Vincenzo Amico

Antioxidant activity of extracts of the marine algal genus Cystoseira in a micellar model system

The antioxidant activity of the lipid extracts of eight marine algae belongingto the Cystoseira genus has been evaluated in a micellar model system.The activity has been ascribed to the presence in the extracts oftetraprenyltoluquinols, which are tocopherol-like compounds characteristicof these algae. Results have been expressed as relative antioxidant efficiency(RAE), defined as the ratio of the antioxidant efficiency (AE) of the testedextract to that of α-tocopherol. From the results a composition-activityrelationship has been deduced.

Marine brown algae of family Cystoseiraceae: Chemistry and chemotaxonomy

The algal family Cystoseiraceae (order Fucales, class Phaeophyceae) includes the genera Acrocarpia, Acystis, Bifurcaria, Bifurcariopsis, Carpoglossum, Caulocystis, Coccophora, Cystophora, Cystoseria, Halidrys, Hormophysa, Landsburgia, Myriodesma, Scaberia and Stolonophora. Among these Cystoseira and Cystophora, the richest in species, are the most representative of the family. Cystoseira is a genus of worldwide distribution with about 80% of the species occurring along the Mediterranean and adjoining Atlantic coasts, while Cystophora is limited to the coasts of Australia and New Zealand. Members of the genus Cystoseira generally synthesise tetraprenyltoluquinols. Compounds of the same structural type have also been isolated from species belonging to the genera Halidrys (northern coasts of England), Bifurcaria (coasts of the Galapagos Islands), and Cystophora. Some species of these last two also elaborate linear diterpenoids as do some Cystoseira species. Tetraprenyltoluquinols have never been found in Caulocystis and Acrocarpia, which instead accumulate acetogenins. Finally, Landsburgia is the sole genus which produces naphthoquinone derivatives. Phytochemical studies of the secondary metabolites of the remaining genera are not reported. The chemistry of secondary metabolites and their distribution in the family Cystoseiraceae will be illustrated, and some taxonomic implications will be discussed.

Diterpenes based on the dolabellane skeleton from dictyota dichotoma

From a variety of Dictyota dichotoma we have isolated, in addition to previously reported dolabellane (6-8) and perhydroazulene diterpenes (9,10), four new diterpenoids (2-5). Their structure have been elucidated by spectral analysis and chemical degradation. All the new dolabellane derivatives possess antimicrobial activity against gram-positive and gram-negative organisms.

ANTIOXIDANT ACTIVITY OF PHENOLIC MERODITERPENOIDS FROM MARINE ALGAE

Abstract The overall 1 O 2 quenching rate constants k Q for three meroditerpenoids from Mediterranean marine algae of the genus Cystoseira were measured using 1,4-dimethylnaphthalene 1,4-endoperoxide as a thermal source of 1 O 2 ( 1 Δ g ). The most active of the compounds tested had a k Q value which is comparable with that of α-tocopherol. These metabolites also act as inhibitors of methyl linoleate peroxidation, while their O .− 2 quenching activity is rather low, similar to α-tocopherol.

Further perhydroazulene diterpenes from marine organisms

3 novel diterpenes,4–6, having the perhydroazulene skeleton already found in pachydictiol A (1) and dictyol A (2) and B (3), have been isolated from both the digestive gland of Aplysia depilans and algae of the family Dictyotaceae.

The effects of light and kinetin on amaranthin synthesis in relation to phytochrome

Abstract The effects of anaerobic conditions and of various inhibitors on amaranthin synthesis, stimulated by short or continuous irradiation with white light in the eventual presence of kinetin were investigated. The results suggest that both light and kinetin act on the pigment synthesis at two distinct levels, activation of genes and control of the availability of energy-rich compounds. Phytochrome seems to be involved only in the responses depending on short irradiations, while under continuous illumination the photosynthetic system is the photoreceptor for the pigment synthesis.

Light control of amaranthin synthesis in isolated Amaranthus cotyledons

Abstract The effect of light on the amaranthin synthesis stimulated by exogenous precursors has been studied in isolated cotyledons of Amaranthus tricolor and A. caudatus . The results indicate that light acts at the level of the formation of the dihydropyridine moiety of the pigment.

Antimicrobial tetraprenyltoluquinol derivatives from Cystoseira spinosa var. Squarrosa

Abstract Six new tetraprenyltoluquinol derivatives have been isolated from the brown alga Cystoseira spinosa var. squarrosa and their structures determined by chemical and spectral methods. Three of these compounds possess antimicrobial activity against both gram-positive and gram-negative bacteria.

Balearone, a metabolite of the brown alga

Abstract The isolation of a new metabolite of mixed biogenesis, balearone 1 from the brown alga Cystoscira balearica is described. The structure was determined by an X-ray diffraction analysis.

A quinone-hydroquinone couple from the Brown alga Cystoseira stricta

Abstract 2′ E ,6′ E )-2-(10′,11′-Dihydroxygeranylgeranyl)-6-methylquinol and 2′ E ,6′ E )-2(10′,11′-dihydroxyeranylgeranyl)-6-methyl-1,4-benzoquinone have been isolated from the brown alga Cystoseira stricta . The structures of the new algal metabolites have been elucidated by spectral analysis and chemical degradation.