Constituintes químicos de duas espécies de musgos (Bryophyta) e ação de seus extratos sobre Spodopiera 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.