In vitro antifungal activity screening of beach-cast seaweeds collected in Yucatan, Mexico.

The use of natural products in fungal disease control is an approach to reduce the negative impact of synthetic fungicides in agriculture and the environment. Although there are many alternatives, beach-cast seaweeds are a natural source of novel compounds that can be useful against fungal phytopathogens. In this study, aqueous extracts (AEs)of five species of beach-cast seaweeds, Agardhiella subulata, Bryothamnion triquetrum, Codium isthmocladum, Dictyota dichotoma, and Halymenia floresii, collected in Yucatan, Mexico, were tested against Fusarium oxysporum, Colletotrichum gloeosporioides, and Pseudocercospora fijiensis by dilution assays. From these, only H. floresii AE showed antifungal activity against P. fijiensis (13.7 mg mL-1). Furthermore, the protein fraction isolated from this AE was also active against P. fijiensis at 0.625 µg mL-1. The chromatographic profile of H. floresii AE with antifungal activity showed three major peaks at retention times (tR)1.6, 23.0, and 23.9 min, respectively. Analysis of solids in H. floresii AE after lyophilization revealed a possibly sulfated polysaccharide (carrageenan)derivative. The toxicity analysis on Artemia salina showed that this aqueous extract is safe.