Marine algae are known to contain a wide variety of bioactive compounds, many of which have commercial applications in pharmaceutical, medical, cosmetic, nutraceutical, food and agricultural industries. Natural antioxidants, found in many algae, are important bioactive compounds that play an important role against various diseases and ageing processes through protection of cells from oxidative damage. In this respect, relatively little is known about the bioactivity of Hawaiian algae that could be a potential natural source of such antioxidants. The total antioxidant activity of organic extracts of 37 algal samples, comprising of 30 species of Hawaiian algae from 27 different genera was determined. The activity was determined by employing the FRAP (Ferric Reducing Antioxidant Power) assays. Of the algae tested, the extract of Turbinaria ornata was found to be the most active. Bioassay-guided fractionation of this extract led to the isolation of a variety of different carotenoids as the active principles. The major bioactive antioxidant compound was identified as the carotenoid fucoxanthin. These results show, for the first time, that numerous Hawaiian algae exhibit significant antioxidant activity, a property that could lead to their application in one of many useful healthcare or related products as well as in chemoprevention of a variety of diseases including cancer.

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Living benthic marine organisms such as sponges and corals are frequently colonized by bacteria that may be pathogenic to them. One of the means by which they are able to combat microbial attack is by chemical defense. We tested the activity of crude organic extracts of 11 dominant Red Sea reef sponges against a panel of bacteria isolated from their natural environment. Amphimedon viridis (Keller) exhibited the highest antimicrobial activity. Bioassay-directed fractionation resulted in the isolation of an active fraction that contained a purified mixture of halitoxin and amphitoxin, which are highly bioactive pyridinium alkaloids. These compounds showed selective activity against specific bacteria rather than being of a broad spectrum. They were highly active against 8 strains of bacteria isolated from the seawater surrounding these sponges, whereas 6 different bacterial strains associated with the sponge A. viridis were resistant to these compounds. This selective toxicity may be important in enabling certain bacteria to live in close association with their sponge host while it maintains a chemical defense against microbial pathogenesis.

Coral reefs are the most biodiverse of all marine ecosystems. Bacteria are known to be abundant and active in seawater around corals, inside coral tissues, and within their surface microlayer. Very little is known, however, about the structure, composition and maintenance of these bacterial communities. In the current study we characterize the culturable bacterial community within the mucus of healthy specimens of the Red Sea solitary coral Fungia scutaria. This was achieved using culture-based methods and molecular techniques for the identification of the bacterial isolates. More than 30% of the isolated bacteria were novel species and a new genus. The culturable heterotrophic bacterial community of the mucus of this coral is composed mainly of the bacterial groups Gammaproteobacteria, Alphaproteobacteria and of Actinobacteria. This study provides the first evidence of actinomycetes isolated from corals.