This work describes the isolation and structural elucidation of compounds from the leaves of Myrcia tomentosa (Aubl.) DC. (goiaba-brava) and evaluates the antimicrobial activity of the crude extract, fractions and isolated compounds against bacteria and fungi. Column chromatography was used to fractionate and purify the extract of the M. tomentosa leaves and the chemical structures of the compounds were determined using spectroscopic techniques. The antibacterial and antifungal activities were assessed using the broth microdilution method. The phytochemical investigation isolated 11 compounds: α-bisabolol, α-bisabolol oxide B, α-cadinol, β-sitosterol, n-pentacosane, n-tetracosane, quercetin, kaempferol, avicularin, juglanin and guaijaverin. The crude ethanolic extract and its fractions were tested against 15 bacteria and 9 yeasts. The crude extract inhibited the in vitro growth of yeasts at concentration of 4 to 32 μg/mL. The hexane, dichloromethane, ethyl acetate and aqueous fractions inhibited Candida sp. at concentrations of 4 to 256 μg/mL, whereas the Cryptococcus sp. isolates were inhibited only by the hexane and dichloromethane fractions in minimal inhibitory concentrations (MICs) at 16 to 64 μg/mL. The flavonoid quercetin-3-O-α-arabinofuranose (avicularin) was the most active compound, inhibiting Candida species in concentrations of 2 to 32 μg/mL. The MIC values suggest potential activity of this plant species against yeast.

This study evaluated the antifungal activity and cytotoxicity profile of the ellagitannin punicalagin, a compound extracted from the L. pacari A. St.-Hil (Lythraceae) leaf, against Cryptococcus neoformans species complex. Minimum inhibitory concentrations (MIC) were checked using the broth microdilution method. Minimum fungicidal concentrations (MFC) and time of death were used to confirm the antifungal activity of the compound. The in vitro cytotoxicity of punicalagin was tested in BALB/c3T3 fibroblasts and A549 human lung cancer cell line, while the hemolytic potential was tested on sheep erythrocytes. The morphological changes induced in yeast strains by the presence of punicalagin were also analyzed. Tested on eight isolates of the C. neoformans complex punicalagin showed MIC of 0.5 to 4.0 μg/mL and MFC> 256 μg/mL. Punicalagin also demonstrated a good growth inhibitory activity in time-kill curves, but it was not able to achieve a statistically significant reduction of fungal growth suggesting a fungistatic effect of the compound. In vitro cytotoxicity studies using the two cell lines showed that punicalagin has low activity on these cells and no activity on sheep erythrocytes. Morphological changes were seen in the yeasts strains studied when treated with punicalagin. Therefore, punicalagin is a potential antifungal for important pathogenic yeasts and presents a low cytotoxicity profile associated with no hemolytic effects.

Introduction: This is the fi rst study to examine the in vitro susceptibility and the expression of virulence factors in Candida species in the presence of Pimenta pseudocaryophyllus (Gomes) L.R. Landrum (Myrtaceae), a Brazilian plant known as paucravo. Additionally, the mechanisms of action of the crude ethanol extract and the ethyl acetate and aqueous fractions of this plant were investigated. Methods: The in vitro susceptibility of Candida was tested using the broth microdilution method, whereas an XTT reduction assay was used for biofi lms. Adherence was determined by counting the number of yeast cells that adhered to 100 oral epithelial cells, and hyphal formation was verifi ed in the hyphal induction medium M199. Flow cytometry with propidium iodide and FUN-1 was performed to assess the mechanism of action. Results: The results revealed that the crude ethanol extract and the ethyl acetate and aqueous fractions of P. pseudocaryophyllus inhibited the growth of Candida isolates at a minimal inhibitory concentration (MIC) ranging from 64 to 256µg/mL, whereas the 50% sessile minimal inhibitory concentration (SMIC 50 ) ranged from 512 to >1,024µg/mL. Adherence and hyphal formation were signifi cantly reduced in the presence of the crude ethanol extract and both fractions. Although cell membrane injury was detected, the predominant mechanism of action appeared to be the alteration of yeast metabolism, as demonstrated by fl ow cytometry. Conclusions: Our results indicated that antifungal activity reduced the expression of virulence factors in yeast via the alteration of yeast metabolism, suggesting that the crude extract of P. pseudocaryophyllus and its fractions may contain novel antifungal agents.

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Cryptococcus neoformans é uma levedura encapsulada encontrada no ambiente, responsável por causar meningoencefalite em pacientes com o sistema imune comprometido. No Brasil, a criptococose é a segunda causa de morte por micoses sistêmicas. A eficácia limitada dos fármacos antifúngicos usados no tratamento desta doença tem estimulado a busca por terapias alternativas como, por exemplo, o uso de plantas medicinais. Thymus vulgaris, popularmente conhecida como tomilho, é uma planta aromática cujo óleo essencial (OE) possui propriedades antifúngicas. Este estudo teve como objetivo avaliar a ação do OE de T. vulgaris em isolados clínicos de C. neoformans. Este óleo, analisado por cromatografia gasosa acoplada à espectrometria de massa (CG/EM), revelou como seus principais compostos: timol, ρ-cimeno e linalool. Testes de microdiluição em caldo mostraram a eficácia deste OE contra os isolados fúngicos, com concentrações inibitórias mínimas (CIMs) variando de 32 a 128μg/mL. Testes de interação in vitro ─ OE de T. vulgaris e fluconazol (FCZ) ─ demonstraram não haver potencialização da atividade antifúngica desse fármaco. Avaliou-se também seu efeito no metabolismo celular fúngico e os resultados mostraram alterações na atividade enzimática mitocondrial apenas em concentrações >1.024μg/mL. Os resultados da ação deste OE em eritrócitos humanos indicaram que ele possui baixa atividade citotóxica em valores de MIC. Ao descrever a ação antifúngica de T. vulgaris, esta pesquisa mostra seu potencial como alternativa para o tratamento contra C. neoformans.