Jean-François Verbist

Lepadiformine, a new marine cytotoxic alkaloid from Clavelina lepadiformis Müller

Abstract A cytotoxic alkaloid, lepadiformine 1, with a new heterocyclic skeleton, has been isolated from the ascidian Clavelina lepadiformis. The structure of 1 was established on the basis of chemical properties and by spectroscopic means : it includes a unique zwitterionic-like moiety.

Proton Nuclear Magnetic Study of Bistramide A, a new cytotoxic drug isolated from Lissoclinum Bistratum Sluiter

Abstract Modern two-dimensional NMR techniques have been used here in order to study the structure of a recently isolated cytotoxic drug, bistramide A. Mass spectroscopy indicated a M r of 704 corresponding to an apparent molecular formula of C 40 H 68 N 2 O 8 . All structural information was obtained from 1 H and 13 C NMR. 1 H- 1 H and 1 H- 13 C COSY in combination with relayed 1 H- 1 H- 13 C COSY and 1 H- 13 C COLOC were used for obtaining all crucial connectivies required for determining the partial structure of this natural product.

Short-time cytotoxicity of mussel extracts: A new bioassay for okadaic acid detection

Okadaic acid (OA), the main toxin responsible for diarrhoeic shellfish poisoning (DSP) has high cytotoxicity for KB cell cultures (apparent after 3 hr of contact), facilitating rapid detection in contaminated mussels. We developed a method to determine the minimal active concentration (MAC) based on direct microscopic study of toxin-induced changes in cell morphology. A high correlation was found between the MAC of tested extracts and corresponding OA concentrations in mussel hepatopancreas as measured by high performance liquid chromatography. This technique is rapid and reproducible and does not require the use of living animals.

Reidispongiolide A and B, two new potent cytotoxic macrolides from the New Caledonian sponge Reidispongia coerulea

Abstract Two new 26-membered macrolides, reidispongiolide A ( 1 ) and B ( 2 ), have been isolated from the New Caledonian marine sponge Redispongia coerulea n.gen.n.sp. Levi and Levi and their structures elucidated. They are related to sphinxolides previously isolated from an unknown nudibranch and later from the sponge Neosiphonia superstes . 1 and 2 co-occurr with sphinxolide B ( 4 ) and D ( 3 ). These macrolides exhibited potent cytotoxicity against various human carcinoma cells.

Toxicity of French strains of the dinoflagellate Prorocentrum minimum experimental and natural contaminations of mussels

Mediterranean strains of Prorocentrum minimum do not appear to have the same toxic component as Japanese strains since they showed no cytotoxicity for hepatocytes in culture. However, their toxic components, which appear to block calcium channels, were detectable by the immobilisation test on Diptera larvae. A bio-accumulation experiment in the laboratory showed that the toxins could accumulate in nearly equivalent amounts in the hepatopancreas and meat of cultured mussels. The same toxicity was found in natural samples collected in a period of bloom of P. minimum. These results suggest that P. minimum could be responsible for shellfish toxicity in the natural environment and thus present a risk for human health.

Three new potent cytotoxic macrolides closely related to sphinxolide from the New Caledonian sponge Neosiphonia superstes

Abstract Three new macrolides 2–4 have been isolated with sphinxolide 1 from the marine sponge N. superstes collected off New Caledonia. The structures of the new compounds were determined by interpretation of NMR spectral data as well as by comparison of spectral data with those of 1 . These compounds were highly cytotoxic against various human carcinoma cells.

Bistramide A, a new toxin from the urochordata Lissoclinum bistratum Sluiter: Isolation and preliminary characterization

Two cases of human intoxication caused by the lyophilized powder of Lissoclinum bistratum Sluiter, a New Caledonian ascidian, are reported. The symptoms observed were caused by a substance designated bistramide A (C40H68N2O8) of hitherto unknown chemical structure. Preliminary toxicological investigations indicate that bistramide A may effect the central nervous system, leading to paresthesia and loss of muscle tone. A progressive decrease in cardiac rhythm was also observed in animals. Bistramide A (1.4 x 10(-6) M) did not alter the resting potential of frog heart and skeletal muscle but reduced the amplitude and duration of cardiac action potential and prolonged the interval between action potentials. Bistramide A also has a marked cytotoxic effect on cancer cells KB (IC50 = 4.5 x 10(-8) M) and P 388 (IC50 = 2.0 x 10(-8) M) and on normal endothelial cells (IC50 = 2.2 x 10(-8) M). However, it has not been possible to relate the cytotoxic property to the symptoms of intoxication. Bistramide A may originate from the urochordate itself or from symbiotic algae.

Cardiovascular effects of lepadiformine, an alkaloid isolated from the ascidians Clavelina lepadiformis (Müller) and C. moluccensis (Sluiter)

The effects of lepadiformine, a natural marine alkaloid isolated from the ascidians Clavelina lepadiformis (Müller) and C. moluccensis (Sluiter), were studied in vivo by arterial blood pressure (aBP) recordings and electrocardiograms (ECG) in anaesthetised rats and in situ by peripheral vascular pressure recordings on perfused rabbit ear. Transmembrane resting (RP) and action (AP) potentials were also recorded by intracellular microelectrodes on electrically stimulated left ventricular papillary muscle and spontaneously beating atrium isolated from rat and frog hearts, respectively. Intravenous injection of lepadiformine (6mg/kg) produced marked bradycardia and a lengthening of ECG intervals as well as a transient decrease of aBP, which rapidly returned to normal. The decrease of aBP may have been related to a vasoconstrictor effect observed in the perfused ear experiment. Lepadiformine did not alter RP, but significantly lengthened the repolarising phase of AP in rat papillary muscle and frog atrium. Lepadiformine also mimicked the effect of Ba(2+) (0.2mM) on the rat AP repolarising phase. Moreover, the lengthening of the AP in frog atrium induced by lepadiformine still developed after the delayed outward K(+) current (I(K)) was blocked by tetraethylammonium (10mM). These observations suggest that lepadiformine-induced lengthening of AP duration was not due to a decrease of I(K), but may reasonably be attributed to a reduction of the inward rectifying K(+) current (I(K1)). This blockade of I(K1) could account for the cardiovascular effects of lepadiformine in vivo and in vitro and suggests that lepadiformine has antiarrhythmic properties.

Combined use of LC/MS and a biological test for rapid identification of marine mycotoxins produced by Trichoderma koningii.

Trichoderma koningii Oudemans, a strain isolated from a shellfish farming area, was selected for its high frequency in samples and its ability to produce metabolites when cultured in natural seawater. Combined use of LC/MS and a biological test on blowfly larvae allowed the characterization of four compounds after purification in only two steps (VLC and HPLC). ESI/MS, a powerful tool for rapid identification and sequence determination of peptides, confirmed that these compounds were peptide, alpha-aminoisobutyric acid and amino alcohol (peptaibols), the usual metabolites of Trichoderma.

Accumulation of gliotoxin, a cytotoxic mycotoxin from Aspergillus fumigatus, in blue mussel (Mytilus edulis)

A strain of Aspergillus fumigatus has been isolated from sediments of a mussel bed. When cultured in hyper saline conditions (with sea-water), it produces a cytotoxic and immunosuppressive toxin, gliotoxin, which is excreted in an exudate. In order to know if this toxin could represent a risk for shellfish consumers, an experiment of bioaccumulation of gliotoxin in mussel has been carried out. After 6 days of contamination, toxin was accumulated in the meat of the mussels, at a level up to 2.9 microg/mg of extract weight, with a mode of contamination different to the classical digestive process described for a majority of marine toxins, but similar to the contamination mode of domoic acid.