Effect of Steeping and Germination on Protein Properties of Mexican Endemic Huauzontle (Chenopodium berlandieri subsp. Nuttalliae)

The Mexican endemic plant huauzontle (Chenopodium berlandieri subsp. Nuttalliae) has been studied in recent years for its functional properties. Because of previous studies in legumes and cereals, this study aimed to evaluate the differences in nutritional value and bioactivity of protein hydrolysates of huauzontle seeds subjected to steeping and germination. A solubility curve was created for each sample (H1: unaltered seeds; H2: steeped; H3: germinated) by adding bidistilled water at a 1:18 (w/w) ratio and adjusting the pH from 2 to 12. After centrifugation, the protein concentration in the supernatants was determined via Bicinchoninic Acid Assay (BAA). An alkaline extraction was performed, and later on concentrated by micro- and ultrafiltration, using a 5 kDa membrane. A posterior alcalase hydrolysis was performed at an E:S ratio of 1:90 (w/w) at 60ºC for 180 minutes at a pH of 8.5. A pH of 10 optimally extracted proteins without risking protein hydrolysis. Similarly, an SDS-PAGE was performed with the concentrated protein samples and hydrolysates. Before hydrolysis, H1 (5.90 mg/ml) presented 5 bands smaller than 63 kDa, whereas H2 (1.10 mg/ml) and H3 (1.13 mg/ml) showed 2 bands smaller than 17 kDa. A biological hydrolysis is hypothesized to occur during steeping and germination. Hydrolyzed samples did not present any bands. An α-amylase inhibition assay demonstrated that, despite its higher concentration, H1 hydrolysates had no inhibitory effect. H2 and H3 presented a hormetic inhibitory effect, where a concentration of 0.2 mg/mL created the highest inhibition (22.7% and 27.2%, respectively). Germination promoted a greater (p<0.05) ABTS radical scavenging in protein hydrolysates (IC50=0.35 mg/mL) than steeped (0.45 mg/mL) and untreated seeds (0.56 mg/mL). The positive effect of seed germination on protein functionality will be further assessed.