Unexplored endemic fruit species from Brazil: Antibiofilm properties, insights into mode of action, and systemic toxicity of four Eugenia spp.

Brazilian endemic fruit species have aroused attention due to their highly valuable, yet unexplored, agro-industrial, food and therapeutic potential. Herein, we describe the antifungal activity of four Eugenia spp. against Candida albicans biofilms, and further demonstrate insights into their potential mode(s) of action and toxicity in vitro and in vivo. Extracts from different parts (seeds, pulps, leaves) of E. leitonii (EL), E. brasiliensis (EB), E. myrcianthes (EM) and E. involucrata (EI) were obtained (S23°23',W45°39') and chemically characterized by GC/MS. The active extracts were tested against C. albicans biofilm viability and architecture, as well as mode of action, and toxicology using RAW 264.7 macrophages and Galleria mellonella larvae. The MIC values ranged from 15.62 to >2000 μg/mL. The most active extracts were EL (seed, 15.62 μg/mL) and EB (leaf and seeds, 31.25 and 15.62 μg/mL, respectively). Treatment with these extracts at 10xMIC reduced biofilm viability by 54-55% (P < 0.0001) as compared to 42% by nystatin. At 10xMIC, all extracts caused damages to biofilm architecture and integrity, and fewer hyphae remained attached to treated biofilms. None of them was found to interfere with cell wall biosynthesis or complexation with ergosterol. The extracts had low toxicity against macrophages in vitro (P > 0.05) and G. mellonella larvae, with mean in vivo LD of 1500 mg/kg (EL, seeds); 2500 mg/kg (EB, seeds); and 1250 mg/kg (EB, leaf). The phenolic compounds epicatechin and gallic acid were the major constituents in the extracts. Our findings may open avenues for the application of these yet unexplored native fruits in the food and pharmaceutical industry.