Exploring the World of Marine Secondary Metabolites: A Frontier of Bioactive
Compounds

Dr. Suchitra Panigrahy, Department of Biotechnology
E-mail id: suchitra.panigrahy@kalingauniversity.ac.in
Secondary metabolites are organic compounds that are distinct from primary metabolites which are not directly involved in the growth or reproduction of the organism. These compounds help marine organisms deter predators, compete for space, defend against microbial infections, and communicate with other species.
Marine ecosystems are some of the most biologically diverse environments on the planet. Organisms living in these ecosystems—such as sponges, corals, mollusks, algae, and bacteria—are exposed to unique environmental pressures such as high salinity, varying light levels, pressure changes, and limited resources. As a result, many of these organisms have evolved to produce complex and unusual secondary metabolites with unique structures not found in terrestrial species.
Marine secondary metabolites can be broadly classified into several chemical groups, including alkaloids, terpenoids, polyketides, peptides, and phenolic compounds. Each of these classes is known for a diverse range of bioactivities:
Alkaloids: These nitrogen-containing compounds are known for their toxicity and pharmacological properties. For example, the marine sponge Monanchora unguifera produces the alkaloid manzamine, which has shown potential as an anticancer, antimalarial, and anti-inflammatory agent.
Terpenoids: Terpenoids are one of the largest classes of secondary metabolites and are produced by various marine organisms. Marine algae, for example, produce diterpenes, which have demonstrated antibacterial, antifungal, and anticancer properties.
Polyketides: These compounds are known for their structural complexity and diverse biological activities. Marine-derived polyketides, such as those from cyanobacteria and fungi, have been studied for their antimicrobial, antiviral, and anticancer effects.
Peptides: Marine organisms such as mollusks and tunicates produce bioactive peptides. These compounds can exhibit antimicrobial, antifungal, and anticancer properties. The tunicate Ecteinascidia turbinata, for example, produces ecteinascidin-743 (trabectedin), which is now used as a chemotherapeutic agent.
Phenolic Compounds: Phenolics are known for their antioxidant and anti-inflammatory properties. Marine algae, in particular, are a rich source of phenolic compounds, which contribute to their defense mechanisms and potential health benefits when used in pharmaceuticals or nutraceuticals.
Marine secondary metabolites have emerged as a treasure trove for drug discovery, particularly in the areas of cancer therapy, antibiotics, and anti-inflammatory agents. Anticancer Agents: Trabectedin, derived from the sea squirt Ecteinascidia turbinata, is a successful example of a marine-derived drug used to treat soft-tissue sarcomas and ovarian cancer. Other marine compounds, such as dolastatin 10 from sea hares, have shown potent anticancer activity and are being explored for use in chemotherapy.
Antimicrobial Agents: With the rise of antibiotic-resistant bacteria, marine secondary metabolites offer hope for new treatments. Compounds such as marine sponges’ halichondrins have shown promise as antibiotics. The bacterium Salinispora tropica, found in marine sediments, produces salinosporamide A, a compound with potent anticancer and antibiotic properties.
Anti-inflammatory Compounds: Marine organisms have also provided a source of anti-inflammatory compounds. For example, pseudopterosins, produced by the sea whip Pseudopterogorgia elisabethae, are used in skin care products for their anti-inflammatory and wound-healing properties. They have also shown potential for treating conditions such as arthritis and autoimmune disorders.
While marine secondary metabolites present tremendous potential, several challenges exist in their discovery and development. One of the primary difficulties is the limited availability of many marine organisms, especially those that are rare or live in deep-sea environments. Additionally, the extraction and purification processes for these compounds can be complex and time-consuming.
To overcome these challenges, scientists are turning to advanced techniques such as marine bioprospecting, synthetic biology, and chemical synthesis. Marine bioprospecting involves the exploration of marine habitats for novel organisms and compounds, while synthetic biology and biotechnology allow for the production of these metabolites in laboratory settings without depleting natural populations.
Furthermore, advancements in genetic sequencing and marine genomics have opened new avenues for understanding how marine organisms produce secondary metabolites. This knowledge enables researchers to potentially manipulate the genes involved in metabolite production, leading to enhanced yields of these valuable compounds.
References
Newman, D. J., & Cragg, G. M. (2020). Marine-sourced anti-cancer and cancer pain control agents. Marine Drugs, 18(12), 619.
Malve, H. (2016). Exploring the ocean for new drug developments: Marine pharmacology. Journal of Pharmacy & Bioallied Sciences, 8(2), 83-91.
Jaspars, M., De Pascale, D., Andersen, J. H., Reyes, F., Crawford, A. D., & Ianora, A. (2016). The marine biodiscovery pipeline and ocean medicines of tomorrow. Journal of the Marine Biological Association of the United Kingdom, 96(1), 151-158.