Isolation and characterization, antioxidant, and antihypertensive activity of novel bioactive peptides derived from hydrolysis of King Boletus mushroom

King Boletus mushroom protein hydrolysate (KBMPH) was prepared using bromelain and isolated by membrane ultrafiltration into four molecular size fractions (>10, 3–10, 1–3, and <1 kDa). All fractions were assessed for their characteristics, antioxidant and angiotensin I-converting enzyme (ACE) inhibitory activities. KBMPHF4 (<1 kDa) showed the highest surface hydrophobicity (S0), and high levels of hydrophobic amino acid (HAA). KBMPHF4 at 1 mg/mL exhibited antioxidative against DPPH• and ABTS•+ and linoleic acid oxidation, and ACE inhibitory activity (IC50 = 0.12 mg/mL). Peptide fraction-51 from ion-exchange-chromatography (IEC) showed high protein content, and biological properties. Three novel peptides (SETGGGHTTSCETDLGEFL, AAPLPGP, and GTDPTGEMLT) from F1 fraction had the highest antioxidant capacity and moderate ACE inhibitory activity. Six novel peptides (DLDLLEKGIRKT, NGGNAPI, VSWNVLQEP, DTGRGLGASH, IDDNLDNLIIKL, and LIYAQGFSK) from F4 fraction had moderate antioxidant capacity and the highest ACE inhibitory activity. LIYAQGFSK peptide had the greatest ACE-binding energy (−9.2 kcal/mol) through hydrogen bonds. Overall, novel peptides from KBMPHF4 could be potential use as natural antioxidants and antihypertensives in functional food and nutraceutical.