Food protein-derived hydrolysates with multi-bioactivities such as antihypertensive and antioxidant properties have recently received special attention since both activities can play significant roles in preventing cardiovascular diseases. This study reports, for the first time, the angiotensin I-converting enzyme (ACE)-inhibition and antioxidant properties of ultrafiltrate fractions (UF) with different molecular weight ranges (<1, 1–3 and ≥3 kDa) obtained from Fucus spiralis protein hydrolysate (FSPH) digested with cellulase–bromelain. The amino acids profile, recovery yield, protein, peptide and total phenolic contents of these FSPH-UF, and the in vitro digestibility of F. spiralis crude protein were also investigated. FSPH-UF ≥3 kDa presented remarkably higher ACE-inhibition, yield, peptide and polyphenolic (phlorotannins) contents. Antioxidant analysis showed that FSPH-UF <1 kDa and ≥3 kDa exhibited significantly higher scavenging of 2,2-diphenyl-1-picrylhydrazyl radical and ferrous ion-chelating (FIC) activity. FSPH-UF ≥3 kDa had also notably higher ferric reducing antioxidant power (FRAP). Strong correlations were observed between ACE-inhibition and antioxidant activities (FIC and FRAP). The results suggest that ACE-inhibition and antioxidant properties of FSPH-UF may be due to the bioactive peptides and polyphenols released during the enzymatic hydrolysis. In conclusion, this study shows the potential use of defined size FSPH-UF for the prevention/treatment of hypertension and/or oxidative stress-related diseases.

This study evaluates, for the first time, the seasonal (winter and summer) and geographical (São Miguel–SMG and Santa Maria–SMA Islands) variability of Fucus spiralis (Fs) biochemical composition (dry weight basis) and antioxidant properties. Protein and carbohydrates presented higher values in Fs-SMG_winter, lipids, total dietary fiber, and energy value in Fs-SMA_summer, and ash and soluble dietary fiber/insoluble dietary fiber ratio in Fs-SMA_winter. The fatty acid (FA) profiles showed a lower SFA in Fs-SMG_summer, whereas MUFA and PUFA presented higher values in Fs-SMG_summer and Fs-SMG_winter, respectively. Excellent dietary ratios of n6/n3 PUFA and hypocholesterolemic/hypercholesterolemic FA were found, with lower values in Fs-SMA_winter and higher in Fs-SMG_summer, respectively. The highest total phenolics was found in Fs-SMA_summer acetone:water extract and total flavonoids showed the higher value in Fs-SMG_winter methanol extract. The best free radical-scavenging activity was observed in the Fs-SMA_winter methanol (EC₅₀ = 0.045 mg/mL) and acetone:water (EC₅₀ = 0.059 mg/mL) extracts. The ferric-reducing antioxidant power showed the best results in Fs-SMA_winter methanol extract (EC₅₀ = 0.016 mg/mL) and Fs-SMA_summer acetone:water extract (EC₅₀ = 0.017 mg/mL). The best ferrous ion-chelating activity was found in Fs-SMG_winter acetone:water extract. Overall, results revealed that F. spiralis nutritional and functional bioactivity values have geographical and seasonal variations and that its regular consumption may add benefits to human health.