Antifungal activity of carrageenan extracts from the red alga Chondracanthus teedei var. lusitanicus

Carrageenans extracted from Chondracanthus teedei var. lusitanicus were studied in order to determine their potential antifungal activity. FTIR-ATR and FT-Raman spectroscopic analysis confirmed the presence of a hybrid kappa/iota carrageenan belonging to the gametophyte phase and a hybrid xi/theta carrageenan in the tetrasporophyte phase. Kappa/iota and xi/theta carrageenan induced the formation of swollen hyphal segments in Alternaria infectoria, upon exposure to 125 and 60 mu g mL(-1), respectively. The observed phenotype was similar to those induced by antifungals targeting the fungal cell wall. When exposed to 87.5 mu g mL(-1) of kappa/iota carrageenan, Aspergillus fumigatus hyphae became shortened and highly branched, a phenotype commonly observed in response to antifungals. These morphological alterations were associated with a decrease of the beta-glucan content in A. infectoria after exposure to 150 mu g mL(-1) of kappa/iota and to 100 mu g mL(-1) of xi/theta carrageenan. On the other hand, the chitin cell wall content of A. fumigatus decreased significantly upon exposure to 150 mu g mL(-1) of both extracts, which triggered an increase in the content of beta-glucan. Overall, the present work shows that carrageenans extracted from C. teedei var. lusitanicus cause alterations on the A. fumigatus and A. infectoria cell walls, indicating a marked antifungal activity.