3 results for Appleton, David

  • Ascidians and sea hares: rich sources of Bioactive Natural Products

    Appleton, David (2003)

    Doctoral thesis
    The University of Auckland Library

    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.

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  • A Convenient New Route to 4-Substituted Benzo[de][3,6]Phenanthrolin-6(6H)-Ones: Important Intermediates in the Synthesis of Ring-A Analogues of the Cytotoxic Marine Alkaloid Ascididemin

    Copp, Brent; Hansen, RP; Appleton, David; Lindsay, Brent; Squire, Christopher; Clark, George; Rickard, Clifton (1999)

    Journal article
    The University of Auckland Library

    4-ethylthio- and 4-(4″-methylphenylthio)benzo[de][3,6]phenanthrolin-6(6H)-one have been synthesised in 4 steps from benzoquinone and then readily converted to the 4-amino (6d) and 4-methoxy (6c) analogues by nucleophilic substitution. Further elaboration of 6d leads to the synthesis of 11-hydroxyascididemin, which we have found to exhibit antiviral activity in vitro.

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  • A new biologically active malyngamide from a New Zealand collection of the sea hare Bursatella leachii

    Appleton, David; Sewell, Mary; Berridge, MV; Copp, Brent (2002)

    Journal article
    The University of Auckland Library

    A new malyngamide, S (1), was isolated from a New Zealand collection of the sea hare Bursatella leachii and structurally characterized by spectroscopic methods and chemical degradation. Malyngamide S exhibited cytotoxicity and antiinflammatory properties.

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