The effect of time and origin of harvest on the in vitro biological activity of Palmaria palmata protein hydrolysates

The effect of starting protein composition, and the origin and time of harvesting on the in vitro tyrosinase, dipeptidyl peptidase (DPP) IV and angiotensin converting enzyme (ACE) inhibitory and antioxidant activity of Palmaria palmata protein hydrolysates were investigated. Electrophoretic profiles showed significant differences in aqueous protein extracts obtained from the red macroalga Palmaria palmata harvested at different times of the year. No significant difference was observed in aqueous protein profiles extracted from wild and aquacultured samples of Palmaria palmata. Protein extracts from Palmaria palmata samples harvested from wild plants in April, July and October, and samples cultivated on longlines and harvested in April were hydrolysed with Alcalase 2.4 L and Corolase PP. The hydrolysates, when tested at 10 mg/ml, were shown to inhibit tyrosinase by 37–56%. The oxygen radical absorbance capacity (ORAC) and ferric reducing antioxidant power (FRAP) values of the hydrolysates ranged from 323–494 and 8.9–19.9 μmol trolox equivalents per gram, respectively. The Palmaria palmata hydrolysates inhibited DPP-IV (IC₅₀: 1.60–4.24 mg/mL) and ACE (IC₅₀: 0.14–0.35 mg/mL) activities. The starting protein composition had a significant effect on the tyrosinase inhibitory activity, while protein composition and hydrolytic enzyme preparation had a significant effect on DPP-IV inhibitory and antioxidant activities. In general, the origin of the samples, wild or cultivated, had no effect on the in vitro biological activity of the protein hydrolysates. The results show that Palmaria palmata hydrolysates may have potential applications as health enhancing ingredients and as food preservatives due to their antioxidant and tyrosinase inhibitory effects.