Detection of proximate, phytochemical compositions, phycocyanin and antioxidant activity of <i>Arthrospira platensis</i> (Spirulina)

Arthrospira platensis (Spirulina), a well-known blue-green microalga, is traditionally used as a food supplement and medical ingredients. This study aimed to evaluate the proximate, phytochemical compositions, phycocyanin and antioxidant activity of Arthrospira platensis commercially recognized as Spirulina. The proximate analysis results indicated high values of protein for Spirulina (61.62% dry wt.). The fat, ash, moisture and crude fibre percentages were 15.77, 11.25, 30.58 and 3.12 respectively. The results of phytochemical screening revealed the presence of saponins, tannins, alkaloids, carbohydrate, fat and starch in this alga. Methanol was used for extraction, and the yield was calculated as 17%. In order to investigate extraction efficiencies, we performed a comparative quantitative study on three different extraction methods (maceration, Soxhlet and ultrasonic) and two types of extracts (polar and non-polar subfractions) for determining of the phytochemicals (total flavonoids, anthocyanins and ascorbic acid): the results showed that the highest total flavonoids content (23.493 mg CAE 100 g‒1), the highest anthocyanin content (0.47 µg C-3-GE 100 g‒1) and the highest ascorbic acid content (1.080 µg 100 g‒1) were recorded in polar subfraction of methanolic extract with maceration extraction method. Phycocyanin extraction was measured using different solvents, including, distilled water, sodium phosphate buffer (pH 7.0), sodium acetate buffer (pH 5.0), and NaCl 0.15 M. According to the result, the highest phycocyanin content found was 5.0 ± 0.76 mg ml‒1 with sodium phosphate buffer. Antioxidant activity was measured by three assays (DPPH, RAA and FRAP) in polar and non-polar subfraction of methanolic extract. The highest antioxidant activity was noticed in the polar subfraction of the extract using three assays. Spirulina is abundant in a variety of nutrients, including high-quality protein, various vitamins and minerals, and plays a crucial role in human health and the prevention of various diseases. Apart from being a nutritional supplement, Spirulina is also widely utilized in medicine and cosmetics industries.