Pigments

Marine animals, including echinoderms, attract our attention because of their fantastic and bizarre colors. The coloration of echinoderms, in most cases, is due to chemical pigments. Carotenoids, melanins, porphyrins and naphthoquinones contribute to the pigmentation of the integument. In addition, the appetizing color of sea urchin roes is precisely that of carotenes. Carotenoids are known as antioxidants and widely used as a food supplement. As echinoderms are not capable of synthesizing carotenoids de novo, they obtain carotenoids from algae or animals that take them from algae. The occurrence of major carotenoids in echinoderms was documented by Fox and Hopkins (1966). The well-known antitumor promoter p-carotene and its derivatives are the most abundant carotenoids in echinoids and

OH 0

HOC2l

HOC2l

OH 0

Fig. 3. Structures of echinochrome A and spinochrome A

H3CCO HO

OH 0

H3CCO HO

OH O

OH 0

OH O

Echinochrome A

Spinochrome A

Fig. 3. Structures of echinochrome A and spinochrome A

asteroids. Preparations of major carotenoids from plants seem more economical than from echinoderms. Pigments other than major carotenoids, which are specific to echinoderm species, will be a focus of pharmaceutical development. Tsushima et al. (1995) carried out extensive studies on echinoderm carotenoids from the viewpoints of comparative biochemistry and pharmacology. They examined 51 carotenoids with different structures for the inhibitory effects on Epstein-Barr virus activation. A novel marine carotenoid from Cucumaria japonica, cucumariaxanthin C, showed such an effect (Tsushima et al. 1996). Quinone sulfates isolated from the crinoids Tro-piometra afra macrodisucus and Oxycomanthus japonicus have shown antifeedant activity on fish (Takahashi et al. 2002). Spinochrome and echinochrome are assumed to show hypotensive activity (Kuzuya et al. 1973; Fig. 3). Pharmaceutical investigation into echinodermal quinones is required for the development of new anticancer reagents.

Venoms

Venoms occur in two echinoderm classes, namely echinoids and asteroids. Their distribution is limited to three echinoid families, Echinothuriidae, Diadematidae and Toxopneustidae. Acanthaster planci is the only species that has been reported to be venomous among starfish. A few studies on sea urchin venoms have been reported. Peditoxin, purified from the pedicellar-iae of Toxopneustes pileolus, is composed of a protein called pedin and a prosthetic group called pedoxin (Kuwabara 1994). Venomous activity results from pedoxin, which has a molecular mass of 206 Da. It causes sedation and anesthetic coma accompanied by muscular relaxation at sublethal doses. Another toxin, which was named contractin A, from the venom of T. pileolus pedicellaria, has been purified and characterized (Nakagawa et al. 1991). Contractin A, having an apparent molecular weight of 18,000 Da for a total of 138 amino-acid residues, caused contraction of the tracheal smooth muscle. Spine venom from A. planci has been extensively investigated by Japan ese researchers. They demonstrated that A. planci venom has various toxic activities. The lethal factor was shown to be a potent hepatotoxic basic gly-coprotein with a molecular weight of 20,000-25,000 Da (Shiomi et al. 1988, 1990). A new anticoagulant peptide with a native molecular mass of 7,500 Da from the spine venom of A. planci, plancinin, inhibits factor X activation in the human blood coagulation cascade (Koyama et al. 1998). A fraction of venom from the crown-of-thorns starfish causes smooth muscle contraction mediated by prostaglandins (Karasudani et al. 1996). In addition, the venom showed vasorelaxing and hypotensive effects, which were assumed to be due to the release of a platelet-activating factor or a factor-like substance (Yara et al. 1992). The fact that the molecular mass of pedoxin from T. pileolus is 206 Da may suggest that the development of its synthesis is possible. Further, pedoxin seems to show low antigenicity because of its low molecular mass when it is subcutaneously or intramuscularly injected. There are still many sea urchin species to be investigated, the venoms of which are not yet characterized.

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