The Experts below are selected from a list of 3945 Experts worldwide ranked by ideXlab platform
Karen L. Cheney - One of the best experts on this subject based on the ideXlab platform.
-
distribution of defensive metabolites in Nudibranch molluscs
Journal of Chemical Ecology, 2018Co-Authors: Anne E. Winters, Nerida G. Wilson, Andrew M. White, Mary J. Garson, Ariyanti Suhita Dewi, Wayan I Mudianta, Louise C Forster, Karen L. CheneyAbstract:Many plants and animals store toxic or unpalatable compounds in tissues that are easily encountered by predators during attack. Defensive compounds can be produced de novo, or obtained from dietary sources and stored directly without selection or modification, or can be selectively sequestered or biotransformed. Storage strategies should be optimized to produce effective defence mechanisms but also prevent autotoxicity of the host. Nudibranch molluscs utilize a diverse range of chemical defences, and we investigated the accumulation and distribution of defensive secondary metabolites in body tissues of 19 species of Chromodorididae Nudibranchs. We report different patterns of distribution across tissues, where: 1) the mantle had more or different (but structurally related) compounds than the viscera; 2) all compounds in the mantle were also in the viscera; and 3) the mantle had fewer compounds than the viscera. We found no further examples of species that selectively store a single compound, previously reported in Chromodoris species. Consistent with other studies, we found high concentrations of metabolites in mantle rim tissues compared to the viscera. Using bioassays, compounds in the mantle were more toxic than compounds found in the viscera for Glossodoris vespa Rudman, 1990 and Ceratosoma brevicaudatum Abraham, 1876. In G. vespa, compounds in the mantle were also more unpalatable to palaemonid shrimp than compounds found in the viscera. This indicates that these species may modify compounds to increase bioactivity for defensive purposes and/or selectively store more toxic compounds. We highlight clear differences in the storage of sequestered chemical defences, which may have important implications for species to employ effective defences against a range of predators.
-
spongian 16 one diterpenes and their anatomical distribution in the australian Nudibranch goniobranchus collingwoodi
Journal of Natural Products, 2017Co-Authors: Louise C Forster, Karen L. Cheney, Anne E. Winters, Robert J. Capon, Pradeep Dewapriya, Mary J. GarsonAbstract:Six new (1-6) spongian-16-one analogues have been characterized from the Australian Nudibranch species Goniobranchus collingwoodi, along with four known spongian-16-one derivatives. The structures and relative configuration were suggested by spectroscopic analyses informed by molecular modeling. Dissection of animal tissue revealed that the mantle and viscera differ in their terpene composition. Whole body extracts were not toxic to brine shrimp (Artemia sp.), but were unpalatable to palaemon shrimp (Palaemon serenus) at a concentration found within the Nudibranch. Individual terpenes were not cytotoxic to human lung (NCIH-460), colorectal (SW620), and liver (HepG2) cancer cells.
-
Choose Your Weaponry: Selective Storage of a Single Toxic Compound, Latrunculin A, by Closely Related Nudibranch Molluscs.
PloS one, 2016Co-Authors: Karen L. Cheney, Anne E. Winters, I. Wayan Mudianta, Ernesto Mollo, Andrew M. White, Michelle Quezada, Robert J. Capon, Mary J. GarsonAbstract:Natural products play an invaluable role as a starting point in the drug discovery process, and plants and animals use many interesting biologically active natural products as a chemical defense mechanism against predators. Among marine organisms, many Nudibranch gastropods are known to derive defensive metabolites from the sponges they eat. Here we investigated the putative sequestration of the toxic compound latrunculin A—a 16-membered macrolide that prevents actin polymerization within cellular processes—which has been identified from sponge sources, by five closely related Nudibranch molluscs of the genus Chromodoris. Only latrunculin A was present in the rim of the mantle of these species, where storage reservoirs containing secondary metabolites are located, whilst a variety of secondary metabolites were found in their viscera. The species studied thus selectively accumulate latrunculin A in the part of the mantle that is more exposed to potential predators. This study also demonstrates that latrunculin-containing sponges are not their sole food source. Latrunculin A was found to be several times more potent than other compounds present in these species of Nudibranchs when tested by in vitro and in vivo toxicity assays. Anti-feedant assays also indicated that latrunculin A was unpalatable to rock pool shrimps, in a dose-dependent manner. These findings led us to propose that this group of Nudibranchs has evolved means both to protect themselves from the toxicity of latrunculin A, and to accumulate this compound in the mantle rim for defensive purposes. The precise mechanism by which the Nudibranchs sequester such a potent compound from sponges without disrupting their own key physiological processes is unclear, but this work paves the way for future studies in this direction. Finally, the possible occurrence of both visual and chemosensory Mullerian mimicry in the studied species is discussed.
-
Conspicuous visual signals do not coevolve with increased body size in marine sea slugs
Journal of Evolutionary Biology, 2014Co-Authors: Karen L. Cheney, Fabio Cortesi, Martin J. How, Nerida G. Wilson, Simon P. Blomberg, Anne E. Winters, Schery Umanzor, N. J. MarshallAbstract:Many taxa use conspicuous colouration to attract mates, signal chemical defences (aposematism) or for thermoregulation. Conspicuousness is a key feature of aposematic signals, and experimental evidence suggests that predators avoid conspicuous prey more readily when they exhibit larger body size and/or pattern elements. Aposematic prey species may therefore evolve a larger body size due to predatory selection pressures, or alternatively, larger prey species may be more likely to evolve aposematic colouration. Therefore, a positive correlation between conspicuousness and body size should exist. Here, we investigated whether there was a phylogenetic correlation between the conspicuousness of animal patterns and body size using an intriguing, understudied model system to examine questions on the evolution of animal signals, namely Nudibranchs (opisthobranch molluscs). We also used new ways to compare animal patterns quantitatively with their background habitat in terms of intensity variance and spatial frequency power spectra. In studies of aposematism, conspicuousness is usually quantified using the spectral contrast of animal colour patches against its background; however, other components of visual signals, such as pattern, luminance and spectral sensitivities of potential observers, are largely ignored. Contrary to our prediction, we found that the conspicuousness of body patterns in over 70 Nudibranch species decreased as body size increased, indicating that crypsis was not limited to a smaller body size. Therefore, alternative selective pressures on body size and development of colour patterns, other than those inflicted by visual hunting predators, may act more strongly on the evolution of aposematism in Nudibranch molluscs.
Anne E. Winters - One of the best experts on this subject based on the ideXlab platform.
-
distribution of defensive metabolites in Nudibranch molluscs
Journal of Chemical Ecology, 2018Co-Authors: Anne E. Winters, Nerida G. Wilson, Andrew M. White, Mary J. Garson, Ariyanti Suhita Dewi, Wayan I Mudianta, Louise C Forster, Karen L. CheneyAbstract:Many plants and animals store toxic or unpalatable compounds in tissues that are easily encountered by predators during attack. Defensive compounds can be produced de novo, or obtained from dietary sources and stored directly without selection or modification, or can be selectively sequestered or biotransformed. Storage strategies should be optimized to produce effective defence mechanisms but also prevent autotoxicity of the host. Nudibranch molluscs utilize a diverse range of chemical defences, and we investigated the accumulation and distribution of defensive secondary metabolites in body tissues of 19 species of Chromodorididae Nudibranchs. We report different patterns of distribution across tissues, where: 1) the mantle had more or different (but structurally related) compounds than the viscera; 2) all compounds in the mantle were also in the viscera; and 3) the mantle had fewer compounds than the viscera. We found no further examples of species that selectively store a single compound, previously reported in Chromodoris species. Consistent with other studies, we found high concentrations of metabolites in mantle rim tissues compared to the viscera. Using bioassays, compounds in the mantle were more toxic than compounds found in the viscera for Glossodoris vespa Rudman, 1990 and Ceratosoma brevicaudatum Abraham, 1876. In G. vespa, compounds in the mantle were also more unpalatable to palaemonid shrimp than compounds found in the viscera. This indicates that these species may modify compounds to increase bioactivity for defensive purposes and/or selectively store more toxic compounds. We highlight clear differences in the storage of sequestered chemical defences, which may have important implications for species to employ effective defences against a range of predators.
-
spongian 16 one diterpenes and their anatomical distribution in the australian Nudibranch goniobranchus collingwoodi
Journal of Natural Products, 2017Co-Authors: Louise C Forster, Karen L. Cheney, Anne E. Winters, Robert J. Capon, Pradeep Dewapriya, Mary J. GarsonAbstract:Six new (1-6) spongian-16-one analogues have been characterized from the Australian Nudibranch species Goniobranchus collingwoodi, along with four known spongian-16-one derivatives. The structures and relative configuration were suggested by spectroscopic analyses informed by molecular modeling. Dissection of animal tissue revealed that the mantle and viscera differ in their terpene composition. Whole body extracts were not toxic to brine shrimp (Artemia sp.), but were unpalatable to palaemon shrimp (Palaemon serenus) at a concentration found within the Nudibranch. Individual terpenes were not cytotoxic to human lung (NCIH-460), colorectal (SW620), and liver (HepG2) cancer cells.
-
Choose Your Weaponry: Selective Storage of a Single Toxic Compound, Latrunculin A, by Closely Related Nudibranch Molluscs.
PloS one, 2016Co-Authors: Karen L. Cheney, Anne E. Winters, I. Wayan Mudianta, Ernesto Mollo, Andrew M. White, Michelle Quezada, Robert J. Capon, Mary J. GarsonAbstract:Natural products play an invaluable role as a starting point in the drug discovery process, and plants and animals use many interesting biologically active natural products as a chemical defense mechanism against predators. Among marine organisms, many Nudibranch gastropods are known to derive defensive metabolites from the sponges they eat. Here we investigated the putative sequestration of the toxic compound latrunculin A—a 16-membered macrolide that prevents actin polymerization within cellular processes—which has been identified from sponge sources, by five closely related Nudibranch molluscs of the genus Chromodoris. Only latrunculin A was present in the rim of the mantle of these species, where storage reservoirs containing secondary metabolites are located, whilst a variety of secondary metabolites were found in their viscera. The species studied thus selectively accumulate latrunculin A in the part of the mantle that is more exposed to potential predators. This study also demonstrates that latrunculin-containing sponges are not their sole food source. Latrunculin A was found to be several times more potent than other compounds present in these species of Nudibranchs when tested by in vitro and in vivo toxicity assays. Anti-feedant assays also indicated that latrunculin A was unpalatable to rock pool shrimps, in a dose-dependent manner. These findings led us to propose that this group of Nudibranchs has evolved means both to protect themselves from the toxicity of latrunculin A, and to accumulate this compound in the mantle rim for defensive purposes. The precise mechanism by which the Nudibranchs sequester such a potent compound from sponges without disrupting their own key physiological processes is unclear, but this work paves the way for future studies in this direction. Finally, the possible occurrence of both visual and chemosensory Mullerian mimicry in the studied species is discussed.
-
Conspicuous visual signals do not coevolve with increased body size in marine sea slugs
Journal of Evolutionary Biology, 2014Co-Authors: Karen L. Cheney, Fabio Cortesi, Martin J. How, Nerida G. Wilson, Simon P. Blomberg, Anne E. Winters, Schery Umanzor, N. J. MarshallAbstract:Many taxa use conspicuous colouration to attract mates, signal chemical defences (aposematism) or for thermoregulation. Conspicuousness is a key feature of aposematic signals, and experimental evidence suggests that predators avoid conspicuous prey more readily when they exhibit larger body size and/or pattern elements. Aposematic prey species may therefore evolve a larger body size due to predatory selection pressures, or alternatively, larger prey species may be more likely to evolve aposematic colouration. Therefore, a positive correlation between conspicuousness and body size should exist. Here, we investigated whether there was a phylogenetic correlation between the conspicuousness of animal patterns and body size using an intriguing, understudied model system to examine questions on the evolution of animal signals, namely Nudibranchs (opisthobranch molluscs). We also used new ways to compare animal patterns quantitatively with their background habitat in terms of intensity variance and spatial frequency power spectra. In studies of aposematism, conspicuousness is usually quantified using the spectral contrast of animal colour patches against its background; however, other components of visual signals, such as pattern, luminance and spectral sensitivities of potential observers, are largely ignored. Contrary to our prediction, we found that the conspicuousness of body patterns in over 70 Nudibranch species decreased as body size increased, indicating that crypsis was not limited to a smaller body size. Therefore, alternative selective pressures on body size and development of colour patterns, other than those inflicted by visual hunting predators, may act more strongly on the evolution of aposematism in Nudibranch molluscs.
Nerida G. Wilson - One of the best experts on this subject based on the ideXlab platform.
-
Mimicry and mitonuclear discordance in Nudibranchs: new insights from exon capture phylogenomics
Ecology and evolution, 2020Co-Authors: Kara K S Layton, Jose I. Carvajal, Nerida G. WilsonAbstract:Phylogenetic inference and species delimitation can be challenging in taxonomic groups that have recently radiated and where introgression produces conflicting gene trees, especially when species delimitation has traditionally relied on mitochondrial data and color pattern. Chromodoris, a genus of colorful and toxic Nudibranch in the Indo-Pacific, has been shown to have extraordinary cryptic diversity and mimicry, and has recently radiated, ultimately complicating species delimitation. In these cases, additional genome-wide data can help improve phylogenetic resolution and provide important insights about evolutionary history. Here, we employ a transcriptome-based exon capture approach to resolve Chromodoris phylogeny with data from 2,925 exons and 1,630 genes, derived from 15 Nudibranch transcriptomes. We show that some previously identified mimics instead show mitonuclear discordance, likely deriving from introgression or mitochondrial capture, but we confirm one "pure" mimic in Western Australia. Sister-species relationships and species-level entities were recovered with high support in both concatenated maximum likelihood (ML) and summary coalescent phylogenies, but the ML topologies were highly variable while the coalescent topologies were consistent across datasets. Our work also demonstrates the broad phylogenetic utility of 149 genes that were previously identified from eupulmonate gastropods. This study is one of the first to (a) demonstrate the efficacy of exon capture for recovering relationships among recently radiated invertebrate taxa, (b) employ genome-wide nuclear markers to test mimicry hypotheses in Nudibranchs and (c) provide evidence for introgression and mitochondrial capture in Nudibranchs.
-
distribution of defensive metabolites in Nudibranch molluscs
Journal of Chemical Ecology, 2018Co-Authors: Anne E. Winters, Nerida G. Wilson, Andrew M. White, Mary J. Garson, Ariyanti Suhita Dewi, Wayan I Mudianta, Louise C Forster, Karen L. CheneyAbstract:Many plants and animals store toxic or unpalatable compounds in tissues that are easily encountered by predators during attack. Defensive compounds can be produced de novo, or obtained from dietary sources and stored directly without selection or modification, or can be selectively sequestered or biotransformed. Storage strategies should be optimized to produce effective defence mechanisms but also prevent autotoxicity of the host. Nudibranch molluscs utilize a diverse range of chemical defences, and we investigated the accumulation and distribution of defensive secondary metabolites in body tissues of 19 species of Chromodorididae Nudibranchs. We report different patterns of distribution across tissues, where: 1) the mantle had more or different (but structurally related) compounds than the viscera; 2) all compounds in the mantle were also in the viscera; and 3) the mantle had fewer compounds than the viscera. We found no further examples of species that selectively store a single compound, previously reported in Chromodoris species. Consistent with other studies, we found high concentrations of metabolites in mantle rim tissues compared to the viscera. Using bioassays, compounds in the mantle were more toxic than compounds found in the viscera for Glossodoris vespa Rudman, 1990 and Ceratosoma brevicaudatum Abraham, 1876. In G. vespa, compounds in the mantle were also more unpalatable to palaemonid shrimp than compounds found in the viscera. This indicates that these species may modify compounds to increase bioactivity for defensive purposes and/or selectively store more toxic compounds. We highlight clear differences in the storage of sequestered chemical defences, which may have important implications for species to employ effective defences against a range of predators.
-
Conspicuous visual signals do not coevolve with increased body size in marine sea slugs
Journal of Evolutionary Biology, 2014Co-Authors: Karen L. Cheney, Fabio Cortesi, Martin J. How, Nerida G. Wilson, Simon P. Blomberg, Anne E. Winters, Schery Umanzor, N. J. MarshallAbstract:Many taxa use conspicuous colouration to attract mates, signal chemical defences (aposematism) or for thermoregulation. Conspicuousness is a key feature of aposematic signals, and experimental evidence suggests that predators avoid conspicuous prey more readily when they exhibit larger body size and/or pattern elements. Aposematic prey species may therefore evolve a larger body size due to predatory selection pressures, or alternatively, larger prey species may be more likely to evolve aposematic colouration. Therefore, a positive correlation between conspicuousness and body size should exist. Here, we investigated whether there was a phylogenetic correlation between the conspicuousness of animal patterns and body size using an intriguing, understudied model system to examine questions on the evolution of animal signals, namely Nudibranchs (opisthobranch molluscs). We also used new ways to compare animal patterns quantitatively with their background habitat in terms of intensity variance and spatial frequency power spectra. In studies of aposematism, conspicuousness is usually quantified using the spectral contrast of animal colour patches against its background; however, other components of visual signals, such as pattern, luminance and spectral sensitivities of potential observers, are largely ignored. Contrary to our prediction, we found that the conspicuousness of body patterns in over 70 Nudibranch species decreased as body size increased, indicating that crypsis was not limited to a smaller body size. Therefore, alternative selective pressures on body size and development of colour patterns, other than those inflicted by visual hunting predators, may act more strongly on the evolution of aposematism in Nudibranch molluscs.
Guido Cimino - One of the best experts on this subject based on the ideXlab platform.
-
A new cytotoxic tambjamine alkaloid from the Azorean Nudibranch Tambja ceutae
Bioorganic & medicinal chemistry letters, 2010Co-Authors: Marianna Carbone, Guido Cimino, Guido Villani, Vinicius Padula, Gonçalo Calado, Francesco Castelluccio, J. Lucas Cervera, Carlo Irace, Francesca Costagliola, Rita SantamariaAbstract:The chemical investigation of Azorean Nudibranch mollusk Tambja ceutae led us to isolate a new member of the tambjamine family, tambjamine K (1). The bryozoan Bugula dentata, prey of the Nudibranch, was also analyzed and found to contain compound 1 in very small amounts together with known blue pigment 2 and tambjamines A (3) and B (4). The structure of tambjamine 1 was elucidated by the interpretation of the spectroscopic data as well as by the comparison with related compounds. Compounds 1 and 2 possess antiproliferative activity, in particular, tambjamine K (1) displayed high cytotoxicity against both tumor and non-tumor mammalian cells.
-
Coloration and defense in the Nudibranch gastropod Hypselodoris fontandraui.
The Biological bulletin, 2010Co-Authors: Markus Haber, Guido Cimino, Margherita Gavagnin, Sonia Cerfeda, Marianna Carbone, Gonçalo Calado, Helena Gaspar, Ricardo Cardoso Neves, Veeramani Maharajan, Michael T. GhiselinAbstract:The striking color patterns of chromodorid (and other) Nudibranchs appear to be indicative of aposematism. In Mullerian mimicry, all the mimic species have a defense mechanism. It has been proposed that a group of blue, white, and yellow Mediterranean and northeastern Atlantic species of the genus Hypselodoris form a Mullerian mimetic circle. One of these, H. fontandraui, lacks the mantle dermal formations (repugnatorial glands) that are typically found in other members of this circle and are reservoirs of feeding deterrent compounds. It therefore seemed possible that this animal lacks chemical defense and acts like a Batesian mimic. Within this study, we found that this Nudibranch contains the furanosesquiterpenoid tavacpallescensin, most probably derived from sponges of the genus Dysidea, upon which it probably feeds. The metabolite concentrations were measured from samples of the mantle rim, other external parts, and internal organs. Concentrations were about 4 times higher in the mantle rim than in th...
-
terpenoid metabolites of the Nudibranch hexabranchus sanguineus from the south china sea
Tetrahedron, 2007Co-Authors: Wen Zhang, Margherita Gavagnin, Ernesto Mollo, Yue-wei Guo, Michael T. Ghiselin, Guido CiminoAbstract:Chemical analysis of the secondary metabolite pattern of the Nudibranch Hexabranchus sanguineus collected from the South China Sea revealed the presence of both sesquiterpenoids and diterpenoids, exhibiting very different structural features. Two new molecules, compounds 1 and 4, were isolated together with known compounds 2 and 3, and chemically characterized. This is the first report of terpenoids from H. sanguineus. The remarkable diversity of metabolites possessed by H. sanguineus supports some recent phylogenetic studies that place the mollusc near the steam of the dorid Nudibranch tree.
-
Isocyanide terpene metabolites of Phyllidiella pustulosa, a Nudibranch from the South China Sea.
Journal of natural products, 2004Co-Authors: Emiliano Manzo, Margherita Gavagnin, M. Letizia Ciavatta, Ernesto Mollo, Yue-wei Guo, Guido CiminoAbstract:A series of isocyanides, compounds 4-11, including diterpenes never before found in Phyllidiid Nudibranchs, have been isolated from a Chinese population of the Nudibranch Phyllidiella pustulosa. Three new sesquiterpenes (8, 10, and 11), with eudesmane, guaiane, and bisabolane skeletons, respectively, have been characterized by spectral methods and chemical comparison with known related molecules. The absolute stereochemistry of the major metabolite, the isocyanide 8, an enantiomer of the known sponge metabolite stylotelline (12), has also been determined.
-
Can molluscs biosynthesize typical sponge metabolites? The case of the Nudibranch Doriopsilla areolata
Tetrahedron, 2001Co-Authors: Margherita Gavagnin, Ernesto Mollo, Gonçalo Calado, Michael T. Ghiselin, Francesco Castelluccio, Guido CiminoAbstract:Abstract The first study on the biosynthesis of terpenoid metabolites in the porostome Nudibranch Doriopsilla areolata is described herein. The de novo origin of two different groups of bi- and tri-cyclic sesquiterpenes, exhibiting opposite A/B ring junctions, has been clearly demonstrated by in vivo incorporation of labeled mevalonate. Surprisingly, metabolites of both series have been previously reported to co-occur in a sponge of genus Dysidea , that could be included in the diet of the Nudibranch.
Yue-wei Guo - One of the best experts on this subject based on the ideXlab platform.
-
bioactive isoquinolinequinone alkaloids from the south china sea Nudibranch jorunna funebris and its sponge prey xestospongia sp
Future Medicinal Chemistry, 2016Co-Authors: Renyong Huang, Wenting Chen, Tibor Kurtan, Attila Mandi, Jian Ding, Yue-wei GuoAbstract:Background: Nudibranchs are slug-like invertebrates, well known as rich sources of biologically active secondary metabolites with highly chemical diversity and complexity. The production of such interesting metabolites was possibly influenced by their diet relationship with sponges such as Xestospongia. Results: Our continuous investigation of South China Sea Nudibranch Jorunna funebris and its sponge-prey Xestospongia sp. led to the isolation of two new and eight known metabolites (1–10). The absolute configurations were determined by time-dependent density functional theory (TDDFT) electronic circular dichroism (ECD) method and by the comparison of ECD spectra. In bioassays, 1–4 and 7 showed strong NF-κB inhibitory activity, 4–6 exhibited considerable cytotoxicity against A549 and HL-60 tumor cell lines. Conclusion: Five unusual isoquinolinequinones (3, 7–10) were discovered from both two animals, further confirmed their predator–prey relationship. Preliminary bioassay results and structure–activity rel...
-
terpenoid metabolites of the Nudibranch hexabranchus sanguineus from the south china sea
Tetrahedron, 2007Co-Authors: Wen Zhang, Margherita Gavagnin, Ernesto Mollo, Yue-wei Guo, Michael T. Ghiselin, Guido CiminoAbstract:Chemical analysis of the secondary metabolite pattern of the Nudibranch Hexabranchus sanguineus collected from the South China Sea revealed the presence of both sesquiterpenoids and diterpenoids, exhibiting very different structural features. Two new molecules, compounds 1 and 4, were isolated together with known compounds 2 and 3, and chemically characterized. This is the first report of terpenoids from H. sanguineus. The remarkable diversity of metabolites possessed by H. sanguineus supports some recent phylogenetic studies that place the mollusc near the steam of the dorid Nudibranch tree.
-
Isocyanide terpene metabolites of Phyllidiella pustulosa, a Nudibranch from the South China Sea.
Journal of natural products, 2004Co-Authors: Emiliano Manzo, Margherita Gavagnin, M. Letizia Ciavatta, Ernesto Mollo, Yue-wei Guo, Guido CiminoAbstract:A series of isocyanides, compounds 4-11, including diterpenes never before found in Phyllidiid Nudibranchs, have been isolated from a Chinese population of the Nudibranch Phyllidiella pustulosa. Three new sesquiterpenes (8, 10, and 11), with eudesmane, guaiane, and bisabolane skeletons, respectively, have been characterized by spectral methods and chemical comparison with known related molecules. The absolute stereochemistry of the major metabolite, the isocyanide 8, an enantiomer of the known sponge metabolite stylotelline (12), has also been determined.
