PURPOSE: A hypotensive peptide mixture isolated from the fermented culture medium of Lactobacillus casei HY418 and an isolation method thereof are provided. The peptide has angiotensin converting enzyme inhibiting activity in vitro and hypotensive effect in vivo. CONSTITUTION: The peptide mixture, which is isolated from the fermented skim milk medium of Lactobacillus casei HY418, inhibits activity of angiotensin converting enzyme in vitro, reduces blood pressure in vivo, and contains angiotensin converting enzyme inhibitor having the amino acid sequence of Leu-Leu-Tyr-Lys-Thr Thr-Met-Pro and Tyr-Tyr-Gln-Gln-Lys-Pro-Val-Ala-Leu-Ile-Asn. The method for isolating the peptide mixture comprises the steps of: centrifuging the fermented skim milk medium of Lactobacillus casei HY418 in the range of pH 3 to pH 5; recentrifuging the fermented skim milk medium of Lactobacillus casei HY418 in the range of pH 8.0 to 8.4; ultra-centrifuging supernatant to obtain the crude peptide; and isolating peptide from the crude peptide by reversed phase chromatography.
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