Seaweed (G. gracilis) Protein Hydrolyzates: A Valuable Source of Short- and Medium-Chain Peptides with Multifunctional Properties

The sustainable valorization
of infesting marine biomass
offers
opportunities to address environmental challenges and emerging nutritional
needs. This study investigated the invasive red alga Gracilaria gracilis as a potential source of bioactive
peptides with antihypertensive and antidiabetic properties. Protein
hydrolyzates were generated via enzymatic digestion and fractionated
by size exclusion chromatography. Peptidomics analysis using liquid
chromatography coupled with high-resolution mass spectrometry identified
362 short-chain and 97 medium-chain peptides. Antioxidant effects
were confirmed via diphenyl-2-picrylhydrazyl radical (DPPH), trolox
equivalent antioxidant capacity (TEAC), and ferric reducing antioxidant
power (FRAP) assays: at 20 mg/mL, short-chain peptides showed a TEAC
of 60.8 ± 0.7% and a FRAP activity of 4638.7 ± 87.8%, significantly
higher than the medium-chain fraction (36.1 ± 3.6% and 2180.6
± 25.8%, respectively). Short-chain peptides also demonstrated
stronger angiotensin-converting enzyme inhibition (19.53 ± 0.64%
at 2.07 mg/mL) compared to medium-chain peptides (12.5 ± 0.42%).
Conversely, medium-chain peptides exhibited superior dipeptidyl peptidase
IV inhibition. Trans-epithelial transport experiments confirmed bioavailability,
with 40 short peptides and 65 medium peptides detected in the basolateral
compartment. These findings demonstrate the potential of converting
invasive seaweeds into multifunctional ingredients for functional
foods or nutraceuticals, supporting marine biotechnology and circular
bioeconomy strategies for preventive healthcare and metabolic disease
management.