LC-HRMS Profiling, Total Flavonoid and Phenolic Content of Brown Algae Originating from the Southern Coast of Indonesia

Brown algae (Sargassum polycystum) are widely distributed in Indonesian marine ecosystems. Despite their abundance, pharmaceutical exploration remains limited compared to red and green algae. This study aimed to profile metabolites and evaluate the total phenolic content (TPC) and total flavonoid content (TFC) of brown algae collected from Indonesia’s southern coast using liquid chromatography-high-resolution mass spectrometry (LC-HRMS). Powdered samples of brown algae were extracted separately by maceration using three different polarity-based solvents: ethanol, ethyl acetate, and n-hexane. The extracts were analysed for TPC and TFC using Folin ciocalteu and aluminium chloride colorimetric assays, respectively. The metabolites profile of the extracts was analysed using LC-HRMS. Ethyl acetate extract exhibited the highest TPC (48.570 ± 0.008 mg GAE/g), while n-Hexane extract showed the highest TFC (85.271 ± 0.017 mg QE/g). LC-HRMS profiling identified 232-328 metabolites across the extracts, with n-hexane yielding the greatest chemical diversity. Key bioactive compounds identified included Xestoaminol C (highest in ethanol extract at 5.57%), Ceramides (13.46% of total content in ethanol extract), and Fucoxanthin (exclusive to ethanol extract, 0.52%). These metabolites are known for their anticancer, neuroprotective, antioxidant and antimicrobial properties. Heatmap analysis of the top 20 metabolites revealed solvent-dependent clustering patterns, highlighting the influence of extraction methods on metabolites recovery. The findings underscore the pharmaceutical and nutraceutical potential of Indonesian brown algae and demonstrate the invaluable role of LC-HRMS for marine natural product research.