Comparison of DPPH FRAP and TAS antioxidant activity assays against TPC for determination of antioxidant activity of various algae from Taiwan  

Photosynthetic organisms, such as microalgae and macroalgae play a key role in the productivity of oceans and constitute the basis of the marine food chain. Microalgae are the primary source of feed for seedlings in hatcheries specially shellfish and crustacean species. Contrary, macroalgae are used less in aquaculture, despite that they are an important source of nutrition for species, such as sea urchins and abalone. This study evaluates the natural antioxidant properties of Spirulina sp., Chlorella sp., Nannochloropsis sp., Sargassum wightii and Ulva lactuca due to their importance and popularity among food scientists as to be used as functional foods. In vitro results have demonstrated their antioxidant potential making of them an attractive additive to be used in the animal industry and counteract the effect of oxidative stress.

Oxidative stress mainly occurs in aerobic organisms which are oxygen-dependent, in healthy condition this organisms can successfully balance the reactive oxygen species (ROS) production and the system to protect cells from ROS exists. Increased levels of ROS production could potentially damage the cells or in the worst case scenario lead to the organism death. Methanol and water extracts were prepared and used on in vitro assays, Diphenyl-2-picrylhydrazyl (DPPH), Ferric Reducing Antioxidant Power  (FRAP) and Total Antioxidant Status (TAS), Total Phenolic Content (TPC) in algae extracts was also measured and used to determine the most accurate antioxidant essay to measure the antioxidant activity of these compounds. However, after statistical correlation analysis, it was concluded that FRAP showed the best correlation at 98% compared against TPC. Methanol extracts exhibited the following iron chelating effect: Spirulina sp. 3548.583µM Fe²⁺, Chlorella sp. 1952.750µM Fe²⁺, Nannochloropsis sp. 3419.417µM Fe², Sargassum wightii 929.417µM Fe2⁺ and Ulva lactuca 2117.750µM Fe2 (All units are expressed as µM Fe²⁺ iron equivalents). The results indicate that the extracts could be used as a successful antioxidant supplementation (feed additive) in feed diets for aquatic organisms. The addition of the extracts will hypothetically improve their resistance against pathogen infections acting as immune stimulants and potentially reducing the use of antibiotics during their growth.  

The aim of the present study was to evaluate the antioxidant capacity of various algae samples.