Polyphenolic content and bioactivity in Norwegian brown macroalgae in response to light intensity, temperature, salinity, and UV-radiation stress
Authors
Sara Roosvall (presenting author) [1, 2]
Ralf Rautenberger [2]
Keywords
Brown macroalgae; Bioactive compounds; Polyphenols; Phlorotannins; Antioxidant activity; Abiotic stress
Abstract
Phlorotannins are polyphenolic compounds that play a key role in mitigating abiotic stress in brown macroalgae. These bioactive antioxidants are unique to brown algae and vary among species and habitats, reflecting adaptations to environmental conditions such as salinity, temperature, light intensity, and UV radiation. As climate change intensifies these environmental stressors, studying phlorotannins has become increasingly important, both for understanding their ecological role and for exploring their potential applications in nutraceutical, pharmaceutical, food, and cosmetic industries. In this study, three brown macroalgae species (Saccharina latissima, Ascophyllum nodosum, and Fucus vesiculosus) were collected from two environmentally distinct locations: Mørkvedbukta (oceanic) and Evenset (estuarine). Algae were exposed for 24 h to four abiotic stressors: light intensity (22 µmol photons m⁻² s⁻¹, control; 100 µmol photons m⁻² s⁻¹, intermediate; 300 µmol photons m⁻² s⁻¹, high), temperature (10 °C, control; 18 °C, high), salinity (15 psu and 30 psu, depending on site-specific control and stress conditions), and UV radiation (UV-A, 320 nm, stress; PAR, 400 nm, control). Each treatment included three biological replicates per species and location (n = 3). Antioxidant activity was assessed using the DPPH radical scavenging assay, expressed as IC₅₀ (mg mL⁻¹), and total polyphenolic content (TPC) was quantified using the Folin–Ciocalteu assay with phloroglucinol as the standard, expressed as mg phloroglucinol equivalents g⁻¹ dry weight (mg PGE g⁻¹ DW).
Funding
Nord University, Faculty of Biosciences and Aquaculture, Bodø, Norway. Master thesis project (No project nr) Granted to Sara Roosvall