The nature and role of pigments of marine invertebrates

Bioactive compounds from marine sponges and their symbiotic microbes: a potential source of nutraceuticals

Sponges are considered as the chemical factory in marine environment because of its immense production of chemically diverse compounds. Other than the chemical diversity, these compounds possess remarkable bioactivities. This great potential has aroused applications of sponge-derived compounds as therapeutics and at present, a number of promising compounds are in clinical and preclinical trials. Recently, nutraceuticals have received considerable interest among the health conscious community because of its multiple therapeutic effects. Natural health-promoting substances gain continuous popularity as nutraceuticals due to its reduced risk of side effects. This overview discusses the potentials of marine sponge-derived bioactivities as natural health-promoting compounds.

Coral fluorescent proteins as antioxidants

BACKGROUND

A wide array of fluorescent proteins (FP) is present in anthozoans, although their biochemical characteristics and function in host tissue remain to be determined. Upregulation of FP's frequently occurs in injured or compromised coral tissue, suggesting a potential role of coral FPs in host stress responses.

METHODOLOGY/PRINCIPAL FINDINGS

The presence of FPs was determined and quantified for a subsample of seven healthy Caribbean coral species using spectral emission analysis of tissue extracts. FP concentration was correlated with the in vivo antioxidant potential of the tissue extracts by quantifying the hydrogen peroxide (H(2)O(2)) scavenging rates. FPs of the seven species varied in both type and abundance and demonstrated a positive correlation between H(2)O(2) scavenging rate and FP concentration. To validate this data, the H(2)O(2) scavenging rates of four pure scleractinian FPs, cyan (CFP), green (GFP), red (RFP) and chromoprotein (CP), and their mutant counterparts (without chromophores), were investigated. In vitro, each FP scavenged H(2)O(2) with the most efficient being CP followed by equivalent activity of CFP and RFP. Scavenging was significantly higher in all mutant counterparts.

CONCLUSIONS/SIGNIFICANCE

Both naturally occurring and pure coral FPs have significant H(2)O(2) scavenging activity. The higher scavenging rate of RFP and the CP in vitro is consistent with observed increases of these specific FPs in areas of compromised coral tissue. However, the greater scavenging ability of the mutant counterparts suggests additional roles of scleractinian FPs, potentially pertaining to their color. This study documents H(2)O(2) scavenging of scleractinian FPs, a novel biochemical characteristic, both in vivo across multiple species and in vitro with purified proteins. These data support a role for FPs in coral stress and immune responses and highlights the multi-functionality of these conspicuous proteins.

The inhibition of TNF-alpha-induced NF-kappaB activation by marine natural products

The deregulated activation of NF-kappaB is associated with cancer development and inflammatory diseases. With an aim to find new NF-kappaB inhibitors, we purified and characterized compounds from extracts of the Fijian sponge Rhabdastrella globostellata, the crinoid Comanthus parvicirrus, the soft corals Sarcophyton sp. nov. and Sinularia sp., and the gorgonian Subergorgia sp. after an initial screening of 266 extracts from different marine origins. Results obtained show that selected purified compounds had a cytotoxic effect on the human leukaemia cell line K562, inhibited both TNF-alpha-induced NF-kappaB-DNA binding as well as TNF-alpha-induced IkappaBalpha degradation and nuclear translocation of p50/p65. Furthermore, we observed the inhibition of NF-kappaB activation induced by an overexpression of IKKbeta. Interestingly, natural products inhibited IKKbeta kinase as well as the 26S proteasome proteolytic activity.

Marine natural products

This review covers the literature published in 2006 for marine natural products, with 758 citations (534 for the period January to December 2006) referring to compounds isolated from marine microorganisms and phytoplankton, green algae, brown algae, red algae, sponges, cnidaria, bryozoans, molluscs, tunicates and echinoderms. The emphasis is on new compounds (779 for 2006), together with their relevant biological activities, source organisms and country of origin. Biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.