The aim of this study was to investigate the inhibitory activity of angiotensin-converting enzyme (ACE) and antihypertensive effects of soybean protein hydrolysate in spontaneously hypertensive rats (SHRs). The inhibitory activities against ACE with an IC50 of the peptidic fraction were 0.82 (casein), 0.73 (soybean protein isolate), and 0.48 mg/mL (soybean acid-precipitated protein), respectively. Peptic hydrolysate containing 1% NaCl was added to the SHRs'feed (5% of each protein hydrolysate). Systolic blood pressure of the soybean protein hydrolysate-supplemented groups were significantly lower than that of the casein hydrolysate-supplemented group in the study period. These data suggested that soybean protein hydrolysate may retard the development of hypertension in SHRs by its ACE inhibitory effect in vivo.

OBJECTIVE: This study investigated the effects of soymilk oil lipid metabolism in Sprague-Dawley rats fed a cholesterol-enriched (0.3%) diet.METHODS: Thirty male Sprague-Dawley rats weighing 230.0 +/- 9.8 g were randomly assigned to one of three groups: control, S1 (containing 15% soymilk powder in the diet), and S2 (22.5%). After 8 wk, lipid profiles of the plasma, liver, and feces were determined.RESULTS: Body weight gain, daily food intake, and feeding efficiency showed no differences across groups (P > 0.05). The experimental groups had significantly lower plasma levels of cholesterol, triacylglycerol, and low-density lipoprotein cholesterol than the control group (P < 0.05) at weeks 4 and 8. However, total fecal excretion of neutral steroid did not significantly differ across groups (P > 0.05).CONCLUSION: Soymilk affects the metabolism of plasma cholesterol in Sprague-Dawley rats. (C)Elsevier-Inc. 2004.

We examined the angiotensin I-converting enzyme (ACE) inhibitory activity and antihypertensive effect of the hot water extract of wakame, Undaria pinnatifida. Ten dipeptides were isolated from the extract by several steps of chromatography, and their amino acid sequences were Tyr-His, Lys-Trp, Lys-Tyr, Lys-Phe, Phe-Tyr, Val-Trp, Val-Phe, Ile-Tyr, Ile-Trp, and Val-Tyr. Both single administration and repeated oral administration of synthetic Tyr-His, Lys-Tyr, Phe-Tyr, and Ile-Tyr significantly decreased blood pressure in spontaneously hypertensive rats.

Peptides having potent antioxidant activity were separated from the hydrolysate of wheat gluten by ion-exchange and gel filtration chromatography. Peptides obtained by SP Sephadex C-25 chromatography of the most active fraction (WP-3) were further separated using reversed-phase high performance liquid chromatography. The amino acid sequences of these peptides were Leu-Gln-Pro-Gly-Gln-Gly-Gln-Gln-Gly and Ala-Gln-Ile-Pro-Gln-Gln.

OBJECTIVE:We investigated lipid metabolism in hypercholesterolemic rats after replacing casein with different amounts of undialyzed soybean protein fraction.METHODS:The hypercholesterolemic rats were fed cholesterol-free diets containing 2%, 5%, or 10% undialyzed soybean protein fraction (UDSP) for 4 wk.RESULTS:The 5% and 10% UDSP groups had significantly lower plasma cholesterol, triacylglycerol, and low-density lipoprotein cholesterol concentrations than did the other groups (P < 0.05). In addition, significantly higher fecal total steroid excretion was observed in these two groups. However, the different amounts of UDSP did not influence liver lipid, plasma high-density lipoprotein cholesterol, body weight gain, daily food intake, or feeding efficiency.CONCLUSION:These results suggested a dose-dependent reduction in plasma cholesterol when casein was replaced stepwise with UDSP (5% or 10%) as a protein source. The hypocholesterolemic effect might have been due to an increase in total fecal steroid excretion.

Peptides having potent antioxidant activity were separated from the hydrolysate of wheat gluten by ion-exchange and gel filtration chromatography. Peptides obtained by SP Sephadex C-25 chromatography of the most active fraction (WP-3) were further separated using reversed-phase high performance liquid chromatography. The amino acid sequences of these peptides were Leu-Gln-Pro-Gly-Gln-Gly-Gln-Gln-Gly and Ala-Gln-Ile-Pro-Gln-Gln.

Peptidic fractions which inhibit angiotensin I-converting enzyme (ACE) were separated from peptic digests of soybean by ion exchange chromatography and gel filtration. Further separation of the peptidic fractions by ODS HPLC afforded active peptides, the amino acid sequences of which were identified by Edman's procedure as: Ile-Ala (inhibitory against ACE with an IC50 of 153 muM), Tyr-Leu-Ala-Gly-Asn-Gln (14 muM), Phe-Phe-Leu (37 muM), Ile-Tyr-Leu-Leu (42 muM), and Val-Met-Asp-Lys-Pro-Gln-Gly (39 muM). The antihypertensive activity of the soybean peptides was also investigated. Peptide fractions (2.0 g/kg body weight, oral administration) markedly lowered the blood pressure of spontaneously hypertensive rats (SHRs).

The peptidic fractions that inhibited angiotensin I–converting enzyme (ACE) were separated from the peptic digests of 2 microalgae, Chlorella vulgaris and Spirulina platensis, by ion exchange chromatography and gel filtration. Oral administration of peptidic fractions into spontaneously hypertensive rats at 200 mg/kg of body weight resulted in marked antihypertensive effects. Further separation of the peptidic fractions by ODS high-performance liquid chromatography furnished the following active peptides: Ile-Val-Val-Glu (inhibitory against ACE with an IC50 of 315.3 μM), Ala-Phe-Leu (63.8 μM), Phe-Ala-Leu (26.3 μM), Ala-Glu-Leu (57.1 μM), and Val-Val-Pro-Pro-Ala (79.5 μM) from C. vulgaris; Ile-Ala-Glu (34.7 μM), Phe-Ala-Leu, Ala-Glu-Leu, Ile-Ala-Pro-Gly (11.4 μM), and Val-Ala-Phe (35.8 μM) from S. platensis.

A peptide fraction having activity against angiotensin I-converting enzyme (ACE) was separated from the peptic digest of protein prepared from wakame (Undaria pinnatifida) by ion-exchange chromatographies and gel-filtration. Fractions with high ACE inhibitory activity were combined and further chromatographed on a reverse-phase column to yield four tetrapeptides with ACE inhibitory properties. These tetrapeptides were identified by sequence analysis and fast atom bombardment mass spectrometry as Ala-Ile-Tyr-Lys (IC(50): 213 microM), Tyr-Lys-Tyr-Tyr (64.2 microM), Lys-Phe-Tyr-Gly (90.5 microM), and Tyr-Asn-Lys-Leu (21 microM). Each tetrapeptide was synthesized and its antihypertensive activity was determined after oral administration in spontaneously hypertensive rats. The blood pressure significantly decreased after tetrapeptide ingestion. The present study demonstrated that dietary wakame may have beneficial effects on hypertension.

A peptide having the strong free radical scavenging activities was separated from casein protein hydrolysate by chromatographic analyses such as ion-exchange and gel filtration. SP-II fraction obtained by SP-Sephadex C-25 chromatography showed the most potent superoxide anion scavenging activity (SOSA), and it was further separated into a peptide using an octadecylsilano-high performance liquid chromatography. The amino acid sequence of the peptide was Tyr-Phe-Tyr-Pro-Glu-Leu (YFYPEL). The concentration of the test compound required to reduce the produced superoxide anion to one-half (IC(50)) value for SOSA was 79.2 microM using tetrazolium salt 3'-{1-[(phenylamino)-carbonyl]-3,4-tetrazolium}-bis(4-methoxy-6-nitro)benzenesulfonic acid hydrate method. The IC50 value for the 1,1-diphenyl-2-picrylhydrazyl radical and hydroxyl radical scavenging activities were 98 and 251 microM, respectively, based on the electron spin resonance method. We characterized SOSA of the C-terminal sequence using EL, PEL, YPEL, and FYPEL. The activities preferred sequences were EL>YFYPEL>FYPEL>YPEL>PEL, suggesting that the Glu-Leu sequence is important for the activity.

The muscle of the prawn Penaeus japonicus was hydrolyzed by various proteases, and antioxidant activity of the hydrolysates was examined. Among the digests, pepsin digest showed the most potent antioxidant activity. Three antioxidant peptides have been isolated from the active peptidic fraction by ion-exchange chromatography, gel filtration, and ODS high-performance liquid chromatography. Their structures were identified as Ile-Lys-Lys, Phe-Lys-Lys, and Phe-Ile-Lys-Lys.

A peptidic fraction having active oxygen scavenging activity was separated from the peptic digest of sardine muscle by ion-exchange chromatography and gel filtration. Further separation by ODS HPLC afforded an active peptide; Leu-Gln-Pro-Gly-Gln-Gly-Gln-Gln. The IC50 value for superoxide scavenging activity was 465 mu M as determined by the tetrazolium salt XTT method, while that for hydroxyl radical scavenging activity was 24.6 mu M as established by ESR.

A concentrate of an aqueous extract of Allium sativum L. (garlic) was fractionated using ion exchange and gel filtration to isolate fractions with angiotensin I-converting enzyme (ACE) inhibitory activity. Fractions with high ACE inhibitory activity were combined and further chromatographed on a reverse-phase column to yield seven dipeptides with ACE inhibitory properties. These dipeptides were identified by sequence analysis and fast atom bombardment mass spectrometry as Ser-Tyr, Gly-Tyr, Phe-Tyr, Asn-Tyr, Ser-Phe, Gly-Phe, and Asn-Phe, with IC50 (the amount of peptide needed to inhibit ACE activity) values of 66.3, 72.1, 3.74, 32.6, 130.2, 277.9, and 46.3 μM, respectively. Each dipeptide was synthesized and its antihypertensive activity was determined after oral administration in spontaneously hypertensive rats. The blood pressure lowering activity of the dipeptides was lower than that of captopril. However, the presence of these dipeptides in garlic suggests that these compounds may, at least in part, be responsible for the observed antihypertensive effect of garlic (or garlic extracts) in animals and humans. Further, long-term use of dietary garlic may have a protective effect against rise in blood pressure.

A peptidic fraction (SP-I) having inhibitory activity against angiotensin I-converting enzyme (ACE) was separated from the peptic digest of protein prepared from the brown alga Hizikia fusiformis by ion-exchange chromatographies and gel filtration. Oral administration of SP-I into spontaneously hypotensive rats at 200 mg/kg resulted in a marked hypotensive effect. Further separation of SP-I by ODS HPLC afforded three active peptides, Gly-Lys-Tyr (IC50; 3.92 mu M), Ser-Val-Tyr (8.12 mu M), and Ser-Lys-Thr-Tyr (11.07 mu M).

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 mu M), Met-Lys-Tyr (7.26 mu M), Ala-Lys-Tyr-Ser-Tyr (1.52 mu M), and Leu-Arg-Tyr (5.06 mu M).

Immunostimulative peptides were isolated from the pepsin digest of soybean by ion exchange, gelfiltration, and reversed-phase high-performance chromatography. The peptides formed blastoids against the splenocytes of C3H/HeN mice. The amino acid sequences of these peptides were: Ala-Glu-Ile-Asn-Met-Pro-Asp-Tyr, Ile-Gln-Gln-Gly-Asn, and Ser-Gly-Phe-Ala-Pro, respectively.

The effect of dietary peptides derived from soybean and casein on the immune responsiveness of Fisher rats has been investigated. The protein efficiency ratio of these diets was similar. The phagocytosis of opsonized sheep red blood cells by alveolar macrophages (AMø) and the mitogenic activity of rats fed both peptides, particularly soybean peptide, were found to be significantly greater than those of rats fed the corresponding proteins of soybean and casein. Furthermore, in the pair-feeding experiment using both peptides, a comparable enhancement of the phagocytic activity of AMø was seen in the rats given the peptides, but little difference in the natural killer cell activity was noted among rats fed each diet. It was suggested that immune activating factors would be presented in the soybean peptide.