Identification of Prostaglandins in the Gorgonian, Plexaura homomalla

Abstract

Hexane extracts of the air-dried cortex of the gorgonian Plexaura homomalla (Esper) were found to contain (15R)-hydroxy-9-oxo-prost-5,10,13-trienoic acid [i.e. (15R)-prostaglandin A,] and its 15-acetate methyl ester in 0.Zo/, and 1.3O/, yield from the cortex by Weinheimer and Spraggins in 1969. Chloroform-methanol extracts of this organism have now been shown to contain these two compounds as major prostaglandin constituents, but also a more complex mixture of prostaglandin derivatives including lln,(l5R)-dihydroxy-9-oxo-prost-5,13-dienoic acid [i.e. (15R)-prostaglandin E,] and the methyl esters of (15R)-prostaglandin E, and (15R)-prostaglandin A,. (15R)-Prostaglandin E, was identified by its chromatographic behavior, by the chromatographic behavior and mass spectrum of its 0-methyloxime, methyl ester, trimethylsilyl ether derivative, and by oxidative ozonolysis to fragments of established structure. The configuration of the 15-hydroxyl group was determined in the cleavage fragment 2-hydroxyheptanoic acid by gas-liquid chromatography of its methyl ester ( -)-menthyloxycarbonyl derivative. Similar degradations of material with chromatographic properties equivalent to prostaglondin A, and prostaglandin E, yielded 2-hydroxyheptanoate with the 8 configuration, demonstrating the presence o€ small amounts of (158)-prostaglandins in the lipid extract.Weinheimer and Spraggins [l] reported the isolation of two prostaglandins, 15-acetyl-( 15R)-prostaglandin A, methyl ester (I) and (15R)-prostaglandin A, (111), from hexane extracts of the airdried cortex of the gorgonian Plexaura homomalla (Esper). The two substances were present in rather high concentrations, 1.3O/, and 0.2O/, of the cortex dry weight, respectively. These C-15 epimers of prostaglandin A, (IV) were devoid of the bloodpressure-lowering effect of prostaglandin A,. Their function in the gorgonian tissue is unknown, but their occurrence is very interesting since the concentration of prostaglandins normally found in various mammalian tissues is much smaller [Z]. They are also of interest as potential synthetic precursors to biologically active prostaglandins of the Az, Ez (VII), or FzG( type [3] because they can be obtained in large quantities.Trival names. Prostaglandin E,, lla-(l5L9)-dihydroxy-9-oxoprost-5,13-dienoic acid; prostaglandin FZa, 9a,1 la,-(15S)-trihydroxy-prost-5,13-dienoic acid; prostaglandin A,, (15S)-hydroxy-9-oxo-prost-5,10,13-trienoic acid; (15 R)-prosttaglandin E,, l l n , (15R)-dihydroxy-9-oxoprost-5,13-dienoic acid; (15R) prostaglandin A,, (15R)-hydroxy-9-oxo-prost-5,10,13-trienoic acid; methyl acetyl (15R)-prostaglandin A,, methyl (15R)-acetoxy-9-oxo-prost-5,10,13-trienoate.Definition. C-value, the "theoretical" number of carbon atoms in the fatty acid chain obt,ained from the retention time by using a calibration curve of logarithm of retention time versus number of carbon atoms in normal fatty acids.Our own interest in the gorgonians originated in their potential use as source of the prostaglandin synthetase. A prerequisite for such ...

Prostaglandins in aquatic fauna: a comprehensive review

“…These compounds possessed the nonmammalian R configuration at CI5 and lacked the vasodilatory effect of the mammalian PGA, in vivo. Similar findings were reported by others (Light & Samuellson 1972) for the same species. Bundy et al (1972) demonstrated that these inactive compounds could be chemically modified to yield biologically active products.…”

The origin of 15 R -prostaglandins in the Caribbean coral Plexaura homomalla : Molecular cloning and expression of a novel cyclooxygenase

“…Further acetylation gives the PGA 2 methyl ester 15-acetate, which then accumulates in the coral. This explains why the 15-acetate of PGA 2 is found in P. homomalla, but PGE 2 occurs only as the methyl ester (1)(2)(3)(4)(5).…”

“…In some experiments designed to reduce the prostaglandin endoperoxide in situ and to simplify the pattern of products, 0.5 mM SnCl 2 was added to the incubation mixtures just before [1][2][3][4][5][6][7][8][9][10][11][12][13][14] C]arachidonic acid. This gave an immediate reduction of the peroxy intermediates to the corresponding hydroxy compounds.…”

“…It was subsequently discovered that P. homomalla colonies collected in other Caribbean locations such as the Cayman Islands and Bahamas contain the same prostaglandin derivatives but with the normal 15S configuration ( Fig. 1B) (2,3). These later studies established that P. homomalla also contains PGE 2 methyl ester (2, 3) as well as minor constituents, including the methyl ester 15-acetate derivatives of 5,6-trans-PGA 2 and 13,14-cis-PGA 2 (4).…”

Evidence of a Cyclooxygenase-related Prostaglandin Synthesis in Coral

“…When the inhibition of intermediates was studied, SnCl 2 (final concentration, 0.5 mM) was added into the incubation mixture. Values are means Ϯ S. D., n ϭ 3. q, total PGs formed in incubations without the reducing agent; f, PGF 2␣ ; OE, ( homomalla, but the latter also contains esters of PGE 2 and PGF 2␣ (25,26), and it now seems to be much more likely that the PGA derivatives are formed from the PGE derivatives rather than the other way around. The isolation of PGG 2 from short incubations of G. fruticosa gave a strong evidence that prostaglandins are synthesized via the endoperoxide pathway (13).…”