Dirceu Martins

Seasonal variation and antimicrobial activity of Myrcia myrtifolia essential oils

This work reports the seasonal variation of the composition of leaf volatile oils and the composition of volatile oils from flowers and fruits of Myrcia myrtifolia DC harvested in the sand dunes of Salvador, Bahia, northeastern region of Brazil between 2002 and 2003. The oils were analyzed by GC-FID and GC-MS so that 28 components were identified. a-Pinene was predominant in a range from 61.5 to 90.9% in all samples analyzed. The leaf oil collected in October 2002 had their antimicrobial properties tested against six bacteria, two yeasts and five filamentous fungi being active against Staphylococcus aureus, methicilin-resistant Staphylococcus aureus, Candida albicans, Cryptococcus neoformans and Aspergillus fumigatus, and showed strongest activity against Microsporum canis and Trichophyton rubrum. The oil displayed moderate toxicity against Artemia salina showing a LC50 of 479.16 µg mL-1.

A sesquiterpene dimer from Xylopia aromatica

Abstract A new guaiane dimer has been isolated from the leaves of Xylopia aromatica. The natural product, whose IUPAC name is [11α,12β,13α,21β]-7-hydroxy-16-oxo-17-isopropylidene-1α,5,5,9β,14α,20-hexamethyl-6- oxaheptacyclo[10.9.1.02,10.04,7.012,21.013,19]docosa-2(10),3,19-triene, seems to have been formed by cycloaddition of two cyclopentadiene precursors, and contains an unusual hemiacetal oxetane ring. The structure was elucidated mainly by 1D and 2D NMR techniques; NOESY spectra were instrumental in the determination of stereochemistry.

Variação sazonal da composição do óleo essencial de Myrcia salzmannii Berg. (Myrtaceae)

This work report the seasonal variation of composition of the volatile oils from leaves and from flowers of Myrcia salzmannii harvested in the sand dunes of Salvador, Bahia, northeastern region of Brazil in the years 2001 and 2003. The oils were analyzed by GC-FID and GC-MS being identified 49 components. Nine essential oil samples of leaves collected on different months and years and one sample of flowers were analyzed. β-Caryophyllene and α-humulene were the only compounds present in all of the samples being the first the majority compound.

Labdane dimers from Xylopia aromatica

From the stem bark of Xylopia aromatica (Annonaceae), have been isolated two new labdane dimers as their methyl esters, together with the known compounds ent-labda-8(17),13(16),14-trien-18-oic acid, sitosterol and stigmasterol. The structures of the dimers were elucidated on the basis of detailed spectroscopic analyses.

Identificação de componentes de óleos voláteis: Análise espectroscópica de misturas de sesquiterpenos

This paper describes a chromatographic method to fractionate volatile oils and to identify their sesquiterpenic constituents. The fractionation process includes flash chromatography over silica gel and chromatography over silica gel/AgNO3, utilising pentane, CH2Cl2 and/or acetone as eluents. GC chromatograms were obtained in order to get the relative percentage of each constituent in the volatile oils, to get the retention time value of them as well as to analyse and combine the fractions eluted from the columns. Such procedure afford mixtures of sesquiterpenes which are analysed by GC/MS, 13C and 1H NMR.

Antibacterial Activity of the Alkaloid-Enriched Extract from Prosopis juliflora Pods and Its Influence on in Vitro Ruminal Digestion

The purpose of this study was to assess the in vitro antimicrobial activity of alkaloid-enriched extracts from Prosopis juliflora (Fabaceae) pods in order to evaluate them as feed additives for ruminants. As only the basic chloroformic extract (BCE), whose main constituents were juliprosopine (juliflorine), prosoflorine and juliprosine, showed Gram-positive antibacterial activity against Micrococcus luteus (MIC = 25 μg/mL), Staphylococcus aureus (MIC = 50 μg/mL) and Streptococcus mutans (MIC = 50 μg/mL), its influence on ruminal digestion was evaluated using a semi-automated in vitro gas production technique, with monensin as the positive control. Results showed that BCE has decreased gas production as efficiently as monensin after 36 h of fermentation, revealing its positive influence on gas production during ruminal digestion. Since P. juliflora is a very affordable plant, this study points out this alkaloid enriched extract from the pods of Prosopis juliflora as a potential feed additive to decrease gas production during ruminal digestion.

A new biphenyl and antimicrobial activity of extracts and compounds from Clusia burlemarxii

Phytochemical investigation on Clusia burlemarxii (Clusiaceae) led to isolation and identification of nine compounds. Were isolated from leaves 3-O-α-L- rhamnopyranosylquercetin, 3-O-α-L-rhamnopyranosylkaempferol, 4-hydroxy-5,5-dimethyldihydrofuran-2-one, 2Z-δ-tocotrienoloic acid and friedelin and were isolated from trunk betulinic acid, protocatechuic acid, lyoniresinol, and a new biphenyl 2,2-dimethyl-3,5-dihydroxy-7-(4-hydroxyphenyl)chromane. The structures were determined by ¹H, ¹³C-NMR, DEPT, HMBC, HMQC, HRESIMS. The Minimal Inhibitory Concentration against Streptococcus mutans, Staphylococcus aureus, Bacillus subtilis, Micrococcus luteus, Escherichia coli, Salmonella choleraesuis, Pseudomonas aeruginosa, Aspergillus niger and Cladosporium cladosporioides was also determined. Extracts and compounds showed significant activity against tested Gram-positive bacteria, none activity against tested Gram-negative bacteria and fungi.

Xantonas, triterpenos e atividade antibacteriana do extrato em diclorometano de Kielmeyera cuspidata Saddi, Clusiaceae

From the dichloromethane extract of trunk of Kielmeyera cuspidata five xanthones were isolated, 1,6-dihydroxy-3,5-dimethoxyxanthone, 2-hydroxy-1-methoxyxanthone, 2,3-methylenedioxyxanthone, 4-hydroxy-2,3-methylenedioxyxanthone and 3-hydroxy-2,4-dimethoxyxanthone and two triterpenes α-amirin and β-amirin. The extract displayed toxicity against Artemia salina and exhibited antibacterial activity against Micrococcus luteus, Bacillus subitilis, Staphylococcus aureus and Streptococcus mutans and it was not active against Escherichia coli, Pseudomonas aeruginosa and Salmonela choleraesuis.

Preliminary studies on the volatile constitution of Mikania species

Volatile oils obtained from the aerial parts of three Mikania species plants were analyzed by GC-MS and NMR. Forty-six terpenes among monoterpenes, sesquiterpenes and diterpenes were identified by this methodology. The analysis classified Mikania hookriana as diterpene producer as the majority Mikania species occurring in Brazil.

Modes of Action of Arjunolic Acid and Derivatives on Trypanosoma cruzi Cells

Chagas disease causes considerable morbimortality in the Americas, with circa 7 to 8 million infected people, causing at least 12,000 annual deaths and 100 million people at risk. Its chemotherapy is poorly selective and effective, associated to severe side effects and unresponsive cases. Thus, R&D on therapeutic alternatives is undoubtedly required. The Brazilian poorly studied biodiversity offers uncountable bioagents, which may be exploited for chemotherapy. The triterpene arjunolic acid (AA), reduced the Trypanosoma cruzi epimastigote in vitro proliferation with an apparent IC₅₀ of 171 µM. Electron microscopy analysis revealed remarkable effects on the parasite surface and architecture. AA-treated parasites displayed minutely corrugated plasma membranes devoid of subpellicular microtubules as well as biogenesis of multiple basal bodies. As the AA effects appeared mainly restricted or originated at the parasite peripheral cytoplasm, including the cytoskeleton membrane linkage, we inferred that the compound targeted primarily the lipid bilayer; therefore, we performed synthetic modification to increase the molecule lipophilicity and thus membrane permeability. The methyl ester (MeAA) and tri-acetylated derivatives (3AcAA) had potentiated trypanocidal activity, producing IC₅₀ values of 21.9 and 15.8 µM, respectively. Both derivatives were able to produce remarkable ultrastructural alterations in the parasites, including inner compartments such as Golgi apparatus and the endocytic/autophagic pathway. Parasites cultured with both derivatives displayed numerous and large autophagic vacuoles, altered flagellar length and cell body connection. These data indicate that synthetically-modified natural products comprise valuable tools in antiparasitic chemotherapy and that electron microscopy may be useful not only in determining the mechanisms of action but also in directing such modifications for rational drug design.