Polyhydroxylated steroids

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]. 

Vazquez, M. J., Quinoa, E., Riguera, R., San-Martin, A., and Darias, J., Antarctic marine metabolites new polyhydroxylated steroidal glycosides from the starfish Odontaster validus, Liebigs Ann. Chem., 1257, 1993. 

In addition to Asteroidea and Holothuroidea, the phylum Echinodermata (Greek echinos, spiny derma, skin) comprises the classes Ophiuroidea (brittle stars), Crinoidea (sea lilies and feather stars) and Echinoidea (sea urchins). There is no report of occurrence of steroid or triterpenoid glycosides in sea lilies, feather stars or sea urchins. Brittle stars contain sulfated polyhydroxylated steroids [10-12] and only two sulfated steroidal monoglycosides have been isolated from the brittle star Ophioderma longicaudum [13]. 

More than one hundred polyhydroxylated steroidal glycosides have been characterized but only few reports on their biological activity have been published. Recently, several examples of new bioactive mono- and diglycosides of polyhydroxysteroids as well as biological studies on known compounds have been reported. 

The starfish Certonardoa semiregularis has shown to be a rich source of bioactive sterols and glycosides of polyhydroxylated steroids. Purification of the brine shrimp active fraction of the methanolic extract of C. semiregularis led to the isolation of nine new sulfated polyhydroxylated steroidal diglycosides [41],... 

Much work has been done in the last thirty years on the isolation and structural characterization of saponins and polyhydroxylated steroid glycosides from starfishes and sea cucumbers. The wide spectrum of biological activities these compounds show must be related to their role in the organisms that produce them and this task must be addressed in future investigations. 

Bertinotti, A., Carrea, G., Ottolina, G., and Riva, S., Regioselective esterification of polyhydroxylated steroids by Candida antarctica lipase B, Tetrahedron, 50, 13165-13172, 1994. 

Starfish (Styracaster caroli) were collected at a depth of 2000 m between the islands of Thio and Lifou (New Caledonia). Polar (aqueous and acetone) extracts of the starfish yielded three unique polyhydroxylated steroidal amines with an unusual 20-epicholanic skeleton, carolisterols A and B (39-41). The separation was achieved by column chromatography (Sephadex LH-20), droplet counter current chromatography, and reversed-phase HPLC (34). 

Haraguchi M, Motidome M, Morita H, Takeya K, Itokawa H, Mimaki Y, Sashida Y (1999) New Polyhydroxylated Steroidal Sapogenin and Saponin from the Leaves of Cestrum sendtenerianum. Chem Pharm Bull 47 582... 

Yang Q-X, Zhang Y-J, Li H-Z, Yang C-R (2005) Polyhydroxylated Steroidal Constituents from the Fresh Rhizomes of Tupistra yurmanensis. Steroids 70 732... 

Cholesterol, whether ingested or formed endogenously, provides the starting material for the biosynthesis of all the other steroids found in mammals. Excess cholesterol is oxidized in the hver to polar compounds called cholic acids. This process converts the terminal side chain in cholesterol to a carboxyhc acid and introduces hydroxyl groups. These polyhydroxylated, steroidal acids play a central role in absorption of fats from the intestine and also excretion of superfluous cholesterol. 

Like vertebrates and fungi, plants produce polyhydroxylated steroidal hormones to regulate and control tissue morphology. In plants these types of hormones are designated brassino-steroids and they are built on a campestanol carbon skeleton (Figure 12.1). The brassinosteroids... 

Figure 12.1. Polyhydroxylated steroids in plants indicating the carbon numbers of brassinosteroids as reprinted with permission from Bishop and Yokota (2001) .

As described by D Auria et al. 20] it is well known that many marine invertebrates are a rich source of polyhydroxylated steroids. One such metabolite, 5a-cholestane-3P,5,6p,9-tetrol, 12, initially isolated by Sjostrand et al. [21] and then later by Schmitz et al. [22], was the first polyhydroxy steroid to be isolated from the marine specie, P. elisabethae. 

Bile alcohols polyhydroxylated steroids structurally related to cholestane. They oecur as sulfate esters in the bile of lower vertebrates, e.g. scymmol (3a,7a,12a,24,25,27-hexahydroxy-5p-cholestane) from shark bile. 

As the glycosides from starfish are steroidal in nature and as some known polyhydroxylated steroids with moderate cytotoxicity have been isolated from these animals, the literature since 1980 dealing with such compounds will be reviewed here. Aside from some monohydroxyste-rols from Echinaster sepositus 646), Acanthaster planci 647) - this being a source of a new cyclopropane sterol Asterias vulgaris 648), and Comasterias lurida 649), the reports deal mainly with polyhydroxylated steroids. 

Minale, L., C. Pizza, F. Zollo, and R, Riccio Trace Polyhydroxylated Steroids from Starfish Hacelia attenuata. J. Nat. Prod. 46, 736 (1983). 

Andersson, L., Nasir, A., Bohlin, L., and Ketme, L. (1987b) Studies of Swedish marine organisms. IX. Polyhydroxylated steroidal glycosides from the starfish Porania pulvdlus. J. Nat. Prod., 50,944—947. 

De Riccardis, F., lorizzi, M., Minale, L, Ricdo, R., and Debitus, C. (1992) The first occurrence of polyhydroxylated steroids with phosphate conjugation from the starfish Tremaster novae-caledoniae. Tetrahedron Lett., 33, 1097-1100. 

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. 

Higuchi, R., Noguchi, Y Komori, T., and Sasaki, T. (1988a) H-NMR Spectroscopy and biological activities of polyhydroxylated steroids from the starfish Asterina pectinifcra Muller et Trochel. Liebigs Ann. Chem., 1185-1189. 

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