Assessment of Total Phenolic Content and In Vitro Antioxidant Activity in Brown Seaweeds Turbinaria conoides and Padina tetrastromatica from the Mandapam Coast

Marine macroalgae have gained considerable scientific interest in recent years due to their noteworthy composition, which includes essential elements such as functional polyphenols, minerals, dietary fibres, proteins, polysaccharides, and vitamins, in addition to their ecological functions. This study aimed to extract these antioxidant-rich bioactive compounds from two brown seaweed species, Turbinaria conoides and Padina tetrastromatica, sourced from the Mandapam Coastal region of Tamil Nadu, India. The extraction process involved using a multi-enzyme complex consisting of a carbohydrase enzyme (Viscozyme® L) and two protease enzymes (Flavourzyme® 1000 L and Alcalase® 2.4L FG), either separately or in combination. The total phenolic content (TPC) and extract yield under different enzyme treatments were assessed, revealing notably higher values for the Alcalase® extract (73.3±1.5% yield and 3.15±0.2 mg GAE/g extract TPC). Further characterization of the extracts involved evaluating their in vitro antioxidant activity through total antioxidant activity (TAA), 1,1-Diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity, and Ferric (Fe3+) reducing antioxidant power (FRAP). The viscozyme® extracted product displayed higher TAA (6.27±1.1 mg AAE/g extract) and DPPH scavenging activity (4.2±0.7 mg IC50). However, the extract from T. conoides treated with the combination of enzymes showed higher FRAP (4.01±0.2 mg GAE/g extract). In conclusion, this research demonstrates the viability of using enzyme-assisted extraction methods to obtain valuable antioxidants from brown algae, paving the way for their use in the health and food industries.