Estudo químico e atividade antifúngica dos óleos essenciais de duas espécies de Psidium L., em função da sazonalidade e em diferentes fases fenológicas

Abstract

The Myrtaceae family is among one of the most representative of Brazilian ecosystems. The presence of secretory structures of essential oils in the vegetative and reproductive organs of these species is a hallmark of the family. Knowledge of the factors that determine the chemical variability of each plant species is very important for chemical and pharmacological investigations. This study aims to evaluate the chemical variability of the essential oils of Psidium myrtoides and Psidium salutare, in different phenological phases and seasonal periods, besides verifying this variation in antifungal activity. The vegetative (foliar and budding) and reproductive (flowering and fruiting) phenotypes were observed as present or absent for two years. To analyze the variability of the chemical constituents of the species, quarterly collections were made during the years 2016 and 2017, including the vegetative and reproductive phases and the rainy and dry seasons. Leaf essential oils were obtained by hydrodistillation in a Clevenger type apparatus and quantified by Gas Chromatography coupled to Mass Spectrometry (GC / MS). The antifungal tests were carried out against fungal strains of Candida albicans, C. tropicalis and C. krusei by broth microdilution method to determine the minimum fungicidal concentration (CFM) from the subculture. Essential oils (CFM / 16) were associated with fluconazole for potentiating effect. The effect on Candida albicans dimorphism was evaluated by optical microscopy in microculture chambers. The essential oils during the two years of study presented yields varying from 0.15 to 0.75% for P. salutare and from 0.35 to 1.17% for P. myrtoides, with higher values in the reproductive period associated with the season rainy A total of 33 constituents were identified in P. myrtoides and 40 in P. salutare, whose major components were 1-8 cineol and γ-terpinene, respectively. Variability in composition and concentration of the compounds was observed, influenced by seasonality and/ or phenophases. The essential oils did not present significant antifungal activity in both species, but they potentiated the effect of the antifungal agent (fluconazole) in all the collection periods. The essential oils affected the morphological transition of C. albicans in increasing concentrations. The results showed that plants sampled in different phenological or seasonal periods have different compositions and, consequently, had vaiations in the bioactive constituents, which in part, may be related to biological activity. Although they are natural products of different plants, the biological effect revealed indicates that species of the genus Psidium may be a potential agent in combating the virulence of fungi of Candida spp., Destined to possible therapeutic uses.