Abstract:
A survey of the metabolite content of fifty-two ascidians collected from New Zealand
and Antarctica is presented. Using biological assays and reversed phase analytical C18 HPLC
techniques, twenty-three specimens were selected for further work. Work on ten of the
selected ascidians is presented in this study. Using standard chromatographic techniques
combined with analytical C18 HPLC, eighteen metabolites were isolated of which sixteen
exhibited biological activity. Ten of the eighteen metabolites were novel, with nine exhibiting
biological activity. The New Zealand endemic ascidian Pycnoclavella kottae, collected from
the Three Kings Islands yielded the novel 2,2,5-trisubstituted imidazol-4-ones, kottamides A -
D (3.1 - 3.4). Three new pyridoacridines (4.80, 4.82, 4.84), along with two known
pyridoacridines and the known benzopentathiepin, varacin were isolated from the New
Zealand endemic ascidian Lissoclinum notti. Varacin was investigated for its use in ADEPT
and a possible prodrug derivative was prepared. In addition, a novel biologically inactive
purine, 8-oxo-1,3-dimethylisoguanine (6.29) was isolated from the New Zealand endemic
ascidian Pseudodistoma cereum. The study of an ascidian of the genus Aplidium, collected
from the Ross Sea, Antarctica resulted in the isolation of two novel quinone derivatives,
rossinones A (5.71) and B (5.72), which exhibited potent cytotoxicity and antiviral activity.
Rossinones A (5.71 ) and B (5.72) provide insights into the biosyntheses of several terrestrial
plant natural products.
In addition, six sea hares of three species collected from the Auckland, New Zealand
region were surveyed using the same methodology, with three novel and seven known
compounds being isolated. The study of the sea hare Aplysia dactylomela resulted in the
isolation of two inactive novel tryptophan dipeptides, dactylamides A (7.9) and B (7.10), the
known ink pigment aplysioviolin and four known sesquiterpenes. A new malyngamide, S
(8.8) along with an algal toxin, lyngbyatoxin A and its acetate were isolated from the sea hare
Bursatella leachii. A survey of nine algae collected from the same locations as the sea hares
resulted in the identification of several of the dietary sources of these sea hares.
Standard spectroscopic techniques were used for structural elucidation, including the
use of natural abundance 1H-15N 2-D NMR where required. All compounds were assayed for
a range of biological activities.