King Boletus mushroom-derived bioactive protein hydrolysate: characterisation, antioxidant, ACE inhibitory and cytotoxic activities

The enzymatic-bromelain King Boletus mushroom protein hydrolysate (eb-KBM) was determined in terms of the biological properties (antioxidant, antihypertensive and cytotoxic activities) and compared with unhydrolysed or water-soluble King Boletus mushroom extract (ws-KBM). The eb-KBM showed high antioxidant activities, as assessed by ABTS (70.9%), DPPH (60.9%) assays and hydroxyl radicals (66.0%) scavenging method. Angiotensin-I converting enzyme (ACE) inhibitory activity of eb-KBM was 21.1% at 1 mg protein mL−1. Anticancer activity-relevant cytotoxicity of eb-KBM in ChaGo-K1 (undifferentiated lung carcinoma) and HEP-G2 (hepatocarcinoma) cells was higher than that of ws-KBM, with lower IC50 values (6.43 and 6.35 µg mL−1, respectively). The great biological activities of eb-KBM were related to its amino acid composition, with high contents of hydrophobic amino acids and aromatic amino acids. These results indicate that King Boletus mushroom protein hydrolysate or bioactive peptide could be used as natural antioxidative, ACE inhibitory and anticancer activities in the nutraceutical and pharmaceutical industries.