Recent Developments in the Molecular Structure of Ciguatoxin

Abstract

Crystalline ciguatoxin isolated from moray eel (Lycodontis = G ymnothorax javanicus) viscera has an LD 50 of 0.45 g/kg (i.p., mice). It has a molecular weight of 1 1 1 1.7 0.2 daltons. 'H NMR studies have shown that it is a polar and highly oxygenated molecule belonging to the class of polyethers. On basic alumina ciguatoxin is reversibly converted to a chromatographically distinct less polar form, which is equally toxic and elicits typical ciguatoxin symptoms in mice.From parrotfish (Scarus sordidus), which originated on a ciguateric reef on Tarawa atoll (Kiribati), we have isolated two toxins that evoke ciguatera symptoms in mice at approximately equal levels. Chromatographic evidence suggests that the two toxins are identical with the two ciguatoxins of different polarity and that the less polar form is the previously described scaritoxin.

Isolation and some properties of ciguatoxin

“…~~~~~~~~~WA 'lM N The purified ciguatoxin gave a H NMR spectrum (Fig. 2) comparable with that reported by Tachibana (1980Tachibana ( , 1987 and by Nukina etal. (1984).…”

“…Livers of the moray eel Gymnothorax (= Lycodontis) javanicus have been found to be the best source of the toxin (Yasumoto & Scheuer, 1967). Subsequently Scheuer's group isolated pure ciguatoxin and presumed the toxin to be a polyether having a molecular weight 1111.7 + 0.3 (Tachibana et al, 1987). However, further chemical studies have been hampered because of the difficulty of collecting toxic fish and because of the tedious purification procedures necessitated by the extremely low concentration of toxin in fish.…”

Are crustaceans linked to the ciguatera food chain?

“…Extensive research has been conducted with respect to determining causal agents and their relationship to ciguatera , Carlson & Tindall1985, Yasumoto et al 1987, dinoflagellate ecology (Carlson & Tindall1985, Taylor 1985, Gillespie et al 1985, pharmacology (Li 1965, Tachibana 1987, Legrand & Bagnis 1984, Yasumoto 1985, Ohizumi et al 1985, Miller & Tindall 1985, Ohizumi 1987, and chemistry (Scheuer et al 1967, Yasumoto & Scheuer 1969, Chungue et al 1977, Miller et al 1984, Bomber et al 1990, Legrand et al 1990). However, much less research has been done on aspects dealing with the food chain dynamics (Helfrich & Banner 1963, Davin et al 1986) and apparently no research has been done to examine the role crustacea may play in the transference of ciguatera toxins.…”

Ciguatoxin enhances quantal transmitter release from frog motor nerve terminals

“…Both CTX and MTX are among the most potent marine toxins known (Tachibana et al, 1987;Yasumoto, 1980). While the effects of MTX are well characterized on excitable membranes (Freedman et al, 1984;Miyamoto et al, 1984;Kobayashi et al, 1985), secretory cells (Takahashi et al, 1983;Login, et al, 1985;Schettini et al, 1984) and at the neuromuscular junction (Kim et al, 1985), the pharmacological actions of CTX (reviewed are less well known mainly due to difficulties in obtaining adequate quantities of chromatographically pure toxin.…”

“…CTX, first purified by Scheuer et al (1967), is a complex lipid-soluble compound. Although H' nuclear magnetic resonance data suggest a molecular weight of 1111.7 + 0.2 daltons, its molecular structure has not yet been completely established (Tachibana et al, 1987). CTX has been shown to affect selectively sodium channels inducing membrane depolarization and spontaneous action potentials in neuroblastoma cells and myelinated axons (Bidart et al, 1984;Benoit et al, 1986).…”