Comparison of different green extraction techniques and their influence on chemical characteristics of sulfated polysaccharide (fucoidan) from Padina tetrastromatica and Turbinaria conoides

Conventionally, fucoidan from brown macroalgae is extracted by solubilizing cell wall polysaccharides in hot water, acidic/alkali, and organic solvents. This study depicts the use of various green extraction techniques, including ultrasound assisted extraction, enzyme assisted extraction and subcritical water extraction, to isolate fucoidan from brown macroalgae (Padina tetrastromatica and Turbinaria conoides) for its conversion to value added products. The result demonstrated that these extraction strategies had a significant impact on extraction yields, chemical characterization, monosaccharide composition, structural properties, microstructures, and biological activities of fucoidan. Subcritical water method produced a higher yield of fucoidan (-13 %) from both the biomass, with the sulfate content of fucoidan up to 33 %. Analysis of monosaccharide composition revealed that fucoidan contained the highest fucose (-83 %) and galactose (-30 %) contents with small amounts of arabinose, glucose, glucuronic acid, mannitol, mannose, rhamnose and xylose. Fucoidan extract contained polyphenolic (5.5 & PLUSMN; 0.6 mg GAE g-1) and flavonoid (3.2 & PLUSMN; 0.2 mg QE g-1) compounds and exhibited effective in vitro 2,2-diphenyl-1-picrylhydrazyl (1.3 & PLUSMN; 0.07 mg mL-1) as well as 2,2 & PRIME;-azino-bis(3-ethylbenzothiazoline-6sulfonic) acid (0.01 & PLUSMN; 0.0 mg mL-1) radical scavenging activities. By investigating the various outcomes, subcritical water technique was considered as the efficient and environmentally friendly approach for the extraction of fucoidan. Consequently, investigating the impact of extraction technologies on key structural components could aid multiple industries, including the nutraceutical, pharmaceutical, and cosmetics sectors, in gaining a better understanding of the benefits and drawbacks of various methods for upscale extraction.