Nove limonóides foram isolados de Carapa guianensis e Cedrela fissilis. Entre eles, a 1,2-diidro-3β-hidroxi-7-desacetoxi-7-oxogedunina é uma substância inédita. Além disso, alguns deslocamentos químicos da xilocensina k foram corrigidos e os dados de RMN 1 H da 7-desacetilgedunina são descritos pela primeira vez na literatura. Seis dos limonóides isolados foram submetidos a ensaios com formigas Atta sexdens rubropilosa e apresentaram atividade inseticida moderada. Nine limonoids were isolated from Carapa guianensis and Cedrela fissilis. Among them, 1,2-dihydro-3β-hydroxy-7-deacetoxy-7-oxogedunin is a new compound. Moreover, the assignments of some chemical shifts of xyloccensin k have been corrected and 1 H NMR data of 7-deacetylgedunin have been assigned for the first time. These isolated limonoids were assayed on Atta sexdens rubropilosa workers showing moderate insecticidal activities.

Since 2009, when sulfluramid was listed in annex B of the Stockholm Convention’s Persistent Organic Pollutants, effort has been made to search for other active ingredients to use in baits for controlling leaf-cutting ants in Brazil. Considering that active ingredients that inhibit insect cellular respiration have been shown to be effective in controlling ants, the current work aimed at assessing the toxicity of hydramethylnon to Atta sexdens rubropilosa workers. Hydramethylnon was dissolved in acetone and in a solution of acetone + soy oil then incorporated in artificial diet at concentrations of 1 µg/mL, 5 µg/mL, 10 µg/mL, 100 µg/mL, 200 µg/mL and 1000 µg/mL. The treatments where ants were daily fed on the diet containing hydramethylnon at 100 µg/mL, 200 µg/mL and 1000 µg/mL, especially those dissolved in soy oil, exhibited high mortality in comparison to the controls. The data presented here confirms the insecticidal activity of hydramethylnon and highlights the importance of employing soy oil in the formulation of baits to control leaf-cutting ants because it enhances hydramethylnon efficiency.

The current study compared the toxicity of different concentrations of boric acid in adult workers of Atta sexdens rubropilosa Forel (Hymenoptera: Formicidae), with toxicological bioassays, and examining the dose-dependent and time-dependent histopathological changes, of the midgut, Malpighian tubules, and postpharyngeal glands. Our results revealed the importance of conducting toxicological bioassays combined with morphological analyses of the organs of ants chronically exposed to insecticides used in commercial ant baits. In vitro bioassays showed that boric acid significantly decreases the survivorship of workers regardless of concentration, whereas the morphological data suggested progressive dose-dependent and time-dependent changes in the organs examined, which were evident in the midgut. The midgut is the first organ to be affected, followed by the postpharyngeal gland and Malpighian tubules. This sequence is in agreement with the absorption pathway of this chemical compound in the midgut, its transference to the hemolymph, possibly reaching the postpharyngeal glands, and excretion by the Malpighian tubules. These progressive changes might be due to the cumulative and delayed effect of boric acid. Our findings provide important information for the understanding of the action of boric acid in ant baits in direct and indirect target organs.

O estudo químico dos frutos de Cipadessa fruticosa (Meliaceae) permitiu o isolamento dos limonóides cipadesina B (inédito) e swietemahonolídeo. Das raízes de Cedrela fissilis (Meliaceae) foi isolado o limonóide 3β-acetoxicarapina, inédito como produto natural, juntamente com os triterpenos ácido oleanólico e ácido oleanônico. Estes compostos, e outros seis mexicanolídeos anteriormente isolados de C. fruticosa, apresentaram atividade inseticida para as formigas cortadeiras Atta sexdens rubropilosa.The chemical investigation of the fruits of Cipadessa fruticosa (Meliaceae) afforded the new limonoid cipadesin B and the known swietemahonolide. From the roots of Cedrela fissilis (Meliaceae) were isolated the limonoid 3β-acetoxycarapin, new as natural product, along with the triterpenes oleanolic and oleanonic acid. These compounds and other six mexicanolide limonoids previously isolated from C. fruticosa showed insecticidal activity against the leafcutting ants Atta sexdens rubropilosa. Keywords: Cedrela fissilis, Cipadessa fruticosa, limonoids, triterpenes, insecticidal activity IntroductionCipadessa fruticosa Blume (Meliaceae) is widely cultivated in the southwest of China. This plant has been reported to contain ent-clerodanes and labdanes diterpenoids, 1,2 limonoids, sterols, sesquiterpenoids, heneicosene derivatives and one coumarin. 3,4 We have recently reported the isolation of six mexicanolide limonoids from this plant. 5 Cedrela fissilis Vell. (Meliaceae) is a valuable tree of timber industry. In Brazil, it can be found from Amazon forest up to north of Espírito Santo State. Previous investigation of fruits and seeds from this species afforded the limonoids fissinolide, mexicanolide and 3β-hydroxyisomexicanolide. 6 In a recent investigation we have isolated several gedunin limonoids from C. fissilis. 7 Extracts and fractions from C. fruticosa and C. fissilis have been shown activity on leaf-cutting workers Atta sexdens rubropilosa. 8,9 Thus, the aim of this work was the chemical investigation of these Meliaceae species associated with biological assays against Atta sexdens rubropilosa. The study of the fruits of C. fruticosa allowed the isolation of a new mexicanolide limonoid: cipadesin B (1) and the known swietemahonolide (2). The limonoid 3β-acetoxycarapin (3) isolated from fruits of C. fissilis, is new as natural product and its spectral data are being described for the first time. The triterpenes oleanolic acid (4) and oleanonic acid (5) were also isolated from C. fissilis. The evaluation of the activity on leaf-cutting ants of these compounds, along with the following mexicanolide limonoids previously isolated from C. fruticosa: cipadesin A (6), ruageanin A (7), cipadesin (8), khayasin T (9), febrifugin (10) and mexicanolide (11) Extraction and isolation of compoundsThe powdered air-dried fruits (990 g) of C. fruticosa were subsequently extracted with hexane, CH 2 Cl 2 and MeOH. The concentrated CH 2 Cl 2 extract (10.9 g) was submitted to vacuum chromatography over silica gel using a hexane-CH 2 Cl 2 ...

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