Purification and identification of angiotensin I-converting enzyme inhibitors from the red alga Porphyra yezoensis.

The potent part of the angiotensin I-converting enzyme (ACE) inhibitory activity from Porphyra yezoensis hydrolysate was fractionated by using ion-exchange and gel-filtration techniques. Oral administration of the most potent inhibitory fraction (SP-I fraction, 200 mg/kg) to spontaneously hypertensive rats (SHR) showed a hypotensive effect. Using octadecylsilano column chromatography, the SP-I fraction was further separated into several peptides with potent inhibitory activities. The amino acid sequences of ACE inhibitory peptides derived from Porphyra yezoensis were Ile-Tyr (IC50: 2.69 µM), Met-Lys-Tyr (7.26 µM), Ala-Lys-Tyr-Ser-Tyr (1.52 µM), and Leu-Arg-Tyr (5.06 µM).