ABSTRACT
Background: The rising prevalence of fungal infections and challenges such as adverse effects and resistance against existing antifungal agents have driven the exploration of new antifungal substances. Methods: We specifically investigated naphthoquinones, known for their broad biological activities and promising antifungal capabilities. It specifically examined the effects of a particular naphthoquinone on the cellular components of Candida albicans ATCC 60193. The study also assessed cytotoxicity in MRC-5 cells, Artemia salina, and the seeds of tomatoes and arugula. Results: Among four tested naphthoquinones, 2,3-DBNQ (2,3-dibromonaphthalene-1,4-dione) was identified as highly effective, showing potent antifungal activity at concentrations between 1.56 and 6.25 µg mL-1. However, its cytotoxicity in MRC-5 cells (IC50 = 15.44 µM), complete mortality in A. salina at 50 µg mL-1, and significant seed germination inhibition suggest limitations for its clinical use. Conclusions: The findings indicate that primary antifungal mechanism of 2,3-DBNQ might involve disrupting fungal membrane permeability, which leads to increased nucleotide leakage. This insight underscores the need for further research to enhance the selectivity and safety of naphthoquinones for potential therapeutic applications.
ABSTRACT
Background: This study aimed at improving a real-time polymerase-chain-reaction (qPCR) assay for the detection of Histoplasma capsulatum, a fungal pathogen that can cause severe respiratory infections in humans, in clinical and soil samples. Methods: Primer and probes were in-silico designed, in-silico and in-vitro evaluated including clinical biopsy materials and finally subjected to a real-world application with collected soil samples. Results: Applying the qPCR assay with liver and lung biopsies from 71 patients each, including 59 patients infected with human immunodeficiency virus (HIV), as well as with Sabouraud (SAB) agar culture as the diagnostic reference standard, diagnostic accuracy of the qPCR assay of 100% (5/5) sensitivity and 96% (63/66) specificity for liver samples and 100% (4/4) sensitivity and 94% (63/67) specificity for the lung samples was recorded. When applying the assay with soil samples from caves near of Presidente Figueiredo city, Amazonas, Brazil, one sample from the Maroaga cave was confirmed as positive. Conclusions: The improved qPCR assessed in this study was successful in detecting H. capsulatum with high efficiency and accuracy in in-vitro evaluation, including the identification of the target pathogen in both clinical and environmental samples.