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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.

Macroalgae are traditionally used in human and animal nutrition. Their protein and fiber content have been widely studied and differ according to the species, their geographic origin and their seasonal conditions. In addition to their value for human nutrition, seaweeds have multiple therapeutically applications (e.g., weight control, hypocholesterolemic, antioxidant and antitumor activities, others) and, in general, contribute and promote human health. In the archipelago of the Azores, the consumption of seaweeds is widespread and accepted as a common practice in some islands. This work is aimed at providing information on the protein and fiber content of the locally consumed species, to promote this regional food product that can be potentially profitable from the biotechnology and commercial perspective, and also benefit public health, particularly, taking into account the low level of marine pollution in the Azores archipelago. Protein and fiber content of eight seaweeds (Porphyra sp., Osmundea pinnatifida, Pterocladiella capillacea, Sphaerococcus coronopifolius, and Gelidium microdon, Rhodophyta; Cystoseira abies-marina and Fucus spiralis, Phaeophyta; Ulva compressa, Chlorophyta) were determined using the Kjeldahl method and the Weende method, respectively. The protein content ranged from 6.81 to 26.62 of dry weight for C. abies-marina and U. compressa, respectively. Fiber content was generally higher as compared with that in seaweeds from other origins and ranged from 33.82 to 63.88 for O. pinnatifida and F. spiralis, respectively.

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