Antioxidant properties of Gracilaria birdiae and Gracilaria cornea, two red seaweeds from the brazilian coasts

Abstract

Several synthetic antioxidants such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), and butylated hydroxyquinone (TBHQ) are commercially available and currently used: however, concerns on their safety and toxicity are hindering their use by the food industry (1, 2, 3). Therefore, the development of alternative antioxidants from natural origins has drawn increasing attention, particularly in the most recent years during which the consumer's awareness on food quality and safety issues has improved very significantly. Research efforts have therefore focused on e.g. medicinal plants for the extraction of natural and low-cost antioxidants that can replace synthetic additives(4). Many researchers have reported the existence of various types of antioxidants in different kinds of higher plants (5, 6). More recently. reports have revealed seaweeds to be a rich source of antioxidant compounds (7,8, 9). The seaweeds are considered a traditional diet in dillrent regions of the globe, particularly in Asian countries. Their chemical composition shows that they arc foods low in calories, with high concentrations of minerals, vitamins and protein, rich in fiber and with relatively high concentrations of poly-unsaturated fatty acids and different antioxidants (10, 11, 12) During their life-cycle, algae are exposed to large amounts of light and high concentrations of oxygen; this combination favors the generation of fret radicals, as well as other powerful oxidizers. It is suggested that the absence of oxidative damage in the structural components of the algae and their stability against adverse conditions are due to the presence of antioxidants (13). Phenolic compounds such as flavonoids, phenolic acids, and tannins are considered to be major contributors to the antioxidant capacity of plants. Phenolics or polyphenols have received considerable attention because of their physiological functions, including antioxidant, antimutagenic and antitumor activities." Phenolic compounds are commonly found in edible brown, green and red seaweeds, whose antioxidant properties have been correlated to their phenolic content (15, 16) Algal polyphcnols, also called phlorotannins, diverge from terrestrial plant polyphenols once the former are derived from phloroglucinol units (1.3.5-trihydroxybentine). Phlorotannins constitute an extremely heterogeneous group of molecules (with different structures and polymerization degrees) providing a wide range of compounds with potential biological activity.(17) In that line, this work aims at investigating the antioxidant properties of two different red seaweed extracts from G. birdiae and G. cornea, collected in the northeast Atlantic coast of Brazil.