Marine organisms: an alternative source of potentially valuable natural products

This paper recalls the outcoming of marine natural products research and reviews a selection of marirne bioactive metabolites in current use together with promising trends in marine pharmacology.

Propriedades antioxidantes de constituintes fenólicos de macroalgas marinhas

Desde tempos remotos que as macroalgas marinhas são utilizadas por comunidades humanas, nomeadamente as orientais, como parte importante da sua dieta alimentar. A composição química das diferentes macroalgas marinhas (algas castanhas – Phaeophyta, algas vermelhas – Rhodophyta e algas verdes – Chlorophyta) confirma que além de terem um valor nutricional satisfatório podem ser uma fonte muito interessante de compostos bioativos como, por exemplo, os compostos fenólicos. Quimicamente os compostos fenólicos caracterizam-se por apresentarem um ou mais grupos hidroxilo ligados a um anel aromático. Estes compostos englobam desde moléculas simples até moléculas poliméricas de grandes dimensões. A maioria dos compostos fenólicos apresenta atividade antioxidante. O interesse pelo estudo de metabolitos secundários das macroalgas com propriedades antioxidantes surgiu, numa primeira fase, como uma tentativa de encontrar substitutos para os antioxidantes sintéticos usados como aditivos alimentares (nomeadamente o BHA e o BHT) que demonstravam possuir efeitos carcinogénicos. No entanto, rapidamente a comunidade científica reconheceu que a aplicação de novos compostos fenólicos naturais é muito mais vasta. Sabe-se hoje que é crucial para a promoção da saúde de um indivíduo que se verifique a manutenção do equilíbrio entre a produção de radicais livres e as respetivas defesas antioxidantes. Quando esse equilíbrio se altera e ocorre uma acumulação de radicais livres no organismo, este entra em stress oxidativo, situação que pode conduzir a danos dos lípidos celulares, proteínas e ácidos nucleicos, o que favorece o aparecimento de diversas doenças e acelera o envelhecimento celular. Assim, atualmente existe um crescente interesse por parte da indústria farmacêutica e da indústria da cosmética no estudo dos compostos fenólicos isolados de macroalgas. De entre estes, destacam-se os florotaninos, que para além das propriedades antioxidantes têm demonstrado possuir outras atividades farmacológicas importantes, tais como atividade antibacteriana, anti-viral, antineoplásica, anti-hipertensora e anti-diabética. Este trabalho consiste numa revisão bibliográfica sobre os diversos compostos fenólicos com atividade antioxidante isolados de macroalgas marinhas e que demonstraram vantagens na sua incorporação, quer em formulações cosméticas, quer em medicamentos, debatendo as suas ações farmacológicas, mecanismos de ação e possíveis aplicações futuras.

Trypanocidal, leislimanicidal and antifungal potential from marine red alga Bostrychia tenella J. Agardli (Rhodomelaceae, Ceraniiales)

Specimens of the red alga Bostrychia tenella J Agardh (Rhodomelaceae, Ceramiales) were collected from the Sao Paulo coast and submitted to loom temperature solvent extraction The resulting extract was fractionated by partitioning with organic solvent The n-hexane (BT-H) and dichloromethane (BT-D) fractions showed antiprotozoal potential in biological tests with Trypanosoma cruzi and Leishmania amazonensis and presented high activity in an antifungal assay with the phytopathogenic fungi Cladosporium cladosporioides and Cladosporium sphaerospermum Chromatography methods were used to generate subfractions from BT-H (H01 to H11) and from BT-D (D01 to 019) The subtractions were analyzed by gas chromatography-mass spectrometry (GC/MS). and the substances were identified by retention index (Kovats) and by comparison to databases of commercial mass spectra The volatile compounds found in marine algae were identified as fatty acids, low molecular mass hydrocarbons, esters and steroids, some of these have been previously described in the literature based on other biological activities Moreover, uncommon substances. such as neophytadiene were also identified In a trypanocidal assay, fractions BT-H and BT-D showed IC(50) values of 168 and 19 1 mu g/mL. respectively, and were mote active than the gentian violet standard (31 mu g/ml.); subfractions H02. H03, D01 and D02 were active against L amasonensis, exhibiting IC(50) values of 1 S. 2 7, 4 4. and 4 3 mu g/mL., respectively (standard amphotericin B IC(50) = 13 mu g/mL.) All fractions showed antifungal potential this work reports the biological activity and identification of compounds by GC/MS for the marine red alga B tenella for the first time (C) 2010 Elsevier B V All lights reserved

Cyclic peroxides and related norterpenes from a southern Australian marine sponge, Mycale sp.

Investigation of a southern Australian marine sponge, Mycale sp., resulted in isolation of the known norsesterterpenes 1-3 as well as two new isomeric norsesterterpenes, mycaperoxide C methyl ester (4) and mycaperoxide D methyl ester (5), and six new norterpenes (6-11).

Mycaperoxides F and G and a related norterpene ketone from southern Australian marine sponges, Mycale species

Investigation of two southern Australian marine sponges, Mycale spp., resulted in isolation of the known norsesterterpene mycaperoxide F methyl ester (5) together with a new norsesterterpene mycaperoxide G methyl ester (10) and a new norterpene ketone 11. All structures were secured by spectroscopic analysis and chemical derivatization. The absolute stereochemistry previously assigned to 5 by application of the Horeau procedure has been revised by application of the Mosher procedure.

Dragmacidins: New protein phosphatase inhibitors from a southern Australian deep-water marine sponge, Spongosorites sp.

A Spongosorites sp. collected during trawling operations off the southern coast of Australia returned the new alkaloid dragmacidin E (3), the structure of which was secured by detailed spectroscopic analysis. Dragmacidin E (3), and its co-metabolite dragmacidin D (1) have been identified as potent inhibitors of serine-threonine protein phosphatases.

Nuapapuin A and sigmosceptrellins D and E: New norterpene cyclic peroxides from a southern Australian marine sponge, Sigmosceptrella sp.

A Sigmosceptrella sp. from the Great Australian Eight, Australia, has yielded the new norditerpene cyclic peroxide, nuapapuin A (2a), and the norsesterterpene cyclic peroxide sigmosceptrellin D (3a), characterized as the corresponding methyl esters 2b and 3b. The crude methylated sponge extract also yielded the new norsesterterpene cyclic peroxide sigmosceptrellin E methyl ester (4). Relative stereochemistry about C2, C3, and C6 was assigned by established empirical rules and absolute stereochemistry by the advanced Mosher procedure. A plausible biosynthetic pathway has been proposed that rationalizes key transformations in the biosynthesis of all known norterpene cyclic peroxides and related norterpene ketones, dienes and sigmosceptrins.

Echinosulfonic acids A-C and echinosulfone A: Novel bromoindole sulfonic acids and a sulfone from a southern Australian marine sponge, Echinodictyum

The crude EtOH extract of an Echinodictyum sp. collected during trawling operations in the Great Australian Eight, Australia, displayed antibacterial and antiparasitic properties. Bioassay-directed fractionation yielded three novel sulfonic acids, the echinosulfonic acids A to C (1-3), and a new sulfone, echinosulfone A (4). Structures were assigned to these compounds on the basis of detailed spectroscopic analysis. It was determined that echinosulfonic acids A-C (1-3) and echinosulfone A(4) contributed to the antibacterial but not antiparasitic activity of the crude extract.

Geodin A magnesium salt: A novel nematocide from a southern Australian marine sponge, Geodia

A Geodia species collected from southern Australian waters of the Great Australian Eight has yielded a potent new in vitro nematocidal agent identified as geodin A Mg salt (1), a new macrocyclic polyketide lactam tetramic acid magnesium salt. The structure for 1 was assigned on the basis of detailed spectroscopic analysis.

1,9-dimethylhypoxanthine from a southern Australian marine sponge Spongosorites species

A Spongosorites sp. collected off southern Australia has yielded 1,9-dimethylhypoxanthine (4). The structure for 4 was solved by spectroscopic analysis.

Clathrins A-C: Metabolites from a southern Australian marine sponge, Clathria species

A Clathria sp. collected in the Great Australian Bight has yielded the novel metabolites clathrins A (6), B (7), and C (8). Structures were assigned to clathrins A-C on the basis of spectroscopic analysis. Clathrin A (6) represents a plausible biosynthetic intermediate that provides an inferred link between marine sesquiterpene/benzenoids and mixed terpene/shikimate biosynthesis.

Discorhabdin R: A new antibacterial Pyrroloiminoquinone from two latrunculiid marine sponges, Latrunculia sp and Negombata sp.

Two sponge's belonging to the family Latrunculiidae (Negombata and Latrunculia sp.) collected during scientific trawling operations in Prydz Bay, Antarctica, and by scuba off Port Campbell, Victoria, have yielded a new antibacterial pyrroloiminoquinone, discorhabdin R (2). The structure was assigned as 2 on the basis of detailed, spectroscopic analysis and comparison with the known co-metabolite discorhabdin B (3).

Lorneamides A and B: Two new aromatic amides from a southern Australian marine actinomycete

A marine actinomycete (MST-MA190) isolated from a sample of beach sand collected near Lorne on the southwest coast of Victoria, Australia, has yielded two new aromatic amides, lorneamide A (1) and lorneamide B (2). The lorneamides belong to a novel class of tri-alkyl-substituted benzenes, and their structures were determined by spectroscopic methods.

Phorbasin A: A novel diterpene from a southern Australian marine sponge, phorbas species

A southern Australian Phorbas species has yielded a novel diterpene, phorbasin A (1), possessing an unprecedented carbon skeleton. The structure for phorbasin A was determined by detailed spectroscopic analysis.

Structure revision and assignment of absolute stereochemistry of a marine C-21 bisfuranoterpene

The C-21 bisfuranoterpene (-)-isotetradehydrofurospongin-1 (6), previously isolated from a Western Australian Spongia sp., has been reisolated from a specimen of Spirastrella papilosa collected during scientific trawling operations in the Great Australian Eight. A 2D NMR analysis of 6 has prompted reassignment of the published structure 5, while degradation and chiral HPLC analysis have allowed determination of the absolute stereochemistry.