Toxicity of sesame extracts to leaf-cutting ant Atta sexdens rubropilosa (Hymenoptera: Formicidae)

Extracts of different sesame plant (Sesamum indicum, Linnaeus) organs were tested through ingestion and contact experiments to investigate their toxicity to Atta sexdens rubropilosa (Forel) workers. Dichloromethane extracts of seeds were toxic to the leaf-cutting ants and the factor responsible for the toxicity does not show seasonal occurrence.

Toxicity of sesame seed to leaf-cutting ant Atta sexdens rubropilosa (Hymenoptera: Formicidae)

Extracts of the ripe seeds of the sesame plant (Sesamum indicum, Linnaeus) were tested through contact experiments to investigate their toxicity to Atta sexdens rubropilosa workers. Dichloromethane extract of seeds was toxic to the ants and the factor responsible for this effect was distributed through the ethyl acetate fraction. This fraction was divided into four sub fractions composed of: A) triglycerides, B) monoglycerides + diglycerides + triglycerides, C) diglycerides + sesamoline + sesamine and D) sesamine. However, when these sub fractions were separated, no toxicity was observed. Therefore, in order to determine why the activity was lost, the concentration of each sub fraction was duplicated, and the possible combinations among them were also tested. We concluded that the toxicity to the ants is due mainly to a mixture of triglycerides, and sesamoline or the combination of sesamoline + sesamine can be a synergistic factor in this fraction.

Oral toxicity of chemical substances found in Dimorphandra mollis (Caesalpiniaceae) against honeybees (Apis mellifera) (Hymenoptera: Apidae)

Dimorphandra mollis is a characteristic plant from Brazilian saP vanna-like vegetation. The pollen of this species could be toxic to bees and the objective of the present investigation was to study the toxicity of methanolic extracts obtained from the flowers, peduncles and stem bark of D. mollis to Apis mellifera workers. For the study, the extracts were incorporated into the diet of the bees for later evaluation of mortality rates. The substances isolated: neoisoastilbin, catechin, astilbin and tannins were tested on adult workers and only catechin did not cause toxic effects. The data obtained in the toxicity bioassays were analyzed statistically by Log Rank test and all methanolic extracts showed significant (p<0.0001) toxic effects. Astilbin is also the major component of pollen grains, and is probably responsible for honeybee mortality during blooming periods.

Astilbin toxicity to leaf-cutting ant Atta sexdens rubropilosa (Hymenoptera: Formicidae)

The toxicity of astilbin, isolated from Dimorphandra mollis, was tested in laboratory ingestion bioassays for the leaf-cutting ant Atta sexdens rubropilosa Forel. Worker ants that were fed an artificial diet daily to which astilbin was added had a higher mortality rate than the controls. The substance astilbin was incorporated into the diet with and without the utilization of a solvent. Results for both methodologies utilized were similar and indicate that astilbin reduces the median survival of ants. All concentrations tested showed toxic effects against ant workers, and the statistical comparison of survivorship rates from control and treated groups was significantly different, confirming the insecticidal properties of the substance astilbin.

Toxicity of Cedrela fissilis to Atta sexdens rubropilosa (Hymenoptera: Formicidae) and its symbiotic fungus

Crude extracts from roots, stems, branches, fruits and leaves of Cedrela fissilis were tested to verify their toxicity to Atta sexdens rubropilosa workers and to their symbiotic fungus Leucoagaricus gongylophorus. The workers that were fed daily on an artificial diet to which crude extracts from this plant were added had a higher mortality rate than the controls, especially for the hexane, dichloromethane and methanol crude extracts from roots (RH, RD and RM) and from leaves (LH, LD and LM). Fungal growth was inhibited by the hexane (RH) and dichloromethane crude extract from roots (RD). The RH, RD and FD crude extracts were fractioned and their fractions were tested. All the fractions tested presented toxicity to the ants and some fractions (RH-H, RH-D, RD-4 and RD-5) completely inhibited fungus development. The possibility of controlling these insects in the future using Cedrela fissilis compounds that can simultaneously target both organisms is discussed.

Toxicity of Cipadessa fruticosa to the leaf-cutting ants Atta sexdens rubropilosa (Hymenoptera: Formicidae) and their symbiotic fungus

Crude extracts from fruits, branches and leaves of Cipadessa fruticosa were assayed on Atta sexdens rubropilosa workers and their symbiotic fungus Leucoagaricus gongylophorus. The results showed that the majority of the extract tested reduced significantly (p < 0.05) the survival of the workers comparable to the neem oil. In addition, the dichloromethane extract from fruits and the hexane extract from branches of C. fruticosa inhibited in 80% the development of the symbiotic fungus. The hexane and dichloromethane extracts from fruits of C. fruticosa were fractionated and their fractions were subjected to new bioassays. Several fractions showed relevant activity on ants, but none of them inhibited significantly the fungal growth. The possibility of controlling leaf-cutting ants in the future using C. fruticosa is discussed.

Leaf-cutting ants toxicity of limonexic acid and degraded limonoids from Raulinoa echinata. X-ray structure of epoxy-fraxinellone

Phytochemical survey of roots extracts of the South Brazilian endemic plant Raulinoa echinata Cowan, Rutaceae led to the isolation of known degraded limonoids: fraxinellone, fraxinellonone and epoxy-fraxinellone. The latter was previously isolated also from the stems, but the relative configuration could not be solved by NMR experiments. This paper deals with the X-ray diffraction analysis of epoxy-fraxinellone and its toxicity to leaf-cutting ants, describes the isolation of fraxinellonone and fraxinellone for the first time in Raulinoa. Epoxy-fraxinellone showed no toxicity to the leaf-cutting ants (Atta sexdens rubropilosa). The limonoid limonexic acid, isolated from stems, presented high toxicity to the leaf-cutting ants, diminishing considerably their longevity. ©2005 Sociedade Brasileira de Química.

Toxicity of Azadirachta indica to leaf-cutting ant Atta sexdens rubropilosa (Hymenoptera: Formicidae)

The leaf-cutting ants are responsible for great economical damages in cultivated areas, and because of this characteristic, they have aroused the interest of researchers around the world. Thus, extracts of neem (Azadirachta indica, A. Juss) were tested through ingestion and contact experiments to investigate their toxicity to Atta sexdens rubropilosa workers. Crude extract of neem seed oil was toxic to the ants by ingestion in all concentrations tested but no toxicity was observed in contact experiments. However, crude extract of neem seed paste produced a significant toxicity to workers by ingestion and by contact.

Toxicity of straight-chain fatty acids to leaf-cutting ants Atta sexdens rubropilosa (Hymenoptera: Formicidae) and the symbiotic fungus Leucoagaricus gongylophorus

This work determined toxicity and attractiveness of straight-chain fatty acids (C 5 to C 12) to Atta sexdens rubropilosa (Forel) workers. The effect to the symbiotic fungus, Leucoagaricus gongylophorus (Singer) Möller, was also tested with the fatty acids C 6 to C 12. A strong mortality of leaf-cutting ants that were fed with an artificial diet containing fatty acids C to C at concentrations above 1.0 mg.ml -1 was observed. Rice flakes impregnated with solutions of these fatty acids were repellent to leaf-cutting ants. Contact experiments showed that treatments with C 6 and C 7 at concentration of 100 mg.ml -1 significantly reduced the survival rate of leaf-cutting ants. The fatty acids C 8 to C 11 were toxic to leaf-cutting ants when topically tested at concentration of 200 mg.ml -1. In relation to the fungus' bioassays, the fatty acids C 6 to C 12 at concentration of 0.1 mg.ml -1 inhibited 100% of the fungal development. Although when the concentration was reduced by half no inhibition effects were observed. The results showed that straight-chain fatty acids have desirable properties for controlling leaf-cutting ants since they directly interfere with both organisms of the symbiotic relationship. The potential of fatty acids as well as ways to control leaf-cutting ants with these compounds are discussed in this article.

Acute toxicity of waters from the urban drainage channels of Santos (São Paulo, Brazil)

The objective of this study was to evaluate the toxicity of water which flows toward the beaches of Santos, SP, Brazil. Water samples were collected from eight urban drainage channels and a small creek, in March, April and August 2005. For each sample, some physical-chemical parameters were analyzed: pH, dissolved oxygen, temperature, salinity, presence of free chlorine and total ammonia contents. Acute toxicity tests (48h) with Daphnia similis were also performed with the samples. The level of ammonia was relatively high in the majority of the samples (≥ 1.5 mg/L), and free chlorine was measurable in most of them. Acute toxicity was observed in four water samples (stations 3, 4, 5 and 7), at least in one occasion. The toxicity was positively correlated with the ammonia concentrations and salinity. Because acute toxicity was detected, actions aiming to control the pollution sources and improve the water quality are recommended.

Desenvolvimento e nutrição do capim-Tanzânia em função da aplicação de zinco

It was aimed to assess the effects of zinc in the development and nutrition of Tanzania grass. The experimental design used was fully randomized, consisting of six doses of zinc (0, 15, 30, 60, 120 and 240 mg dm'3) and four repetitions. The experimental unit was formed in a vase filled with a Red Latosol dystrophic (Zn = 0.4 mg dm). There were two cuts, the first after 53 days of transplanting seedlings and the second 35 days after the first cut. Was evaluated the concentration of zinc in the soil, the content of zinc leaf, the number of tillers, number of leaves, plant height, the dry mass of the shoot, root system and the whole plant. The doses of zinc influenced the concentration of zinc in soil and plant, and production of dry mass of Tanzania grass, especially the first cut. The Tanzania grass shows high tolerance to the toxicity of zinc, and toxic critical level of 273 mg kg-1.

A simple method based on HR-CS FAAS for multi-element determination of Cu, Fe, Mn and Zn in medicinal plants

A simple method to determine Cu, Fe, Mn and Zn in single aliquots of medicinal plants by HR-CS FAAS is proposed. The main lines for Cu, Mn and Zn, and the alternate line measured at the wing of the main line for Fe at 248.327 nm allowed calibration within the 0.025 - 2.0 mg L-1 Cu, 1.0 - 20.0 mg L-1 Fe, 0.05 - 2.0 mg L-1 Mn, 0.025 - 0.75 mg L-1 Zn ranges. Nineteen medicinal plants and two certified plant reference materials were analyzed. Results were in agreement at a 95% confidence level (paired t-test) with reference values. Limits of detection were 0.12 μg L-1 Cu, 330 μg L-1 Fe, 1.42 μg L-1 Mn and 8.12 μg L-1 Zn. Relative standard deviations (n=12) were ≤ 3% for all analytes. Recoveries in the 89 - 105% (Cu), 95 - 108% (Fe), 94 - 107% (Mn), and 93 - 110% (Zn) ranges were obtained.

Evaluation of the toxicity of Virola sebifera crude extracts, fractions and isolated compounds on the nest of leaf-cutting ants

The phytochemical study of Virola sebifera leaves led to the isolation of three lignans: (+)-sesamin, (-)-hinokinin, and (-)-kusunokinin and three flavonoids: quercetin-3-O - L-rhamnoside, quercetin-3-O - D-glucoside, and quercetin-3-methoxy-7-O - D-glucoside by using techniques as high-speed counter-current chromatography and high-performance liquid chromatography. The crude extracts, fractions, and isolated compounds were evaluated for their insecticidal and fungicidal potential against Atta sexdens rubropilosa and its symbiotic fungus Leucoagaricus gongylophorus. The bioassay results showed a high insecticidal activity for the methanol crude extract of the leaves of V. sebifera and its n-hexane, dichloromethane and ethyl acetate fractions. The fungicidal bioassay revealed high toxicity of the lignans against L. gongylophorus. © 2012 Keylla Utherdyany Bicalho et al.

Toxicidade de águas e sedimentos em um rio afetado por atividades mineradoras pretéritas

The Ribeira de Iguape River basin received intense mining activities for lead exploiting and, as a result, the river received the discharges of estimated amounts of 5.5 tons/month of material rich in As, Ba, Cd, Pb, Cu, Cr and Zn. In this article, the toxicity of waters and sediments collected in Ribeira de Iguape River was assessed aiming to estimate environmental quality. Three sampling campaigns were conducted, from 2009 to 2010. Toxicity tests with the cladoceran Daphnia similis were done for water samples and for sediments, in this case using sediment-water interface exposure. Results showed in general absence of toxicity for sediments and waters, and only eventually were acute effects registered (marginal toxicity). Results are consistent with the conditions indicated by the literature, of low concentrations of metals in waters and sediments; however they differ from the monitoring made by the state environmental agency, which registered chronic toxicity. The occurrence of eventual acute toxicity indicates that although Ribeira de Iguape River quality is being restored, conditions still are not totally under control.