Browsing by Author "Fernandes, Chantal"
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- The antifungal activity of extracts of Osmundea pinnatifida, an edible seaweed, indicates its usage as a safe environmental fungicide or as a food additive preventing post-harvest fungal food contaminationPublication . Silva, Paulo; Fernandes, Chantal; Barros, Lillian; Ferreira, Isabel C.F.R.; Pereira, Leonel; Gonçalves, TeresaIn the present work, we explored the antifungal activity of the wild edible seaweed Osmundea pinnatifida (Rhodophyta) collected from the Portuguese coast, which is used as a food seasoning in Scotland, Ireland and Portugal. We performed a sequential extraction of the seaweed components with methanol, dichloromethane and n-hexane. These extracts showed an antifungal activity against Alternaria infectoria and Aspergillus fumigatus. The n-hexane fraction of the seaweed inhibited the sporulation of Alternaria infectoria at 30 μg mL −1 and induced a statistically significant decrease in β-glucan content. Furthermore, liquid cultures of Aspergillus fumigatus supplemented with 10 μg mL −1 of the n-hexane fraction showed abnormal conidiophores, completely devoid of phialides and conidia associated with a decrease of 18.3% in the chitin content. The n-hexane fraction analysis by GC-MS revealed that it includes palmitic acid (29.6%), phytol isomer 1 (12.8%), oleic acid (9.6%), stearic acid (6.2%) and D-(−)-tagatofuranose (4.1%), among other compounds present at lower concentrations. The present study reveals Osmundea pinnatifida as a promising source of biologically active compounds inhibiting fungal growth and conidiation, the main dispersal mechanism of filamentous fungi as Aspergillus fumigatus and Alternaria alternata, revealing its utility both as an environmental fungicide against fungal diseases and as a food preservative against fungal post-harvest food contamination.
- Antifungal activity of spent coffee ground extractsPublication . Calheiros, Daniela; Dias, Maria Inês; Calhelha, Ricardo C.; Barros, Lillian; Ferreira, Isabel C.F.R.; Fernandes, Chantal; Gonçalves, TeresaCoffee is one of the most popular and consumed products in the world, generating tons of solid waste known as spent coffee grounds (SCG), containing several bioactive compounds. Here, the antifungal activity of ethanolic SCG extract from caffeinated and decaffeinated coffee capsules was evaluated against yeasts and filamentous fungi. These extracts had antifungal activity against Candida krusei, Candida parapsilosis, Trichophyton mentagrophytes, and Trichophyton rubrum, all skin fungal agents. Moreover, SCG had fungicidal activity against T. mentagrophytes and T. rubrum. To understand the underlying mechanisms of the antifungal activity, fungal cell membrane and cell wall components were quantified. SCG caused a significant reduction of the ergosterol, chitin, and β-(1,3)-glucan content of C. parapsilosis, revealing the synthesis of this membrane component and cell wall components as possible targets of these extracts. These extracts were cytotoxic for the tumoral cell lines tested but not for the non-tumoral PLP2 cell line. The analysis of the phenolic compounds of these extracts revealed the presence of caffeoylquinic acid, feruloylquinic acid, and caffeoylshikimic acid derivatives. Overall, this confirmed the antifungal activity of spent coffee grounds, presenting a potential increase in the sustainability of the life cycle of coffee grounds, as a source for the development of novel antifungal formulations, especially for skin or mucosal fungal infections.
- Pyomelanin synthesis in alternaria alternata inhibits DHN-Melanin synthesis and decreases cell wall chitin content and thicknessPublication . Fernandes, Chantal; Mota, Marta; Barros, Lillian; Dias, Maria Inês; Ferreira, Isabel C.F.R.; Piedade, Ana P.; Casadevall, Arturo; Gonçalves, TeresaThe genus Alternaria includes several of fungi that are darkly pigmented by DHNmelanin. These are pathogenic to plants but are also associated with human respiratory allergic diseases and with serious infections in immunocompromised individuals. The present work focuses on the alterations of the composition and structure of the hyphal cell wall of Alternaria alternata occuring under the catabolism of L-tyrosine and L-phenylalanine when cultured in minimal salt medium (MM). Under these growing conditions, we observed the released of a brown pigment into the culture medium. FTIR analysis demonstrates that the produced pigment is chemically identical to the pigment released when the fungus is grown in MM with homogentisate acid (HGA), the intermediate of pyomelanin, confirming that this pigment is pyomelanin. In contrast to other fungi that also synthesize pyomelanin under tyrosine metabolism, A. alternata inhibits DHN-melanin cell wall accumulation when pyomelanin is produced, and this is associated with reduced chitin cell wall content. When A. alternata is grown in MM containing L-phenylalanine, a L-tyrosine percursor, pyomelanin is synthesized but only at trace concentrations and A. alternata mycelia display an albino-like phenotype since DHN-melanin accumulation is inhibited. CmrA, the transcription regulator for the genes coding for the DHN-melanin pathway, is involved in the down-regulation of DHN-melanin synthesis when pyomelanin is being synthetized, since the CMRA gene and genes of the enzymes involved in DHN-melanin synthesis pathway showed a decreased expression. Other amino acids do not trigger pyomelanin synthesis and DHN-melanin accumulation in the cell wall is not affected. Transmission and scanning electron microscopy show that the cell wall structure and surface decorations are altered in L-tyrosine- and L-phenylalanine-grown fungi, depending on the pigment produced. In summary, growth in presence of L-tyrosine and L-phenylalanine leads to pigmentation and cell wall changes, which could be relevant to infection conditions where these amino acids are expected to be available.
- The chemical profile, and antidermatophytic, anti-inflammatory, antioxidant and antitumor activities of Withania chevalieri A.E. Gonc. ethanolic extractPublication . Correia, Edmilson Emanuel Monteiro; Figueirinha, Artur; Rodrigues, Lisa; Pinela, José; Calhelha, Ricardo C.; Barros, Lillian; Fernandes, Chantal; Salgueiro, Lígia; Gonçalves, TeresaWithania chevalieri, endogenous from Cape Verde, is a medicinal plant used in ethnomedicine with a large spectrum of applications, such as treating skin fungal infections caused by dermatophytes. The aim of this work was to chemically characterize the W. chevalieri crude ethanolic extract (WcCEE), and evaluate its bioactivities as antidermatophytic, antioxidant, anti-inflammatory and anticancer, as well as its cytotoxicity. WcCEE was chemically characterized via HPLC-MS. The minimal inhibitory concentration, minimal fungicidal concentration, time-kill and checkerboard assays were used to study the antidermatophytic activity of WcCEE. As an approach to the mechanism of action, the cell wall components, & beta;-1,3-glucan and chitin, and cell membrane ergosterol were quantified. Transmission electron microscopy (TEM) allowed for the study of the fungal ultrastructure. WcCEE contained phenolic acids, flavonoids and terpenes. It had a concentration-dependent fungicidal activity, not inducing relevant resistance, and was endowed with synergistic effects, especially terbinafine. TEM showed severely damaged fungi; the cell membrane and cell wall components levels had slight modifications. The extract had antioxidant, anti-inflammatory and anti-cancer activities, with low toxicity to non-tumoral cell lines. The results demonstrated the potential of WcCEE as an antidermatophytic agent, with antioxidant, anti-inflammatory and anticancer activity, to be safely used in pharmaceutical and dermocosmetic applications.