Optimizing the synthesis of dimeric peptides: influence of the reaction medium and effects that modulate kinetics and reaction yield.

Peptides are remarkably interesting alternatives to several applications. In particular, antimicrobial sequences have raised major interest of the scientific community due to the resistance acquired by commonly used antibiotics. Amongst these, some dimeric peptides have shown very promising characteristics as strong biological activities and resistance against degradation by peptidases. However, despite such promising characteristics, a relatively small number of studies address dimeric peptides, mainly due to the synthesis-related obstacles in their production, whereas the well-implemented routines of solid phase peptide synthesis-which includes the possibility of automation-makes life significantly easier. Here, we present kinetic investigations of the dimerization of a cysteine-containing sequence to obtain the homodimeric antimicrobial peptide homotarsinin. Based on the structural and membrane interaction data already available for the dimer and its monomeric chain, we have proposed distinct dimerization protocols in selected environments, namely, aqueous buffer, TFE:H2O and micellar solutions. The experimental results were adjusted by a theoretical model. Both the kinetic profiles and the reaction yields are dependent on the reaction medium, clearly indicating that aggregation, peptide structure, and peptide-membrane interactions play major roles in the formation of the disulfide bond. Finally, the rationalization of the different aspects addressed here is expected to contribute to research and applications that demand the obtainment of dimeric peptides.

Epimers l- and d-Phenylseptin: How the relative stereochemistry affects the peptide-membrane interactions.

In recent decades, several epimers of peptides containing d-amino acids have been identified in antimicrobial sequences, a feature which has been associated with post-translational modification. Generally, d-isomers present similar or inferior antimicrobial activity, only surpassing their epimers in resistance to peptidases. The naturally occurring l-Phenylseptin (l-Phes) and d-Phenylseptin (d-Phes) peptides (FFFDTLKNLAGKVIGALT-nh2) were reported with d-epimer showing higher activity against Staphylococcus aureus and Xanthomonas axonopodis in comparison with the l-epimer. In this study, we combine structural (CD, solution NMR), orientational (solid-state NMR) and biophysical (ITC, DSC and DLS) studies to understand the role of the d-phenylalanine in the increase of the antimicrobial activity. Although both peptides are structurally similar in the helical region ranging from D4 to the C-terminus, significant structural differences were observed near the peptides' N-termini (which encompasses the FFF motif). Specific aromatic interactions involving the phenylalanine side chains of d-Phes is responsible to maintaining the F1-F3 residues on the hydrophobic face of the peptide, increasing its amphipathicity when compared to the l-epimer. The higher capability of d-Phes to exert an efficient anchoring in the hydrophobic core of the phospholipid bilayer indicates a pivotal role of the N-terminus in enhancing the interaction between the d-peptide and the membrane interface in relation to its epimer.

NMR structures in different membrane environments of three ocellatin peptides isolated from Leptodactylus labyrinthicus.

The peptides ocellatin-LB1, -LB2 and -F1 have previously been isolated from anurans of the Leptodactylus genus and the sequences are identical from residue 1-22, which correspond to ocellatin-LB1 sequence (GVVDILKGAAKDIAGHLASKVM-NH2), whereas ocellatin-LB2 carries an extra N and ocellatin-F1 extra NKL residues at their C-termini. These peptides showed different spectra of activities and biophysical investigations indicated a direct correlation between membrane-disruptive properties and antimicrobial activities, i.e. ocellatin-F1 > ocellatin-LB1 > ocellatin-LB2. To better characterize their membrane interactions, we report here the detailed three-dimensional NMR structures of these peptides in TFE-d2:H2O (60:40) and in the presence of zwitterionic DPC-d38 and anionic SDS-d25 micellar solutions. Although the three peptides showed significant helical contents in the three mimetic environments, structural differences were noticed. When the structures of the three peptides in the presence of DPC-d38 micelles are compared to each other, a more pronounced curvature is observed for ocellatin-F1 and the bent helix, with the concave face composed mostly of hydrophobic residues, is consistent with the micellar curvature and the amphipathic nature of the molecule. Interestingly, an almost linear helical segment was observed for ocellatin-F1 in the presence of SDS-d25 micelles and the conformational differences in the two micellar environments are possibly related to the presence of the extra Lys residue near the peptide C-terminus, which increases the affinity of ocellatin-F1 to anionic membranes in comparison with ocellatin-LB1 and -LB2, as proved by isothermal titration calorimetry. To our knowledge, this work reports for the first time the three-dimensional structures of ocellatin peptides.

Ocellatin peptides from the skin secretion of the South American frog Leptodactylus labyrinthicus (Leptodactylidae): characterization, antimicrobial activities and membrane interactions.

BACKGROUND: The availability of antimicrobial peptides from several different natural sources has opened an avenue for the discovery of new biologically active molecules. To the best of our knowledge, only two peptides isolated from the frog Leptodactylus labyrinthicus, namely pentadactylin and ocellatin-F1, have shown antimicrobial activities. Therefore, in order to explore the antimicrobial potential of this species, we have investigated the biological activities and membrane interactions of three peptides isolated from the anuran skin secretion. METHODS: Three peptide primary structures were determined by automated Edman degradation. These sequences were prepared by solid-phase synthesis and submitted to activity assays against gram-positive and gram-negative bacteria and against two fungal strains. The hemolytic properties of the peptides were also investigated in assays with rabbit blood erythrocytes. The conformational preferences of the peptides and their membrane interactions have been investigated by circular dichroism spectroscopy and liposome dye release assays. RESULTS: The amino acid compositions of three ocellatins were determined and the sequences exhibit 100% homology for the first 22 residues (ocellatin-LB1 sequence). Ocellatin-LB2 carries an extra Asn residue and ocellatin-F1 extra Asn-Lys-Leu residues at C-terminus. Ocellatin-F1 presents a stronger antibiotic potential and a broader spectrum of activities compared to the other peptides. The membrane interactions and pore formation capacities of the peptides correlate directly with their antimicrobial activities, i.e., ocellatin-F1 > ocellatin-LB1 > ocellatin-LB2. All peptides acquire high helical contents in membrane environments. However, ocellatin-F1 shows in average stronger helical propensities. CONCLUSIONS: The obtained results indicate that the three extra amino acid residues at the ocellatin-F1 C-terminus play an important role in promoting stronger peptide-membrane interactions and antimicrobial properties. The extra Asn-23 residue present in ocellatin-LB2 sequence seems to decrease its antimicrobial potential and the strength of the peptide-membrane interactions.

Structure and membrane interactions of the homodimeric antibiotic peptide homotarsinin.

Antimicrobial peptides (AMPs) from amphibian skin are valuable template structures to find new treatments against bacterial infections. This work describes for the first time the structure and membrane interactions of a homodimeric AMP. Homotarsinin, which was found in Phyllomedusa tarsius anurans, consists of two identical cystine-linked polypeptide chains each of 24 amino acid residues. The high-resolution structures of the monomeric and dimeric peptides were determined in aqueous buffers. The dimer exhibits a tightly packed coiled coil three-dimensional structure, keeping the hydrophobic residues screened from the aqueous environment. An overall cationic surface of the dimer assures enhanced interactions with negatively charged membranes. An extensive set of biophysical data allowed us to establish structure-function correlations with antimicrobial assays against Gram-positive and Gram-negative bacteria. Although both peptides present considerable antimicrobial activity, the dimer is significantly more effective in both antibacterial and membrane biophysical assays.

Ocellatin peptides from the skin secretion of the South American frog Leptodactylus labyrinthicus (Leptodactylidae): characterization, antimicrobial activities and membrane interactions

Abstract Background The availability of antimicrobial peptides from several different natural sources has opened an avenue for the discovery of new biologically active molecules. To the best of our knowledge, only two peptides isolated from the frog Leptodactylus labyrinthicus, namely pentadactylin and ocellatin-F1, have shown antimicrobial activities. Therefore, in order to explore the antimicrobial potential of this species, we have investigated the biological activities and membrane interactions of three peptides isolated from the anuran skin secretion. Methods Three peptide primary structures were determined by automated Edman degradation. These sequences were prepared by solid-phase synthesis and submitted to activity assays against gram-positive and gram-negative bacteria and against two fungal strains. The hemolytic properties of the peptides were also investigated in assays with rabbit blood erythrocytes. The conformational preferences of the peptides and their membrane interactions have been investigated by circular dichroism spectroscopy and liposome dye release assays. Results The amino acid compositions of three ocellatins were determined and the sequences exhibit 100% homology for the first 22 residues (ocellatin-LB1 sequence). Ocellatin-LB2 carries an extra Asn residue and ocellatin-F1 extra Asn-Lys-Leu residues at C-terminus. Ocellatin-F1 presents a stronger antibiotic potential and a broader spectrum of activities compared to the other peptides. The membrane interactions and pore formation capacities of the peptides correlate directly with their antimicrobial activities, i.e., ocellatin-F1 > ocellatin-LB1 > ocellatin-LB2. All peptides acquire high helical contents in membrane environments. However, ocellatin-F1 shows in average stronger helical propensities. Conclusions The obtained results indicate that the three extra amino acid residues at the ocellatin-F1 C-terminus play an important role in promoting stronger peptide-membrane interactions and antimicrobial properties. The extra Asn-23 residue present in ocellatin-LB2 sequence seems to decrease its antimicrobial potential and the strength of the peptide-membrane interactions.

Ocellatin peptides from the skin secretion of the South American frog Leptodactylus labyrinthicus (Leptodactylidae): characterization, antimicrobial activities and membrane interactions

Background The availability of antimicrobial peptides from several different natural sources has opened an avenue for the discovery of new biologically active molecules. To the best of our knowledge, only two peptides isolated from the frog Leptodactylus labyrinthicus, namely pentadactylin and ocellatin-F1, have shown antimicrobial activities. Therefore, in order to explore the antimicrobial potential of this species, we have investigated the biological activities and membrane interactions of three peptides isolated from the anuran skin secretion. Methods Three peptide primary structures were determined by automated Edman degradation. These sequences were prepared by solid-phase synthesis and submitted to activity assays against gram-positive and gram-negative bacteria and against two fungal strains. The hemolytic properties of the peptides were also investigated in assays with rabbit blood erythrocytes. The conformational preferences of the peptides and their membrane interactions have been investigated by circular dichroism spectroscopy and liposome dye release assays. Results The amino acid compositions of three ocellatins were determined and the sequences exhibit 100% homology for the first 22 residues (ocellatin-LB1 sequence). Ocellatin-LB2 carries an extra Asn residue and ocellatin-F1 extra Asn-Lys-Leu residues at C-terminus. Ocellatin-F1 presents a stronger antibiotic potential and a broader spectrum of activities compared to the other peptides. The membrane interactions and pore formation capacities of the peptides correlate directly with their antimicrobial activities, i.e., ocellatin-F1 > ocellatin-LB1 > ocellatin-LB2. All peptides acquire high helical contents in membrane environments. However, ocellatin-F1 shows in average stronger helical propensities. Conclusions The obtained results indicate that the three extra amino acid residues at the ocellatin-F1 C-terminus play an important role in promoting stronger peptide-membrane interactions and antimicrobial properties. The extra Asn-23 residue present in ocellatin-LB2 sequence seems to decrease its antimicrobial potential and the strength of the peptide-membrane interactions.(AU)

Membrane interactions of phylloseptin-1, -2, and -3 peptides by oriented solid-state NMR spectroscopy.

Phylloseptin-1, -2, and -3 are three members of the family of linear cationic antimicrobial peptides found in tree frogs. The highly homologous peptides encompass 19 amino acids, and only differ in the amino acid composition and charge at the six most carboxy-terminal residues. Here, we investigated how such subtle changes are reflected in their membrane interactions and how these can be correlated to their biological activities. To this end, the three peptides were labeled with stable isotopes, reconstituted into oriented phospholipid bilayers, and their detailed topology determined by a combined approach using (2)H and (15)N solid-state NMR spectroscopy. Although phylloseptin-2 and -3 adopt perfect in-plane alignments, the tilt angle of phylloseptin-1 deviates by 8° probably to assure a more water exposed localization of the lysine-17 side chain. Furthermore, different azimuthal angles are observed, positioning the amphipathic helices of all three peptides with the charged residues well exposed to the water phase. Interestingly, our studies also reveal that two orientation-dependent (2)H quadrupolar splittings from methyl-deuterated alanines and one (15)N amide chemical shift are sufficient to unambiguously determine the topology of phylloseptin-1, where quadrupolar splittings close to the maximum impose the most stringent angular restraints. As a result of these studies, a strategy is proposed where the topology of a peptide structure can be determined accurately from the labeling with (15)N and (2)H isotopes of only a few amino acid residues.

Anti-inflammatory effects in muscle injury by transdermal application of gel with Lychnophora pinaster aerial parts using phonophoresis in rats.

BACKGROUND: Lycnophora pinaster is used by the traditional Brazilian medicine for the treatment of inflammations. Anti-inflammatory activity of Lycnophora pinaster was investigated for extracts, fractions, and isolated compounds of their aerial parts. The hexane extract (HE) provided α-amyrin, lupeol, mixture of α-amyrin and lupeol, mixture of 3-O-acetyl-lupeol and 3-O-acetyl-pseudotaraxasterol, and mixture of the steroids stigmasterol and sitosterol. The aqueous extract (WE) provided a fraction containing alkaloids (AF) and another one containing phenolic compounds (PF). METHODS: The crude hexane extract obtained from aerial parts of L. pinaster was submitted to chromatographic fractionation. The fractionation of PF was performed by preparative HPLC analysis, providing the flavonoid quercetin. The extracts, fractions, and compounds isolated from L. pinaster were tested to evaluate the anti-inflammatory activity by experimental model of impact injury, followed by transdermal application of gels with these samples. The application of the gels was performed using phonophoresis in rat paws after induction of muscle injury. Histological analysis was based on scores assigned by the capacity of decreasing the lesion. RESULTS: HE and WE exhibited anti-inflammatory activity. Some fractions, triterpenes, and steroids also reduced the inflammatory infiltrates caused by muscle injury. Lupeol promoted a significant reduction of inflammation. Quercetin also provided significant results, promoting the greatest decreases in muscle injury. CONCLUSION: The results of this work suggest that topical application of triterpenes, steroids and flavonoid significantly decreases the inflammatory process generated by muscle injury. The transdermal application using phonophoresis in rat paws of gel with lupeol and quercetin attenuates the inflammation.

Evaluation of the bactericidal and trypanocidal activities of triterpenes isolated from the leaves, stems, and flowers of Lychnophora pinaster

The phytochemical investigation on the aereal parts of Lychnophora pinaster Mart., Asteraceae, was carried to isolation of triterpenes. 3-O-Acetyl-lupeol (1), 3-O-acetyl-pseudotaraxasterol (2), and 3-O-acetyl-α-amyrin (3) were isolated from hexanic extract and 4,4-dimethyl-cholesta-22,24-dien-5-ol (4), α-amyrin (5), and lupeol (6) were isolated from hexanic/dichlorometanic extract of the leaves. Compounds Δ7-bauerenyl acetate (7), friedelin (8), stigmasterol (9), and sitosterol (10) were isolated from the hexanic/dichlorometanic extract of the stems. The steroids 9 and 10 were also isolated from the hexanic/dichlorometanic extract of the flowers. Triterpenes 1, 3, 4, and 7 are described for the first time in the genus Lychnophora. The apolar fractions of the leaf and stem extracts and some isolated triterpenes showed low trypanocidal activity. Moreover, apolar fractions of the leaf and stem extracts and 5 showed antibacterial action against Staphylococcus aureus.

Chemical constituents from the stem of Brosimum potabile (Moraceae) / Constituintes químicos do cerne de Brosimum potabile (Moraceae)

Three coumarins, 5-methoxypsoralene, xanthyletin, and (-)-marmesin, have been isolated from the ethanolic extract of the stem of the Amazonian plant Brosimum potabile. The structures were determined on the basis of NMR analyses and by comparison with spectroscopic data in the literature. The analysis of the hexane fractions by GC-MS in EIMS mode suggested the presence of (1-methylpentyl)-benzene; α,α-dimethyl-4-(1-methylethyl)-benzenemethanol; 1-methyl-3,5-bis(1-methylethyl)-benzene; urs-12-ene; chola-5,22-dien-3ß-ol; cholesta-4,6-dien-3ß-ol; sitosteryl 9(Z)-octadecenoate; cholesta-5,22-dien-3ß-ol; cholesta-4,6,22-trien-3-one; and cholesta-4,22-dien-3-one. NMR data of other hexane fractions indicated the presence of 3ß-acetoxy-lup-12,20(29)-diene; 3ß-acetoxy-olean-12-ene; 3ß-acetoxy-urs-12-ene; and adian-5-ene. All these compounds are first described in B. potabile.

Três cumarinas, 5-metoxipsoraleno, xantiletina e (-)-marmesina, foram isoladas no extrato etanólico do cerne da planta amazônica Brosimum potabile. Suas estruturas foram determinadas a partir das análises por RMN e por comparação com dados espectroscópicos da literatura. As análises das frações hexânicas por CG/EM sugeriram a presença de (1-metilpentil)-benzeno; α,α-dimetil-4-(1-metiletil)-benzenometanol; 1-metil-3,5-bis(1-metiletil)-benzeno; urs-12-eno; cola-5,22-dien-3ß-ol; colesta-4,6-dien-3ß-ol; (9Z)-octadecenoato de sitosterila; colesta-5,22-dien-3ß-ol; colesta-4,6,22-trien-3-ona e colesta-4,22-dien-3-ona. Dados de RMN de outras frações hexânicas indicaram a presença de 3ß-acetóxi-lup-12,20(29)-dieno; 3ß-acetóxi-olean-12-eno; 3ß-acetóxi-urs-12-eno e adian-5-eno. Todos esses compostos foram identificados pela primeira vez em B. potabile.

Synthesis, antiproliferative activity in cancer cells and theoretical studies of novel 6α,7ß-dihydroxyvouacapan-17ß-oic acid Mannich base derivatives.

Natural products are great prototypes for the design of new anticancer agents. The plant-derived natural product 6α,7ß-dihydroxyvouacapan-17ß-oic acid (1) is promising for the development of more potent antiproliferative agents against human cancer cells. Indeed, its lactone derivative 6α-hydroxyvouacapan-7ß,17ß-lactone (2), a non-natural furanoditerpene, exhibited higher anticancer activity than compound 1. Herein, we describe the synthesis and antiproliferative activity of six new Mannich derivatives of compound 2 against nine cancer cell lines. Overall, our results revealed that Mannich derivatives 3-8 were more potent than compound 2 in inhibiting the proliferation of cancer cells. Theoretical studies also supported our findings, revealing the nucleophilic character of furan ring as an important feature for antiproliferative activity of the studied Mannich derivatives.

Membrane structure and conformational changes of the antibiotic heterodimeric peptide distinctin by solid-state NMR spectroscopy.

The heterodimeric antimicrobial peptide distinctin is composed of 2 linear peptide chains of 22- and 25-aa residues that are connected by a single intermolecular S-S bond. This heterodimer has been considered to be a unique example of a previously unrecorded class of bioactive peptides. Here the 2 distinctin chains were prepared by chemical peptide synthesis in quantitative amounts and labeled with (15)N, as well as (15)N and (2)H, at selected residues, respectively, and the heterodimer was formed by oxidation. CD spectroscopy indicates a high content of helical secondary structures when associated with POPC/POPG 3:1 vesicles or in membrane-mimetic environments. The propensity for helix formation follows the order heterodimer >chain 2 >chain 1, suggesting that peptide-peptide and peptide-lipid interactions both help in stabilizing this secondary structure. In a subsequent step the peptides were reconstituted into oriented phospholipid bilayers and investigated by (2)H and proton-decoupled (15)N solid-state NMR spectroscopy. Whereas chain 2 stably inserts into the membrane at orientations close to perfectly parallel to the membrane surface in the presence or absence of chain 1, the latter adopts a more tilted alignment, which further increases in the heterodimer. The data suggest that membrane interactions result in considerable conformational rearrangements of the heterodimer. Therefore, chain 2 stably anchors the heterodimer in the membrane, whereas chain 1 interacts more loosely with the bilayer. These structural observations are consistent with the antimicrobial activities when the individual chains are compared to the dimer.

Effect of 6 alpha,7 beta-dihydroxyvouacapan-17 beta-oic acid and its lactone derivatives on the growth of human cancer cells.

The furanditerpene 6 alpha,7 beta-dihydroxyvouacapan-17 beta-oic acid (1) is a natural product biosynthesized by some species from the genus Pterodon (Leguminosae). This secondary metabolite has multiple biological activities that include anti-inflammatory, analgesic, plant growth regulatory, anti-edematogenic, photosystem II inhibitory and photosynthesis uncoupler, and antifungal properties. However, few studies on the antiproliferative profile of compound 1 and/or its derivatives have been reported up to date. Here, we describe the isolation of compound 1 from hexane extract of P. polygalaeflorus fruits as well as the semisynthesis of three lactone derivatives: 6 alpha-hydroxyvouacapan-7 beta,17 beta-lactone (2), 6 alpha-acetoxyvouacapan-7 beta,17 beta-lactone (3), and 6-oxovouacapan-7 beta,17 beta-lactone (4). Additionally, antiproliferative activity of these compounds against nine human cancer cell lines was investigated. Our results revealed that 6 alpha-hydroxyvouacapan-7 beta,17 beta-lactone (2) was the most potent furanditerpene against all cancer cell lines studied. The presence of non-substituted hydroxyl group at C-6 and the presence of 7 beta,17 beta-lactone ring are important for the antiproliferative activity of these compounds.

13C-NMR data of diterpenes isolated from Aristolochia Species.

The genus Aristolochia,an important source of physiologically active compounds that belong to different chemical classes, is the subject of research in numerous pharmacological and chemical studies. This genus contains a large number of terpenoid compounds, particularly diterpenes. This work presents a compilation of the 13C-NMR data of 57 diterpenoids described between 1981 and 2007 which were isolated from Aristolochia species. The compounds are arranged skeletonwise in each section, according to their structures, i.e., clerodane, labdane, and kaurane derivatives. A brief discussion on the 13C chemical shifts of these diterpenes is also included.

Structure and membrane interactions of the antibiotic peptide dermadistinctin K by multidimensional solution and oriented 15N and 31P solid-state NMR spectroscopy.

DD K, a peptide first isolated from the skin secretion of the Phyllomedusa distincta frog, has been prepared by solid-phase chemical peptide synthesis and its conformation was studied in trifluoroethanol/water as well as in the presence of sodium dodecyl sulfate and dodecylphosphocholine micelles or small unilamellar vesicles. Multidimensional solution NMR spectroscopy indicates an alpha-helical conformation in membrane environments starting at residue 7 and extending to the C-terminal carboxyamide. Furthermore, DD K has been labeled with (15)N at a single alanine position that is located within the helical core region of the sequence. When reconstituted into oriented phosphatidylcholine membranes the resulting (15)N solid-state NMR spectrum shows a well-defined helix alignment parallel to the membrane surface in excellent agreement with the amphipathic character of DD K. Proton-decoupled (31)P solid-state NMR spectroscopy indicates that the peptide creates a high level of disorder at the level of the phospholipid headgroup suggesting that DD K partitions into the bilayer where it severely disrupts membrane packing.

Synthesis, characterization, absolute structural determination and antifungal activity of a new chlorinated aromatic avenaciolide analogue.

BACKGROUND: Avenaciolide, a natural product isolated from Aspergillus avenaceus H. Smith, possesses several interesting biological properties, such as antifungal and antibacterial activities and inhibition of glutamate transport in mitochondria. In a study aiming to discover new compounds with antifungal activity, a bis-gamma-lactone analogous to avenaciolide was prepared and characterized by elemental analysis, mass spectrometry, and infrared and NMR spectroscopy. RESULTS: The absolute structures of this compound and of the synthetic precursor (also a bis-gamma-lactone) were determined by X-ray diffraction analysis. The bis-gamma-lactones synthesized crystallize in the orthorhombic space group P2(1)2(1)2(1), and the crystal packings are supported by C--H...O hydrogen bonds. The compound showed antifungal activity against Colletotrichum gloeosporioides (Penz.) Penz. & Sacc., while the synthetic precursor was inactive under the in vitro test conditions employed. CONCLUSION: The results indicate that it is not only the bis-gamma-lactone skeleton that is important to antifungal activity. The latter also depends on the presence of the exocyclic double bond possibly due to a Michael addition type reaction with the fungal enzymes.

Analysis of a Brazilian green propolis from Baccharis dracunculifolia by HPLC-APCI-MS and GC-MS / Análise de uma própolis verde brasileira da Baccharis dracunculifolia por CLAE-ICPA-EM e CG-EM

Ethanol and dichloromethane extracts of a Brazilian green propolis from Baccharis dracunculifolia were analyzed by HPLC-APCI-MS and GC-MS, respectively. The HPLC-APCI-MS technique, at the positive mode, furnished a complete and unequivocal chemical composition of the green propolis sample. It serves as fingerprint for different propolis samples. The composition of the ethanol extract consisted mainly of cinnamic acid and derivatives, flavonoids, benzoic acid and a few benzoates, non-hydroxylated aromatics, and aliphatic acids and esters, which are normally not reported in the literature because they do not absorb UV light. The main constituents of the dichloromethane extract were prenylated compounds, alkanes and terpenoids.

Os extratos em etanol e diclorometano de uma própolis verde de Baccharis dracunculifolia foram analisados por CLAE-ICPA-EM e CG-EM, respectivamente. A técnica de CLAE-EM-ICPA, no modo positivo, forneceu uma completa e inequívoca composição química da amostra de própolis verde. Ela serve como impressão digital para amostras diferentes de própolis. A composição do extrato em etanol consistiu fundamentalmente de ácido cinâmico e derivados, flavonóides, ácido benzóico e alguns benzoatos, aromáticos não hidroxilados, e ácidos e ésteres alifáticos, os quais são normalmente ignorados na literatura porque não absorvem luz UV. Os constituintes principais do extrato em diclorometano foram compostos prenilados, alcanos e terpenóides.

Antischistosomal activity of aminoalkanethiols, aminoalkanethiosulfuric acids and the corresponding disulfides.

This paper discusses the development of a series of sulfur-containing compounds that show an interesting in vivo activity against infection by Schistosoma mansoni. These substances include the aminoalkanethiols, aminoalkanethiosulfuric acids and aminoalkyl disulfides, among others. Although the aminoethanethiols and their disulfide derivatives have presented a relatively high toxicity for the host animal, the aminoalkanethiosulfuric acids have a low toxicity and a high specificity for the adult female S. mansoni worms. In vitro studies with schistosomula, lung-phase schistosomula and adult worms have demonstrated effects on the tegument and the metabolism on these different stages of S. mansoni worms. The encapsulation of these drugs in a nanoemulsion has resulted in an increase in the in vitro activity.

Um marcador químico de fácil detecção para a própolis de Alecrim-do-Campo (Baccharis dracunculifolia) / An easily detectable chemical marker for the Baccharis dracunculifolia propolis

O presente trabalho apresenta um marcador químico (MQ) volátil, de fácil detecção por cromatografia gasosa, para a própolis do alecrim-do-campo (Baccharis dracunculifolia). Trata-se do composto volátil mais abundante no extrato em diclorometano de própolis verdes dessa planta, mas que aparece, também, em diferentes concentrações, em extratos de diclorometano de própolis marrom, preta, vermelha e amarela, provenientes de regiões que contêm Baccharis dracunculifolia. O MQ está presente no extrato dos ápices vegetativos de alecrim em concentração significativa, mas sua concentração na folha de alecrim é baixa. Própolis de regiões sem alecrim não possuem o MQ. Este composto foi isolado recentemente e se trata do 3-prenilcinamato de alila. Amostras comerciais de extratos etanólicos de própolis verdes foram analisadas e a de primeira qualidade, tipo exportação, apresentou maior concentração de MQ. Tal descoberta facilita o rápido controle de qualidade de extratos etanólicos de própolis verdes.

In the present work a volatile chemical marker (CM) for the Baccharis dracunculifolia (Bd) propolis is proposed, which is easily detectable by gas chromatography. It is the most abundant volatile compound in dichloromethane extracts of green propolis from this plant, but it appears also, in different concentrations, in dichloromethane extracts of brown, dark and red propolis from regions where Bd grows. The CM is present in significative concentration in the bud extract of Bd, in contrast to the leaf extract where its concentration is low. Propolis from regions without Bd does not contain the CM. This compound was recently isolated; it is the allyl 3-prenylcinnamate. Commercial samples of green propolis ethanol extract were analyzed and the first quality one (exportation standard) presented the highest concentration on CM. This finding makes easier the quality control of green propolis extracts sold at the market.