Binding competition of okadaic acid derivatives to anti-okadaic acid antibody.

The serologic activities of structurally related okadaic acid derivatives have been determined. Binding of [3H]okadaic acid to rabbit anti-okadaic acid is inhibited with equal effectiveness by okadaic acid, dinophysistoxin-1, acanthifolicin, okadaic acid tetramethyl ether, and okadaic acid spiroketal II. Okadaic acid spiroketal I, which lacks the F- and G-rings of okadaic acid, inhibits serologic binding about 60 times less effectively. The F- and G-rings of okadaic acid may comprise part of the epitopes recognized by some of the polyclonal antibodies.