Antifungal efficacy of Eugenia uniflora leaves extract: In vitro and in silico investigations against Candida albicans, C. auris and C. glabrata

Abstract

Ethnopharmacological relevance

Eugenia uniflora L. (Myrtaceae), commonly known as pitanga or Brazilian cherry, is widely used in traditional medicine across South America, particularly in Brazil's semi-arid regions, to treat fever, gastrointestinal disorders, and microbial infections. Its therapeutic potential is attributed to phenolic compounds such as myricitrin, gallic acid, and ellagic acid, which exhibit well-documented antimicrobial and anti-inflammatory properties. In the context of the growing global threat posed by multidrug-resistant fungal pathogens, especially species of the Candida genus, exploring natural sources like E. uniflora for antifungal drug development is both timely and necessary.

Aim of the study

Evaluating the antifungal activity of a spray-dried leaf extract of E. uniflora (SDEEu) against Candida spp. (C. albicans, C. glabrata, and C. auris) using in vitro assays and in silico modeling.

Material and methods

The hydroalcoholic extract was spray-dried and subjected to antifungal evaluation. Antifungal activity was initially assessed by determining the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) against Candida albicans, C. glabrata, and C. auris. To analyze time-dependent inhibitory effects, growth kinetics were monitored. Membrane integrity and morphological alterations were investigated using flow cytometry and scanning electron microscopy. Mechanistic assays included ergosterol-binding and biofilm inhibition analyses. Checkerboard assays were conducted to evaluate synergistic interactions with amphotericin B and nystatin. Finally, molecular docking simulations were performed to assess the binding affinity of major phytochemicals to fungal enzymes involved in membrane and cell wall biosynthesis.

Results

The extract exhibited promising antifungal activity, particularly against C. glabrata and C. auris, with MIC and MFC values of 31.25 μg/mL and 62.50 μg/mL, respectively. The growth curve revealed sustained inhibition over 48 h, particularly during the early metabolic adaptation phase. SDEEu induced predominantly necrotic cell death in all tested strains, while C. glabrata also exhibited apoptotic features, accompanied by marked morphological alterations such as membrane disruption and loss of budding. The extract showed strong interaction with membrane sterols and synergistic effects with amphotericin B and nystatin, notably reversing resistance in C. auris, the most drug-resistant strain, with FICI values as low as 0.022. Furthermore, SDEEu inhibited biofilm formation in all strains, reaching up to 50 % inhibition in C. albicans. In silico docking studies demonstrated strong binding affinities of myricitrin with squalene monooxygenase (−7.8 kcal/mol) and 1,3-β-glucan synthase (−9.0 kcal/mol), supporting a multitarget mechanism of action.

Conclusion

These findings validate the traditional use of Eugenia uniflora in the treatment of infectious diseases and underscore its potential as a natural source of antifungal agents. By combining membrane-targeting effects with multitarget enzymatic inhibition, the spray-dried extract demonstrates a robust antifungal profile. Altogether, SDEEu represents a promising candidate for the development of novel therapeutic strategies against drug-resistant Candida infections.