Antioxidant and enzyme-inhibitory activities of bromelain-derived rice bran protein hydrolysates and ultrafiltered peptide fractions

Bioactive peptides derived from proteins are widely used as functional foods and dietary supplements. This study focused on producing bioactive peptides from rice bran (Khao Dawk Mali 105). The enzymatic bromelain rice bran protein hydrolyzate (eb-RBPH) was separated into five fractions by ultrafiltration: < 1 kDa, 1–3 kDa, 3–5 kDa, 5–10 kDa, and > 10 kDa. The 1–3 kDa (F4) fraction showed the greatest DPPH and ABTS radical-scavenging activities (IC50 values of 696.02 and 444.13 µg protein/mL, respectively), elastase inhibition (IC50 = 51.90 µg protein/mL), collagenase inhibition (IC50 = 17.84 µg protein/mL), and gelatinase inhibition (IC50 = 27.72 µg protein/mL), followed by the < 1 kDa (F5) fraction and the unfractionated segment (eb-RBPH). Moreover, the 1–3 kDa fraction showed no cytotoxic effects toward African green monkey kidney fibroblasts, human immortal keratinocyte cells, or mouse subcutaneous connective tissue, suggesting its suitability for use as a functional ingredient. Chemometric analysis confirmed that the antioxidant and anti-aging properties of the eb-RBPH and its fractions were associated with bioactive peptides.