Chemical Studies of Egyptian Opisthobranchs: Spongian Diterpenoids from <i>Glossodoris atromarginata</i>

Five new spongian diterpenoids 1−5 have been isolated from the mollusk Glossodoris atromarginata along with four known related metabolites (6−9). The structures were solved by extensive spectroscopic analysis and chemical correlation. The absolute stereochemistry of compound 2 was determined by Mosher's method. A dietary origin is inferred for all these molecules on the basis of their structural analogies with known sponge metabolites, but their transfer from the digestive glands to the dorsal skin suggests a defensive role to thwart predation

Spongian Diterpenes from Australian Nudibranchs: An Anatomically Guided Chemical Study of <i>Gloss</i><i>o</i><i>doris </i><i>a</i><i>tromarginata</i>

An Australian population of the nudibranch mollusk Glossodoris atromarginata has been found to contain furanoditerpenes of the spongian series. Spongia-13(16),14-dien-3-one (1) and 3β-acetoxy-19-hydroxyspongia-13(16),14-dien-2-one (2) were isolated for the first time from a natural source, along with a series of known diterpenes (3−7). Anatomical dissection of the animals revealed the relative distribution and chemical variation of secondary metabolites. Structural studies have provided a basis for chemical comparisons between populations from different geographic locations

Structure and Absolute Stereochemistry of Syphonoside, a Unique Macrocyclic Glycoterpenoid from Marine Organisms

The glycoterpenoid syphonoside (1) is the main secondary metabolite of both the marine mollusk Syphonota geographica and the sea-grass Halophila stipulacea, two Indo-Pacific species migrated to the Mediterranean Sea through the Suez Canal. The structure and the absolute stereochemistry of 1, which displays unique structural features, has been accomplished by using a combination of spectroscopic techniques, degradation reactions, and conformational analysis methods. Compound 1 was able to inhibit high density induced apoptosis in a number of human and murine carcinoma cell lines

Subtle Effects of Biological Invasions: Cellular and Physiological Responses of Fish Eating the Exotic Pest <em>Caulerpa racemosa</em>

<div><p>The green alga <em>Caulerpa racemosa</em> var. <em>cylindracea</em> has invaded Mediterranean seabed including marine reserves, modifying the structure of habitats and altering the distributional patterns of associated organisms. However, the understanding of how such invasion can potentially affect functional properties of Mediterranean subtidal systems is yet to be determined. In this study, we show that <em>C. racemosa</em> changes foraging habit of the native white seabream, <em>Diplodus sargus</em>. In invaded areas, we found a high frequency of occurrence of <em>C. racemosa</em> in the stomach contents of this omnivorous fish (72.7 and 85.7%), while the alga was not detected in fish from a control area. We also found a significant accumulation of caulerpin, one of the main secondary metabolites of <em>C. racemosa</em>, in fish tissues. The level of caulerpin in fish tissues was used here as an indicator of the trophic exposure to the invasive pest and related with observed cellular and physiological alterations. Such effects included activation of some enzymatic pathways (catalase, glutathione peroxidases, glutathione S-transferases, total glutathione and the total oxyradical scavenging capacity, 7-ethoxy resorufin <em>O</em>-deethylase), the inhibition of others (acetylcholinesterase and acylCoA oxidase), an increase of hepatosomatic index and decrease of gonadosomatic index. The observed alterations might lead to a detrimental health status and altered behaviours, potentially preventing the reproductive success of fish populations. Results of this study revealed that the entering of alien species in subtidal systems can alter trophic webs and can represent an important, indirect mechanism which might contribute to influence fluctuations of fish stocks and, also, the effectiveness of protection regimes.</p> </div

PERMANOVA testing differences in two antioxidant biomarkers (CAT and GPx) and activity of EROD of fish population among locations and between invaded (TG and BR) <i>vs</i>. non-invaded locations (PC).

<p>ns = not significant;</p>***<p><i>p</i><0.001.</p

Isolation of Norsesterterpenes and Spongian Diterpenes from <i>Dorisprismatica</i> (= <i>Glossodoris</i>) <i>atromarginata</i>

Ten new norscalarane metabolites (<b>1</b>–<b>10</b>) with the mooloolabene skeleton in which the C-8 methyl substituent of a scalarane is replaced by a C-7/C-8 double bond are described from the nudibranch <i>Doriprismatica</i> (= <i>Glossodoris</i>)<i> atromarginata</i> and characterized by extensive 1D and 2D NMR studies, together with MS data. Also isolated was the known scalarane 12-deacetoxy-12-oxo-deoxoscalarin together with 26 furanoterpenes, nine of which (<b>11</b>–<b>19</b>) are reported for the first time. The high diversity of chemical compounds and variation between individuals and locations could reflect a varied sponge diet or an enzymatic detoxification mechanism

PERMANOVA testing differences in general condition markers of fish population among locations and between invaded (TG and BR) <i>vs</i>. non-invaded locations (PC).

<p>ns = not significant;</p>**<p><i>p</i><0.01.</p

nMDS ordination of the Euclidean distance measure from normalized biomarker data.

<p>A subset of 18 individuals ×15 biomarker responses was used. On each individual, grey circles of increasing size with increasing caulerpin concentration in liver were superimposed.</p

Canonical analysis of principal coordinates discriminating biochemical responses along caulerpin concentration gradient.

<p>CAP was based on the Euclidean distance matrix of the subset multivariate data. Caulerpin concentration in fish liver was represented with grey circles of increasing size superimposed on each specimen.</p

General condition markers and antioxidant biomarkers mean values for three study locations.

<p>Mean (±SE, n=15) of general condition markers (CF, HSI and GSI), antioxidant biomarkers (CAT and GPx) and activity of EROD were represented as a black bar for fish speared in the invaded locations (BR and TG) and white for non invaded area (PC).</p