IMPACT OF ALPHA-AMYLASE ON LUTEIN ANTIOXIDANT ACTIVITY

Lutein (LUT) plays a crucial role for preventing age-related macular degeneration and other diseases due to antioxidant activity. However, little is known about how digestive enzymes, such as salivary alpha-amylase (AAM), can affect its antioxidant capacity. In this context, this study aimed to assess the impact of AAM on the antioxidant activity of LUT. To investigate this connection, we conducted in vitro analyses at a pH reflecting found in saliva (pH=7.0). The concentrations of AAM in solutions containing lutein ([LUT]=2.5x10-6 mol∙L-1) were varied ([AAM]= 0 to 2.6x10-6 mol∙L-1), and the resulting total antioxidant activity (TAA) was evaluated through DPPH● and ABTS●+ assays. In both methods, the TAA of LUT declined with an increase in AAM concentration. In the DPPH● assay, the TAA decreased from 2.9 to 1.4 mM Trolox/100 g of sample as the AAM concentration increased from 0 to 8.6x10-7 molL-1. The same trend was observed in the ABTS●+ analysis, with a decrease in TAA from 60 to 40.4 mM Trolox/100 g sample ([AAM=0 to 8.6x10-7 molL-1). At higher concentrations of AAM (up to 1x10-6 mol∙L-1), it appears that the enzyme had no effect, as the TAA of LUT remained constant. The effect of AAM can be explained by the blocking of hydroxyl groups (OH) on LUT when it interacts with the enzyme. It is known that the TAA of LUT is attributed not only to its conjugated double bonds but also to the two OH at both ends of its molecule. Proteins rich in proline are particularly effective in blocking OH because proline represents the primary site for OH binding. This is exemplified by AAM, which possesses 23 proline residues out of its total 511 amino acids. These findings can help optimize dietary and supplementation strategies to maximize the benefits of LUT without the negative effects of AAM.