Abstract: The food gap/crisis coincided with the exacerbation of chemically synthetic drugs in most countries of the world. Therefore, the world's attention is directed to the search for untraditional foods and biologically active compounds from natural sources. The present study aims to investigate the Brown algae (Sargassum subrepandum) located on the Egyptian seashores as a valuable source of nutrients and bioactive compounds with important biological/therapeutic roles. Results indicated that carbohydrates were the largest compound (55.83 – 62.19%) followed by crude fiber (11.76 - 15.69%), ash (9.33 - 13.06%), total protein (4.74 - 5.95%) and crude fat (0.51 -1.07%) in Sargassum subrepandum powder (SSP). Also, polysaccharides were the largest compound ranged 132.45 to 173.7 mg starch equvalent. g-1 followed by phenolics (103.66 to 158.98 mg gallic acid equvalent. g-1), carotenoids (27.84 to 49.17 mg .g-1), flavonoids (27.11 to 37.98 mg catechin equivalent. g-1) and anthocyanin's (5.91 to 8.03 mg Cyanidin 3-glucoside, CCy3G equivalent.100g-1) in the same samples. This high content of biologically active constituents in SSP has encountered by many significance biological roles such as antioxidant and free radical scavenging activities. The degree of biological activity was also affected by the difference in the extraction medium, where the organic extracts (methanolic and ethanolic) recorded the highest values of activities, followed by the aqueous ones. The activities degree of organic extracts is coming well i.e. closing to the value of 50 mg α-tocopherol followed by the aquatic extracts.

Keywords: Sargassum subrepandum powder, chemical composition, nutritional evaluation, antioxidant, scavenging activity.