Dr Ian Van Altena

Chemical investigation of the dichloromethane extracts of Dioscorea luzonensis Schauer. tubers led to the isolation of long chain alkyl trans-ferulates (1), a mixture of 1 and ß-sitosterol (2), and fatty acids from the skin; and ursolic acid (3) and fatty acids from the inner portion. The structures of 1-3 were identified by comparison of their NMR data with literature data.

Chemical investigation of the dichloromethane extract of the leaves of Hoya pubicalyx Merr. yielded taraxerol (1), ß-sitosterol (2) and stigmasterol (3). The structures of 1-3 were identified by comparison of their NMR data with those reported in the literature.

Larvae of the ascidian Clavelina moluccensis do not settle in the field on the sponge Crella incrustans and are deterred from settling by crude chemical extracts of the sponge. Progressive refinement of extracts, guided by bioassays, led to the identification of lyso-platelet-activating factor (lyso-PAF) from the sponge, lyso-PAF is inhibitory in assays using ascidian, bryozoan, barnacle, and algal settlement and mussel byssal attachment. Its role in the field has not yet been demonstrated. © 1996 Plenum Publishing Corporation.

A new cytotoxic aromatic alkaloid, pantherinine [1], and a mixture of nucleosides including 7-deazainosine [3] have been isolated from the ascidian Aplidium pantherinum collected at Stenhouse Bay, South Australia. The structures were determined primarily from 1H and 13C-nmr data, especially one-bond and multiple-bond proton-carbon correlations. Although 7-deazainosine [3] has been known as a synthetic compound for several decades, this appears to be the first report of its isolation as a natural product. © 1993, American Chemical Society. All rights reserved.

Detailed spectroscopic and cytotoxicity data are reported for two new isoquinolinequinones, perfragilins A [1] and B [2], which were isolated from the bryozoan Membranipora perfragilis collected in South Australia. Both compounds, which are speculated to be of microbial origin, contain a relatively uncommon thiomethyl ether functionality. © 1993, American Chemical Society. All rights reserved.

Estes and Steinberg hypothesized that the intensity of sublittoral marine plant-herbivore interactions among different temperate regions has differed over the past 5-10 million yr, due to differences in the influence of diving mammals that prey on marine herbivores. They argued that because diving predators have not occurred in temperate Australasia, densities of sublittoral herbivores have been historically higher there than in comparable North American systems. This has resulted in marine algae and herbivores in temperate Australasia having strong selective effects on each other. Estes and Steinberg predicted that one result of these strong interactions would be that invertebrate herbivores in temperate Australasia should have evolved greater tolerance to brown algal phlorotannins (polyphenolic compounds that are the dominant secondary metabolites in temperate brown seaweeds) than similar herbivores in North America. We tested this prediction for five invertebrate herbivores in temperate Australasia, Most work was done on three herbivores from New South Wales, Australia, the sea urchins (echinoids) Tripneustes gratilla and Centrostephanus rodgersii, and the gastropod (snail) Turbo undulata. Additional experiments were done using Evechinus chloroticus (urchin) and Cookia sulcata (gastropod) from New Zealand. Both the short-term effects of phlorotannins on feeding behavior, and the longer term effects of phlorotannins on the growth or mortality of herbivores were assessed by (a) feeding the herbivores an array of algal species that varied in their phenolic content, and (b) extracting mixed fractions of phlorotannins from the algae and using these extracts to experimentally manipulate the phlorotannin content of palatable agar disks. The phenolic content of algae used in feeding experiments in Australia was sampled seasonally for 3 yr, and the algae were divided into two groups. These included a phenolic-rich group of five species with a mean phenolic content = 7.02% dry mass (range of species means 6.6-7.2%), and a phenolic-poor group of four species with a mean of 2.69% (range of means = 2.23.1%). In strong contrast to earlier results from North America, no Australian herbivore consistently preferred phenolic-poor species over those rich in phenolics. Algal phenolic levels also were not correlated with feeding preferences of the New Zealand herbivores. The Australian herbivores were generally not deterred by the addition of extracted phlorotannins to agar disks at concentrations of 5 mg/mL (13.5% dry mass) in the disks. However, some extracts deterred some herbivores, indicating that the effects of phlorotannins on the herbivores are variable. The effects of phlorotannins at higher concentrations (8 mg/mL or 18.5% dry mass) were equivocal. Deterrence was increased in some instances, but elevated concentrations of phlorotannins from Carpophyllum maschalocarpum enhanced feeding by Tripneustes gratilla. Algal phenolic levels were not correlated with the growth of juvenile Tripneustes gratilla raised on a variety of algal diets for 7 mo in the field. Conversion efficiencies of algal biomass to urchin biomass by these echinoids also did not covary with algal phenolic content. Growth of T. gratilla on agar diets for 7 mo was not affected by the addition of phlorotannins extracted from Sargassum vestitum to the agar at a concentration of 5 mg/mL. Growth of the gastropod Turbo undulata over 9.5 mo on selected algal diets was fastest for one measure of growth for snails fed a diet of the phenolic-poor Sargassum linearifolium, but algal phenolic levels were not correlated with growth of T. undulata for two other measures of growth. Moreover, conversion efficiencies of Turbo undulata did not vary with diet, indicating that any differences in growth among different diets were due to differences in consumption rather than some physiological effect. This last conclusion was supported in an experiment where T. undulata was grown on agar...

Recent work indicates that the responses of marine hervibores to brown algal (Phaeophyta) phlorotannins (polyphloroglucinols) differ between herbivores from temperate North America and Australasia. One possible explanation for this difference is that phlorotannins from algae from the two regions differ chemically, and hence affect hervibores differentially. We tested this idea by comparing 13C NMR spectra, elemental analyses, and molecular weight distributions of pholorotannins from three species of Australasian brown algae with analogous published data from phlorotannins of North American phaeophytes. NMR spectra and the results of elemental analyses of algal phlorotannins from the two hemispheres were similar. Compounds from the Australasian algae generally had lower molecular weight distributions, although the number of species compared (two from each region) was small. We conclude that chemical differences among the compounds do not adequately explain the differences in their effects on hervibores from the two hemispheres. Several additional arguments are presented which further support this conclusion. © 1992.

Some 63% of larvae of the colonial ascidian Podoclavella moluccensis settled on their first contact with the substratum, while a small percentage made ten or more contacts prior to settlement. Two species of subtidal sponge, Mycale sp. and Crella incrustans, were consistently avoided by settling larvae. Settlement by ascidian larvae may be inhibited by natural products released from or at the surface of these sponges. -from Authors

High levels of polyphloroglucinol phenolics in marine brown algae are usually interpreted as a defensive response to herbivory. However, tropical brown algae generally contain very low levels of phenolics, even though herbivory in many tropical systems (e.g. coral reefs) is intense. This apparent paradox would be explained if polyphenolics did not deter tropical herbivores, in which case selection by herbivores for high levels of phenolics in tropical algae would be weak. To examine this hypothesis, in February 1989 we presented mixed assemblages of herbivorous fishes on the Great Barrier Reef with tropical, phenolic-poor brown algae (primarily Sargassum spp.) and closely related (conspecifics in one instance) phenolic-rich temperate species. Different species of brown algae were eaten at very different rates, but these differences were not correlated with variation in the phenolic levels among the plants. TLC and NMR analyses showed no evidence of other, non-polar, metabolites in these algae, with the exception of the temperate species Homoeostrichus sinclairii. Thus, variation in non-polar metabolites also did not explain the differences in susceptibility to herbivores among these algae. We conclude that the herbivorous fishes studied here were not deterred by phenolic-rich algae, which suggests that levels of phenolics in many tropical algae may generally be low due to their ineffectiveness as defences. However, alternative explanations for the pattern are possible, and these are discussed. © 1991 Springer-Verlag.

The metabolites of the sponge Euryspongia sp. (Dysideidae) were investigated. The sponge was shown to contain the previously unknown sesquiterpene epoxides (15) and (16), and three known compounds, dehydrodendrolasin (1), thiofurodysinin acetate (13) and thiofurodysin acetate (14). Based on the spectral data of (1) and the synthetic compounds (l'E)- and (1'Z)-3-(4', 8'-dimethylnon-1-enyl)furan (5) and (6), the structures of ¿the cis isomer of dehydrodendrolasin¿ (2), tetradehydrofurospongian-1 (3) and the related C21 furanoterpene (4) should be reevaluated. © 1989 ASEG.

The alga Cystophora moniliformis contains two new bisnorsesquiterpenes, (5E, 9E)-5, 6-epoxy-6, 10, 14-trimethylpentadeca-9, 13-dien-2-one (3) and its cyclized derivative (4), and the (2E) and (2Z) isomers of geranylgeranal epoxide, (5) and (6), respectively. The structures of the new compounds were deduced by spectroscopic means. Geranylacetone (1) was the major metabolite present in the alga. © 1988 ASEG.

The metabolites produced in liquid culture by the Ascomycetous fungus Gremmeniella abietina (Lagerb.) Morelet, the causative agent of Sclerodems canker in pines, have been investigated. The major metabolite, which we have named sclerodin, is (-)-4,7-dihydroxy-2,3,3,9-tetramethyl-2,3-dihydronaphtho[1,2-b]furan-5,6-dicarboxylainch ydride (I), the enantiomer of the so-called "naphthalic anhydride from atrovenetin". Several highly colored compounds, including the enantiomer of atrovenetinone (3), the blue compound 6, the red acenaphthenequinone derivative 8 (sclerodione), and the yellow 8-hydroxysclerodin (12) were also obtained. The blue compound 6, named Sclerodems blue, has been prepared from 3, and sclerodione (8) has been transformed into sclerodin (1).

A furanoquinol, C22H28O3, extracted from a sinularian soft coral has been shown to have the structure (3) based on spectroscopic evidence and the preparation of the related furanoquinone (4). Tables of 1H and 13C n.m.r. values for compounds (3) and (4) are given in two solvents. The compound (3) is best regarded as a modified polyprenylated quinol, and has the systematic name: 2-[3', 7'-dimethyl-8'-(4"-methyl-2"-furyl)octa-2, 6'-dienyl]-5-methylhydroquinone. © 1978, CSIRO. All rights reserved.

A new bicyclic diterpene, (3E, 5E)-2-methyl-6-[(2'7R*, 4a'S*, 8a'R*)-4a'-methyl-8-methylene-trans-per- hydronaphthalen-2'-yl]hepta-3, 5-dien-2-ol (1), is reported as the major terpenoid component from Lobophytum hedleyi. It represents the first non-cembranoid diterpene to be reported from soft corals. A minor component in the coral is tentatively identified as the 7-hydroxy derivative of (1). Evidence for the structure of (1) is mainly spectroscopic but final proof rests on degradation and conversion into a known compound. © 1978, CSIRO. All rights reserved.