Bioactive Properties of Enzymatically Hydrolyzed Mulberry Leaf Proteins: Antioxidant and Anti-Inflammatory Effects

Oxidative stress and inflammatory responses often occur concomitantly, and they are key causative factors in various human and animal diseases. Evidence suggests that mulberry leaf protein (MLP) may have potential antioxidant and anti-inflammatory properties, but there are significant challenges in enhancing their bioactivities. In this study, MLP was enzymatically hydrolyzed using papain, protamex, alkaline protease, trypsin, and neutral protease, followed by comprehensive evaluation of the antioxidant capacity, anti-inflammatory properties, and cytotoxicity of the hydrolysates. Our findings revealed that some enzymes significantly enhanced the peptide production and antioxidant activity of MLP (p < 0.01), and its activity was positively correlated with the degree of hydrolysis. Among the five hydrolysates, neutral protease hydrolysate (NeuH) exhibited the best antioxidant properties, with free radical scavenging rates of 71.58 ± 0.42% (ABTS), 26.38 ± 0.15% (OH), and 73.91 ± 0.37% (DPPH) at a concentration of 0.1 mg/mL. In addition, NeuH significantly suppressed IL-6 secretion (p < 0.01) and downregulated mRNA expression of IL-6, iNOS, and COX-2 inflammatory markers. This study not only establishes a correlation between enzymatic parameters and MLP biological functions but also demonstrates the potential of optimized MLP hydrolysates, particularly NeuH, as valuable natural antioxidant and anti-inflammatory ingredients for functional foods or nutraceuticals aimed at mitigating oxidative stress and inflammation-related disorders.