Didemnid tunicate

Thiazole-containing linear peptides have also been isolated from tunicates. Virenamides A-E (412-416) were obtained from the didemnid tunicate Diplosoma virens, which contains symbiotic prokaryotic algae in its cloacal cavity. The structures of virenamides A-C were determined by HPLC analysis using Marfey s procedure [323] while the absolute stereochemistry of virenamide E (416) was proven by its synthesis from virenamide A (412) [324], Compounds 412-416 showed modest cytotoxicity toward a panel of cultured cells and 412 also exhibited topoisomerase II inhibitory activity. 

Patellazoles A-C (77-79), 24-membered thiazole-containing macrolides, were isolated from two specimens of didemnid tunicate, Lissoclinum patella, which were collected from the Fiji Islands [148] and Piti Bomb Holdes, Guam [149]. The patellazoles were potent cytotoxins in the NCI human cell line protocol with mean IC50 values of 10" to 10 pg/ml and antifungal activity against Candida albicans. 

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). 

Excepting didemnins and Aplidin , only a few examples of depsipeptides have been isolated from didemnid tunicates. Tamandarins A and B are cyclic depsipeptides that are distinguished from didemnin B and nordidemnin B only by the presence of 2-hydroxyisovaleric acid (Hiv ), which replaces 2-hydroxyisovaleryl-2-propionic acid... 

Sesin, D.F. and Ireland, C.M. (1984) lodinated phenethylamine products from a didemnid tunicate. Tetrahedron Lett., 25, 403-404. 

The Caribbean tunicate Trididemnum solidum and its larvae contain a complex mixture of didemnin/ nordidemnin metabolites that act as feeding deterrents in field-based assays at below natural concentrations. The most potent metabolite is nordidemnin B 147.28 Crude extract mixtures enriched in didemnin B 148 induce vomiting in the spotted pinfish L. rhomboides, causing these fish to avoid feeding.173 The larvae of other didemnid ascidians are also protected by the presence of deterrent chemicals.28 174... 

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