Exploring the antioxidant and antimicrobial potential of three common seaweeds of Saint Martin's Island of Bangladesh

Antioxidants, which have long been deemed an indispensable guardian of human health, play a pivotal role in bolstering the body's defense against a plethora of diseases. Three well-recognized seaweeds in Bangladesh, including Caulerpa racemosa, Padina tetrastromatica, and Hypnea musciformis, were subjected to meticulous analysis to reveal their phytochemical composition, antioxidant activity, and antimicrobial efficacy using advanced spectroscopic and disc diffusion methods. Intriguingly, we observed that C. racemosa emerges as frontrunners, possessing a substantial arsenal of phenol (143.08 ± 18.51 mg gallic acid equivalent g^─1) and flavonoid (63.79 ± 2.16 mg rutin equivalent g^─1). More fundamentally, C. racemosa exhibits a notable enrichment in the content of tannin (73.58 mg RE g^─1) and chlorophyll (13.50 mg g^─1), as well as, antioxidant capacity (4457.67 μg g^─1). P. tetrastromatica, on the other hand, displayed commendable effectiveness in scavenging the DPPH radical, with percentages ranging from 53.98 to 62.17%. In terms of hydroxyl radical (OH^•) scavenging activity, C. racemosa exhibited the highest efficacy at 400 g mL^─1. Fascinatingly, C. racemosa exhibited an impressive antioxidant potential, as evidenced by its exceptionally low IC₅₀ value of 5.58 μg mL⁻¹ for OH^• scavenging, whereas P. tetrastromatica showed impressively low value of 0.96 μg mL⁻¹ for DPPH scavenging. Although the three seaweeds demonstrated limited efficacy against a spectrum of five human pathogenic bacteria, their potential as abundant sources of antioxidants remains unscathed. Notably, heatmap and PCA analysis revealed that C. racemosa and P. tetrastromatica emerge as the leading contender for studied antioxidant compounds, demonstrating their proclivity for antioxidant extraction, a trait that could be exploited for large-scale production of these valuable compounds.