perfume industry, but after decades of predatory extraction it is at risk of extinction. The extraction of the essential oil from wood implies the cutting of the tree, and then the study of oil extracted from the leaves is important as a sustainable alternative. The goal of this study was to test the applicability of Raman spectroscopy and Partial Least Square Discriminant Analysis (PLS-DA) as means to classify the essential oil extracted from different parties (wood, leaves and branches) of the Brazilian tree A. rosaeodora. For the development of classification models, the Raman spectra were split into two sets: training and test. The value of the limit that separates the classes was calculated based on the distribution of samples of training. This value was calculated in a manner that the classes are divided with a lower probability of incorrect classification for future estimates. The best model presented sensitivity and specificity of 100%, predictive accuracy and efficiency of 100%. These results give an overall vision of the behavior of the model, but do not give information about individual samples; in this case, the confidence interval for each sample of classification was also calculated using the resampling bootstrap technique. The methodology developed have the potential to be an alternative for standard procedures used for oil analysis and it can be employed as screening method, since it is fast, non-destructive and robust.

Chemical composition and antimicrobial activity of the essential oil of Lippia grandis Schauer (Verbenaceae) from the western Amazon.

Lippia grandis Schauer is an aromatic plant that has been used as a spice in Brazilian culinary and in traditional medicine to treat liver disease, disorders of the stomach and throat infections. We determined the chemical composition of the essential oil of L. grandis and evaluated its potential for the treatment of clinically-important pathogenic micro-organisms. The essential oil was obtained by hydrodistillation and analyzed by gas chromatography-mass spectrometry (GC-MS), giving carvacrol (37.12%), ρ-cymene (11.64%), and thymol (7.83%) as the main components. The agar disk diffusion method of the essential oil was effective against 75% of the micro-organisms analyzed, in particular, Staphylococcus aureus, Enterococcus faecalis, and Escherichia coli. The minimum inhibitory concentration was 0.57 mg/ml for E. faecalis and 1.15 mg/ml for all the other strains. The results indicate that the essential oil of L. grandis contains chemical compounds with good potential for the treatment of infections.

Rosewood Exploitation in the Brazilian Amazon: Options for Sustainable Production

The authors report on ongoing work in the Brazilian Amazon to assess the current and prospective management of rosewood (Aniba rosaeodora Ducke) populations threatened by a half-century of predatory extraction for the valuable essential oil linalool used widely in perfumery. The report synthesizes prior research on rosewood exploitation and markets and recent research to develop new essential oil products derived from rosewood leaves and stems. The study suggests alternative rosewood production systems, to guide investment in management and certification of sustainable rosewood oil supplies.RésuméOs autores relatam estudos passados e atualmente em curso referente ao manejo de populações de Pau-rosa (Aniba rosaeodora Ducke) ameaçadas por meio-século de extração predatória para a produção de óleo essencial, rico em linalol, extensivamente usado em perfumaria. O trabalho sintetiza os resultados de pesquisas sobre a exploração e mercados do Pau-rosa, fundamentada em entrevistas feitas com representantes governamentais, cientistas locais, comerciantes e produtores de Pau-rosa. O estudo sugere alternativas para a organização de um sistema sustentável de prodção de Pau-rosa que conduzam ao investimento, manejo e certificação de fontes sustentáveis de óleo essencial de Pau-rosa.

Isolation of chavibetol from essential oil of Pimenta pseudocaryophyllus leaf by high-speed counter-current chromatography

Counter-current chromatography (CCC) was used to isolate chavibetol from the essential oil of leaves of Pimenta pseudocaryophyllus (Gomes) Landrum. Chavibetol was obtained in high purity (98%) and mass recovery (94.4%). Methyleugenol was also isolated. The CCC biphasic solvent system used was composed of hexane:n-butanol:methanol:water (12:4:4:3, v/v/v/v).