Assessment of the Insecticidal Potential of the Eupatorium buniifolium Essential Oil Against Triatoma infestans (Hemiptera: Reduviidae). A Chiral Recognition Approach.

In this research, bioactivities toward the Chagas' disease vector Triatoma infestans (Klug) (Hemiptera: Reduviidae) by the essential oil (EO) of Eupatorium buniifolium H. et A. (Asteraceae) are reported. The tests were designed in order to determine ovicidal activity as well as the response to vapor exposure (fumigant) and to topical application (contact toxicity) and as repellent. In the last three bioassays, nymphs from the 3rd and 4th instar were used. The assayed materials were obtained from aerial parts of plants collected during the months of March and December, throughout 4 years, in two locations. The EO samples were subjected to a qualitative analysis by GC-MS and the relative area of each component was reported by GC-FID. The main monoterpene detected was α-pinene and by using a chiral column through GC-MS experiments and having both stereoisomers as standards, we were able to determine that the enantiomer present was S,S-(-)-α-pinene. Although usually in studies of EOs changes in chemical composition are often observed due to the time of collection and the environment where the plant develops, in our case the differences were, with some exception, only at the level of the minor components. The best results were obtained in the experiments to determine ovicidal activity, fumigant action, and repellency. No worthy response was found as insecticide in the trials designed for contact toxicity. The results of the studied bioactivities were independent of the location, month, and year of collection of the plant material. This behavior provides an interesting scope in relation to the potential use of this natural blend for the control of this insect at the nymph stage as repellent as well as for decreasing the population by ovicidal effect. Notably, in the course of the two-choice repellency test, it was possible to demonstrate recognition of one of the enantiomers of the α-pinene, giving rise to a non-common chirality/response effect. In this assay, the levorotatory isomer was the most active as repellent. Considering the abundance of the wild plant under study and the fact that its EO is easy to obtain, it is suggested that it could be an adequate natural resource to control this vector in a sustainable way as a complementary approach to conventional methods.

The in vivo trypanocidal effect of the diterpene 5-epi-icetexone obtained from Salvia gilliesii.

The search for new compounds with trypanocidal activity is crucial for the treatment of Chagas' disease. Previous in vitro studies have shown that the diterpene 5-epi-icetexone (ICTX) is active against Trypanosoma cruzi. The aim of this work was to evaluate the effect of ICTX on the parasites in infected mice, in an experimental model that mimics the acute phase of the disease. Swiss albino mice were infected with T. cruzi and treated daily with 10mg/kg/day ICTX (i.p.). Infected mice and mice injected with either saline or the vehicle DMSO were used as controls. Animals' survival and parasitemia were monitored once a week and histological studies were made at necropsy by the 5th week after infection. It was observed that the administration of ICTX increased the survival of mice infected, and induced a significant decrease in the parasitemia, as compared to controls. A similar protective effect was observed when animals were treated orally with benznidazole (BZN, used as a control of antiparasitic effect). By the 5th week post-infection, the presence of amastigote nests was observed within the fibers of the cardiac and skeletal muscle in controls, but not in animals treated with either ICTX or BZN. In addition, inflammatory infiltrates were observed in the tissues of controls, but not in animals treated with the drugs. We conclude that ICTX has an antiparasitic effect against T. cruzi, thus constituting an interesting option for the treatment of Chagas' disease, alone or combined with other drugs.

An abietane diterpene from Salvia cuspidata and some new derivatives are active against Trypanosoma cruzi.

The Plant Kingdom is an excellent source for obtaining natural compounds with antiprotozoal activity. In the present work, we studied the effect of the diterpene 12-hydroxy-11,14-diketo-6,8,12-abietatrien-19,20-olide (HABTO) obtained from the aerial parts of Salvia cuspidata on Trypanosoma cruzi epimastigotes. This compound was found to inhibit parasite growth even at low concentrations (IC50 5 µg/mL) and with low toxicity on mammalian cells. In addition, this diterpene induced an intense vacuolization within the parasites. In order to obtain analogs with greater lipophilicity, chemical modifications on the enol moiety were carried out to obtain the acetyl (AABTO), the sylil (SABTO) and the allyl (ALLABTO) derivatives. We observed that the SABTO was the most effective one on the parasites, and the effect could be attributed to a greater lipophilicity of this compound. Taking into account these data we conclude that the increase of lipophilicity by chemical modifications is an adequate strategy for improving the trypanocidal activity of this kind abietane diterpenes.

Inhibition of Taq DNA polymerase by iridoid aglycone derivates.

Faithful replication of DNA molecules by DNA polymerases is essential for genome integrity and correct transmission of genetic information in all living organisms. DNA polymerases have recently emerged as important cellular targets for chemical intervention in the development of anti--cancer agents. Herein we report additional synthesis of simplified bicyclic aglycones of iridoids and their biological activity against Taq DNA polymerase with the object to find out some of the likely molecular targets implicated in the biological activity showed for this kind of compounds. The compounds 14, 33 and 34 showed inhibitory activity against Taq DNA polymerase with IC(50) values of 13.47, 17.65 and 18.31 µM, respectively. These results would allow proposing to DNA polymerases as the molecular targets implicated in this bioactivity and enhance the iridoid aglycones as leader molecule to develop new drugs for cancer therapy.

The trypanocidal activity of the alkaloid oliverine involves inhibition of DNA synthesis.

The Trypanosoma cruzi parasite is an etiologic agent of the American trypanosomiasis called Chagas disease. This pathology affects more than 24 million persons and represents one of the most important public health problems in Latin America. Taking into account this, it is necessary the search of new antitrypanosomal agents that show a major level of efficacy and minor indexes of toxicity in affected patients. Vast source of them are the natural products from plants with enormous structural diversity. A particular type of these compounds is represented by aporphinoid alkaloids. In our experiments, anonaine (2), oliverine (3) and guatterine (5) displayed antitrypanosomal activity. The compound 3 showed the most important activity with an IC50 = 12.00 ± 0.36 μM. Its mechanism of action may include inhibition of DNA synthesis.

Inhibition of DNA topoisomerase I and growth inhibition of human cancer cell lines by an oleanane from Junellia aspera (Verbenaceae).

DNA topoisomerases and DNA polymerases are enzymes that play a crucial role in DNA metabolism events such as replication, transcription, recombination, and chromosome segregation during mitosis. Thus, DNA topoisomerases and DNA polymerases inhibitors could be expected to have antitumor effects. Naturally occurring triterpenoids isolated from Junellia aspera (Gillies & Hook; Moldenke) (Verbenaceae) were assayed for human DNA topoisomerase I and Taq DNA polymerase inhibitory activities. Maslinic acid (2) and its diacetyl derivative (7) showed human DNA topoisomerase I inhibitory activity with IC50 values in the range of 76-80 microM and growth inhibition against various human solid tumour cell lines with GI50 values in the range of 5-18 microM. The triterpene frames could be used for screening new inhibitors of the enzyme, and computer-simulated drug design using the frame and pocket structure of enzyme may in theory be a possible approach to develop new inhibitors.

A novel icetexane diterpene, 5-epi-icetexone from Salvia gilliessi is active against Trypanosoma cruzi.

In this work the effect of a novel compound, 5-epi-icetexone (ICTX) obtained from Salvia gilliessi Benth. (Labiatae), is studied on cultured epimastigotes of Trypanosoma cruzi (Tulahuen). It was found that the compound exerts an antiproliferative effect on the parasites at concentrations between 2.8 and 4.2 microM, and similar sensitivity in other strains (Dm28c, CL-Brener and Y-strain). The compound was deleterious at concentrations higher than 4.2 microM, with an estimated IC50 of 6.5+/-0.75 microM, but with low cytotoxicity to mammalian cells. These effects were irreversible, even at short times of exposure to the drug. In solution, ICTX showed to be stable for at least 96 h at 29 degrees C. With cytostatic dose a little percentage of parasites was resistant to the action of ICTX, and they continued growing although with different kinetic. By electron transmission microscopy, at dose of 4.2 microM an external vesiculization was observed on the first day of exposure to the compound, but the parasite cytoplasm became plenty of vacuoles and exhibited nuclear disorganization from the second day of exposure. It was concluded that ICTX is active against T. cruzi and may act by multiple mechanisms. In future, this novel icetexane diterpene may be a good candidate for therapeutic use against Chagas' disease.

Determination and assay validation of the bioactive sesquiterpene lactone xanthatin isolated from Xanthium cavanillesii using capillary electrophoresis.

This study describes the development and validation of a method for quantification of the antiulcer experimental drug xanthatin in tablets by capillary electrophoresis (CE). Solid oral dosage forms based on xanthatin were designed and assayed on rats. A CE methodology was developed; the parameters evaluated were: background electrolyte composition, concentration and pH, applied voltage and sample preparation. The method was validated in terms of range of linearity, limits of detection (LOD) and quantification (LOQ), accuracy, precision and selectivity and then applied to the pharmaceutical dosage forms. Xanthatin determination was carried out in less than 3 min with a 20 mM sodium tetraborate buffer, pH 9.20. Drug concentration per tablet found was 2.97 +/- 0.2 mg. Calibration plots were linear over at least three orders of magnitude of analyte concentrations, LOD and LOQ were 7.6 and 26 microg mL(-1) respectively. For accuracy evaluation a recovery test was performed, the values being better than 98.6%. With respect to precision, the results obtained were better than 1.02 RSD% (repeatability) and 1.54% (intermediate precision). After the manufacturing process the resulting tablets were biologically active. The methodology developed is useful, simple and rapid for xanthatin determination in tablets.

Stereo- and regioselective hydroxylation of grindelic acid derivatives by Aspergillus niger.

Stereo- and regioselective hydroxylation of grindelane derivatives on position 3beta was catalyzed by cultures of Aspergillus niger. Grindelic acid (1), methyl grindelate (2), 15-hydroxy-7(8)-en-9alpha,13(S)-oxide-ent-labdane (3) and 7alpha,8alpha-epoxymethylgrindelate (4) were bioconverted into the corresponding 3beta-hydroxy derivatives as the only biotransformation products. 13(S),15-dihydroxy-8(9)-en-ent-labdane (5) remained unreacted under the same conditions. The conformational and electronic studies of the substrates are discussed.

Inhibition of Taq DNA polymerase by catalpol.

DNA polymerases have recently emerged as important cellular targets for chemical intervention in the development of anti-cancer agents. This report describes a PCR assay as a method to investigate the action mechanism of the inhibition of Taq DNA polymerase by catalpol. This inhibition was not primer or template specific, nor was it due to chelation of Mg2+ ions. In assays of hyperchromicity of double-stranded DNA, catalpol did not affect melting profile. The inhibitory effect of catalpol does not appear to depend on DNA concentration. In contrast, increasing dNTP concentration rescue the Taq DNA polymerase activity, suggestingthat catalpol acts in a competitive way with dNTPs at the binding site of the enzyme. Theoretical calculations reinforce the experimental data and the proposed mode of action of catalpol.

Two new labdane diterpene glycosides from flowers of Baccharis medullosa DC.

From the flowers of Baccharis medullosa DC (Asteraceae) two new ent-labdane-type diterpene glycosides were isolated. Structures were established by application of various spectroscopic techniques. The sugar residues were identified after acid hydrolysis of the isolated products.

Icetexane and abietane diterpenoids from Salvia gilliessi.

One icetexane and two abietane diterpenes were isolated from the aerial parts of Salvia gilliesii, and characterized as 5-epi-icetexone; 12-hydroxy-11,14-diketo-6,8,12-abietatrien-19,20-olide and 6 alpha,12,19-trihydroxy-11,14-diketo-8,12-abietadien-20,7 beta-olide, respectively. The structures were established by analysis of their 1H and 13C NMR spectra with the aid of 2D experiments. The triterpene oleanolic acid was isolated from the same source.

Structure-antifeedant activity relationship of clerodane diterpenoids. Comparative study with withanolides and azadirachtin.

A structure-antifeedant activity relationship (SAR) study of clerodane diterpenoids was carried out. Attention was focused on the feeding-deterrent activities exhibited toward Tenebrio molitor by clerodane diterpenoids and withanolides. Azadirachtin was chosen as a reference compound. SAR studies on the clerodane compounds indicate that the stereoelectronic factors are more important than the hydrophobic aspects as determinants of antifeedant activity. A furan ring in the side chain and a carbonyl alpha,beta-unsaturated (or spiro-epoxide) group appear to be indispensable for the biological response. A conformational study indicate that the optimum interatomic distance between these moieties is a range between 9.5 and 10.5 A. In addition, a similar stereoelectronic response was found among withanolides and azadirachtin. On the basis of these results it is reasonable to imagine a closely related chemical mechanism for these compounds.

Diterpenes from Laennecia sophiifolia.

From the aerial parts of Laennecia sophiifolia (Kunth) G.L. Nesom, a neo-clerodane and an acyclic furano diterpene were isolated, along with four known compounds, 2beta-hydroxyhardwickiic acid, hawtriwaic acid, apigenin, and beta-sitosterol. Their structures were established as 12-epi-bacchotricuneatin A and (2E,6E)-9-(3-furyl)-6-methyl-2-(4-methylpent-3-enyl)-nona-2,6-dienoic acid, by analysis of spectral evidence. The absolute structure of 12-epi-bacchotricuneatin A was determined by a circular dichroism spectral comparison with that of bacchotricuneatin A.

Enhancement of tessaric acid production in Tessaria absinthioides cell suspension cultures.

The total production of the sesquiterpene tessaric acid (TA) by cell cultures of Tessaria absinthioides at day 25 of the culture period reached 0.086 mg g-1 DW, with intracellular accumulation accounting for 0.059 mg g-1 DW. Dimethylsulfoxide-induced permeabilization of the cells effected both total production and extracellular accumulation of the sesquiterpene to reach levels of 148% and 271%, respectively. Cultures treated with elicitor preparations of Verticillum sp., Monodyctis cataneae, Acremonium sp., and Aspergillus niger produced TA at levels of 281%, 197%, 149%, and 139%, respectively. Treatment of cell suspension cultures with cis-(-)-jasmonic acid (5 µM) increased production to 267%, whereas jasmonic acid pretreatment and subsequent elicitation raised external tessaric acid to 702%.

Anti-inflammatory activity of acetophenones from Ophryosporus axilliflorus.

Seven acetophenone derivatives were isolated from the aerial parts of Ophryosporus axilliflorus (Griseb.) Hieron. These compounds were subjected to the carrageenan-induced mouse paw edema test where tremetone (7) showed extremely anti-inflammatory activity. Furthermore, the non-benzofuran acetophenones 5 and 6, showed a significant response.