This thesis describes investigations of marine algal secondary metabolites, with
particular interest in their biomedical and agrichemical potential. Invaluable in such
pursuits have been the access and application of advanced spectroscopic techniques,
such as NMR, and the ability to assess the biological activity of the algal samples in a
variety of diverse protocols, through in-house evaluation and industrial collaborations.
As an in-house bioassay, a survey of algal extracts for molluscicidal activity has
led to the isolation of the previously reported chondrocole C (Portieria hornemanni),
tanikolide (Lyngbya majuscula), and debromoaplysiatoxin (L majuscula).
Debromoaplysiatoxin is 100 times more potent than niclosamide, the commercially
utilized molluscicide. Such activity may make debromoaplysiatoxin an attractive agent
for molluscan biological control to prevent the spread of schistosomiasis in artificial
waterways such as irrigation channels and rice paddies.
The isolation of chondrocole C led to further chemical investigations of P.
hornemanni. A total of six related polyhalogenated monoterpenes were isolated from
this collection. While four of these compounds were previously reported,
taviochtodene represents the newest member of this class of secondary metabolites.
Previously, this alga has yielded compounds with great potential anticancer utility, but
naturally and synthetically elusive. The discovery of this class of chemistry potentially
locates new geographic territory to search for such anticancer metabolites.
While there has been little reported biological activity attributed to the
malyngamides, they form the most prevalent class of secondary metabolites isolated
from Lyngbya majuscula. To this list we have added malyngamides L, Q, and R. Of
particular note, malyngamides Q and R were the first malyngamides to have been
reported with altered stereochemistry at the vinyl chloride carbon. Subsequently, and
in part stimulated by this finding, this alternate stereochemistry has been defined for
some newly reported malyngamides.
Also from L majuscula, tortugin and lyngbyabellin B were isolated as toxic
cyclic depsipeptides. Both of these compounds displayed relatively potent biological
activity (brine shrimp and antifungal). Each possessing particular structural motifs
previously seen in invertebrate secondary metabolites, they lend further evidence for
cyanobacteria as the producer of many of the polyhalogenated compounds often
attributed to de novo invertebrate biosynthesis. / Graduation date: 2002
|10 October 2001
|Milligan, Kenneth Edward
|Gerwick, William H.
|Oregon State University
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