Adrian J. Blackman

Cylindricines A and B, novel alkaloids from the ascidian clavelina cylindrica

Abstract The ascidian Clavelina cylindrica, which was collected in Tasmania, has yielded two novel alkaloids, cylindricine A, rel-(3R, 4R, 5S, 7aR, 11aR)-3-chloromethyl-5-hexyl-perhydro-pyrrolo-[2,1-j]quinolin-7-one, (12), and cylindricine B, rel-(3S, 5R ,6S ,8aR ,12aR)-3-chloro-6-hexyl-perhydropyrido[2,1-j]quinoline-8-one, (13). Cylindricine B is the first example of the new pyrido-[2,1-j]-quinoline ring system while cylindricine A is the first pyrrolo[2, 1-j]quinoline known from nature. Single crystal X-ray studies support the assignment of the two alkaloids.

Fouling, surface bacteria and antibacterial agents of four bryozoan species found in Tasmania, Australia

Extracts from four species of bryozoans, found in Tasmanian coastal waters, have been demonstrated to exhibit selective antibacterial activity. The four species showed gradations in fouling by encrusting organisms and differential surface bacterial numbers. The two chemically defended species Amathia wilsoni and Orthoscuticella ventricosa had the most active antibacterial extracts and the lowest levels of fouling. In contrast, extracts of Cellaria pilosa and Bugularia dissimilis, which have no known secondary metabolites, had weak antibacterial properties, and colonies showed large numbers of encrusting fouling organisms. Counts of bacteria over the surfaces of the four species revealed that O. ventricosa had the lowest numbers; B. dissimilis and C. pilosa had higher numbers while A. wilsoni had the highest counts, but the most patchy distribution.

Metabolic fate of dietary terpenes from Eucalyptus radiata in common ringtail possum (Pseudocheirus peregrinus)

Arboreal marsupials consume terpenes in quantities that are toxic to other mammals, indicating that they possess special detoxification mechanisms. The metabolic fate of dietary terpenes was studied in the common ringtail possum (Pseudocheirus peregrinus). Three animals were fedEucalyptus radiata leaf for 10 days. Leaf consumption increased over three days to an average steady state of about 10–15 mmol total terpenes per day. GCMS analysis identified six urinary terpene metabolites, which were dicarboxylic acids, hydroxyacids, or lactones. Another nine metabolites could only be shown to be terpene-derived but of unknown structure. The amounts excreted were estimated by GC-FID, using response factors based on carbon content. Total 24-hr excretion of terpene-derived metabolites increased to 6.2–7.6 mmol on days 5–10, while glucuronic acid excretion remained constant at about 1.5 mmol. No other conjugates of terpene metabolites were found. The strategy used by the possum to detoxify dietary terpenes seems to be to polyoxygenate the molecules forming highly polar, acidic metabolites that can be readily excreted. Conjugation is minimal, perhaps to conserve carbohydrate and amino acids.

Distribution of the pigment caulerpin in species of the green alga Caulerpa

Abstract The distribution of the pigment caulerpin in the algal genus Caulerpa has been investigated. Specimens from Bermuda, Florida and Tasmania were examined directly and the results compared with literature reports of the occurrence or absence of caulerpin in various species from diverse locations. These surveys revealed a general correlation of the presence of caulerpin with the absence of peroxidase activity and the presence of bilateral rather than radial morphology.

Localisation of the amathamide alkaloids in surface bacteria of Amathia wilsoni Kirkpatrick, 1888 (Bryozoa: Ctenostomata)

The marine bryozoan Amathia wilsoni contains several brominated secondary metabolites, the alkaloid amathamides A–F. Energy dispersive X-ray analysis coupled with scanning electron microscopy was used to localise bromine in sections of Amathia wilsoni. Bromine concentrations higher than background levels were only found on the surface of the bryozoan and not within any of the different internal cell types. The correlation between bromine levels and a rod-shaped bacterium, ubiquitous to the tip region, points to the bacterium being closely associated with the range of amathamides found in Amathia wilsoni.

Distribution of amathamide alkaloids within single colonies of the bryozoanAmathia wilsoni.

The content and distribution of amathamide alkaloids within single colonies of the bryozoanAmathia wilsoni (Ctenostomata) varied depending on the location in the colony. Three colonies in all, collected from the same site at the same time, were analyzed and gave very similar results. The outermost, more exposed, tips of the colony had an alkaloid content of nearly 9% of dry weight, while basal parts were apparently devoid of alkaloids. Samples taken midway between tips and base yielded intermediate concentrations of about 1%. Very little variation in the proportions of individual amathamides A, B, C, E occurred between exposed tips of the colonies. However, some differences in ratios were found between tips from exposed and more protected regions.

Bryozoan Secondary Metabolites and their Chemical Ecology

Publisher Summary Bryozoans are sedentary, colonial invertebrates that are widely distributed throughout the marine environment, but are less common in fresh water. Many of the compounds from bryozoans exhibit biological activity, most notably the anitineoplastic action of the bryostatins. Despite this, the chemical ecology of compounds from only four bryozoans has been investigated, often as crude extracts rather than pure compounds. One area worthy of more study, not least because of its economic implications, is the effects that bryozoan secondary metabolites have on potential fouling organisms. Meriting further investigation is the generality of the finding that, in the case of one bryozoan there is intercolonial variation of chemical defence. The two observations that pycnogonids sequester bryozoan metabolites show that this phenomenon deserves further study.

Volatile and odorous compounds from the bryozoan Biflustra perfragilis

Volatile components of the malodorous bryozoan Biflustra perfragilis were investigated by GC-MS and the foul smell established as being due to dimethyl disulphide, dimethyl sulphide and methanethiol. Methanol, dichloromethane and chloromethane were also shown to be present. The relative proportions of these compounds were found to vary at different collection sites and over the three-day period of analysis. The probable source of these compounds is also discussed.

Secondary Metabolites from the Marine Alga Caulerpa brownii (Chlorophyta)

The green seaweed Caulerpa brownii (Chlorophyta, Caulerpaceae) occurs in Tasmania in two morphological forms (branched and unbranched) and each form has a different profile of diterpenoid secondary metabolites. Unbranched specimens gave rise to the novel secondary metabolites 11, 13, 14, 17, and 18, the secondary metabolite 8 that has been isolated for the first time as a natural product, as well as the known compounds 1 and 3–7. Branched specimens of C. brownii yielded the novel terpenoid esters 21 and the known compounds 1 and 2.

Halogenated phloroglucinols from Rhabdonia verticillata

Abstract Six bromo- and/or chloro- derivatives of phloroglucinol have been obtained from the red alga Rhabdonia verticillata .