Identification of wild seaweeds at Nipah beach, Indonesia, and study of their antioxidant potential

Abstract

The extracts from seaweeds are rich sources of phenolic acids, flavonoids, carotenoids, vitamins, sulphated polysaccharides, and phycobiliproteins, which confer antioxidant, anti-inflammatory, antimicrobial, and bioactive properties. Nipah Beach, Lombok (Indonesia) hosts biodiverse intertidal macroalgae whose functional traits remain under-documented. Objectives: This study aimed to identify prevalent taxa and quantify antioxidant capacity and pigments under in situ conditions. Methods: In May 2025, thalli of Padina australis, Sargassum crassifolium, Chondracanthus sp. , and Halimeda opuntia were collected at three intertidal stations; methanolic extracts were assessed for DPPH radical scavenging (% inhibition at 517 nm), chlorophyll-a was derived from A664/A647, and R-phycoerythrin was read at 565 nm with 730 nm turbidity correction by UV–Vis spectrophotometry. Concurrent field measurements (temperature, salinity, pH, dissolved oxygen, illuminance; handheld meters) indicated stable conditions; total dissolved solids were recorded verbatim but not interpreted. Results: Results are descriptive (TEAC/IC50 not computed): Padina australis showed the highest %DPPH inhibition, chlorophyll-a peaked in Sargassum crassifolium, and Chondracanthus sp. exhibited the strongest R-phycoerythrin signal, consistent with lineage-specific pigment architecture. Elevated daytime dissolved oxygen likely reflects wave action and/or photosynthesis. Conclusion: These findings provide an integrated local baseline linking ecology to functional traits and nominate Padina australis as an antioxidant lead, Sargassum crassifolium for chlorophyll-a/fucoxanthin potential, and Chondracanthus sp. as a source of R-phycoerythrin. Priorities include seasonal replication, TEAC/IC50 and ABTS/FRAP/ORAC assays, continuous photosynthetically active radiation (PAR) logging, and strengthened taxonomy, with curated datasets and code planned for release in subsequent project updates.