Photodynamic activity of Tagetes minuta extracts against superficial fungal infections

Abstract

Candida and dermatophyte species are the most common causes of superficial mycoses because their treatment can be difficult due to limitations of current antifungal drugs in terms of toxicity, bioavailability, interactions, narrow-spectrum activity, and development of resistance. Photodynamic therapy (PDT) involves the topical administration of a photosensitizer in combination with light of an appropriate wavelength and molecular oxygen that produces reactive oxygen species (ROS), which promote damage to several vital components of the microorganism. Tagetes species are known as a source of thiophenes, biologically active compounds whose antifungal activity is enhanced by irradiation with UVA. The present investigation evaluated Tagetes minuta extracts as a photosensitizer on growth of Candida and dermatophytes and their effect on Candida virulence factors. T. minuta root hexane and dichloromethane extracts demonstrated high photodynamic antifungal activity. Bioautographic assays and chromatographic analysis revealed the presence of five thiophenes with reported photodynamic antifungal activities under UVA. Analysis of ROS production indicated that both type I and II reactions were involved in the activity of the extracts. In addition, the extracts inhibited virulence factors of Candida, such as adherence to epithelial surfaces and germ tube formation and showed efficacy against different Candida morphologies: budding cells, cells with germ tube and biofilms. Results suggested that PDT with T. minuta extracts might become a valuable alternative to the already established antifungal drugs for the treatment of superficial fungal infections.

Natural Photosensitizers in Antimicrobial Photodynamic Therapy

“…Saint John’s wort extract was also studied against human enteric virus under solar irradiation [ 117 ]. Giacone et al [ 118 ] studied the photodynamic effects of Tagetes minuta extracts on Candida species. In addition, APDT approaches using Hibiscus sabdariffa extract in the sanitation of food [ 119 ], Indigofera truxillensis extract against multidrug-resistant microorganisms [ 110 ], Porophyllum obscurum (Spreng.)…”

Evaluation of the antifungal photodynamic activity of Thymophylla pentachaeta extracts against Candida albicans and its virulence factors

“…Subsequently, each plate was sprayed with an aqueous solution of MTT (1 mg/ml) and incubated for another 2 h at 30°C. Yellow inhibition zones appeared against a dark brown background (Giacone et al, 2019;Postigo et al, 2017).…”

“…The culture medium, composed of 1% peptone, 3% glucose, 1 M NaCl, 5 mM CaCl 2 and 1.5 % agar, was autoclaved. When the medium was cooled (50°C), 8% v/v sterile egg yolk emulsion was added and poured into Petri dishes (10 ml in 90-mm Petri dishes) (Giacone et al, 2019). Phospholipase activity produces a dense precipitation zone around the enzymeexpressing colony.…”

“…The culture medium, composed of 0.1 % KH 2 PO 4 , 0.5 % MgSO 4 , 1 % glucose and 1.5 % agar, was adjusted to pH 5.0 and autoclaved. When the medium was cooled (50°C), 0.2 % BSA (as the sole nitrogen source) was added and poured into Petri dishes (10 ml in 90-mm Petri dishes) (Giacone et al, 2019). Cleavage of BSA by aspartyl proteinase results in a clearance zone around the colony that expresses enzymes.…”

“…DC. and Tagetes minuta L. employing standardized methodologies based on Clinical and Laboratory Standards Institute (CLSI) consensus documents (CLSI 2017, Giacone et al, 2019Postigo et al, 2017). Thymophylla pentachaeta (DC.)…”