Guido Cimino

Dorid nudibranch elaborates its own chemical defense.

A biosynthetic experiment with mevalonic acid labeled with carbon-14 showed that the nudibranch Dendrodoris limbata elaborates polygodial, a sesquiterpenoid dialdehyde stored in the mantle, which constitutes its chemical defense against predators. Previously described nudibranchs drew defensive chemicals from their preys.

Isolation and X-ray crystal structure of a novel bromo-compound from two marine sponges

A novel bromo-compound, C 11 H 10 N 5 O 2 Br, has been isolated from the sponges Axinella verrucosa and Acanthella aurantiaca . The structure was determined as 2 on special grounds and by X-ray analysis.

LOX-Induced Lipid Peroxidation Mechanism Responsible for the Detrimental Effect of Marine Diatoms on Zooplankton Grazers

Some marine diatoms negatively affect the reproduction of dominant zooplankton grazers such as copepods, thus compromising the transfer of energy through the marine food chains. In this paper, the metabolic mechanism that leads to diatom‐induced toxicity is investigated in three bloom‐forming microalgae. We show that copepod dysfunctions can be induced by highly reactive oxygen species (hROS) and a blended mixture of diatom products, including fatty acid hydroperoxides (FAHs); these compounds display teratogenic and proapoptotic properties. The process is triggered by the early onset of lipoxygenase activities that elicit the synthesis of species‐specific products, the basic structures of which were established (1–20); these compounds boost oxidative stress by massive lipid peroxidation. Our study might explain past laboratory and field results showing how diatoms damage zooplankton grazers even in the absence of polyunsaturated aldehydes, a class of molecules that has been formerly implicated in mediating the toxic activity of diatoms on copepods.

A new antitumor isoquinoline alkaloid from the marine nudibranch Jorunna funebris

Abstract A new dimeric isoquinoline alkaloid, jorumycin (3), has been isolated from the skin and the mucus of the Pacific nudibranch Jorunna funebris. The structure has been fully elucidated on the grounds of ESMS data and of an extensive 2D NMR analysis. The cytotoxicity of 3 was evaluated against various human cancer cell lines and was found to be slightly less potent than Et 743 (2).

Chemical defense and evolutionary trends in biosynthetic capacity among dorid nudibranchs (Mollusca: Gastropoda: Opisthobranchia)

Summary. An evolutionary scenario incorporating recent advances in phylogenetic research begins with an opisthobranch-pulmonate common ancestor that was herbivorous and had some diet-derived chemical defense. The Nudibranchia and their closest relatives, the Notaspidea, form a lineage the ancestors of which had switched to feeding upon sponges and deriving protection from metabolites contained in them. Subsequently there have been repeated shifts in food and defensive metabolites, and trends are evident in the ability to detoxify, sequester and utilize metabolites from food, as well as to synthesize defensive compounds de novo. The Notaspidea display a minor adaptive radiation that foreshadows a more extensive one in the various lineages of nudibranchs. This review emphasizes changes that have occurred within the Holohepatica, or dorid nudibranchs (order Doridacea). Their sister-group, the Cladohepatica, consists of three other orders, Dendronotacea, Arminacea, and Aeolidiacea, in which there has been a shift from sponges to Cnidaria as food. The Dendronotacea often feed upon Octocorallia, which combine spicules, chemical defense, and stinging capsules and thereby suggest a transition from feeding on sponges. A previous diet of Octocorallia is suggested by the defensive use of prostaglandins in the dendronotacean Tethys fimbria, which eats crustaceans. A shift to bryozoans in some Arminacea is accompanied by use of different metabolites. Dorid nudibranchs evidently began as sponge-feeders, but some lineages have shifted to a variety of other food organisms, and others have specialized in the kind of sponges they feed on and how they do it. There have been shifts to bryozoans (Ectoprocta) and ascidians (Chordata: Urochordata) that track metabolites rather than the taxonomy of the food. There is a crude correlation between the genealogy and the defensive metabolites of the sponge-feeding dorids. De novo synthesis is well documented in this order and the metabolites are appropriately positioned so as to have an adaptive effect. The hypothesis that the capacity for de novo synthesis was acquired by gene transfer across lineages is rejected, partly on the basis of different chirality of metabolites in the nudibranchs and their food organisms. Instead it is proposed that there has been a preadaptive phase followed by evolution in a retrosynthetic mode, with selection favoring enzymes that enhance the yield of end products that are already present in the food.

Polyprenyl derivatives from the sponge Ircinia spinosula : 2-Polyprenylbenzoquinones, 2-polyprenylbenzoquinols, prenylated furans and a C-31 difuranoterpene

Abstract Unsubstituted prenylated benzoquinones, a novel group of terpenoid quinones, the corresponding quinols, together with the hydroxylated 2-octaprenyl-quinol (VII) have been identified in the marine sponge Ircinia spinosula. From the same sponge we have also isolated the prenylated furan derivatives XI, XII and XIII, named furospinosulin-1, -2 and -3, and an unusual C-31 difuranoterpene, difurospinosulin (XIV). The synthesis of 2-heptaprenyl-1,4-benzoquinol (V) is reported.

New birth-control aldehydes from the marine diatom Skeletonema costatum: characterization and biogenesis

Abstract The paper describes the identification of short-chain aldehydes ( 4 – 7 ) from the marine diatom Skeletonema costatum , and their effects on copepod egg viability and sea urchin cell division. Compounds 4 – 7 were isolated as carboethoxyethylidene (CET) derivatives and their characterization was performed by NMR and GCMS analyses. Evidence is presented to support the defensive role and biosynthetic origin of these compounds in S. costatum .

Chemistry of oxylipin pathways in marine diatoms

Oxylipins are important signal transduction molecules widely distributed in animals and plants where they regulate a variety of events associated with physiological and pathological processes. The family embraces several different metabolites that share a common origin from the oxygenase-catalyzed oxidation of polyunsaturated fatty acids. The biological role of these compounds has been especially studied in mammalians and higher plants, although a varied and very high concentration of these products has also been reported from marine macroalgae. This article gives a summary of our results concerning the oxylipin chemistry of marine diatoms, a major class of planktonic microalgae that discourage predation from their natural grazers, zooplanktonic copepods, using chemical warfare. These apparently harmless microscopic cells produce a plethora of oxylipins, including short-chain unsaturated aldehydes, hydroxyl-, keto-, and epoxyhydroxy fatty acid derivatives, that induce reproductive failure in copepods through abortions, congenital malformations, and reduced larval growth. The biochemical process involved in the production of these compounds shows a simple regulation based on decompartmentation and mixing of preexisting enzymes and requires hydrolysis of chloroplast-derived glycolipids to feed the downstream activities of C16 and C20 lipoxygenases.

Ircinin-1 and -2, linear sesterterpenes from the marine sponge Ircinia oros

Abstract Two isomeric linear difurano sesterterpenes, ircinin-1 and -2, have been identified in the sponge Ircinia oros .

The chemical defense of nudibranch molluscs: structure, biosynthetic origin and defensive properties of terpenoids from the dorid nudibranch Dendrodoris grandiflora

Abstract Nudibranch molluscs, apparently defenseless against potential predators, possess secondary metabolites localized on the body wall which help them to escape from predation. These metabolites are largely of dietary origin; in one case the biosynthetic ability of a nudibranch to elaborate its own chemical defense has been shown. From the mantle extracts of Dendrodoris grandiflora polygodial ( 1 ) and 6β-acethoxyolepupuane ( 4 ), a new sesquiterpene triacetate, was isolated. These two drimane sesquiterpenoids, both endowed with antifeedant properties, are biosynthesized de novo by the nudibranch. Extracts from the digestive glands of the same nudibranch yielded the previously known sesquiterpene esters 3 , microcionin-1, -2, -3, -4 ( 7 – 10 ), fasciculatin ( 11 ), furospongin-1 acetate ( 12 ), a new C-21 furanoterpene 14 and a mixture of new prenylated chromanols 17 . All these compounds, with the exception of 3 , appear to be of dietary origin. The structures of the new compounds were determined by spectral and chemical means.