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Demospongic Acids Revisited

Demospongic Acids Revisited Mar. Drugs 2010, 8, 2569-2577; doi:10.3390/md8102569 OPEN ACCESS Marine Drugs ISSN 1660-3397 www.mdpi.com/journal/marinedrugs Review Jean-Michel Kornprobst * and Gilles Barnathan Groupe Mer, Molécules, Santé MMS/EA 2160, Equipe 7: Lipides marins à activité biologique, Pôle Mer et Littoral, Faculté de Pharmacie, Université de Nantes, France; E-Mail: gilles.barnathan@univ-nantes.fr * Author to whom correspondence should be addressed; E-Mail: jean-michel.kornprobst@univ- nantes.fr; Tel.: +33 2 51 12 56 89; Fax: +33 2 51 12 56 79. Received: 7 September 2010; in revised form: 27 September 2010 / Accepted: 30 September 2010 / Published: 8 October 2010 Abstract: The well-known fatty acids with a 5,9 unsaturation system were designated for a long period as demospongic acids, taking into account that they originally occurred in marine Demospongia sponges. However, such acids have also been observed in various marine sources with a large range of chain-lengths (C –C ) and from some terrestrial 16 32 plants with short acyl chains (C –C ). Finally, the 5,9 fatty acids appear to be a 18 19 particular type of non-methylene-interrupted fatty acids (NMA FAs). This article reviews the occurrence of these particular fatty acids in marine and terrestrial organisms and shows the biosynthetic connections between 5,9 fatty acids and other NMI FAs. Keywords: demospongic acids; marine lipids; sponges; marine invertebrates; non-methylene interrupted fatty acids 1. Introduction The well-known notion of demospongic acid appeared for the first time in 1976 in a historical paper from Litchfield and Morales [1], but at that time only as «demospongiae fatty acids». In another paper published in 1980 [2], Litchfield et al. used the term «demospongic fatty acids» probably for the first time. Since then and up until now [3–5], this term has widely been used. However, about 35 years after Litchfield’s work on sponge lipids, the notion of demospongic acid seems to no longer have significance, mainly due to their controversial definition and to their wide distribution among marine invertebrates and some terrestrial plants. At the time, it seemed to be of interest to precisely identify Mar. Drugs 2010, 8 2570 the function of demospongic acids, in consideration of their biological activities as topoisomerase inhibitors or against cancer cells as recently reviewed [6], whereas the biological interests of terrestrial short-chain 5,9 fatty acids (FAs) had already been demonstrated [7,8]. 2. What Exactly Is a Demospongic Acid? The definition of a demospongic acid has never been very clear [1,2]. In their first papers, Litchfield et al. only mentioned very long-chain C –C or C –C acids with the unusual 5,9 24 30 24 34 unsaturation pattern, but at that time, only fatty acids with an even number of carbons had been found [1,9]. In the 1980s, a lot of work was published on sponge FAs, and it became apparent that “demospongic acids” also contained all odd FAs from C –C [10]. Within this field of research, a 23 31 consensus was quickly established that agreed that demospongic acids were very long-chain fatty acids, mainly C –C , with the atypical 5,9-diunsaturation system, independent of the total number of 24 30 double bonds. Some years later—and due to many papers being devoted to FAs from sponges—it appeared that: (i) the distinction between long-chain fatty acids (LCFAs, C –C ?) and very long-chain FAs 20 22 (VLCFAs, ≥C23 ?) is not clear and often depends on the authors’ interpretation [10–17]. (ii) the presence of the ever-mentioned 5,9-diunsaturation pattern cannot be considered as characteristic of “demospongic acids” due to the elongation process during their biosynthetic pathways, and diunsaturations such as 5,9-, 7,11-, 9,13-, 11,15-, 17,21-, 19,23- 21,25- and 23,27- can be considered as being similar [18], but other dienoic patterns with short chains such as 6,11-18:2 and 6,11-20:2 have also been considered as “demospongic” acids [19]. Furthermore, several “demospongic acids” display E and Z configurations for 5 and 9 double bonds [20]. Currently, the best definition for a demospongic acid would be that of Christie [18], stating “bis-methylene-interrupted cis-double bonds, ranging in chain-length from C to C with a 16 34 cis,cis-dienoic system, either with the double bonds in position 5 and 9, or derived from 5,9-16:2 by chain elongation”. At present, the question is whether such acids are not at all specific to demosponges, but have been found in other groups of sponges, especially among hexactinellida, in different phyla of marine invertebrates and in several species of terrestrial plants, especially conifers, and in some species of Apocynaceae, Malvaceae, and Ranunculaceae. 3. Occurrence of “Demospongic” Acids among Other Organisms Table 1 presents a non-exhaustive list of more than 40 FAs that correspond to Christie’s definition of demospongic acids found in microorganisms, marine invertebrates and terrestrial plants. A particularly interesting point is the presence of 6-Br-5,9-FAs that are very common in demosponges but quite rare in other organisms. To the best of our knowledge only some Cnidaria Hexacorallia were shown to contain these brominated FAs [21–23], which prove the existence of bromoperoxidases in this group of Cnidaria since it has been proved that these brominated demospongic acids are synthesized by the sponge itself in the final stage of biosynthesis [24]. Mar. Drugs 2010, 8 2571 Table 1. Occurrence of “demospongic”* acids in organisms that are not demosponges. Acids Genera/species Kind of organisms Ref. 5,9-16:2 Stoichactis helianthus Cnidaria (Hexacorallia) [22] 5,9-17:2 Dictyostelium discoideum Microorganism, soil-living [25] amoeba 5,9-18:2 Condylactis gigantea, Palythoa caribaeorum, Cnidaria (Hexacorallia) [22,23] taxoleic acd Stoichactis helianthus Cellana grata, Collisella dorsuosa Marine molluscs [26,27] Tripneustes esculentus Echinoderm [28] Ginkgo biloba Terrestrial plant [7] 5,9,12-18:3 Abies sp., Cedrus sp., Cupressus sp., Juniperus Terrestrial plants [8,29] pinolenic acid sp., Laryx sp., Picea sp., (conifers, gymnosperms) (Z,Z,Z) and/or Pinus sp., Sequoia sp., Thuya sp. columbinic acid Anemone leveillei (Ranunculaceae) [30] (E,Z,Z) 5,9,12,15-18:4 Perna canaliculus Marine mollusc [31] (Lamellibranchiata) Abies sp., Cedrus sp., Cupressus sp., Terrestrial plants [8,29] Juniperus sp., Laryx sp., Picea sp., Sequoia sp., (conifers) Thuya sp. 5,9-19:2 Allamanda cathartica (Apocynaceae) Terrestrial plants [32] Malvaviscus arboreus (Malvaceae) (angiosperms) i-5,9-19:2 Allamanda cathartica (Apocynaceae) Terrestrial plants [32] Malvaviscus arboreus (Malvaceae) (angiosperms) ai-5,9-19:2 Allamanda cathartica (Apocynaceae) Terrestrial plants [32] Malvaviscus arboreus (Malvaceae) (angiosperms) 5,9,12,16-19:4 Perna canaliculus Marine mollusc [31] (Lamellibranchiata) 5,9-20:2 Condylactis gigantea, Palythoa caribaeorum, Cnidaria (Hexacorallia) [22,23] Stoichactis helianthus 6-Br,5,9-20:2 Condylactis gigantea, Cnidaria (Hexacorallia) [22,23] Palythoa caribaeorum 7,11-20:2 Penaeus setiferus Arthropod (shrimp) [33] 5,9-21:2 Condylactis gigantea, Cnidaria (Hexacorallia) [22,23] Stoichactis helianthus 6-Br,5,9-21:2 Stoichactis helianthus Cnidaria (Hexacorallia) [22] 5,9,12,15,18-21:5 Perna canaliculus Marine mollusc [23] 5,9-22:2 Condylactis gigantea, Palythoa caribaeorum, Cnidaria (Hexacorallia) [22,23] Stoichactis helianthus Cellana grata, Collisella dorsuosa Marine molluscs [26-27] 6-Br,5,9-22:2 Stoichactis helianthus Cnidaria (Hexacorallia) [22] 9,13-22:2 Penaeus setiferus Arthropod (shrimp) [33] 5,9,15-22:3 Collisella dorsuosa Marine molluscs [27] 5,9,19-22:3 Stoichactis helianthus Cnidaria (Hexacorallia) [22] 5,9-23:2 Stoichactis helianthus Cnidaria (Hexacorallia) [22] Mar. Drugs 2010, 8 2572 Table 1. Cont. 5,9-24:2 Condylactis gigantea, Cnidaria (Hexacorallia) [23] Palythoa caribaeorum Cellana grata, Chromodoris sp., Marine molluscs [26,27,34] Collisella dorsuosa, Phyllidia coelesti 5,9,15-24:3 Cellana grata, Collisella dorsuosa Marine molluscs [26,27] 5,9,17-24:3 Cellana grata, Collisella dorsuosa Marine molluscs [26,27] 5,9,15,18-24:4 Cellana grata Marine mollusc [26] 5,9,15,18,21-24:5 Cellana grata Marine mollusc [26] 5,9-25:2 Chromodoris sp., Phyllidia coelesti Marine molluscs [34] Bebryce studeri Cnidaria (Octocorallia) [35] i-5,9-25:2 Phyllidia coelesti Marine molluscs [33] 5,9-26:2 Heterochone sp. Marine sponge, Hexactinellida [36] Marine molluscs Chromodoris sp., Phyllidia coelesti Cnidaria (Octocorallia) [34] Bebryce studeri [35] i-5,9-26:2 Chromodoris sp., Phyllidia coelesti Marine molluscs [34] 5,9,19-26:3 Bebryce studeri Cnidaria (Octocorallia) [35] 5,9-28:2 Aulosaccus cf. mitsukuri, Heterochone sp., Marine sponges, Hexactinellida [36] Rosella sp., Sympagella nux Cnidaria (Octocorallia) Bebryce studeri [35] 5,9,19-28:3 Bebryce studeri Cnidaria (Octocorallia) [35] 5,9,23-28:3 Hyalonema sp. Marine sponge, Hexactinellida [36] 5,9-29:2 Hyalonema sp. Marine sponge, Hexactinellida [36] 5,9,22-29:3 Acanthascus sp., Aulosaccus cf. mitsukuri, Marine sponges, Hexactinellida [36] Euplectella sp., Heterochone sp., Hyalonema sp. 5,9,21-30:3 Acanthascus sp., Aulosaccus cf. mitsukuri, Marine sponges, Hexactinellida [36] Euplectella sp., Hyalonema sp., Heterochone sp., Staurocalyptus sp., Sympagella nux 5,9,23-30:3 Acanthascus sp., Aulosaccus cf. mitsukuri, Marine sponges, Hexactinellida [36] Euplectella sp., Farrea sp., Heterochone sp., Hyalonema sp., Ipheteon panicea, Staurocalyptus sp., Sympagella nux 5,9,25-30:3 Hyalonema sp. Marine sponges, Hexactinellida [36] 5,9-31:2 Hyalonema sp. Marine sponge, Hexactinellida [36] 5,9,21-31:3 Staurocalyptus sp. Marine sponge, Hexactinellida [36] 5,9,22-31:3 Acanthascus sp., Marine sponges, Hexactinellida [36] Aulosaccus cf. mitsukuri, 5,9,23-32:3 Ipheteon panicea, Staurocalyptus sp. Marine sponges, Hexactinellida [36] * According to Christie’s definition. 4. Towards a Classification of Non-Methylene-Interrupted Fatty Acids? Demospongic acids represent a particular type of non-methylene-interrupted FA and, according to Christie’s definition, it could be interesting to consider at least three classes of non-methylene- interrupted fatty acids (NMI FAs) depending on the number of methylene groups situated between the Mar. Drugs 2010, 8 2573 two first double bonds. Then, group 1 would contain all bis-methylene-interrupted cis-double bonds and would correspond to the series 5,9; 7,11; 9,13… dienoic or polyenoic acids (demospongic acids). Group 2 would be that of tetra-methylene-interrupted cis-double bonds and would contain the series 5,11; 7,13; 9,15… NMI FAs, such as the acids 7,13-20:2 found in the Brittle star (Echinoderm, Ophiuroidea) Ophiura sarsi [37] and in the maritime pine Pinus pisaster [29], or the acid 7,13-22:2 found in the sponge Petrosia ficiformis [38]. Finally, group 3 would contain hexamethylene- interrupted cis-double bonds corresponding to the series 5,13; 7,15; 9,17… NMI FAs, such as the acid 7,15-20:2 found in the sponge Dysidea fragilis [39]. Some other acids of these three groups have been identified in marine invertebrates, especially molluscs and arthropods, and in numerous terrestrial plants, especially gymnosperms, and all of them can be deduced from accepted biosynthetic pathways implying elongases and 5- and 9-desaturases. Figures 1 and 2 give an overview of these putative biosyntheses from palmitic acid (16:0), palmitoleic acid (9-16:1) and linoleic acid (9,12-18:2). These schemes are currently used and have appeared recently in several publications, along with recent reviews on elongases and polyketide synthases [3,9,10,12,40–44]. Figure 1. Currently accepted pathways for the main long-chain NMI FAs (≤C ) E 5Ds E E 5Ds 20:1 20:2 22:2 24:2 24:3      5Ds E E E 9Ds 18:2 20:2 22:2 24:2 18:1      E5Ds E E 20:2 20:3 22:3 24:3     12Ds 18:2  5Ds 18:3 18:0  E 9Ds 5Ds 22:0 22:1 22:2   E E 5Ds 9Ds 20:0 22:2 20:1 20:2 22:2     9Ds 16:0 20:1  5Ds 9Ds E 16:1 16:2 18:2    E E E 5Ds 24:2 20:1 20:2 22:2     9Ds E 18:1 16:1   5Ds E 18:2 20:2   E: elongase; nDs: n-desaturase All framed NMI FAs have been identified in several marine invertebrates and terrestrial plants. Mar. Drugs 2010, 8 2574 Figure 2. Currently accepted pathways for the main very long-chain NMI FAs (>C ) 5Ds/9Ds E E E E E E 18:0 20:0 22:0 24:0 26:0 28:0 28:2 9Ds/5Ds  5Ds/9Ds 26:3*  9Ds/5Ds 16:0 5Ds? 9Ds 26:3** 26:2   9Ds E E E E E 16:1 18:1 20:1 22:1 24:1 26:1       5Ds/9Ds 28:3 28:1  9Ds/5Ds  9Ds 30:2  E E 28:1 30:1   5Ds/9Ds 30:3 E: elongase; nDs: n-desaturase All framed NMI FAs have been identified in several marine invertebrates and terrestrial plants.  9Ds/5Ds * Biosynthesis demonstrated in Microciona prolifera 3 ** Although they are very likely the acids 5,19-26:2, 5,21-28:2, 9,21-28:2 and 5,23-30:2 are still hypothetical. 5. Conclusion To end this point of view, we think that the former notion of demospongic acid should no longer be used mainly because bis-methylene interrupted 5,9-diunsaturated FAs and related acids are distributed among several phyla of marine organisms and several classes of terrestrial plants. 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Demospongic Acids Revisited

Marine Drugs , Volume 8 (10) – Oct 8, 2010

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Abstract

Mar. Drugs 2010, 8, 2569-2577; doi:10.3390/md8102569 OPEN ACCESS Marine Drugs ISSN 1660-3397 www.mdpi.com/journal/marinedrugs Review Jean-Michel Kornprobst * and Gilles Barnathan Groupe Mer, Molécules, Santé MMS/EA 2160, Equipe 7: Lipides marins à activité biologique, Pôle Mer et Littoral, Faculté de Pharmacie, Université de Nantes, France; E-Mail: gilles.barnathan@univ-nantes.fr * Author to whom correspondence should be addressed; E-Mail: jean-michel.kornprobst@univ- nantes.fr; Tel.: +33 2 51 12 56 89; Fax: +33 2 51 12 56 79. Received: 7 September 2010; in revised form: 27 September 2010 / Accepted: 30 September 2010 / Published: 8 October 2010 Abstract: The well-known fatty acids with a 5,9 unsaturation system were designated for a long period as demospongic acids, taking into account that they originally occurred in marine Demospongia sponges. However, such acids have also been observed in various marine sources with a large range of chain-lengths (C –C ) and from some terrestrial 16 32 plants with short acyl chains (C –C ). Finally, the 5,9 fatty acids appear to be a 18 19 particular type of non-methylene-interrupted fatty acids (NMA FAs). This article reviews the occurrence of these particular fatty acids in marine and terrestrial organisms and shows the biosynthetic connections between 5,9 fatty acids and other NMI FAs. Keywords: demospongic acids; marine lipids; sponges; marine invertebrates; non-methylene interrupted fatty acids 1. Introduction The well-known notion of demospongic acid appeared for the first time in 1976 in a historical paper from Litchfield and Morales [1], but at that time only as «demospongiae fatty acids». In another paper published in 1980 [2], Litchfield et al. used the term «demospongic fatty acids» probably for the first time. Since then and up until now [3–5], this term has widely been used. However, about 35 years after Litchfield’s work on sponge lipids, the notion of demospongic acid seems to no longer have significance, mainly due to their controversial definition and to their wide distribution among marine invertebrates and some terrestrial plants. At the time, it seemed to be of interest to precisely identify Mar. Drugs 2010, 8 2570 the function of demospongic acids, in consideration of their biological activities as topoisomerase inhibitors or against cancer cells as recently reviewed [6], whereas the biological interests of terrestrial short-chain 5,9 fatty acids (FAs) had already been demonstrated [7,8]. 2. What Exactly Is a Demospongic Acid? The definition of a demospongic acid has never been very clear [1,2]. In their first papers, Litchfield et al. only mentioned very long-chain C –C or C –C acids with the unusual 5,9 24 30 24 34 unsaturation pattern, but at that time, only fatty acids with an even number of carbons had been found [1,9]. In the 1980s, a lot of work was published on sponge FAs, and it became apparent that “demospongic acids” also contained all odd FAs from C –C [10]. Within this field of research, a 23 31 consensus was quickly established that agreed that demospongic acids were very long-chain fatty acids, mainly C –C , with the atypical 5,9-diunsaturation system, independent of the total number of 24 30 double bonds. Some years later—and due to many papers being devoted to FAs from sponges—it appeared that: (i) the distinction between long-chain fatty acids (LCFAs, C –C ?) and very long-chain FAs 20 22 (VLCFAs, ≥C23 ?) is not clear and often depends on the authors’ interpretation [10–17]. (ii) the presence of the ever-mentioned 5,9-diunsaturation pattern cannot be considered as characteristic of “demospongic acids” due to the elongation process during their biosynthetic pathways, and diunsaturations such as 5,9-, 7,11-, 9,13-, 11,15-, 17,21-, 19,23- 21,25- and 23,27- can be considered as being similar [18], but other dienoic patterns with short chains such as 6,11-18:2 and 6,11-20:2 have also been considered as “demospongic” acids [19]. Furthermore, several “demospongic acids” display E and Z configurations for 5 and 9 double bonds [20]. Currently, the best definition for a demospongic acid would be that of Christie [18], stating “bis-methylene-interrupted cis-double bonds, ranging in chain-length from C to C with a 16 34 cis,cis-dienoic system, either with the double bonds in position 5 and 9, or derived from 5,9-16:2 by chain elongation”. At present, the question is whether such acids are not at all specific to demosponges, but have been found in other groups of sponges, especially among hexactinellida, in different phyla of marine invertebrates and in several species of terrestrial plants, especially conifers, and in some species of Apocynaceae, Malvaceae, and Ranunculaceae. 3. Occurrence of “Demospongic” Acids among Other Organisms Table 1 presents a non-exhaustive list of more than 40 FAs that correspond to Christie’s definition of demospongic acids found in microorganisms, marine invertebrates and terrestrial plants. A particularly interesting point is the presence of 6-Br-5,9-FAs that are very common in demosponges but quite rare in other organisms. To the best of our knowledge only some Cnidaria Hexacorallia were shown to contain these brominated FAs [21–23], which prove the existence of bromoperoxidases in this group of Cnidaria since it has been proved that these brominated demospongic acids are synthesized by the sponge itself in the final stage of biosynthesis [24]. Mar. Drugs 2010, 8 2571 Table 1. Occurrence of “demospongic”* acids in organisms that are not demosponges. Acids Genera/species Kind of organisms Ref. 5,9-16:2 Stoichactis helianthus Cnidaria (Hexacorallia) [22] 5,9-17:2 Dictyostelium discoideum Microorganism, soil-living [25] amoeba 5,9-18:2 Condylactis gigantea, Palythoa caribaeorum, Cnidaria (Hexacorallia) [22,23] taxoleic acd Stoichactis helianthus Cellana grata, Collisella dorsuosa Marine molluscs [26,27] Tripneustes esculentus Echinoderm [28] Ginkgo biloba Terrestrial plant [7] 5,9,12-18:3 Abies sp., Cedrus sp., Cupressus sp., Juniperus Terrestrial plants [8,29] pinolenic acid sp., Laryx sp., Picea sp., (conifers, gymnosperms) (Z,Z,Z) and/or Pinus sp., Sequoia sp., Thuya sp. columbinic acid Anemone leveillei (Ranunculaceae) [30] (E,Z,Z) 5,9,12,15-18:4 Perna canaliculus Marine mollusc [31] (Lamellibranchiata) Abies sp., Cedrus sp., Cupressus sp., Terrestrial plants [8,29] Juniperus sp., Laryx sp., Picea sp., Sequoia sp., (conifers) Thuya sp. 5,9-19:2 Allamanda cathartica (Apocynaceae) Terrestrial plants [32] Malvaviscus arboreus (Malvaceae) (angiosperms) i-5,9-19:2 Allamanda cathartica (Apocynaceae) Terrestrial plants [32] Malvaviscus arboreus (Malvaceae) (angiosperms) ai-5,9-19:2 Allamanda cathartica (Apocynaceae) Terrestrial plants [32] Malvaviscus arboreus (Malvaceae) (angiosperms) 5,9,12,16-19:4 Perna canaliculus Marine mollusc [31] (Lamellibranchiata) 5,9-20:2 Condylactis gigantea, Palythoa caribaeorum, Cnidaria (Hexacorallia) [22,23] Stoichactis helianthus 6-Br,5,9-20:2 Condylactis gigantea, Cnidaria (Hexacorallia) [22,23] Palythoa caribaeorum 7,11-20:2 Penaeus setiferus Arthropod (shrimp) [33] 5,9-21:2 Condylactis gigantea, Cnidaria (Hexacorallia) [22,23] Stoichactis helianthus 6-Br,5,9-21:2 Stoichactis helianthus Cnidaria (Hexacorallia) [22] 5,9,12,15,18-21:5 Perna canaliculus Marine mollusc [23] 5,9-22:2 Condylactis gigantea, Palythoa caribaeorum, Cnidaria (Hexacorallia) [22,23] Stoichactis helianthus Cellana grata, Collisella dorsuosa Marine molluscs [26-27] 6-Br,5,9-22:2 Stoichactis helianthus Cnidaria (Hexacorallia) [22] 9,13-22:2 Penaeus setiferus Arthropod (shrimp) [33] 5,9,15-22:3 Collisella dorsuosa Marine molluscs [27] 5,9,19-22:3 Stoichactis helianthus Cnidaria (Hexacorallia) [22] 5,9-23:2 Stoichactis helianthus Cnidaria (Hexacorallia) [22] Mar. Drugs 2010, 8 2572 Table 1. Cont. 5,9-24:2 Condylactis gigantea, Cnidaria (Hexacorallia) [23] Palythoa caribaeorum Cellana grata, Chromodoris sp., Marine molluscs [26,27,34] Collisella dorsuosa, Phyllidia coelesti 5,9,15-24:3 Cellana grata, Collisella dorsuosa Marine molluscs [26,27] 5,9,17-24:3 Cellana grata, Collisella dorsuosa Marine molluscs [26,27] 5,9,15,18-24:4 Cellana grata Marine mollusc [26] 5,9,15,18,21-24:5 Cellana grata Marine mollusc [26] 5,9-25:2 Chromodoris sp., Phyllidia coelesti Marine molluscs [34] Bebryce studeri Cnidaria (Octocorallia) [35] i-5,9-25:2 Phyllidia coelesti Marine molluscs [33] 5,9-26:2 Heterochone sp. Marine sponge, Hexactinellida [36] Marine molluscs Chromodoris sp., Phyllidia coelesti Cnidaria (Octocorallia) [34] Bebryce studeri [35] i-5,9-26:2 Chromodoris sp., Phyllidia coelesti Marine molluscs [34] 5,9,19-26:3 Bebryce studeri Cnidaria (Octocorallia) [35] 5,9-28:2 Aulosaccus cf. mitsukuri, Heterochone sp., Marine sponges, Hexactinellida [36] Rosella sp., Sympagella nux Cnidaria (Octocorallia) Bebryce studeri [35] 5,9,19-28:3 Bebryce studeri Cnidaria (Octocorallia) [35] 5,9,23-28:3 Hyalonema sp. Marine sponge, Hexactinellida [36] 5,9-29:2 Hyalonema sp. Marine sponge, Hexactinellida [36] 5,9,22-29:3 Acanthascus sp., Aulosaccus cf. mitsukuri, Marine sponges, Hexactinellida [36] Euplectella sp., Heterochone sp., Hyalonema sp. 5,9,21-30:3 Acanthascus sp., Aulosaccus cf. mitsukuri, Marine sponges, Hexactinellida [36] Euplectella sp., Hyalonema sp., Heterochone sp., Staurocalyptus sp., Sympagella nux 5,9,23-30:3 Acanthascus sp., Aulosaccus cf. mitsukuri, Marine sponges, Hexactinellida [36] Euplectella sp., Farrea sp., Heterochone sp., Hyalonema sp., Ipheteon panicea, Staurocalyptus sp., Sympagella nux 5,9,25-30:3 Hyalonema sp. Marine sponges, Hexactinellida [36] 5,9-31:2 Hyalonema sp. Marine sponge, Hexactinellida [36] 5,9,21-31:3 Staurocalyptus sp. Marine sponge, Hexactinellida [36] 5,9,22-31:3 Acanthascus sp., Marine sponges, Hexactinellida [36] Aulosaccus cf. mitsukuri, 5,9,23-32:3 Ipheteon panicea, Staurocalyptus sp. Marine sponges, Hexactinellida [36] * According to Christie’s definition. 4. Towards a Classification of Non-Methylene-Interrupted Fatty Acids? Demospongic acids represent a particular type of non-methylene-interrupted FA and, according to Christie’s definition, it could be interesting to consider at least three classes of non-methylene- interrupted fatty acids (NMI FAs) depending on the number of methylene groups situated between the Mar. Drugs 2010, 8 2573 two first double bonds. Then, group 1 would contain all bis-methylene-interrupted cis-double bonds and would correspond to the series 5,9; 7,11; 9,13… dienoic or polyenoic acids (demospongic acids). Group 2 would be that of tetra-methylene-interrupted cis-double bonds and would contain the series 5,11; 7,13; 9,15… NMI FAs, such as the acids 7,13-20:2 found in the Brittle star (Echinoderm, Ophiuroidea) Ophiura sarsi [37] and in the maritime pine Pinus pisaster [29], or the acid 7,13-22:2 found in the sponge Petrosia ficiformis [38]. Finally, group 3 would contain hexamethylene- interrupted cis-double bonds corresponding to the series 5,13; 7,15; 9,17… NMI FAs, such as the acid 7,15-20:2 found in the sponge Dysidea fragilis [39]. Some other acids of these three groups have been identified in marine invertebrates, especially molluscs and arthropods, and in numerous terrestrial plants, especially gymnosperms, and all of them can be deduced from accepted biosynthetic pathways implying elongases and 5- and 9-desaturases. Figures 1 and 2 give an overview of these putative biosyntheses from palmitic acid (16:0), palmitoleic acid (9-16:1) and linoleic acid (9,12-18:2). These schemes are currently used and have appeared recently in several publications, along with recent reviews on elongases and polyketide synthases [3,9,10,12,40–44]. Figure 1. Currently accepted pathways for the main long-chain NMI FAs (≤C ) E 5Ds E E 5Ds 20:1 20:2 22:2 24:2 24:3      5Ds E E E 9Ds 18:2 20:2 22:2 24:2 18:1      E5Ds E E 20:2 20:3 22:3 24:3     12Ds 18:2  5Ds 18:3 18:0  E 9Ds 5Ds 22:0 22:1 22:2   E E 5Ds 9Ds 20:0 22:2 20:1 20:2 22:2     9Ds 16:0 20:1  5Ds 9Ds E 16:1 16:2 18:2    E E E 5Ds 24:2 20:1 20:2 22:2     9Ds E 18:1 16:1   5Ds E 18:2 20:2   E: elongase; nDs: n-desaturase All framed NMI FAs have been identified in several marine invertebrates and terrestrial plants. Mar. Drugs 2010, 8 2574 Figure 2. Currently accepted pathways for the main very long-chain NMI FAs (>C ) 5Ds/9Ds E E E E E E 18:0 20:0 22:0 24:0 26:0 28:0 28:2 9Ds/5Ds  5Ds/9Ds 26:3*  9Ds/5Ds 16:0 5Ds? 9Ds 26:3** 26:2   9Ds E E E E E 16:1 18:1 20:1 22:1 24:1 26:1       5Ds/9Ds 28:3 28:1  9Ds/5Ds  9Ds 30:2  E E 28:1 30:1   5Ds/9Ds 30:3 E: elongase; nDs: n-desaturase All framed NMI FAs have been identified in several marine invertebrates and terrestrial plants.  9Ds/5Ds * Biosynthesis demonstrated in Microciona prolifera 3 ** Although they are very likely the acids 5,19-26:2, 5,21-28:2, 9,21-28:2 and 5,23-30:2 are still hypothetical. 5. Conclusion To end this point of view, we think that the former notion of demospongic acid should no longer be used mainly because bis-methylene interrupted 5,9-diunsaturated FAs and related acids are distributed among several phyla of marine organisms and several classes of terrestrial plants. 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Published: Oct 8, 2010

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