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Devi KP, Suganthy N, Kesika P, Pandian SK. Bioprotective properties of seaweeds: in vitro evaluation of antioxidant activity and antimicrobial activity against food borne bacteria in relation to polyphenolic content. BMC Complement Altern Med. 2008 Jul 10;8:38. PMID: 18613983

With a view to developing safer food preservatives, researchers in Tamil Nadu have elucidated, for the first time, the antioxidant properties of ten edible seaweeds:

• Gelidiella acerosa (Rhodophyta)
• Gracilaria edulis (Rhodophyta)
• Turbinaria conoides (Phaeophyta)
• Padina gymnospora (Phaeophyta)
• Chondrococcus hornemanni (Rhodophyta)
• Hypnea pannosa (Rhodophyta)
• Dictyota dichotoma (Phaeophyta)
• Jania rubens (Rhodophyta)
• Sargassum wightii (Phaeophyta)
• Haligra sps.

The authors turned to the waters of the Gulf of Mannar Marine Biosphere Preserve for their study, which could be of signal scientific and commercial importance. From the Background:

"Refrigerated, ready-to-eat products, especially dairy foods, have become increasingly popular in recent years because of their convenience. Many pathogenic organisms spoil such foods, reducing their shelf life and often leading to food poisoning. It has been estimated that as many as 30% people in industrialized countries suffer from a food poisoning every year. In addition to microbial contamination, all packed and refrigerated food also undergoes gradual changes during storage, due to auto oxidation which releases reactive oxygen species (ROS) including free radicals like superoxide anion (O₂^•-) and hydroxyl radicals (OH^•) and non-free radical species like singlet oxygen (¹O₂) and hydrogen peroxide (H₂O₂) into the food. These ROS induce peroxidation of lipids (polyunsaturated fatty acids) generating secondary oxidants like heptanol and hexanal, which contributes to oxidative rancidity, deteriorating the flavor of the food. These not only cause a loss in food quality but are also believed to be associated with carcinogenesis, mutagenesis, arthritis, diabetes, inflammation, cancer and genotoxicity. To overcome these problems a wide range of synthetic antimicrobial agents (sodium benzoate, calcium benzoate, sorbate) and synthetic antioxidants (butylhydroquinone, propyl gallate, butylated hydroxy toluene (BHT), butylated hydroxy anisole (BHA), have been used as food preservatives. However, these preservatives can cause liver damage and are suspected to be mutagenic and neurotoxic. Hence, most consumers prefer additive-free foods or a safer approach like the utilization of more effective antioxidants and antimicrobials of natural origin. Recently, various phytochemicals like polyphenols, which are widely distributed in plants, have been reported to act as free radical scavengers and antimicrobial agents. Marine plants, like seaweeds, also contain high amounts of polyphenols. For example, high concentrations of polyphenols such as catechin, epicatechin, epigalloctechin gallate and gallic acid are reported in the seaweed Halimada (Chlorophyceae). Since many types of seaweed have still to be investigated, we were prompted to take up this study. The Gulf of Mannar is a Marine Biosphere Reserve situated along the east coast of India and Sri Lanka, an area of about 10,500 sq. km which has a luxuriant growth of about 680 species of seaweed belonging to the Rhodophyta, Pheaophyta and Chlorophyta, in both the inter-tidal and deep water regions. Seaweed constitutes a commercially important marine renewable resource. Sargassum, Padina, Dictyota and Gracilaria sps. Are used by common people as fertilizers, food additives and animal feed. The sulphated polysaccharides of Sargassum act as a potent free radical scavenger and anticancer agent. Gelidella and Gracilaria sps are widely used for the production of agar and for the treatment of gastrointestinal disorders. The methanolic extract of brown seaweeds such as Ecklonia cava and Hizikia fusiformis exhibit potent antioxidant activity. Although seaweeds possess wide application in food and in the pharmaceutical industry, the antioxidant and antimicrobial activity of many types of seaweed in the South Indian coastal area are still unexplored. The main objective of the present study is to evaluate the antioxidant and antimicrobial activities of seaweeds obtained from the Thondi, South Coastal Area of Tamil Nadu, India."

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