Jean-François Biard

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.

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.

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.

Dichlorolissoclimide, a new cytotoxic labdane derivative from Lissoclinum voeltzkowi Michaelson (Urochordata)

Spectral methods were used to determine the siruciure o/ a new cytotoxic compound, dichlorolissoclimide I, isolatedfrom the New Caledonia ascidian Lissoclinum voeltzkowi Michaelson. It is known that ascidians usually contain original nitrogenous compounds192. We isolated a new nitrogenous labdane cytotoxic substance, dichlorolissoclimide 1 (0.004%), from the EtOH extract of Lissoclinum voeltzkowi Michaelson (Urochordata, Didemnidae) gathered in 1988 on Platier du Mont Dore, New Caledonia. Isolation was performed by 1iquidAiquid purification and HPLC and monitored by cytotoxic bioassay using SESAME mathematical analysis3. The molecular formula of compound 1, C20H2gC12N04, = -20, was determined by analysis of its spectral mass and NMR data(Tab1e 1). The 13C spectra revealed 20 carbons attached to a total of 26 hydrogen atoms. The highest FAB mass peaks at m/z 418,420 and 422 (C~OH~OCI~NO~+) were thus attributed to the (M H+) ion. FAI3 mass spectra revealed other peaks at m/z 400, 402 and 404 (C~OH~~CI~NO~+) attributable to (M H+-H2O) fragmentation. The highest mass peak at m/z 399.1367 (C20H27N0335C12) in the EIHRMS confirmed the loss of a molecule of H20 (The 400/402/404 (loo%, 87%, 37%) ratio is consistent with two chlorine atoms). The deshielded 13C NMR resonances of s 184.8 (C) and 182.6 (C) indicated the presence of

Marine natural products and related compounds as anticancer agents: an overview of their clinical status.

Marine ecosystems constitute a huge reservoir of biologically active secondary metabolites. Consequently during the last past few decades, several marine-derived molecules have been approved for anticancer treatment or are under clinical trials. This review reports the present state of the art of the sixteen molecules approved or currently on the clinical pipeline for anticancer chemotherapy. The molecules are classified according to their current status in the phase (approved / phase IV / phase III / phase II / phase I) and data are updated to April 2012.

Structural investigation and elucidation of new communesins from a marine-derived Penicillium expansum Link by liquid chromatography/electrospray ionization mass spectrometry

Penicillium expansum is a ubiquitous species for which there are only few reports for chemical investigation in marine environments. Among the numerous secondary metabolites produced by this species, communesins represent a new class of cytotoxic and insecticidal indole alkaloids. In this study, we investigated a marine P. expansum strain exhibiting neuroactivity on a Diptera larvae bioassay. Bio-guided purification led to the isolation and the identification of communesin B as the main active compound by HRMS and 1H and 13C NMR. Liquid chromatography analyses with detection by electrospray ionization coupled with tandem mass spectrometry (LC/ESI-MS/MS) and high-resolution tandem mass spectrometry (LC/HRMS/MS) allowed the identification and characterization of four other known communesins (A, D, E and F) in the crude extract. A fragmentation model for dimethyl epoxide communesins was proposed after detailed interpretation of their MS/MS spectra. Further analyses of the extract using the modelled fragmentations led to the detection of seven new communesins found as minor compounds. Chemical structural elucidation of these new derivatives is discussed based on their fragmentation characteristics.

Effects of bistramide A on a non-small-cell bronchial carcinoma line

SummaryThe antiproliferative effects of bistramide A, a nitrogenous dilactam polyether fromLissoclinum bistratum Sluiter (Urochordata), were studied at the level of the cell cycle in asynchronous cells of the NSCLCN6-L16 line. Bistramide A has a dual mechanism that induces blockade in the G1 phase (compatible with differentiation properties reported elsewhere) and causes polyploidy that is suggestive of inaptitude for cytokinesis. These effects confirm the results of cytomorphology studies in electron microscopy.

Enhancement of domoic acid neurotoxicity on Diptera larvae bioassay by marine fungal metabolites

Peptaibols are small linear fungal peptides which are produced in the marine environment. They exhibit neurotoxicity by forming pores in neuronal membranes. This work describes their combine effect with domoic acid, a neurotoxic phycotoxin, on Diptera larvae. The Acute toxicity bioassay on this biological model was tested with a panel of different toxins (microbial, algal or fungal). It allowed the discrimination of neurotoxins and non-neurotoxic toxins, and an evaluation of the toxicity level (MED and ED(50)) which were correlated with published LD(50) in mice for neurotoxins tested. The highest activities on this test were found for Na(+) channel blockers tetrodotoxin (ED(50) = 0.026 mg/kg) and saxitoxin (ED(50) = 0.18 mg/kg). Domoic acid was less active with an ED(50) = 7.6 mg/kg. For synergism study, longibrachin-A-I, a 20-mer peptaibol isolated from cultures of a marine-derived strain of Trichoderma longibrachiatum Rifai was chosen. Bioassay results confirmed its neuroactivity. Its level of toxicity (ED(50) = 270 mg/kg) was lower than those of phycotoxins tested but higher than mycotoxin ones. Injected together, longibrachin-A-I and domoic acid exhibited an increase of their activities. With doses of longibrachin-A-I below its Minimal Effective Dose (MED), the synergism factor which expresses the enhancement of domoic acid toxicity could reach 34.5. Both domoic acid and longibrachin-A-I are acting on ion channels and pores in neuronal membranes which contribute to the intake of Ca(2+) into cells.

Lissoclimides, Cytotoxic Diterpenes from Lissoclinum voeltzkowi Michaelsen

Abstract Chlorolissoclimide, a monochloro diterpene, was identified in Lissoclinum voeltzkowi Michaelsen, a New-Caledonian tunicate. Its structure was determined in relation to that of the previously described dichlorolissoclimide. In vitro cytotoxicity, structure-activity relationships, biosynthetic origin and involvement in human food poisoning are discussed.