Functional Properties of Nori Seaweed (Pyropia yezoensis) with Different Quality and Ulva sp.

Abstract

ABSTRACT Nori (Pyropia yezoensis) is a widely eaten red seaweed, and its quality is decreased by the environment in which it is grown, resulting in discolored nori. Ulva sp. is green seaweed that grows in large quantities due to eutrophication. The functions of the two seaweeds were investigated for effective utilization. The total phenolic contents of discolored nori with poor quality and Ulva sp. were 56.6% and 13.0% of that in normal nori, respectively. For superoxide dismutase (SOD)-like activity, the IC50 value of normal nori was 4.33 ± 2.18 mg/mL, while that of discolored nori was 7.1-fold higher. For the coloring components, discolored nori showed a much smaller carotenoid absorbance at 400–500 nm. The amounts of hydrolysate obtained from discolored nori and Ulva sp. using protease were 74% and 30% of that of normal nori, respectively. Regarding angiotensin I-converting enzyme (ACE) inhibitory activity of the hydrolysate, normal and discolored nori seaweed had similar activities. Green seaweed Ulva sp. had a higher ACE inhibitory activity than that of nori (IC50 values: 0.045 mg/mL for Ulva sp. and 0.170 mg/mL for nori). Nori and Ulva sp. extracts had small inhibitory activities for α-glucosidase and sucrase, which manages the sugar level in blood.