Robert Valls

Antifouling activity of meroditerpenoids from the marine brown alga halidrys siliquosa

Nine tetraprenyltoluquinol-related metabolites (1-9) have been isolated from the organic extract of the temperate brown alga Halidrys siliquosa that exhibits antifouling properties. The planar structure of compounds 1-9 was elucidated on the basis of extensive spectroscopic analysis and by comparison of the data with those of related metabolites. Antifouling and toxicity tests were conducted on these compounds: the most active (compounds 2, 6, and 9) inhibited both the growth of four strains of bacteria (MICs < 2.5 microg/mL) and settlement of cyprids of Balanus amphitrite (EC50 < 5 microg/mL), the latter at nontoxic concentrations (LC50 > 5 microg/mL).

(S)-13-hydroxygeranylgeraniol-derived furanoditerpenes from Bifurcaria bifurcata

Two new diterpenes were isolated from a sample of the brown alga Bifurcaria bifurcata collected from Brittany on the Atlantic coast and their structures established by spectroscopic methods. The new diterpenes are derived from (S)-13-hydroxygeranylgeraniol by terminal cyclization and oxidation leading to a furan-3-yl ring or a beta,gamma-epoxy-gamma-lactone. One of them showed a cytotoxic effect to fertilized sea urchin eggs. The chemical shifts of the methyl groups and quaternary carbons in (S)-13-hydroxygeranylgeraniol have been revised to take account of the results obtained in a 2D NMR long-range C-H correlation experiment and the absolute configuration at C-13 determined for the first time. The geographical variation in the diterpenoid composition of B. bifurcata was also studied.

Linear diterpene with antimitotic activity from the brown alga Bifurcaria bifurcata

A new linear diterpene, isolated from the brown alga Bifurcaria bifurcata collected on the Atlantic coasts from Morocco, has been characterized by spectral methods and chemical reactions. This compound revealed a potent cytotoxicity to fertilized sea urchin eggs which was compared to that of previously described acyclic diterpenes. The seasonal and geographical variations in the diterpenoid composition of this species are also studied and the results discussed.

Mediterraneol a, a novel rearranged diterpenoid-hydroquinone from the marine alga cystoseira mediterranea

The isolation and structure determination by combined chemical and spectral methods of a novel biologically active metabolite mediterraneol A (Ia) from Cystoseira mediterranea are reported. Mediterraneol A was found to be an inhibitor of mitotic cell division.

An acyclic diterpene from the brown alga Bifurcaria bifurcata

Abstract Structure elucidation and total assignment of the 13 C NMR spectrum of 12-( S )-hydroxygeranylgeraniol, a new acyclic diterpene from the grown alga Bifurcaria bifurcata , was accomplished through the use of 1 HNMR, 13 C NMR and 2D NMR spectroscope including 2D long range 1 H- 13 C chemical shift correlations.

Geranylgeraniol-derived diterpenoids from the brown alga Bifurcaria bifurcata

Three novel diterpenes were isolated from the brown alga Bifurcaria bifurcata collected oA the Atlantic coast from Brittany, and their structures established by spectroscopic methods. Two of them are acyclic diterpenoids derived from 13ketogeranylgeraniol, while the third is a b,g-epoxy-g-butyrolactone derived from (S)-hydroxygeranylgeraniol. Some assignments of 13 C- and 1 H-NMR signals in 13-ketogeranylgeraniol and related diterpenoids were revised to take account of the results obtained in 2D NMR long-range C‐H correlation experiments. These results are discussed from a chemotaxonomic point of view. # 1999 Elsevier Science Ltd. All rights reserved.

Acyclic diterpenes from Bifurcaria bifurcata

Abstract Two new acyclic diterpenes have been isolated from the brown alga Bifurcaria Bifurcata. They were characterized by spectral and chemical methods.

Secondary metabolites from morocco brown algae of the genus Cystoseira

Abstract Two new epimeric tetraprenyltoluquinols with a chromane moiety have been isolated from the brown alga Cystoseira baccata and characterized by spect

(S)-12-hydroxygeranylgeraniol-derived diterpenes from the brown alga Bifurcaria bifurcata.

Four novel diterpenes were isolated from the brown alga Bifurcaria bifurcata collected off the Atlantic coast from Morocco, and their structures established by spectral and chemical methods. These compounds are acyclic diterpenes derived from (S)-12-hydroxygeranylgeraniol. One of them is its dehydration product at C-12, while the others are its oxidation derivatives: the methyl ester of the acid at C-1 and two stereoisomers (Z and E) of the aldehyde at C-1. These results are discussed from a chemotaxonomic point of view.

Determination of sterols and diterpenoids from brown algae (Cystoseiraceae)

Abstract A high-performance liquid chromatographic method is described for the determination of secondary metabolites that belong to the brown algae of the Cystoseiraceae family. The study was focused on sterols, which are globally determined as fucosterol, and on the main structural families of diterpenes (mero- and linear diterpenes). An example is given of the analysis of three characteristic extracts from Atlantic and Mediterranean species.