Abstract
Background: Opportunistic fungal infections are increasingly common, with Candida albicans being the most common etiological agent; however, in recent years, episodes of candidiasis caused by non-albicans Candida species have emerged. Plants belonging to the Lauraceae family have shown remarkable antifungal effects. This study assessed the anti-Candida activity of Ocotea glomerata extracts and fractions, time of death and the synergistic effects with conventional antifungals. The possible mechanism of action was also addressed. Methods: Minimal inhibitory concentrations (MIC) were determined by broth microdilution technique, and the mechanism of action was assessed by ergosterol, sorbitol, cell viability, reactive oxygen species (ROS) generation and phosphatidylserine externalization tests. Results: All the tested extracts evidenced antifungal activity, but the methanol extract was revealed to be the most effective (MIC = 3.12 μg/mL) on C. krusei. The combination of methanol extract with ketoconazole and fluconazole revealed a synergistic effect for C. krusei and C. albicans, respectively. Fractions 1 and 5 obtained from the methanol extract had fungicidal activity, mainly against C. krusei. Methanol extract did not reveal effects by ergosterol and sorbitol assays; however, it led to an increase in intracellular ROS levels, decreased cell viability, and consequently, cell death. Conclusion: O. glomerata methanol extract may be viewed as a rich source of biomolecules with antifungal activity against Candida spp.
Highlights
Candida species has a high adaptive potential, being able to develop in diverse nutrient-rich environments, and under distinct temperature, pH, osmolarity and oxygen quantity conditions [1].The geographical distribution of Candida spp. has changed over the past few decades, with a decrease in the incidence of C. albicans and an increase in cases of non-albicans Candida species. geographical distribution has a high impact, the clinical features of patients pose a trigger.The epidemiological modification of C. albicans infections in relation to non-albicans Candida species is clinically relevant due to the high rates of resistance to fluconazole among some species [2]
For methanol fraction 1 (FEM1), the presence of gallic acid was observed at 6.443 min, along with others cinnamic derivatives (5.650 min) and flavonoids (25.293 min), which correspond to that found in the O. glomerata methanolic extract (OGME), indicating extract fractionation
The flavonoids found in FEM5 (25.263 and 27.177 min) correspond to the flavonoids in OGME
Summary
Candida species has a high adaptive potential, being able to develop in diverse nutrient-rich environments, and under distinct temperature, pH, osmolarity and oxygen quantity conditions [1]. The high mortality rates, mainly in the Intensive Care Units (ICU), correspond to 15% of the cases of candidemia and are responsible for 50–70% of the systemic cases of fungal infections [3,4] These characteristics associated with a high resistance to antifungals, virulence features and its ability to form biofilms with other species [5], turn Candida spp. into a threat to human health. Natural products provide the basis for many anti-infectious therapies currently in use, including polyenes, echinocandins and flavonoids, three major classes of naturally antifungal drugs [9,10] With this in mind, the Lauraceae botanical family, known for its commercial interest owing to its essential oils, includes approximately 50 genera and 2500 species, of which the Ocotea genus stands out [11]. The present study aimed to chemically characterize the extracts of O. glomerata, as well as to determine its antifungal activity, mainly against Candida spp., and to elucidate its mechanism of action
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