Exploring phenolic compound extraction from marine seaweeds of south coast India: in vitro antioxidant and antimicrobial evaluation

Recently, researchers have turned their attention to seaweeds. This was because their biological activities had multiple human applications. Chaetomorpha ligustica, Acanthaphora spicifera, Gracilaria edulis, and Gracilaria corticata were some of the seaweeds collected from the coastal fishing village of Olaikuda, Mandapam. Therefore, phytochemical screening meant analyzing the secondary metabolites of seaweeds, which show their medicinal benefits and biological activities. Thirteen different phytochemicals were identified. Four solvents, such as water, hexane, methanol, and chloroform, were used for the extraction of preliminary phytochemical screening. Phytochemical analysis showed that methanol had extracted maximum number of phytochemicals compared to other solvents. TPC (total phenolic content) in obtained extraction seemed to have been high in Acanthaphora spicifera (0.86 ± 0.14 mg GAE g⁻¹), while it was found to be low in Gracilaria edulis (0.53 ± 0.17 mg GAE g⁻¹). The antimicrobial properties of purified polyphenolic substances were assessed against four bacterial and one fungal pathogenic agents. Purified polyphenolic extracts of the selected seaweed were used to measure DPPH radical scavenging, ABTS inhibition, ionic chelate scavenging, phosphomolybdenum assay, and hydroxyl radical scavenging. Chlorophyll a, chlorophyll c, lutein, fucoxanthin, violaxanthin, and β-carotene were identified as major pigments in selected seaweed. Polyphenol compound was analyzed and identified by GC–MS and FTIR. Findings of this research showed that seaweed extract possesses favorable antioxidant and antimicrobial properties, making it suitable for utilization in both food and pharmaceutical industries.