Antifúngicos naturais e tiabendazol no controle de Colletotrichum gloesporioides, Alternaria alternata e Fusarium solani

Abstract

Fruit production contributes significantly to the Brazilian agribusiness, however, post-harvest loss can reach up to 30% of fruit production, and pathogenic fungal infection is one of the main causes. The anthracnose, caused by the fungus Colletotrichum gloeosporioides, is involved in the deterioration of fruits such as papaya, mango, passion fruit, avocado, sugar-apple and strawberry, Fusarium solani in papaya and passion fruit and Alternaria alternata in papaya, citrus, strawberry, melon and mango. Due to the emergence of resistant fungal strains, concern for food safety and environmental issues has grown, raising interest in alternative methods to control post-harvest losses. In this context, natural compounds, among them antimicrobial peptides and carvacrol, have been highlighted as an alternative in the control due to their high specificity, low level of resistance and wide spectrum of action. The present study aimed to chemically synthesize and to apply dipeptides as antifungal agents, as well as to apply carvacrol alone and in combination with thiabendazole as antifungal agents. Material and methods: peptides c(D-Tyr-L-Leu) and c(D-Pro-D-Tyr) were synthesized in the liquid phase by the coupling between protected amino acid residues and the cyclization reactions of the esterified dipeptides under reflux. The synthetic products were analyzed in liquid chromatograph and their chemical identity confirmed by mass spectrometry. The antifungal activity of the compounds was evaluated in vitro by the microdilution method against C. gloesporioides, F. solani and A. alternata. The synergism test was performed using the "checkerboard" method. The c(D-Tyr-L-Leu) and c(D-Pro-D-Tyr) showed no inhibitory action against C.gloesporioides, F. solani and A. alternata at the concentrations evaluated. Carvacrol presented MICs of 282 μg mL-1, 282 μg mL-1 and 563 μg mL-1 for C. gloesporioides, F. solani and A. alternata, respectively. Yet, it was able to kill these three fungi in concentration of 563 μg mL-1. When carvacrol was associated with thiabendazole, it showed an additive effect against C. gloesporioides (FICI 0.5) and synergistic against A. alternata (FICI 0.141). This way, it was possible to reduce the concentration of carvacrol and thiabendazole by 75% for C. gloesporioides and 87.5% and 98.4% for A. alternata, respectively. The combination of carvacrol and thiabendazole is a proposal to reduce the amount of commercial antimicrobials to be applied in fruit farming.