Potencial antifúngico de microalgas eucarióticas

Abstract

Microalgae constitute a heterogeneous and diverse group of photosynthesizing microorganisms, which integrate phytoplankton and can be found in the most varied ecosystems. Due to the adaptive physiological capacity of the group, it is considered a rich source of biologically active secondary metabolites. Despite this, there are few published studies on the antifungal potential of microalgae and many species have not yet been contemplated. The aim of this study was to evaluate antifungal potential of the microalgae Ankistrodesmus falcatus, Chaetoceros neogracilis, Desmodesmus brasiliensis, Dunaliella tertiolecta, Kirchneriella lunaris and Tetraselmis gracilis. In the first chapter, a narrative review of the literature on the antifungal activity of extracts and compounds of microalgae against dermatophytes was performed. In the second chapter, the antifungal potential of the ethanolic extracts was tested against the dermatophytes Nannizzia gypsea, N. nana, Trichophyton mentagrophytes and T. tonsurans. The methodology used was broth microdilution, and the range of 0.0115 to 6 mg mL-1 was tested. All microalgal extracts showed antifungal activity, especially the extracts of the microalgae C. neogracilis, D. brasiliensis and K. lunaris, which totally inhibited the growth of all dermatophyte species evaluated. The lowest MIC values recorded were for D. brasiliensis and K. lunaris (MIC 0.188 mg mL-1), against T. tonsurans and N. nana. In the third chapter, a systematic review of the literature on the antifungal activity of microalgae against phytopathogenic fungi was performed. In the fourth chapter, the ethanolic extracts of the microalgae were tested against the phytopathogenic fungi Colletotrichum fructicola, C. gloeosporioides, Fusarium oxysporum and Neoscytalidium dimidiatum. The methodology used was microdilution in broth, being applied the range of 0.0115 to 6 mg mL-1. Four of the extracts evaluated showed antifungal activity (A. falcatus, C. neogracilis, D. brasiliensis and K. lunaris) against two species of fungi (C. fructicola and C. gloeosporioides). The lowest MIC values recorded were for the extract of K. lunaris against C. fructicola (MIC 0.047 mg mL-1) and C. gloeosporioides (MIC 0.75 mg mL-1). This study is a pioneering work on the antifungal activity of these microalgae, but further research can be carried out directed to the isolation and identification of target biomolecules. As well as, in the future, new drugs and biopesticides may be formulated from these extracts, and molecules.