Construction of a paralytic shellfish toxin analyzer and its application

Separation of paralytic shellfish poisoning toxins on Chromarods-SIII by thin-layer chromatography with the Iatroscan (mark 5) and flame thermionic detection

Thin-layer chromatography (TLC) on Chromarods-SIII with the Iatroscan (Mark-5) and a flame thermionic detector (FTID) was used to develop a rapid method for the detection of paralytic shellfish poisoning (PSP) toxins. The effect of variation in hydrogen (H2) flow, air flow, scan time and detector current on the FTID peak response for both phosphatidylcholine (PC) and PSP were studied in order to define optimum detection conditions. A combination of hydrogen and air flow-rates of 50 ml/min and 1.5-2.0 l/min respectively, along with a scan time of 40 s/rod and detector current of 3.0 A (ampere) or above were found to yield the best results for the detection of PSP compounds. Increasing the detector current level to as high as 3.3 A gave about 130 times more FTID response than did flame ionization detection (FID), for PSP components. Quantities of standards as small as 1 ng neosaxitoxin (NEO), 5 ng saxitoxin (STX), 5 ng B1-toxins (B1), 2 ng gonyautoxin (GTX) 2/3, 6 ng GTX 1/4 and 6 ng C-toxins (C1/C2) could be detected with the FTID. The method detection limits for toxic shellfish tissues using the FTID were 0.4, 2.1, 0.8 and 2.5 micrograms per g tissue for GTX 2/3, STX, NEO and C toxins, respectively. The FTID response increased with increasing detector current and with increasing the scan time. Increasing hydrogen and air flow-rates resulted in decreasing sensitivity within defined limits. Numerous solvent systems were tested, and, solvent consisting of chloroform: methanol-water-acetic acid (30:50:8:2) could separate C toxins from GTX, which eluted ahead of NEO and STX. Accordingly, TLC/FTID with the Iatroscan (Mark-5) seems to be a promising, relatively inexpensive and rapid method of screening plant and animal tissues for PSP toxins.

Fluorometric detection of paralytic shellfish poisoning toxins

A rapid qualitative screening method was developed for the fractionation of paralytic shellfish poisoning toxins. Periodic acid, t-butyl hydroperoxide, and hydrogen peroxide were tested as oxidants for the fluorometric detection of paralytic shellfish toxins. Hydrogen peroxide was found to be the most convenient and efficient oxidant since the fluorescence can be detected after the incubation of toxins at 100 degrees C for 3-5 min. In addition to the structure of the compound, the incubation temperature and time, the amount of acid, and the peroxide concentration affect the fluorescence reaction. This method was more efficient than the previously published peroxidation methods which involved lengthy incubation periods or time-consuming pH adjustment. Also, far greater sensitivity was achieved with the new method with levels of 0.027, 0.054, 0.023, 0.003, 0.0002, and 0.0006 pmol being easily detected for saxitoxin, neosaxitoxin, gonyautoxin 1 and 4, gonyautoxin 2 and 3, C toxins, and B toxins, respectively. The method is particularly valuable for the screening of fractions separated by column chromatography.

Use of a channel biosensor for the assay of paralytic shellfish toxins

Gonyautoxin (GTX), saxitoxin (STX) and tetrodotoxin (TTX), also known as paralytic shellfish poisons (PSP), block Na+ channels, including those in the frog bladder membrane. A tissue biosensor has been developed, consisting of a Na+ electrode covered with a frog bladder membrane integrated within a flow cell. The direction of Na+ transfer, investigated in the absence of Na+ channel blockers, established that active transport of Na+ occurs across the frogs bladder membrane from the internal to the external face. Transfer was shown to be TTX sensitive. The tissue sensor response to each of the different PSP was recorded and the results compared with toxicities determined by the standard mouse bio-assay. Using high concentrations of TTX from the puffer fish Takifugu niphobles, a linear correlation was found between the results from the two assay systems. However, the tissue biosensor system was also able to detect very low concentrations of TTX in samples from two species of puffer fish (Takifugu niphobles and Takifugu pardalis) at concentrations below the detection limit of the mouse bio-assay.

High-performance liquid chromatographic methods for determination of marine biotoxins

Paralysing and diarrhetic shellfish poisonings (PSP and DSP) are important intoxications caused by the consumption of shellfish, mainly bivalve molluscs, contaminated by certain species of toxic dinoflagellates present in the marine phytoplankton. Their appearance and massive reproduction take place in some periods of the year, causing the phenomenon commonly known as 'red tide'. This causes significant problems to health and to the economy of the Galician region. The AOAC mouse bioassay is the most commonly used method of analysis for these toxic compounds, being the official method in most countries. Owing to the lack of sensitivity and selectivity of the biological assay, HPLC methods were developed as an alternative methodology. In this paper work carried out on the improvement of the chromatographic conditions in order to achieve accurate information about the PSP and DSP compounds present in the studied samples is reported.

Analysis of paralytic shellfish poisons by capillary electrophoresis

A capillary electrophoresis (CE) method with UV detection is described for the separation and determination of underivatized toxins associated with paralytic shellfish poisoning (PSP). Confirmation of the electrophoretic peaks was facilitated by mass spectrometric (MS) detection using an ionspray CE-MS interface and by high-performance liquid chromatography with fluorescence detection. The determination of PSP toxins, such as saxitoxin and neosaxitoxin, in toxic dinoflagellates and scallops is demonstrated and comparisons are made with existing techniques.

Evaluation of chicken embryo, brine shrimp, and bacterial bioassays for saxitoxin

The chicken embryo, brine shrimp (Artemia salina) and selected bacteria (Staphylococcus epidermidis, Micrococcus flavus, and Bacillus subtilis) were evaluated as alternative test systems for the determination of paralytic shellfish poisoning toxicity (saxitoxin). Dose levels ranging from 0.045 to 0.3 microgram were administered to the developing embryo through the air cell at either 0 or 96 h following incubation. Embryos dosed 96 h after incubation were the most sensitive, with 100% mortality at the 0.11-microgram dose level 24 h following exposure. Embryo mortality was 42% at to 0.3-microgram dose level when the toxin was administered at 0 h. Some embryonic malformations were observed in the 0-h treatment group. Brine-shrimp larvae were sensitive to saxitoxin at a dose level of 5 micrograms. A dose response based on mortality was apparent only 48 h after dosing. Limited growth inhibition was observed with the bacteria tested at concentrations between 0.0035 and 0.35 microgram and 0.35 microgram/well.

Paralytic shellfish poisons produced by the freshwater cyanobacterium Aphanizomenon flos-aquae NH-5

A single filament clonal isolate of Aphanizomenon flos-aquae was made from a water bloom sample taken at a small pond near Durham, New Hampshire, in 1980. When batch cultured the strain was toxic to mice and had an i.p. LD50 of about 5.0 mg/kg. Using an extraction procedure originally designed for paralytic shellfish poisons and other neurotoxins of freshwater cyanobacteria, a purification method was developed. The procedure involved acidified water/ethanol extraction of the cells followed by ultrafiltration, gel filtration, use of C18 cartridges to remove pigments, ion-exchange and high performance liquid chromatography using u.v. detection at 220 or 240 nm. Thin-layer chromatography and high performance liquid chromatography results indicate that Aphanizomenon flos-aquae NH-5 may produce paralytic shellfish poisons, mainly neo-saxitoxin and saxitoxin. Three labile toxins were also detected which were not similar to any of the known paralytic shellfish poisons.

Separation of tetrodotoxin and paralytic shellfish poisons by high-performance liquid chromatography with a fluorometric detection using o-phthalaldehyde

Tetrodotoxin (TTX) and a variety of paralytic shellfish poisons (PSPs) were extracted from toxic specimens of puffer and scallop, and quantitated by high-performance liquid chromatography with a fluorometric detection using o-phthalaldehyde. Fluorescence spectra for the TTX- and PSP-fluorophors in 0.05 M borate buffer (pH 10) showed maxima at 453 nm with 332-nm excitation. The fluorescence intensity per nM of TTX was found to be 3 and those of PSP to be 4-12. This fluorometric technique may be useful for the simultaneous quantitation of TTX and PSP in small volumes of toxin extracts.

Comparison of the toxins of the blue-green alga Aphanizomenon flos-aquae with the Gonyaulax toxins

A toxic strain of Aphanizomenon flos-aquae (NH-1), isolated from a toxic bloom in a pond in Durham, New Hampshire, has been mass cultured in the laboratory. The toxin was extracted by ultrasonic disruption of the cells and purified by; (a) filtration through a 10 kilodalton filter, and (b) chromatography on a strong cation exchange resin column using 0.01 M, then 0.1 M, pH 5, sodium acetate buffer followed by 0.75 M hydrochloric acid. Mouse assays and fluorescence generated by hydrogen peroxide oxidation were used to monitor the fractions. Only a nonfluorescent toxic peak followed immediately by a fluorescent less-toxic peak were detected, both eluting with the hydrochloric acid fractions. The toxins were identical in behavior to neosaxitoxin and saxitoxin, respectively, when compared with elution profiles of the paralytic shellfish poisons from Gonyaulax tamarensis var. excavata and by paper electrophoretic and thin-layer chromatographic comparisons. The toxin profile appears to be different from that of a previously isolated strain of A. flos-aquae from Kezar Lake.

Nonprotein neurotoxins

Nonprotein neurotoxins are continuing to play a major role as molecular probes in studying nervous processes. They also have clinical importance as some of them, such as saxitoxin and its analogues, are the source of public health problems, or have potential use in therapy. This review covers clinical, biological, pharmacological, and chemical aspects of certain nonprotein neurotoxins, with emphasis on three well-known ones: tetrodotoxin, saxitoxin, and batrachotoxin. The distribution of the toxins is discussed as well as their symptomatology, treatment of affected patients, and effects of their structures on their physiological activity. With so many outstanding problems remaining in neuropharmacology, the study of nonprotein neurotoxins thrives as a fertile area of research.