New Esters of Okadaic Acid in Seawater and Blue Mussels (Mytilus edulis)

Abstract

Marine algal toxins of the okadaic acid (OA) group can occur as diol esters and sulfated diol esters in algae and as fatty acid esters in shellfish. Several of these ester forms have been identified, but the most common procedure for detecting OA group toxin esters is by measuring the increase in parent toxin after alkaline hydrolysis. Use of this alkaline hydrolysis method led to the discovery of high levels of conjugates of OA and dinophysistoxins-2 (DTX2) in seawater and of OA, DTX1, and DTX2 in blue mussel hepatopancreas (HP) from Flødevigen, Norway, during a bloom of Dinophysis spp. In the water sample, a C 8-diol ester, a C 9-diol ester, and a previously undescribed C 8-triol ester of OA were characterized using HPLC-MS (2), -MS (3), and -MS (4) in combination with various derivatization procedures. Palmitic acid (16:0) ester derivatives of these diol/triol esters were found in mussel HP and characterized using HPLC-MS (2), -MS (3), and -MS (4). To the authors' knowledge, hybrid diol-fatty acid esters of OA have not been previously described. Mass spectral analysis showed the presence of two forms of hybrid esters: one with the fatty acid conjugated to the 7-OH of the OA moiety and the other with the fatty acid conjugated to the OH group in the "diol" moiety. In the water sample, the C 8-diol ester was the most abundant, whereas in the mussels, the 16:0-C 9-diol hybrid ester was most abundant, and only minor amounts of the 16:0-C 8-diol hybrid ester were detected, suggesting that C 8- and C 9-diol esters of OA may be metabolized differently in blue mussels. 7- O-acyl esters of OA, DTX1, and DTX2 are thought to contribute to shellfish toxicity by being hydrolyzed in the human stomach to the parent toxins, and the newly characterized hybrid esters are likely to contribute similarly.

Toxin profiles of five geographical isolates of Dinophysis spp. from North and South America

“…Cruz and co-workers suggested that different phytoplankton species can be associated with the production of specific enol esters and that sulfate derivatives of each reported diol-ester exist. In addition to diol-esters, a C8-triol OA derivative was more recently observed in seawater collected during a Dinophysis bloom in Norway (Torgersen et al, 2008a).…”

“…The cells were rinsed on the sieve with fresh f/2 media, and kept wet to minimize breakage. The cells were washed into a 15-mL Falcon tube Tachibana and Scheuer, 1981;(2) Murata et al, 1982;(3) Larsen et al, 2007;(4) Yasumoto et al, 1985;(5) Marr et al, 1992 (6) Hu et al, 1995a;(7) Hu et al, 1995b;(8) Cruz et al, 2006;(9) Fernandez et al, 2003;(10) Suarez-Gomez et al, 2005;(11) Yasumoto et al, 1989;(12) Hu et al, 1992a;(13) Suarez-Gomez et al, 2001;(14) Miles et al, 2006;(15) Torgersen et al, 2008a;(16) Norte et al, 1994. using fresh f/2 media (13 mL), and the tube immersed in a water bath at 100 C for 5 min. The samples were frozen at À20 C, thawed at room temperature, and sonicated in a water bath (Fisher ultrasonic cleaner, Model FS30H) for 15 min before solid-phase extraction (SPE).…”

“…Esterification can occur with a wide range of fatty acid esters from C 14 to C 22 with unsaturation number up to 6, which often leads to a complex toxin profile (Yasumoto et al, 1985;Marr et al, 1992;Torgersen et al, 2008b). Furthermore, fatty acid esters resulting from the bio-transformation of OA diol-esters were recently discovered in mussels, and include those of the 7-OH of the OA moiety and of the OH group of the diol moiety (Torgersen et al, 2008a). The structures of the compounds belonging to the OA group are shown in Fig.…”

Okadaic Acid Meet and Greet: An Insight into Detection Methods, Response Strategies and Genotoxic Effects in Marine Invertebrates

“…Although a role in OA acylation was initially ascribed to bacteria present in the bivalve gut [46], it was later demonstrated that in mussels the OA is primarily transformed in the endoplasmic reticulum [47]. Acylation seems to play a major role in OA depuration, yet, further studies are still needed in order to ascertain the mechanisms underlying depuration rates of different toxins in different bivalve species [48]. …”

Current Techniques for Detecting and Monitoring Algal Toxins and Causative Harmful Algal Blooms

“…Two new pectenotoxins, 36S-PTX-12 and 36R-PTX-12 in Dinophysis spp, occurred as a pair of equilibrating diasteroisomers that were different from PTX-2 [76]. With the use of alkaline hydrolysis, several groups of new conjugates of okadaic acid (OA) and dinophysisoxins-2 (DTX2) in seawater were identified [77]. A C8-dio ester, a C9-dio ester, and new C8-triol ester of OA were characterized using QIT with multiple stages of mass spectrometry (HPLC-MS 2 , MS 3 , and MS 4 ) in combination with various derivatization procedures.…”