Didemnum species

Urea derivatives have been reported as constituents of marine ascid-ians belonging to the genus Didemnum. Ireland et al. (JIS) isolated N,N -diphenethylurea (1037), which was apparently a product of phenylalanine metabolism, from Didemnum ternatanum and N,N -(3,5-diiodo-4-methoxyphenethyl)-urea (1038) has been found in addition to 3,5-diiodo-4-methoxyphenethylamine (1039) as a metabolite from an unidentified Didemnum species 719). Compound 1037 was found to be a weak depressant lacking acute toxicity and 1039 showed in... 

Lamellarins were originally extracted from a marine prosobranch mollusk Lamdlaria sp. and subsequently from primitive chordate ascidians (tunicates) [23]. These ascidian species, knovm to produce many bioactive metabolites, likely represent the original producer of lamellarins because these organisms are presumed to be the dietary source of the Lamdlaria mollusks. Lamellarins have been isolated from different tunicates, including recently from the Indian ascidian Didemnum obscurum... 

The ascidian fauna of southern Africa are poorly known and the 145 species presently described are thought to represent only a small fraction of the overall ascidian biodiversity [3]. Not unexpectedly, common Pacific and Atlantic fouling species e.g. Cystodytes delechiajei, Clavellina lepadiformis, Didemnum listerianum and Ciona intestinalis frequent harbours in the southern African region [3]. 

Three ethylenic amino alcohols, which may derive from the degradation of ceramides or cerebrosides and which are strongly antifungal (Candida albicans), were isolated from another undetermined species of the genus Didemnum harvested on the Great Barrier Reef. Other long-chain amino alcohols seem specific to the family Polyclinidae (see below). 

Serinohpids contain a serinol molecule, which is 2-amino-l,3-propanediol, and it was not imtil 1999 that the first serinohpids of marine origin were isolated these were didemniserinolipids A-C, which were extracted from an imdetermined species of Didemnum harvested on the coast of Sidawesi (Indonesia). A subsequent study has shovm that the derivatives pubhshed in 1999 were forms of authentic natural compoimds desulfated at carbon 31 (Gonzalez, Rodriguez, and Jimenez, 1999 Kiyota et al., 2002). 

Shermila is a character in Indian mythology ot Mahabaratha and the first name of the daughter of the first author of the publication. Piakinidine D has been tound independently by two teams from different species of the genus Didemnum harvested in the Mariana Islands and Indonesia. The two publications appear in the same issue of J. Nat. Pmd. 

Bromotryptamine and two bis-indolic derivatives, one of which contains a piperazine, have been isolated from the species Didemnum candidum collected on the roots of mangrove trees in a mangrove swamp in the Gulf of California (Fahy, Potts, and Faulkner, 1991). 

Some atypical indolic derivatives comprising an imidazole and a maleimide were isolated from the two species Didemnum conchyliatum and D. granulatum. Didemni-mides A-D are powerful repellents against carnivorous... 

Didemnolines A-D form an original series of P-carbo-line alkaloids in which a thioether-containing imidazole is linked to nitrogen 9 of the heterocyclic system. Isolated from an imdetermined species of Didemnum genus harvested in the Mariana Islands (Rota Island), didemnolines are only moderately cytotoxic, but also have antibacterial and antifungal activities (Schumacher and Davidson, 1995). 

Cyclic peptides and depsipeptides constitute the bulk of the nitrogenous metabolites of didemnid tunicates and several publications have been devoted to them, either wholly or in part, such as Ireland et al. (1989), Davidson (1993) and Lehrer et al. (2003). However, many publications devoted to cyclic peptides of Didemnidae are concerned with only three species, Didemnum molle, Lissoclinum bistratum and Lissoclinum patella, which is the most prolific didemnid as regards cyclic peptides. The two Lissoclinum species were harvested in the Western Pacific (Australia, Fiji, Guam, Indonesia, Palau, Philippines, Pohnpei and Singapore) and Didemnum molle in the Indian Ocean (Comoros, Mozambique). 

Vitilevuamide might be the only currently known bicy-clic depsipeptide from a species of Didemnidae it was isolated from Didemnum cuculliferum harvested in Vitilevu Island, Fiji, and Polysyncraton lithostrotum. One of the vitilevuamide rings contains an ester bond, and the other contains only amino adds and rare derivatives, such as lanthionine, 2-homoisoleucine, dehydroalanine and methoxinine, which is an amino derivative of sucdnic add (Fernandez et al., 1998). This derivative is highly toxic to various cancer cell lines, with an LD50 value of about... 

Curiously, the conformation of ds-decalin in lepadin A is the same as that of pumiliotoxin C, extracted from toads of the family Dendrobatidae, especially Den-drobates pumilio (Daly et al, 1969). Subsequently, lepadins B-H were isolated from the same species, Clavelina lepadiformis, harvested in Norway and from its predator, the platyhelminth Prostheceraeus villatus, from the species Aplidium tabascum and an undetermined species of the genus Didemnum, both collected in Australia on the Great Barrier Reef The ds-decalin nuclei of lepadins exist with two different conformations depending on whether the NH bond is located in an axial or equatorial position... 

---