Pseudopterosin A is a diterpene

glycoside In chemistry, a glycoside is a molecule in which a sugar is bound to another functional group via a glycosidic bond. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycosides. ...

isolated from the gorgonian sea whip ''

Antillogorgia elisabethae ''Antillogorgia elisabethae'' is a species of soft coral found in the Caribbean Sea in the shape of a sea plume (also called a sea whip). It resides from depths of to , often at reef drop-offs. It looks like a plume of feathery appendages with ...

'', found in the Bahamas and Florida Keys.A. Kohl, A. Ata, R. Kerr. ''J. Ind Microbiol Biotechnol'' (2003) 30: 495-499. Pseudopterosins A-D, which differ in the degree of acetylation at the sugar ring, were first isolated and reported in 1986. There are at least 25 unique diterpenes isolated from this species of marine animal. Samples of ''P. elisabethae'' from the Bahamas are found to have higher concentrations of pseudopterosins than populations from the Florida Keys, which have a greater diversity in diterpene structures.

Uses

Pseudopterosins have anti-inflammatory and analgesic activity, with a mechanism of action different from the common non-steroidal anti-inflammatory drugs, NSAIDs. Commercially, pseudopterosins are found in skin creams as topical anti-inflammatory agents.A. Mayer, P. Jacobson, W. Fenical, R. Jabocs and K. Glaser. ''Life Sciences'' (1998) 62: 401-407.

Biosynthesis

Elisabethatriene (2) has been identified as a key intermediate for the synthesis of the class of pseudopterosins and ''seco''-pseudopterosins. A proposed mechanistic pathway for the synthesis of elisabethatriene from geranylgeranyl pyrophosphate (GGPP, 1), is described below. Elisabethatriene synthase, a diterpene cyclase enzyme, catalyzes the transformation of the diterpene GGPP to a 10-membered carbon skeleton followed by hydride migration towards the bicyclic ring system.R. Kerr, A. Kohl, and T. Ferns. ''J. Ind Microbiol Biotech'' (2006) 33: 532-538. This cyclase enzyme has been identified as a key enzyme in forming the carbon skeleton of pseudopterosins in one step. An alternative mechanism has been proposed in which a six-membered ring is formed first, then a second ring closing for the bicyclic system. : The biosynthesis of the pseudopterosins continues with an aromatization to erogorgiaene (3), two oxidations to a dihyroxyerogorgiaene (4, then 5), and another oxidation to an ortho-hydroxyquinone (6). Ring closure (7), re-aromatization to (8) and glycosylation yield Pseudopterosin A (9). This is a plausible biosynthetic pathway, and intermediates 2, 3, 6, 7, and 8 have been identified using radio labeling studies. An alternative mechanism has been proposed with no hydroxyquinone intermediate (6). Rather, molecule 3 undergoes two subsequent oxidations at C-6 and C-7 to a structure resembling 8, then glycosylation to pseudopterosin. : The branching point for the biosynthesis of the tricyclic pseudopterosins versus the bicyclic ''seco''-pseudopterosins occurs at compound 11, the aromatized bicycle erogorgiaene. 11 is oxidized once then hydroxylated followed by glycosylation to make the bicyclic ''seco''-pseudopterosins. The proposed synthesis of artificial anti-inflammatory metabolites is modeled after pseudopterosins and is based on the bicyclic ''seco''-pseudopterosin structure 6.

References

{{reflist Phenol glycosides Diterpenes