Identification and Evaluation of Antioxidant and Anti-Aging Peptide Fractions from Enzymatically Hydrolyzed Proteins of Spirulina platensis and Chlorella vulgaris

Microalgae are a promising source of bioactive compounds, particularly proteins and peptides, with potential applications in skin health and the cosmetic industry. This study investigated the antioxidant and anti-aging properties of peptide fractions derived from <i>Spirulina platensis</i> and <i>Chlorella vulgaris</i>. Both microalgae were cultivated, and their proteins were subsequently extracted, enzymatically hydrolyzed with alcalase, and fractionated through ultrafiltration. Alkaline extraction yielded 82% protein from <i>S. platensis</i> and 72% from <i>C. vulgaris</i>. Enzymatic hydrolysis predominantly yielded <3 kDa peptides, which exhibited strong antioxidant activity reaching 78% for 2,2-diphenyl-1-picrylhidrazol (DPPH), 82% for 2,2'-azinobis-3-etilbenzothiazoline-6-sulfonic acid (ABTS), and 74% for ferric reducing antioxidant power (FRAP), with IC₅₀ values as low as 23.44 µg/mL for ABTS inhibition in <i>C. vulgaris</i>. These peptides also significantly inhibited skin-aging enzymes, showing 84% inhibition of elastase, 90% of collagenase, and 66% of tyrosinase. Mass spectrometry and GNPS molecular networking of the <3 kDa fraction identified several di- and tri-peptides, including Lys-Val, Val-Arg, His-Ile, Lys-Leu, Ile-Leu, and Leu-Phe, Tyr-Phe, and Leu-Gly-Leu, potentially contributing to these bioactivities. These findings suggest that the enzymatic hydrolysis of <i>S. platensis</i> and <i>C. vulgaris</i> proteins provides a sustainable and natural source of bioactive peptides for antioxidant and anti-aging applications in food, pharmaceutical, and cosmetic industries.