Evaluation of the proximate composition and antioxidant capacity of some seaweeds from the Konkan coast of India

Minerals, antioxidants, and other nutrients that promote health can be found in abundance in seaweeds. In this study, we evaluated the proximate composition and antioxidant capacity of some seaweeds from Konkan coast of India. There were notable differences in the proximate compositions between the species. The highest protein content was found in Pyropia vietnamensis (~49 mg. g⁻¹ dw), whereas the highest carbohydrate (~83 mg. g⁻¹ dw), lipids (56 mg. g⁻¹ dw) and vitamins were found in Stoechospermum marginatum. Total phenolic content (TPC) and antioxidant activity were estimated from a Methanolic extracts. The antioxidant capacity of the seaweeds was evaluated using 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, ABTS (2,2-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid), ferric reducing antioxidant power (FRAP) assay and hydrogen peroxide free radical scavenging activity assay. Folin-Ciocalteu method was used to quantify total phenolic content (TPC), and Ulva fasciata had the highest TPC (24.30 ± 3 mg GAE. g⁻¹ dry weight). In U. fasciata, the antioxidant activity was ~62 %, with an IC₅₀ value of 0.057 ± 0.01 mM. Acanthophora spicifera was found to have a strong reducing power, with an IC₅₀ value 0.012 ± 0.002 mM. H₂O₂ scavenging activity (~79 %) with an IC₅₀ value of 0.006 ± 0.001 mM and 67 % ABTS radical scavenging activity (IC₅₀ = 0.005) was highest in S. marginatum. Analysis showed that TPC exhibited strong positive correlation with both the ferric reducing antioxidant potential and DPPH antioxidant activity. These results showed that these seaweeds have significant antioxidant capacity and rich nutritional properties, which suggest they could be useful sources of functional ingredients for dietary supplements and other food products.