Revisiting the Neuroblastoma Cell-Based Assay (CBA-N2a) for the Improved Detection of Marine Toxins Active on Voltage Gated Sodium Channels (VGSCs).

The neuroblastoma cell-based assay (CBA-N2a) is widely used for the detection of marine biotoxins in seafood products, yet a consensus protocol is still lacking. In this study, six key parameters of CBA-N2a were revisited: cell seeding densities, cell layer viability after 26 h growth, MTT incubation time, Ouabain and Veratridine treatment and solvent and matrix effects. A step-by-step protocol was defined identifying five viability controls for the validation of CBA-N2a results. Specific detection of two voltage gated sodium channel activators, pacific ciguatoxin (P-CTX3C) and brevetoxin (PbTx3) and two inhibitors, saxitoxin (STX) and decarbamoylsaxitoxin (dc-STX) was achieved, with EC50 values of 1.7 ± 0.35 pg/mL, 5.8 ± 0.9 ng/mL, 3 ± 0.5 ng/mL and 15.8 ± 3 ng/mL, respectively. When applied to the detection of ciguatoxin (CTX)-like toxicity in fish samples, limit of detection (LOD) and limit of quantification (LOQ) values were 0.031 ± 0.008 and 0.064 ± 0.016 ng P-CTX3C eq/g of flesh, respectively. Intra and inter-assays comparisons of viability controls, LOD, LOQ and toxicity in fish samples gave coefficients of variation (CVs) ranging from 3% to 29%. This improved test adaptable to either high throughput screening or composite toxicity estimation is a useful starting point for a standardization of the CBA-N2a in the field of marine toxin detection.

Evaluation of Matrix Issues in the Applicability of the Neuro-2a Cell Based Assay on the Detection of CTX in Fish Samples.

Ciguatoxins (CTXs) are a group of neurotoxins responsible for the syndrome ciguatera fish poisoning (CFP) as a result of the consumption of contaminated fish. The presence of these toxins has been detected around the Pacific, Caribbean and Indian coasts. Recent reports indicate the emergence of CFP in other geographic areas, in particular in European coasts, of the Canary Islands (Spain) and Madeira (Portugal). A neuroblastoma cell line of murine origin (N2a) has been applied to assay different groups of neurotoxins, acting on voltage-gated sodium channel (VGSC) of excitable cells, N2a-MTT. The great potential of N2a-MTT as a sensitive tool for the CTXs screening is clearly recognized, notably because it allows the detection of these toxins at levels below recommended as security levels. However, the complexity of the matrix is a critical point on the application of N2a-MTT, which needs to be evaluated. The aim of this work is to provide recommendations for an implemented N2a-MTT method for CTXs determination in fish that avoids matrix effects, particularly those related to high lipid content.

Biological activities and pharmacokinetics of aconitine, benzoylaconine, and aconine after oral administration in rats.

Aconitine (AC), benzoylaconine (BAC), and aconine (ACN) are three representative alkaloids in Aconitum tubers. Knowing that the drug disposal process in vivo is closely related to the toxicity and efficacy of a drug, it is important to classify the disposal properties of these alkaloids. In this study, the pharmacokinetics of the three alkaloids was investigated. The results showed that the three alkaloids could be quickly absorbed, especially BAC, whose Tmax was 0.31 ± 0.17 h. Their Cmax was 10.99, 3.99, and 4.29 ng·mL(-1) respectively, indicating that AC had better absorption than BAC and ACN. Subsequently, we further investigated their absorption mechanism using the Caco-2 cell monolayer model in vitro. The results showed that they were poorly absorbed, and the absorption of AC and BAC was inhibited by P-gp, while the absorption of ACN was in a form of passive diffusion. The t1/2 of AC, BAC and ACN was 1.41, 9.49, and 3.32 h, respectively, indicating that the metabolic or excretion rate of AC was quicker than that of BAC and ACN. Therefore, their metabolic stability was further investigated by using rat liver microsomes in vitro, which showed that AC was easier to be metabolized than BAC and ACN. The excretion experiments showed that AC and ACN were primarily excreted in urine, while BAC was excreted in faeces. In addition, the results of tissue distribution experiments showed that the three alkaloids distributed throughout all the organs, although the distribution rate of AC was slower than that of BAC and ACN. Copyright © 2015 John Wiley & Sons, Ltd.

Quantification of aconitine in post-mortem specimens by validated liquid chromatography-tandem mass spectrometry method: three case reports on fatal 'monkshood' poisoning.

The diester-diterpene alkaloid aconitine was quantified by liquid chromatography-tandem mass spectrometry in post-mortem specimens of three cases where suicidal ingestion of Aconitum napellus L. ('monkshood') was supposed. In an attempt at rationalization, sample preparation and chromatographic conditions of plasma/serum drug analysis routine were utilized. Linearity was established from 0.5 to 20 µg L⁻¹ using newborn calf serum (NCS) as a surrogate calibration matrix for all sample types and mesaconitine as an internal standard. Validation (selectivity, sensitivity, precision, accuracy, recovery of the extraction procedure, matrix effect, processed sample stability) confirmed the applicability of the analytical method to various post-mortem matrices. Internal standard selection was based on multi-matrix process efficiency data. In human post-mortem peripheral blood a lower limit of quantification of 0.51 µg L⁻¹ and a limit of detection of 0.13 µg L⁻¹ were accomplished (0.1 ml sample aliquots). Aconitine was degraded to a large extent in different sample types when being stored at +20 °C for 30 days, while at -20 °C and for some matrices also at +4 °C no appreciable degradation occurred. Aconitine concentrations in real samples were 10.3-17.9 µg L⁻¹ (peripheral blood, n = 3), 14.9-87.9 µg L⁻¹ (heart blood, n = 3), 317-481 µg L⁻¹ (urine, n = 2), 609-4040 µg L⁻¹ (stomach content, n = 3), 139-240 µg L⁻¹ (bile, n = 2), 8.4 µg L⁻¹ (vitreous humor, n = 1), 54.7 µg L⁻¹ (pericardial fluid, n = 1), 492 µg kg⁻¹ (liver, n = 1), 15.2-19.7 mg L⁻¹ (unknown liquids secured onsite, n = 3). Together with concomitant circumstances the analytical data provided compelling evidence for acute Aconitum poisoning as being the cause of death.