. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. OH Me". FIGURE 4. (i) Molecular structure of okadaic acid. (2) Molecular structure of brevetoxin B. bled ciguatoxin. Scaritoxin was reported to cause severe hind limb paralysis in mice, a symptom not normally observed with ciguatoxin. Recently, we (Joh and Scheuer, in press) examined parrotfish (Scams sordidus) from a toxic reef on Tarawa atoll, Republic of Kiribati. We also isolated two toxins separable on DEAE cellulose. However, by manipulation on basic alumina we were able to interconvert the two toxins. By TLC comp
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. OH Me". FIGURE 4. (i) Molecular structure of okadaic acid. (2) Molecular structure of brevetoxin B. bled ciguatoxin. Scaritoxin was reported to cause severe hind limb paralysis in mice, a symptom not normally observed with ciguatoxin. Recently, we (Joh and Scheuer, in press) examined parrotfish (Scams sordidus) from a toxic reef on Tarawa atoll, Republic of Kiribati. We also isolated two toxins separable on DEAE cellulose. However, by manipulation on basic alumina we were able to interconvert the two toxins. By TLC comparison we showed that scaritoxin and the less polar ciguatoxin (Nukina et al, 1984) are identical, though this finding remains to be confirmed by spectral comparison. When Yasumoto (Murakami et al., 1982) examined the constituents of the toxic dinoflagellate Prorocentrum lima, he made the surprising discovery that on TLC analysis one of the constituents was indistinguishable from ciguatoxin. The substance proved not to be ciguatoxin but okadaic acid (Fig. 4, i), a compound which we had shortly before reported from a sponge, Halichondria okadai (Tachibana et al., 1981). The two compounds differ greatly in size (1111 vs. 804 daltons) and lethality ( vs. 192 Mg/kg), but evidently not in polarity because of their similar chromatographic behavior. This was the first clear indication that ciguatoxin belongs to the class of polyethers, as does, inter alia, brevetoxin B (Fig. 4, 2) (Lin et al., 1981). These com- pounds are highly oxygenated long-chain fatty acids, in which most of the oxygen atoms occur as cyclic ether linkages. Okadaic acid (Fig. 4, i), possesses one carboxyl, four hydroxyls, and seven oxa rings, in addition to three carbon-carbon double bonds. This information allows us to extrapolate safely to the ciguatoxin structure, which evidently is a complex polyether possessing five hydroxyls and four carbon- carbon double bonds. This close structural analogy to okadaic a
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