Constituintes químicos de duas espécies de musgos (Bryophyta) e ação de seus extratos sobre Spodoptera frugiperda (J. E SMITH) (Lepidoptera: Noctuidae) em milho (Zea mays L.).

Abstract

Bryophytes (mosses, liverworts and hornworts) are widely distributed plants in the world with approximately 15,100 species. The chemical analyzes of this group began in the nineteenth century and in recent decades, the phytochemical researches of the bryophytes constituents and their biological activity is progressing. This is possible due to the greater understanding of the biology of their species and the progressive refinement in analytical techniques. Approximately 1,000 species of bryophytes have been analyzed for their chemical and the results demonstrated that the identified substances are of interest, belonging to the classes of terpenes, aromatic and phenolic compounds, aldehydes, steroids, acetogenins, alkaloids (flavonoids), tannins, saponins, fatty acids, cardiac glycosides, which showed characteristic aromas, bitter or pungent taste, besides exhibiting medicinal, antibiotic, antifungal, antiviral, antifeedant, cytotoxic, and other properties. In Brazil, the chemical knowledge is confined to two works of bryophytes. Facing a promising field for the science and considering the scientific evidences, the present study aimed to determine the chemical composition of Sematophyllum subsimplex (Hedw.) Mitt. and Leucobryum martianum (Hormnsch.) Hampe ex Múll. Hal. occurring in the Brazilian Amazon, and assess the bioactivity of its compounds in controlling of the fall armyworm Spodoptera frugiperda J. E. Smith (Lepidoptera: Noctuidae) in the second instar on com. The collections were made in Parque Ecológico de Gunma, municipality of Santa Bárbara, Pará State, the material was dried under the sun and kept refrigerated. The process for identifying, sorting, and dehydration was performed and the volatile constituents were obtained by micro simultaneous distillation extraction (SDE) and analyzed by gas chromatography / mass spectrometry (GC-MS) in Thermo system. The extract was obtained by trituration and cold maceration with PA ethanol and diluted in dimethylsulfoxide (DMSO). Five treatments were applied (2.0, 1.0, 0.5 and 0.25 ug/uL. and the control with DMSO) for the realization of mortality and antifeedant tests in larvae of second instar of S. frugiperda with evaluation at intervals of 24, 48 and 72 hours. The experimental data were subjected to analysis of variance, for antifeedant and their means compared by Mann-Whitney U test and for mortality was applied Fischer's test with Tocher's modification. 42 chemical constituents were identified belonging to the group of terpenes, fatty acids, aldehydes, aromatic hydrocarbon, alcohol, esters and ethers. The aromatic hydrocarbon naphthalene obtained the highest relative area in both species, the safrole compound is found for the first time in moss. According to the analyzes of the volatile compound, it is possible to estimate that studied species are sources of terpenes, fatty acids, aromatic aldehydes. The bioassays with S. subsimplex revealed that the concentration of 0.25 ug/uL were positive for the antifeedant effect after 24 hours and increased mortality in all treatment concentrations, suggesting toxic effect. To Leucobryum martianum, the application of the extract suggested antifeedant effect independent of concentration, and in mortality the treatment in the concentration of 0.25 ug /uL presented a possible toxic effect after 48 hours. It was concluded that the concentration of 0.25 ug/uL is sufficient to control the caterpillar in the second instar. This work is the first in Brazil to test the insecticide effects and/or antifeedant activity of species of mosses selected for the study, serving as a resource for future works that may also embark to this promising branch that is the knowledge of the active chemical constituents of bryophytes.

The bryophytes are a group of plants with a wide variety of species distributed worldwide. Tn recent years, due to the development of new analytical techniques, it has been verified a great scientific breakthrough involving the chemical studies of bryophytes, managing to elucidate the organic chemicals of this group, their complex molecular structures, and to evaluate the activity of their extracts. The lack of information on the phytochemical of the species is still a big gap, so to contribute to the knowledge of the volatile chemical compounds of bryophytes, the aim of this study was to determine the volatile chemical constituents of mosses species Sematophyllum subsimplex and Leucobryum martianum occurring in the Amazon Brazilian. The samples were collected in Parque Ecológico do Gunma, municipality of Santa Bárbara, Pará State, dried, identified, screened with the aid of tweezers and magnifying glass, kept refrigerated and submitted to extraction by simultaneous distillation-extraction (SDE) to obtain the volatile compounds, which were analyzed by gas chromatography / mass spectrometry (GC-MS). Were identified 42 chemical constituents in pentanics extracts of the two studied species, belonging mainly to the group of terpenes, aromatic hydrocarbons, fatty acids and aldehydes. The aromatic hydrocarbon naphthalene was predominant in both species (S. subsimplex, 26.62% and L. martianum, 72.51%). Leucobrium martianum is the first moss species to present the compound safrole. This study is the first report of the chemical composition for the two selected taxa, in which the results show these mosses as natural sources of compounds such as terpenes, fatty acids and aldehydes.

The com (Zea mays L.) is one of the most important cereals in the world as it is the basis of human and animal nutrition. An important factor that causes extreme losses of up to 60% in production is the attack of the fall armyworm Spodoptera frugiperda J.E. Smith (Lepidoptera: Noctuidae), the key pest of this crop. Your control is mainly done with the application of synthetic insecticides, which cause a number of negative impacts in the environment. The selection of new plant species with insecticidal potential, associated with the integrated pest management, has been considered the most promising technology to control pests. Thus, the bryophytes are a potential group in the discovery of biologically active substances, which can be used to control pests. The aim of this study was to evaluate the antifeedant and/or insecticide effect of the ethanol extract of the moss Sematophyllum subsimplex (Hedw.) Mitt. (Bryophyta) in different concentrations, on larvae in 2nd instar of the fall armyworm, Spodoptera frugiperda, on maize leaves (Zea mays L.) under controlled conditions. The work was conducted in Laboratório de Bioecologia de Insetos of the Universidade Federal Rural da Amazônia (UFRA) / ICA. The creation of the caterpillars were made in the laboratory, under conditions of temperature of 24 + 2 ºC, relative humidity of 70 + 10%, of postures from UFRA. After preparation of the ethanol extract of S. subsimplex, was added 50 uL on com leaf discs in concentrations of 2.0, 1.0, 0.5 and 0.25 ug/uL and the control with DMSO, with five replications, in no-choice tests. 25 larvae in 2nd instar were selected to be fed with the treated maize leaves, and one larva was inoculated into each Petri dish " Herbivory and mortality rates were measured after 24, 48 and 72 hours of application ot the plant extract. The experimental data were submitted to analysis of variance, for antifeedant, and their means compared by Mann-Whitney U test (Siegel, 1956). For mortality was applied Fischer's test (Siegel, 1956). All tests are one-sided, and use a = 0.05 confidence level. To test the significance of not as extreme diferences, was used the Tocher's modification. All analyzes were performed using the BioEstat 5.0 software (Ayres et al., 2007). It was observed that the concentration of 0.25 ug/uL were positive for antifeedant after 24 hours, while mortality in all concentrations, it was found death, suggesting toxic effect. This is the first scientific work reporting the insecticide and/or antifeedant activity of extract of the moss Sematophyllum subsimplex on larvae of 2nd instar of Spodoptera frugiperda.

The fall armyworm Spodoptera frugiperda J.E. Smith is considered key pest of com, by damaging their different physiological stages, causing economically significant damage to production. The control of this insect is made using synthetic chemicals that lead to many environmental problems. The use of plant extracts has been a more and more constant practice, which permits the use of a substance of low toxicity to the environment, while preserving the agroecosystems. The bryophytes can be used for this purpose by the positive evidence of the studies on insecticidal and/or antifeedant activity, in the control of this insect. The aim of this work was to evaluate the effect of the ethanol extract of the moss Leucobryum martianum (Hornsch.) Hampe ex Múll. Hal. (Bryophyta) in different concentrations on 2nd instar larvae of fall armyworm, S. frugiperda on com leaves. The experiment was conducted in Laboratório de Bioecologia de Insetos of the Universidade Federal Rural da Amazônia (UFRA), in ICA, under temperature of 24 + 2 ºC and relative humidity of 70 + 10%. The bioassay was conducted with 25 caterpillars, a completely randomized design, with five treatments (2.0, 1.0, 0.5 and 0.25 ug/uL and the control with DMSO) and five replications. Each repetition was made up of one 2nd instar larva, containing corn leaf discs treated with L. martianum extract. The evaluations of herbivory and mortality were performed after 24, 48 and 72 hours of the extract application. The results were submitted to analysis of variance and the means compared by the Mann Whitney U test, to antifeedant effect and mortality was applied the Fischer's test with Tocher's modification. All tests with a = 0.05 confidence level and analyzes made by BioEstat 5.0 software. The results showed antifeedant effect independent of concentration. For mortality the treatment at concentration of 0.25 ug/uL showed toxic effect after 48 hours. This work is the first in Brazil to test the insecticide and/or antifeedant activity of L. martianum, serving as a resource for future researches.