Marine pharmaceuticals

Antiangiogenic molecules from marine actinomycetes and the importance of using zebrafish model in cancer research

Blood vessel sprouting from pre-existing vessels or angiogenesis plays a significant role in tumour progression. Development of novel biomolecules from marine natural sources has a promising role in drug discovery specifically in the area of antiangiogenic chemotherapeutics. Symbiotic actinomycetes from marine origin proved to be potent and valuable sources of antiangiogenic compounds. Zebrafish represent a well-established model for small molecular screening and employed to study tumour angiogenesis over the last decade. Use of zebrafish has increased in the laboratory due to its various advantages like rapid embryo development, optically transparent embryos, large clutch size of embryos and most importantly high genetic conservation comparable to humans. Zebrafish also shares similar physiopathology of tumour angiogenesis with humans and with these advantages, zebrafish has become a popular model in the past decade to study on angiogenesis related disorders like diabetic retinopathy and cancer. This review focuses on the importance of antiangiogenic compounds from marine actinomycetes and utility of zebrafish in cancer angiogenesis research.

Marine Snails and Slugs: a Great Place To Look for Antiviral Drugs

Molluscs, comprising one of the most successful phyla, lack clear evidence of adaptive immunity and yet thrive in the oceans, which are rich in viruses. There are thought to be nearly 120,000 species of Mollusca, most living in marine habitats. Despite the extraordinary abundance of viruses in oceans, molluscs often have very long life spans (10 to 100 years). Thus, their innate immunity must be highly effective at countering viral infections. Antiviral compounds are a crucial component of molluscan defenses against viruses and have diverse mechanisms of action against a wide variety of viruses, including many that are human pathogens. Antiviral compounds found in abalone, oyster, mussels, and other cultured molluscs are available in large supply, providing good opportunities for future research and development. However, most members of the phylum Mollusca have not been examined for the presence of antiviral compounds. The enormous diversity and adaptations of molluscs imply a potential source of novel antiviral compounds for future drug discovery.

Detection of secondary metabolites in marine macroalgae using the marsh periwinkle,Littorina irrorata say, as an indicator organism

Twenty-four chemically profiled organic macroalgal extracts and seven purified natural products were bioassayed using the mesogastropodLittorina irrorata Say to determine if the presence of secondary metabolites in crude algal extracts could be correlated with the activity of the snail. Avoidance behavior by snails in the assay was highly correlated with the presence of secondary metabolites in the macrophyte extracts.

In vitro antiviral activity against herpes simplex virus in the abalone Haliotis laevigata

As viruses are extremely abundant in oceans, marine organisms may have evolved novel metabolites to protect themselves from viral infection. This research examined a well-known commercial gastropod, abalone (Haliotidae), which in Australia have recently experienced disease due to a neurotropic infection, abalone viral ganglioneuritis, caused by an abalone herpesvirus (AbHV). Due to the lack of molluscan cell lines for culturing AbHV, the antiviral activity of the abalone Haliotis laevigata was assessed against another neurotropic herpesvirus, herpes simplex virus type 1 (HSV-1), using a plaque assay. The concentration range at which abalone extract was used for antiviral testing caused minimal (<10 %) mortality in Vero cells. Haemolymph (20 %, v/v) and lipophilic extract of the digestive gland (3000 μg ml(-1)) both substantially decreased the number and size of plaques. By adding haemolymph or lipophilic extract at different times during the plaque assay, it was shown that haemolymph inhibited viral infection at an early stage. In contrast, the antiviral effect of the lipophilic extract was greatest when added 1 h after infection, suggesting that it may act at an intracellular stage of infection. These results suggest that abalone have at least two antiviral compounds with different modes of action against viral infection, and provide a novel lead for marine antiviral drug discovery.

Drug discovery: past, present and future

New drug discovery from early on involved a trial-and-error approach on naturally derived materials and substances until the end of the nineteenth century. The first half of the twentieth century witnessed systematic pharmacological evaluations of both natural and synthetic compounds. However, most new drugs until the 1970s were discovered by serendipity. With the exponential development of molecular biology on one hand and computer technology on the other, it became possible from 1980 onwards to place drug discovery on a rational basis. Cloning of genes has led to the development of methodologies for specific receptor-directed and enzyme-directed drug discoveries. Advances in recombinant DNA and transgenic technologies have enabled the production of human hormonal and other endogenous biomolecules as new drugs. As we understand more about the co-ordinating and regulating powers of the cerebral cortex during the next century, especially of the frontal lobe, man may be able to use bio-feedback training to voluntarily regulate the release of neurotransmitters, hormones, and other molecules involved in the regulation of various physiological processes in health as well as in disease.

Marine products as a source of antiviral drug leads

A survey is presented of the occurrence of organic compounds from aquatic organisms that have been reported to have antiviral activities. Studies of the chemical structures and antiviral properties of unusual metabolic products of aquatic life have demonstrated that marine organisms offer excellent prospects in the search for antiviral drugs.

Drug molecules of marine origin

Somewhat accelerated developments in the chemistry and pharmacology of marine molecules during the eighties are a clear indication of the biomedical potential of marine organisms for the twenty-first century. Unfortunately, the overall effort toward the field is still insignificant. Both industry and governments are spending only a token share of R&D funds in pursuit of pharmacologically active substances from the sea. A critical appraisal of the literature reveals the existence of fascinating molecules with unusual and potent activities. The challenge of harnessing the clinical potential of these molecules is clearly evident. It is only awaiting the awakening of the academic, industrial, and federal researchers and resources. Only a concerted and a massive effort can shorten the time between now and the first clinical drug from the sea.

Cytotoxicity of synthetic racemic ptilocaulin: a novel cyclic guanidine

(+)-Ptilocaulin, a novel cyclic guanidine extracted from the Caribbean sponge Ptilocaulis aff. P. Spiculifer, is reported to have broad spectrum antimicrobial activity in vitro as well as in vitro activity against L1210 murine leukemia. To more fully evaluate this compound as an anticancer agent, the in vitro cell growth inhibitory potencies of synthetic racemic ptilocaulin and ten clinical anticancer drugs were determined and compared in 16 different normal and transformed human and murine cell populations. Potency, expressed as the 50% inhibitory concentration (IC50), was determined by a tetrazolium reduction (MTT) assay. Ptilocaulin showed a fairly broad spectrum of in vitro activity against colon and mammary adenocarcinomas, melanomas, leukemias, transformed fibroblasts and normal lymphoid cells (IC50s 0.05- greater than 10 micrograms/ml). This activity was comparable to that of many of the clinical drugs, including vinca alkyloids, antibiotics, alkylators and antimetabolites. Cell viability was affected only after a 72 hr exposure to the compound. In a clonogenic assay, cytocidal effects were observed after 24-72 hr exposures to 10 x IC50 concentrations of ptilocaulin, as evidenced by failure of cells to resume growth after removal of the compound. Cytostatic effects were observed at less than or equal to IC50 concentrations, as evidenced by resumption of growth to near-control levels after removal of the compound. Ptilocaulin was toxic at 50 and 25 mg/kg in an in vivo L1210 tumor model and was ineffective at lower concentrations (T/Cs 100-112%). In vivo studies in a more sensitive tumor system are recommended but are limited by the lack of availability of sufficient quantities of the compound.

Drugs from the Sea: A Bibliography

In case any of you are expecting a tale of mystery and intrigue on the high seas—complete with ships in hidden coves—I'm afraid I must disappoint you. My Drugs from the Sea story is not so dramatic, although it has its excitement (since the potential is always there for discovering a miracle drug from life in the sea).

Biotechnology in the Marine Sciences

Genetic engineering applied to the production of fish, molluscs, algae, algal products, and crustaceans in natural environments and hatchery systems is still at the rudimentary stage. Cloning systems for producing commercially important chemicals, pharmacologically active compounds, and metamorphosis-stimulating substances present in marine organisms are being sought. Attempts are being made to develop useful drugs from the sea, including antineoplastic, antibiotic, growth-promoting (or -inhibiting), analgesic, and antispasmodic agents. Immediate commercial applications can be expected from engineered systems involving polysaccharide and specialty chemical production, with marine microorganisms as the source of genetic material.

Potent inhibition of oxidative phosphorylation by marine natural products

Many lipid-soluble extracts from various marine organisms have a nonspecific depressant effect on smooth muscle contractions. Novel compounds isolated from such lipid-soluble extracts were tested for their effects on the respiration of rat liver mitochondria and produced potent stimulation or inhibition of oxygen uptake by the mitochondria.

Drugs from the sea--fact or fantasy?

Drugs from the sea are as much a potential marine resource as cultivated fish, and mineral deposits. The study of the chemical structure and properties of unusual metabolic products of marine life is a subject where marine ecology and the experimental sciences of chemistry, biochemistry, pharmacology and medicine share a common and complementary interest. The development of ad hoc collaboration between specialists has advanced basic knowledge and resulted in a significant feedback to marine biology and ecology as well as in the development of some useful drugs.

Inhibition of herpesvirus replication by marine algae extracts

Extracts from two species of marine red algae, Cryptosyphonia woodii and Farlowia mollis, specifically inhibited herpes simplex virus replication in vitro.