CHAPTER 17 . Characterization of Marine Toxins with LC-ESI-MS
333
In a more recent study (Lewis and Jones 1997), the application of LC-ESI-MS allowed (i) the determination of up to fourteen ciguatoxin congeners in highly purified
extracts of Pacific Ocean moray eel viscera and (ii) the determination of the major
congener (P-CTX-1) in crude extracts. It is noteworthy that eleven congeners were
present at trace levels and could not be detected by mouse bioassay. In another LCESI-MS study (Vernoux and Lewis 1997), Lewis and co-workers could demonstrate that
the ciguatoxin congeners present in contaminated fish from the Caribbean Sea (CCTXs) are different from those arising from fish of the Pacific Ocean (P-CTXs), thus
justifying the different symptoms described for ciguatera intoxication in the two regions. The major component of the Caribian mixture C-CTX-1 was found to be 30 Da
larger than the major component of Pacific Ocean ciguatoxin mixture P-CTX -1. C-CTX1 is also more hydrophobic and 10 times less toxic than P-CTX-1. The NMR and
ESI mass spectral features for C-CTX -1 and P-CTX -1 are very close to one another, confirming the similarity of their structures. However, the precise chemical structure
of C-CTX-1, and its differences from P-CTX-1, have not been elucidated yet (Poli et
al.1997). The ESI mass spectra of C-CTX-1 and -2 at, respectively, 120 and 80 V skimmer voltage are presented in Fig. 17.9. Signals are evident at m/z 1179.9 [M + Kj+,
1163.8 [M+Naj+,1158.8 [M+NH4t,1141.8 [MHj+,1123.8 [MH-H20j+,l105.8 [MH2 H20t, 1087.9 [MH - 3 H20j+, 1069.7 [MH -4 H20j+, 1051.6 [MH- 5 H20j+. These
spectral features confirm both the high alkali metal ion affinity and the polyhydroxylated nature of ciguatoxins. It is noteworthy that high orifice (skimmer) voltages favor the formation of both alkali cationized ions and extensively dissociated fragments.
While extensive fragmentation is expected, according to an energetic "in -source" CID,
the reasons for enhancement of alkali cationized species are unclear.
C-CTX-2
1141.6
100
100
1123.8
~
1123.6
...: 50
.5
1100.6
1158.8
75
£
1124.9
~
0
1100
1150
~
m/z
'iii
c
l!l 50
.5
~
.~
1105.8
£
1141.8
1158.8
25
1087.9
1163.8
051.6
0
1060
1080
1100
1120
1140
1160
1180
m/z
Fig. 17.9. ESI mass spectra of C-CTX-1 and C-CTX-2 (inset). The skimmer voltage was set to respectively 120 V and 80 V (reprinted with permission from Vernoux and Lewis 1997)
333
In a more recent study (Lewis and Jones 1997), the application of LC-ESI-MS allowed (i) the determination of up to fourteen ciguatoxin congeners in highly purified
extracts of Pacific Ocean moray eel viscera and (ii) the determination of the major
congener (P-CTX-1) in crude extracts. It is noteworthy that eleven congeners were
present at trace levels and could not be detected by mouse bioassay. In another LCESI-MS study (Vernoux and Lewis 1997), Lewis and co-workers could demonstrate that
the ciguatoxin congeners present in contaminated fish from the Caribbean Sea (CCTXs) are different from those arising from fish of the Pacific Ocean (P-CTXs), thus
justifying the different symptoms described for ciguatera intoxication in the two regions. The major component of the Caribian mixture C-CTX-1 was found to be 30 Da
larger than the major component of Pacific Ocean ciguatoxin mixture P-CTX -1. C-CTX1 is also more hydrophobic and 10 times less toxic than P-CTX-1. The NMR and
ESI mass spectral features for C-CTX -1 and P-CTX -1 are very close to one another, confirming the similarity of their structures. However, the precise chemical structure
of C-CTX-1, and its differences from P-CTX-1, have not been elucidated yet (Poli et
al.1997). The ESI mass spectra of C-CTX-1 and -2 at, respectively, 120 and 80 V skimmer voltage are presented in Fig. 17.9. Signals are evident at m/z 1179.9 [M + Kj+,
1163.8 [M+Naj+,1158.8 [M+NH4t,1141.8 [MHj+,1123.8 [MH-H20j+,l105.8 [MH2 H20t, 1087.9 [MH - 3 H20j+, 1069.7 [MH -4 H20j+, 1051.6 [MH- 5 H20j+. These
spectral features confirm both the high alkali metal ion affinity and the polyhydroxylated nature of ciguatoxins. It is noteworthy that high orifice (skimmer) voltages favor the formation of both alkali cationized ions and extensively dissociated fragments.
While extensive fragmentation is expected, according to an energetic "in -source" CID,
the reasons for enhancement of alkali cationized species are unclear.
C-CTX-2
1141.6
100
100
1123.8
~
1123.6
...: 50
.5
1100.6
1158.8
75
£
1124.9
~
0
1100
1150
~
m/z
'iii
c
l!l 50
.5
~
.~
1105.8
£
1141.8
1158.8
25
1087.9
1163.8
051.6
0
1060
1080
1100
1120
1140
1160
1180
m/z
Fig. 17.9. ESI mass spectra of C-CTX-1 and C-CTX-2 (inset). The skimmer voltage was set to respectively 120 V and 80 V (reprinted with permission from Vernoux and Lewis 1997)