A study of some Jamaican seaweeds revealed that
Acantharus chirurgus (doctor fish) avoided the Jamaican
variety of Laurencia obtusa but that they found a second
species of the same genus, Laurencia papillosa to be quite
palatable.
A chloroform-methanol extract from Laurencia obtusa was
found to be highly toxic to the fish. The absence of
biological activity in Laurencia papillosa compared to
Laurencia obtusa prompted a chemical investigation of
both species.
Extracts from Laurencia papillosa revealed a mixture of fats and bioactivity studies, which included the brine shrimp assay and the fungal disc assay, indicated that the extract contained no bioactive components.
On the other hand, Laurencia obtusa afforded the known toxin, (+)-elatol, in addition to two novel sesquiterpenes, 2-chloro-3-hydroxy-a-chamigren-9-one and 2-chloro-3,7-epoxy-a-chamigran-9-one, which were closely related to elatol. The results of the tests showed that the extract and the above-mentioned compounds were bioactive.
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