Structures and Partial Stereochemical Assignments for Prymnesin-1 and Prymnesin-2:  Potent Hemolytic and Ichthyotoxic Glycosides Isolated from the Red Tide Alga Prymnesium parvum

Abstract

Two glycosidic toxins, prymnesin-1 (PRM1) and prymnesin-2 (PRM2) have been isolated from cultured cells of the red tide phytoflagellate Prymnesium parvum, and the gross structure of PRM2 C96H136Cl3NO35 has been reported in a previous contribution. The molecule possesses unique structural features: a C90 unbranched carbon chain except for a single methyl, five contiguous ether rings (6/6/6/7/6), four distinct 1,6-dioxadecalin units, conjugated double and triple bonds, chlorine and nitrogen atoms, and an uncommon l-xylose. Potent ichthyotoxic and hemolytic properties of the two toxins were also demonstrated. However, the stereochemistry of PRM2 and the structure of PRM1 remained unknown. In the present paper the relative stereochemistry of the polycyclic ether moiety of PRM2 and the structure of PRM1 C107H154Cl3NO44 are reported. Structural elucidation was carried out by extensive analysis of NMR data. Difficulties arising from the poor solubility of the toxins in NMR solvents were overcome by preparing N-acetyl, peracetyl, perhydro, and dehydrochlorinated derivatives of the toxins. These derivatives were also effective in improving the precision of signal assignments. 13C NMR measurements were facilitated by a 13C-enriched N-acetate from cultures of the flagellate in the presence of Na13CO3. Comparison of the NMR data between N-acetylprymnesin-1 and N-acetylprymnesin-2 and chiral GC analysis of the glycosidic residues indicated that PRM1 possessed α-d-ribofuranosyl, α-l-arabinopyranosyl, and β-d-galactofuranosyl residues at C77, C78, and C82 positions, respectively, on the same aglycone structure as PRM2. In the polycyclic parts (C20−C74) of both toxins, all ring fusions were trans and all rings took a chair conformation. The stereochemistry at C14 and C76−C85 remains unknown.

An experimental analysis of harmful algae–zooplankton interactions and the ultimate defense

“…parvum is an invasive and harmful algal species that produces a number of toxins (Shilo 1971(Shilo , 1981. Igarashi et al (1999) identified the toxins prymnesin 1 and prymnesin 2 as two potent ichthyotoxins. However, recent work by Henrikson et al (2010) found that the primary toxins in our cultures and in Lake Texoma were galactoglycolipids, collectively called parvisides, with most toxicity in laboratory cultures due to the derivative stearidonic acid, a fatty acid component that is freed from the parvisides by esterase activity.…”

Structural Features of Dinoflagellate Toxins Underlying Biological Activity as Viewed by NMR

“…Brevetoxins (BTXB 2 and BTXA 7), the first members of LSPs, have been extensively studied by Nakanishi's 76 and Shimizu's groups. 77 Besides these toxins, ciguatoxin, 78-81 maitotoxin, prymnesins, 82,83 and yessotoxins (YTX 9) [84][85][86] have been found in association with fish-killing red tides or toxic seafood. More than 50 compounds belonging to LSP have been reported so far.…”

Isolation and Characterization of a Double Stranded DNA Megavirus Infecting the Toxin-Producing Haptophyte Prymnesium parvum

“…However, the toxic metabolites responsible for bloom toxicity are not established in Heterosigma akashiwo , making studies of viral impact on toxicity difficult. On the other hand, reports of toxic P. parvum metabolites are numerous and include fatty acids [48], glycerolipids [49] and very large ladder-frame polyether toxins, known collectively as the prymnesins [50,51,52]. Reports of cases of toxic and non-toxic blooms of Prymnesium and other harmful algal species [37] has led to speculation that an ecological trigger exists for toxicity.…”