Phenolic composition and medicinal usage of Psidium guajava Linn.: Antifungal activity or inhibition of virulence?

Abstract

Psidium guajava is a Myrtaceae plant whose medicinal properties are recognized in several locations. The use of teas and tinctures prepared from their leaves has been used to combat infections caused by fungi of the genus Candida. In this study, aqueous extracts of leaves and hydroethanolic were tested to verify the antifungal potential and its chemical composition has been investigated. The microbiological assays were performed by broth microdilution to determine the minimum inhibitory concentration (MIC) and from these the minimum fungicidal concentration was performed (MFC) by subculturing on solid media. A cell viability curve was obtained for demonstration of inhibition of fungal growth of strains of Candida albicans and Candida tropicalis. Tests to check morphological changes by the action of the extracts were performed in microcultive cameras depleted environment at concentrations of MIC/2, MIC and MIC × 2. Extracts analyzed by high performance liquid chromatography demonstrated flavonoids and phenolic acids. The extracts showed fungistatic effect and no fungicide with MIC >8192 μg/mL, MFC above 8192 μg/mL. The IC₅₀ was calculated ranging from 1803.02 to 5623.41 μg/mL. It has been found that the extracts affect the morphological transition capability, preventing the formation of pseudohyphae and hyphae. Teas and tinctures, therefore, have the potential antifungal, by direct contact, causing inhibition of fungal multiplication and its virulence factor, the cell dimorphism, preventing tissue invasion. Further studies are needed to elucidate the biochemical pathways and genes assets involved in these processes.

Keywords: Fungistatic effect; Inhibition of dimorphism; Tea; Tincture.

Figure 1

Chromatogram of Psidium guajava extracts. High performance liquid chromatography phenolics and flavonoids profile of Psidium guajava. (A) Hydroethanolic Extract of P. guajava (HEPG); (B) Aqueous Extract of P. guajava Decoction (AEPGD); Aqueous Extract of P. guajava Infusion (AEPGI); gallic acid (peak 1), catechin (peak 2), chlorogenic acid (peak 3), caffeic acid (peak 4), epicatechin (peak 5), rutin (peak 6), quercitrin (peak 7), isoquercitrin (peak 8), quercetin (peak 9), kaempferol (peak 10) and luteolin (peak 11).

Figure 2

Cell viability curve Candida strains under the effect of Psidium guajava. CA: Candida albicans; CT: Candida tropicalis; INCQS: Instituto Nacional de Controle de Qualidade em Saúde; LM: Laboratório de Micologia; AEPGI: Aqueous Extract of P. guajava Infusion; AEPGD: Aqueous Extract of P. guajava Decoction; HEPG: Hydroethanolic Extract of P. guajava.

Figure 3

Controls used in micromorphology tests. Cell forms of Candida: a: pseudohiphae; b: hiphae; c: yeast; 1, 4, 7 and 10: Growth control; 2, 5, 8 and 11: DMSO 0.05%; 3, 6, 9 and 12: Fluconazole; CA: Candida albicans; CT: Candida tropicalis; INCQS: Instituto Nacional de Controle de Qualidade em Saúde; LM: Laboratório de Micologia. Images inspected under a light microscope using a 40× objective.

Figure 4

Effect of Psidium guajava extracts on the morphology of Candida albicans. Concentrations MIC/2, MIC and MIC × 2 (4096, 8192 and 16384 μg/mL, respectively). Aqueous Extract of P. guajava Decoction (AEPGD): 1–6; Aqueous Extract of P. guajava Infusion (AEPGI): 7–12; Hydroethanolic Extract of P. guajava (EHPG): 13–18. INCQS: Instituto Nacional de Controle de Qualidade em Saúde; LM: Laboratório de Micologia. Images inspected under a light microscope using a 40× objective.

Figure 5

Effect of Psidium guajava extracts on the morphology of Candida tropicalis. Concentrations MIC/2, MIC and MIC × 2 (4096, 8192 and 16384 μg/mL, respectively). Aqueous Extract of P. guajava Decoction (AEPGD): 1–6; Aqueous Extract of P. guajava Infusion (AEPGI): 7–12; Hydroethanolic Extract of P. guajava (EHPG): 13–18. INCQS: Instituto Nacional de Controle de Qualidade em Saúde; LM: Laboratório de Micologia. Images inspected under a light microscope using a 40× objective.