Investigation of the Chemical Composition and Biological Activities of Six Edible Macroalgae

INTRODUCTION: Meeting the rising food demands of a growing global population is a critical challenge. This study proposes seaweeds as a nutrient-rich, low-fat solution. Although macroalgae are reported to be rich in nutrients and bioactive compounds, they still remain underutilized due to misunderstanding of their flavour and aroma.

METHODS: This work explores the chemical composition of six edible macroalgae, Chondrus crispus, Gracilaria gracilis, Porphyra dioica, Palmaria palmata, Porphyra haitanensis, and Ulva rigida, identifying unique compounds, many reported in this study for the first time. Additionally, screening was conducted to assess the bioactivity of the ethanolic algae extracts, including their ability to prevent lipid peroxidation, inhibit aldose reductase and tyrosinase enzyme activity, and inhibit 5-lypoxygenase, thus mediating inflammation processes.

RESULTS: Porphyra sp. showed higher TPC (10.8-14.8mg_GA-Eq/g) and proteins (1.0-2.4mg_BSA-Eq/g), while P. palmata had the maximum sugars (22mg_S-Eq/g). Forty-seven volatile compounds were identified in the six macroalgae, mainly acids (8), aldehydes (14), and alcohols (10). Pyrazines were only found in P. dioica, P. haitanensis, and P. palmata, terpenes in P. haitanensis and U. rigida, and lactones, specifically ϒ-butyrolactone, in P. haitanensis and P. palmata. P. haitanensis and P. dioica exhibited the highest inhibition rates for lipid peroxidation (IC₅₀=1.08 and 0.86mg/mL, respectively), with the former demonstrating the highest aldose reductase inhibition (IC₅₀=1.00 mg/mL). Although the ability of the examined algae to inhibit tyrosinase was limited (<30% at the highest tested concentration), they showed superior anti-inflammatory potential, especially P. haitanensis (IC₂₅=0.26 mg/mL).

CONCLUSIONS: The evaluated algae resulted to be rich in proteins, sugars, and phenolic compounds. This study identified previously unreported compounds, filling gaps in the existing literature. These compounds influence algae’s unique aroma, flavor, and bioactivity, suggesting their potential as novel ingredients in food processing and culinary applications. However, further research is needed to understand their bioavailability and interactions.