Variação sazonal na produção de metabólitos secundários e na atividade antimicrobiana de espécies vegetais do semiárido brasileiro

Abstract

The Brazilian semiarid region, where the dominant biome is Caatinga, presents high phytodiversity when compared to other tropical natural formations, but this phytodiversity is not explored about its pharmacological potential. The Caatinga biome, being inserted into a region with soil and environmental peculiar characteristics, features differentiated metabolism of species presented, and in particular plant species. The objective of this study was to evaluate the chemical composition and antimicrobial activity against Streptococcus salivarius, Streptococcus oralis, Straphylococcus aureus, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Candida albicans, Candida krusei and Candida guilliermondii of the extracts from plant species Guapira graciliflora (Mart.) Lundell and Pseudobombax marginatum (A. St .- Hil., Juss. Cambess &.) A. Robyns, testing the hypothesis that there would be differences in the production of analyzed secondary metabolites due to climatic changes occurring between the rainy and dry seasons, the seasonality of rainfall striking the Brazilian semiarid region. The collects of plant specimens were carried out during the dry season (February 2011) and at the end of the rainy season (August 2011) in Vereda Grande location (7 ° 32.013 'S, 36 ° 3.018' W), municipality of Barra Santana. After drying of the plants the ethanolic extracts were obtained, and subjected to qualitative and quantitative phytochemical screening, in order to determine the content of total polyphenols and total flavonoids. Further microbial screening of extracts was conducted against gram positive, gram negative bacteria and yeasts by broth microdilution method, defining the MIC and the MMC. It was detected the presence of tannins, phenols, flavonoids and alkaloids in tested species for both two time periods, however the concentration of polyphenols was higher in the winter for P. marginatum and summer for G. graciliflora, while for the flavonoids occurred otherwise. Antimicrobial activity only P. marginatum showed inhibition against S. salivarius, S. oralis, S. aureus, E. faecalis, E. coli, K. pneumoniae and C. guilliermondii and antibiosis against S. salivarius, S. aureus, K. pneumoniae and E. coli, with variation in MIC and MMC between the two stations. The results presented indicate that these plants can be used as a natural source of materials for medicinal purposes and as a basis for the production of synthetic substances for therapeutic purposes against the organisms that were sensitive in this study.