Myxoderma platyacanthum

The taurine residue can also be found as an amide derivative of the 26-carboxylic acid function in the 3p,5a,6p,15a-polyhydroxylated steroids 328 and 329, which were obtained from the starfish Myxoderma platyacanthum [245]. The structures of both compounds were determined from spectral data and chemical correlations. The bile of the sunfish Mola mola has been shown to contain a new bile acid conjugated with taurine (330) together with sodium taurocholate. Compound 330 was identified as sodium 2-[3a,7a, 11 a-trihydroxy-24-oxo-5P-cholan-24-yl]amino]ethane-sulfonate on the basis of its physicochemical data and chemical transformations [246]. 

Fig. 15. New glycosides and polyhydroxysteroids from the starfish Myxoderma platyacanthum (89).

The species Myxoderma platyacanthum and Tremaster novaecaledoniae contain unusual polyhydroxy-sterols for which there are no known equivalents in other species. In the first species (M. platyacanthum), the side chain is an amide whose carbonyl derives from the oxidation of carbon 26 and the nitrogenous part of taurine. The second species (T. novaecaledoniae) contains the first knovm example of a phosphoric ester in position 6a with a classical side chain. This phosphoric ester is in addition associated with asterosaponins, also phosphorylated (see below). The role of these exceptional derivatives in these two sea stars seems not yet be known. Minutoside B is a glycoside isolated from the starfish Anasterias minuta harvested in Patagonia whose aglycone has the same atypical side chain of steroids as that found in Myxoderma platyacanthum (Chludil and Maier, 2005). 

Finamore, E., Minale, L, Ricdo, R., Rinaldo, G., and ZoUo, F. (1991) Novel marine polyhydroxylated steroids from the starfish Myxoderma platyacanthum. J. Org. Chem., 56,1146-1153. 

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