Structure and relative potency of several karlotoxins from Karlodinium veneficum

Abstract

The karlotoxins are a family of amphidinol-like compounds that play roles in avoiding predation and in prey capture for the toxic dinoflagellate Karlodinium veneficum. The first member of the toxin group to be reported was KmTx 1 (1), and here we report an additional five new members of this family (3-7) from the same strain. Of these additional compounds, KmTx 3 (3) differs from KmTx 1 (1) in having one less methylene group in the saturated portion of its lipophilic arm. In addition, 64-E-chloro-KmTx 3 (4) and 10-O-sulfo-KmTx 3 (5) were identified. Likewise, 65-E-chloro-KmTx 1 (6) and 10-O-sulfo-KmTx 1 (7) were also isolated. Comparison of the hemolytic activities of the newly isolated compounds to that of KmTx 1 shows that potency correlates positively with the length of the lipophilic arm and is disrupted by sulfonation of the polyol arm.

Figure 1

Fragmentation pathways for 3, 4, and 6. For each compound [M + Na]⁺ was selected as precursor and all fragment masses include sodium ions. Note that the fragments resulting from scission of C-41/C-42 and from scission of C-48/C-49 indicate that differences between the structures occur in the lipophilic arm.

Figure 1

Fragmentation pathways for 3, 4, and 6. For each compound [M + Na]⁺ was selected as precursor and all fragment masses include sodium ions. Note that the fragments resulting from scission of C-41/C-42 and from scission of C-48/C-49 indicate that differences between the structures occur in the lipophilic arm.