Phytochemical composition, antioxidant, and antibacterial potential of three brown seaweeds from Japan

The impacts of various extracting solvents on the phytochemical composition, antioxidant, and antibacterial activity of three brown seaweeds, such as Sargassum horneri , Undaria pinnatifida , and Laminaria japonica were assessed. Various concentrations of ethanol (100%, 80% and 50%) were used as the extracting solvent. The DPPH (1,1-diphenyl-1-picrylhydrazyl) and ABTS (2,2′- azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging activity, and CUPRAC (cupric reducing antioxidant capacity) was performed for antioxidant assays. Extracts obtained from 100% ethanol exhibited significantly (p < 0.05) the highest total phenolic content (TPC) and total flavonoid content (TFC), while the lowest amount was observed in 50% ethanolic extracts of each seaweed. The lowest EC 50 values of DPPH and ABTS were found in the 100% ethanolic extracts of S. horneri , which indicate the highest antioxidant capacity. Similarly, 100% ethanolic extract of S. horneri exhibited the lowest CUPRAC value (EC A0.50 = 0.24 mg/ml), while the highest EC A0.50 value was found in 50% ethanolic extract (7.01 mg/ml) of L. japonica . Fucoxanthin was identified as a dominant pigment across all species, particularly in S. horneri and U. pinnatifida . The association among TPC, TFC, and antioxidant parameters was confirmed by multivariate analysis. The 100% ethanolic extracts of S. horneri showed comparatively higher zones of inhibition against all the bacterial strains at 50 mg/ml than other seaweed extracts. The outcome of this research revealed that 100% ethanolic extract of S. horneri demonstrated comparatively better activity against oxidation and bacteria, therefore, this could be utilized in the food and pharmaceutical industries. • Antioxidant and antibacterial activity of seaweed crude extracts were evaluated • Ethanolic extract of Sargassum horneri exhibited higher antioxidant activity • Ethanolic extracts of S. horneri strongly inhibited the bacterial growth • Fucoxanthin was identified as a dominant carotenoid in brown seaweeds • PCA established the correlation between TPC and various antioxidant capacity assays • Brown seaweed can be used as a potential natural additive in food processing