r acl r on. Vol . 34 No . 1z, va . 1593- 1ssa.1 994 0041- 0101( 94) 00110- 3 Pr i nt ed Copyr i ght t Br i ~vi n t ee . v aal - 0101/ 94 $7 . ao+ .OD COMPARATI VE STUDY OF THE STABI LI TY OF SAXI TOXI N AND NEOSAXI TOXI N IN ACI DI C SOLUTI ONS AND LYOPHI LI ZED SAMPLES A . ALFoNso, M . C . LouzAo, M . R . VI EYTES and L . M . BOTANA* Depart ament os de Farmacol ogi a y Fi si ol ogi a, Facul t ad de Vet er i nar i a, 27002 Lugo, Spai n ( Recehwd 13 May 1994; accept ed 23 Jul y 1994) A . ALFONSO, M . C . LouzAo, M . R . Vmr ms and L . M . BOTANA. Comparat i ve st udy of t he st abi l i t y of saxi t oxi n and neosaxi t oxi n in aci di c sol ut i ons and l yophi l i zed sampl es . Toxi con 32, 1593- 1598, 1994 . - Par al yt i c shel l f i sh poi son ( PSP) has hi st or i cal l y been a pr obl em f or t he shel l f i sh i ndust r y . In or der to pr event t he market i ng of cont am i nat ed seaf ood pr oduct s, gover nment s have i mpl ement ed moni t ori ng pr ogr ams wher e st andar ds of t oxi ns ar e necessar y . The st abi l i t y of t hese st andar d t oxi ns is ver y i mport ant . In t hi s paper we anal ysed t he st abi l i t y of saxi t oxi n ( STX) and neosaxi t oxi n in aci di c sol ut i on and l yophi l i zed sampl es . I ndi vi dual t oxi ns wer e det er m i ned in each sampl e usi ng a hi gh- per f or mance l i qui d chr omat ogr aphi c pr ocedur e empl oyi ng post - col umn oxi dat i on of t he t oxi ns to f or m f l uor escent der i vat i ves . Our r esul t s demonst rat e t hat STX is ver y st abl e in sol ut i on sampl es and coul d be adopt ed as a r ef er ence st andar d . Thi s t oxi n can be kept i n di l ut e aci di c sol ut i ons f or 18 months wi t hout l oss of pot ency . However , neosaxi t oxi n is unst abl e, possi bl y due to t r ansf or mat i on t o ot her t oxi ns . I NTRODUCTI ON BLOOMS or r ed t i des have f or ced annual cl osur es of shel l f i sh har vest , r esul t i ng in ser i ous econom ic consequences f or r egi onal mus s el i ndust r i es in t he nor t hwest of Spai n . Mussel s of t en become t oxi c by i ngest i on of t oxi c phyt opl ankt on dur i ng a r ed t i de and cause par al yt i c shel l f i sh poi soni ng in humans and mari ne ani mal s ( KODAMA, 1988) . PSP t oxi ns appear to be t r ansi ent l y st or ed in t he hepat opancr eas in mussel s ( HALSTTAD and Vnvci , 1988) , owi ng to unspeci f i c pr ot ei ns of t he mus s el whi ch ar e i nvol ved in t hi s bi ndi ng ( LouzAo et al ., 1992) . PSP t oxi ns ar e im i dazol i ne der i vat i ves . St r uct ur al l y, t hey coul d be di vi ded i nt o carbamat e t oxi ns, sul f amat e t oxi ns and decar bamoyl t oxi ns . We have obt ai ned t he pr of i l e of t he t oxi ns ext r act ed f r om Spani sh mussel s by hi gh per f or mance l i qui d chr omat ogr aphy ( HPLC) anal ysi s ( ALxoNso et al ., 1993) , and obt ai ned a pr of i l e t hat shows a hi gh pr opor t i on of t he sul f amat e and car bar nat e t oxi ns . Saxi t oxi n ( STX) , whi ch was pur i f i ed in 1957 ( SCHANTZ et al ., 1957) , is t he mos t r epr esent at i ve t oxi n of t he gr oup. Neosaxi t oxi n ' Aut hor to whom cor r espondence shoul d be addr essed. 1593