| Summary: | This study was the first to evaluate new world algal species for compounds with
potential for plant virus chemotherapy. Methanolic extracts from 30 species of
marine algae were assayed for antiviral activity against potato virus X (PVX) in
local lesion assays using Chenopodium quinoa L. as host. Extracts from six
algal species (Fucus gardneri Silva, Alaria nana Schrader, Ralfsia sp. (Berkley),
Codium fragile (Suringar) Hariot, Fragilaria oceanica Cleve, Egregia
menziesii (Turner) J.E. Areschoug) inhibited PVX infectivity by more than
80%, with a disproportionate number of these extracts coming from the
phylum Heterokontophyta. Of the six most active extracts, it is the first time
that Fucus gardneri, Ralfsia sp. and Fragilaria oceanica have been reported
as sources of antiviral agents. Antiviral activity from the most potent extract, F.
gardneri, was selected for phytochemical analysis. Fractionation of the crude
extract resulted in the isolation and identification of the polysaccharide alginate
as a source of bioactivity. Alginate inhibited potato virus X infectivity by 95%,
and preliminary transmission electron microscopy indicates that the mode of
action may be related to aggregation of virus particles. Bioactivity in a second
fraction was the result of phenolic and amino-based compounds that have yet
to be positively identified. === Science, Faculty of === Botany, Department of === Graduate
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