JoséJ. Fernández

New alkaloids from a marine zoanthid

Abstract Five new alkaloids zoanthenol 7,3-hydroxynorzoanthamine 8, 30-hydroxynorzoanthamine 9,11-hydroxynorzoanthamine 10 and 11-hydroxyzoanthamine 11 have been isolated from a marine zoanthid. Their structures were determined through the interpretation of 2D-NMR spectral data. Their relative stereochemistries were proposed on the basis of ROESY data.

Terpenoids of the red alga laurencia pinnatifida

Abstract The structures of three brominated terpenoids which are natural products from the red alga Laurencia pinnatifida (Gmal. Lamour) are described. The structures of the sesquiterpenes 4 and 5 were determined by spectral comparison and chemical interconversion. The structure of the squalene-derived terpenoid 8 was secured by chemical transformation into thyrsiferol, a brominated triterpene previously isolated from the red alga Laurencia thyrsifera.

Thyrsenols A and B, two unusual polyether squalene derivatives

Abstract Two new polyether squalene derivatives, thyrsenol A 2 and thyrsenol B 3, have been isolated from the red alga Laurencia viridis. Their structures, which possess an unusual enol-ether moiety, were determined through the interpretation of 2D-NMR spectral data. The relative stereochemistry is proposed on the basis of ROESY and NOEDIFF data. Their cytotoxic activities were evaluated.

TWO NEW ANTITUMORAL POLYETHER SQUALENE DERIVATIVES

Two new polyether squalene derivatives isodehydrothyrsiferol 2 and 10-epidehydrothyrsiferol 3 have been isolated from the red alga Laurencia viridis. Their structures were determined through the interpretation of 2D NMR spectra and their antitumoral activity was established.

New polyether squalene derivatives from Laurencia

Abstract Five new triterpenoid polyethers with a squalene carbon skeleton have been isolated from the red alga Laurencia viridis . Their structures were determined through the interpretation of 2D-NMR spectral data. The relative stereochemistry is proposed on the basis of ROESY and NOEDIFF data.

Epioxyzoanthamine, a new zoanthamine-type alkaloid and the unusual deuterium exchange in this series

Abstract A new alkaloid, epioxyzoanthamine 4 , has been isolated from a marine zoanthid. Its structure and relative stereochemistry were determined through the interpretation of NMR spectral data. This compound as well as norzoanthamine, showed an unusual deuterium exchange at the methylene C-11 after treatment with D 2 O.

Evaluation of the cytotoxic activity of polyethers isolated from Laurencia.

In this paper, we report on the conformational analysis of several polyether triterpenes with a squalene carbon skeleton which exhibited significant cytotoxic activity using a Monte Carlo conformational search and spectroscopical data. These studies indicate that the conformation of the side chain C-14/C-19 and the arrangement and direction of this chain may be among the fundamental factors related to the activity of this type of metabolites.

Aplysinadiene and (r,r) 5 [3,5-dibromo-4-[(2-oxo-5-oxazolidinyl)] methoxyphenyl]-2-oxazolidinone, two novel metabolites from aplysina aerophoba synthes

Abstract Two novel constituents, biogenetically derived from dibromotyrosine, were obtained from a sponge Aplysina aerophoba . The structure of aplysinadiene 1 was established on the basis of its spectral properties and by synthesis of 1 and its isomers 7 and 8 . The structure and absolute configuration of the oxazolidinone 5a was established by X-ray diffraction analysis as (R,R) 5 [3, 5-dibromo-4-[(2-oxo-5- oxazolidinyl)] methoxyphenyl]-2-oxazolidinone.

Influence of amino acids on okadaic acid production

Okadaic acid (OA) (1)) was the first example of a group of polyether toxins known to be produced by marine microalgae, which are responsible for the natural phenomena known as Diarrhetic Shellfish Poisoning (DSP) red tides. It is also a highly selective inhibitor of protein phosphatases type 1 (PP1) and 2A (PP2A), as well as being a potent tumour promoter. For these reasons, OA is an extremely useful tool for studying cellular processes and an important standard for polluted shellfish control. In this paper, we report on a double objective: to improve the production of toxins and verify the apparent participation of amino acids in the formation of these polyethers by monitoring their influence on the promotion of growth, total cell yield and increased in toxicity in Prorocentrum lima of the PL2V strain in batch cultures, in a modified K medium.

Inhibitory effects of okadaic acid on rat uterine contractile responses to different spasmogens

Summary— In the present study, we examined the effects of okadaic acid, a selective inhibitor of type 1 and 2A protein phosphatases, on the mechanical responses evoked by oxytocin, K+‐ and Na+‐modified solutions and ouabain in estrogen‐primed rat myometrium. Oxytocin elicited a rapid, phasic contraction followed by rhythmic oscillations. The phasic response was partially resistant to the absence of external Ca2+. Okadaic acid (1 μM) and the L‐type calcium channel blocker nifedipine (1 μM) abolished the oscillatory component and reduced the initial, phasic response to about 80% of the control response. High K+ (60 mM) solution, ouabain (1 mM), K+‐free medium and low Na+ (25 mM) solution induced extracellular Ca2+‐dependent biphasic responses composed by an early rapid (KCl, ouabain and K+‐free solution) or slower developed (25 mM Na+ solution) phasic contraction followed by a sustained increase in tension. Okadaic acid and nifedipine, alone or in combination, abolished or decreased similarly the contractile response evoked by these stimulants. The okadaic acid‐ and nifedipine‐insensitive responses to ouabain, K+‐free and low Na+ solution were enhanced by increasing the extracellular concentration of Ca2+ in the medium and were inhibited in a dose‐dependent manner by amiloride (0.05–0.5 mM). These data suggest that, in estrogen‐primed rat uterus, dephosphorylating mechanisms by OA‐sensitive protein phosphatases play an important role in regulating myometrial contractions elicited by Ca2+ entry through voltage‐sensitive Ca2+ channels.