title: Epimers of azaspiracids: Isolation, structural elucidation, relative LC-MS response, and in vitro toxicity of 37-epi-azaspiracid-1.
abstract: Since azaspiracid-1 (AZA1) was identified in 1998, the number of AZA analogues has increased to over 30. The development of an LC-MS method using a neutral mobile phase led to the discovery of isomers of AZA1, AZA2, and AZA3, present at ~2-16% of the parent analogues in phytoplankton and shellfish samples. Under acidic mobile phase conditions, isomers and their parents are not separated. Stability studies showed that these isomers were spontaneous epimerization products whose formation is accelerated with the application of heat. The AZA1 isomer was isolated from contaminated shellfish and identified as 37-epi-AZA1 by nuclear magnetic resonance (NMR) spectroscopy and chemical analyses. Similar analysis indicated that the isomers of AZA2 and AZA3 corresponded to 37-epi-AZA2 and 37-epi-AZA3, respectively. The 37-epimers were found to exist in equilibrium with the parent compounds in solution. 37-epi-AZA1 was quantitated by NMR, and relative molar response studies were performed to determine the potential differences in LC-MS response of AZA1 and 37-epi-AZA1. Toxicological effects were determined using Jurkat T lymphocyte cells as an in vitro cell model. Cytotoxicity experiments employing a metabolically based dye (i.e., MTS) indicated that 37-epi-AZA1 elicited a lethal response that was both concentration- and time-dependent, with EC50 values in the subnanomolar range. On the basis of EC50 comparisons, 37-epi-AZA1 was 5.1-fold more potent than AZA1. This data suggests that the presence of these epimers in seafood products should be considered in the analysis of AZAs for regulatory purposes.
authors: Marine Institute, Rinville, Oranmore, County, Galway, Ireland.
authors: Jane
authors: J
authors: Kilcoyne
authors: Pearse
authors: P
authors: McCarron
authors: Michael J
authors: MJ
authors: Twiner
authors: Ciara
authors: C
authors: Nulty
authors: Sheila
authors: S
authors: Crain
authors: Michael A
authors: MA
authors: Quilliam
authors: Frode
authors: F
authors: Rise
authors: Alistair L
authors: AL
authors: Wilkins
authors: Christopher O
authors: CO
authors: Miles
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D006801:Humans; D066298:In Vitro Techniques; D007536:Isomerism; D019169:Jurkat Cells; D009682:Magnetic Resonance Spectroscopy; D008387:Marine Toxins / Q000737:chemistry / Q000302:isolation & purification* / Q000633:toxicity; D015394:Molecular Structure; D012758:Shellfish / Q000032:analysis; D013141:Spiro Compounds / Q000737:chemistry / Q000302:isolation & purification* / Q000633:toxicity; D053719:Tandem Mass Spectrometry / Q000379:methods*; D000095702:Polyether Toxins
chemical_list: D008387:Marine Toxins; D013141:Spiro Compounds; C406592:azaspiracid; D000095702:Polyether Toxins