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Ocean acidification improves the nutritive and medicinal value of a brown seaweed

30 Sep 2020 | Science Notes

From CO2Science: Seaweeds are an important food source around the world, as well as an important source for pharmacological compounds. Therefore it is important to understand the effect of ocean acidification on their biological properties. A recent study by Kumar et al. analyzed carbohydrate levels, antioxidant capacity, antibacterial, antifungal, antiprotozoal and anticancer properties, as well as the antimutagenic potential of the fleshy brown algae Sargassum vulgare growing at two sites off the coast of Ischia Island, Italy. One of the sites surrounds underwater CO2 vents that naturally elevate/reduce the pCO2/pH of the nearby seawater to a pH value of 6.7. The second site, approximately 6 km away, is nearly identical with the exception that there are no nearby CO2 vents, resulting in a surrounding seawater pH of 8.1. It turns out the extra CO2/acidification is a positive benefit for the seaweed.

Paper Reviewed: Kumar, A., Buia, M.C., Palumbo, A., Mohany, M., Wadaan, M.A.M., Hozzein, W.N., Beemster, G.T.S. and AbdElgawad, H. 2020. Ocean acidification affects biological activities of seaweeds: A case study of Sargassum vulgare from Ischia volcanic CO2 vents. Environmental Pollution 259: 113765.

Writing as background for their study, Kumar et al. (2020) note the use of seaweeds around the world for food and medicine. This is largely because seaweeds are “rich sources of proteins, vitamins, lipids, sugars, dietary fiber, and nutrients essential for human nutrition (Perumal et al., 2019).” Moreover, seaweeds are also known “for their importance in pharmacology, being a rich source of bioactive compounds against bacteria, fungi, virus, protozoa and various cancers (Hao et al., 2019; Smit, 2004).”

Continuing, the researchers explain how the production of bioactive compounds, or bioactivities, in seaweeds “are attributed to primary and secondary metabolites, e.g. meroterpenoids, phlorotanins, polysaccharides, phytosterols, polyunsaturated fatty acids and glycolipids,” citing the works of Torres et al. (2007), Sousa et al. (2008), Liu et al. (2012), Dore et al. (2013), Kolsi et al. (2017) and Hao et al. (2019). They also discuss how rising aqueous CO2 (i.e., so-called ocean acidification) has “the potential to alter the carbon physiology of seaweeds and levels of metabolites, including bioactive compounds and nutritional value.” Therefore, they acknowledge it is important to understand the potential effects of ocean acidification on seaweed metabolites given their importance to both the food and pharmacological industries.

In discussing their findings, Kumar et al. report “extracts for the algal population from the acidified site showed a higher antioxidant capacity, anti-lipid peroxidation, antibacterial, antifungal, antiprotozoal, anticancer activities and antimutagenic potential compared to the control population.” Such observations, in the words of the authors “can be seen as a positive sign for marine drug discovery considering the improvement in the medicinal properties of S. vulgare” observed in high pCO2 waters. What is more, they demonstrate the beneficial effects of higher levels of CO2, which improve plant photosynthesis and the production of primary and secondary metabolites, which in turn tend to have important nutritive and medicinal value.

Dore, C.M.P.G., Faustino Alves, M.G.d.C., Pofírio Will, L.S.E., Costa, T.G., Sabry, D.A., de Souza Rego, L.A.R., Accardo, C.M., Rocha, H.A.O., Filgueira, L.G.A., and Leite, E.L. 2013. A sulfated polysaccharide, fucans, isolated from brown algae Sargassum vulgare with anticoagulant, antithrombotic, antioxidant and anti-inflammatory effects. Carbohydrate Polymers 91: 467-475.

Hao, H., Fu, M., Yan, R., He, B., Li, M., Liu, Q., Zhang, X., Huang, R., 2019. Chemical composition and immunostimulatory properties of green alga Caulerpa racemose var peltata. Food and Agricultural Immunology 30: 937-954.

Kolsi, R.B.A., Salah, H.B., Jardak, N., Chaaben, R., Jribi, I., Feki, A.E., Rebai, T., Jamoussi, K., Allouche, N., Blecker, C., Belghith, H. and Belghith, K. 2017. Sulphated polysaccharide isolated from Sargassum vulgare: characterization and hypolipidemic effects. Carbohydrate Polymers 170: 148-159.

Liu, L., Heinrich, M., Myers, S. and Dworjanyn, S.A. 2012. Towards a better understanding of medicinal uses of the brown seaweed Sargassum in traditional Chinese medicine: a phytochemical and pharmacological review. Journal of Ethnopharmacology 142: 591-619.

Perumal, B., Chitra, R., Maruthupandian, A., Viji, M., 2019. Nutritional assessment and bioactive potential of Sargassum polycystum C. Agardh (Brown Seaweed). Indian Journal of Geo Marine Sciences 48: 492-498.

Smit, A.J. 2004. Medicinal and pharmaceutical uses of seaweed natural products: a review. Journal of Applied Phycology 16: 245-262.

Sousa, A.d.P.A., Barbosa, P.S.F., Torres, M.R., Martins, A.M.C., Martins, R.D., Alves, R.d.S., Sousa, D.F.d., Alves, C.D., Costa-Lotufo, L.V. and Monteiro, H.S.A. 2008. The renal effects of alginates isolated from brown seaweed Sargassum vulgare. Journal of Applied Toxicology 28: 364-369.

Torres, M.R., Sousa, A.P.A., Silva Filho, E.A.T., Melo, D.F., Feitosa, J.P.A., de Paula, R.C.M. and Lima, M.G.S. 2007. Extraction and physicochemical characterization of Sargassum vulgare alginate from Brazil. Carbohydrate Research 342: 2067-2074.

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