Antioxidant and angiotensin I converting enzyme inhibitory activity of Bambusae caulis in Liquamen

Bambusae caulis in Liquamen (BCL) is a nutritious liquid that can be extracted from heat-treated bamboo stems. It is also an important herbal medicine in Asia. In this study, antioxidant and angiotensin I converting enzyme (ACE) inhibitory activity of BCL were investigated. BCL significantly quenched DPPH and peroxyl radicals measured by electron spin resonance (ESR) spectroscopy, while IC₅₀ values were 79.85 and 28.85 μg/ml, respectively. The ability of BCL to inhibit the oxidative damage of DNA was assessed in vitro by measuring the conversion of supercoiled pBR322 plasmid DNA to the open circular form. It was found that BCL significantly protected hydroxyl radical-induced DNA damage in a dose-dependant manner, while also inhibiting apoptosis in hydrogen peroxide-induced PC-12 cells and angiotensin I converting enzyme (ACE) activity. These findings suggest that BCL may be a beneficial ingredient in functional foods and/or pharmaceuticals.     

Identification of angiotensin converting enzyme inhibitory and antioxidant peptides in a whey protein concentrate hydrolysate produced at semi‐pilot scale

Antioxidant and angiotensin converting enzyme (ACE) inhibitory peptides were identified in a 5 kDa ultrafiltration permeate of a whey protein hydrolysate generated at semi‐pilot scale. Further laboratory scale ultrafiltration of this 5 kDa permeate resulted in a 0.65 kDa permeate with antioxidant, (1.11 ± 0.074 μmol TE per mg dry weight, oxygen radical absorbance capacity, ORAC) and ACE inhibitory (ACE IC₅₀ 0.215 ± 0.043 mg mL^?1) activities. Semi‐preparative (SP) reverse phase high‐performance liquid chromatography (RP‐HPLC) of the 0.65 kDa permeate resulted in a fraction (SP_F3) with a 4.4‐fold increase in ORAC activity (4.83 ± 0.45 μmol TE mg dry weight) and a 1.3‐fold increase in ACE inhibitory activity (84.35 ± 1.36% inhibition when assayed at 0.28 mg mL^?1). Peptides within SP_F3 were identified using UPLC‐ESI‐MS/MS. Met‐Pro‐Ile had the highest ORAC activity (205.75 ± 12.08 μmol TE per mmol peptide) while Met‐Ala‐Ala and Val‐Ala‐Gly‐Thr had the highest ACE inhibitory activities (IC₅₀:515.50 ± 1.11 and 610.30 ± 2.41 μm , respectively).     

Antioxidant enzyme activities and antioxidant capacity in longissimus muscle from bulls fed diets rich in polyunsaturated fatty acids

The effect of a treatment diet composed of grass silage and concentrate including rapeseed (with/without feeding restriction) was compared with a control diet of maize silage/grass silage (70:30) and concentrate including soybean, on the antioxidant enzyme activities of fresh longissimus muscle from German Simmental bulls. Additionally, the effect of diet on antioxidant capacity (AOC) of hydrophilic and lipophilic antioxidants was evaluated in fresh and stored beef muscle using the FRAP-ferric reducing ability and TEAC – Trolox-equivalent antioxidant capacity assays at different reaction times. Catalase and superoxide dismutase activities were significantly higher in the treatment diet groups, and glutathione peroxidase activity was not different. AOC was not affected by the diet. However, storage affected the values of FRAP and TEAC assays, and the results were time-depending. 30 min were found like a minimum reaction time for both assays. Generally, AOC values of the hydrophilic antioxidants were significantly higher than lipophilic values.     

Antioxidant,enzyme inhibitory and antiproliferative activity of polyphenolic‐rich fraction of commercial dry ginger powder

Polyphenolic‐rich fraction obtained from locally produced dry ginger powder in Brahmaputra valley, India, and commercially available dry ginger (Zingiber officinale) rhizome powder consisted of [6]‐gingerol (41.9%), [6]‐shogaol (24.3%), 1‐dehydro‐6‐gingerdione (8.6%), [8]‐gingerol (7.2%), [10]‐gingerol (5.1%), [6]‐paradol (5.9%) and [4]‐gingerol (3.6%). Traces of methyl‐[6]‐gingerol and methyl‐[8]‐gingerol (both at 1.8%) were also detected. The fraction exhibited high antioxidant capacity [total phenolics (TP), ferric reducing antioxidant power (FRAP), oxygen radical absorbance capacity (ORAC) and cellular antioxidant activity (CAA assay)], effectively inhibited isolated digestive enzymes (α‐glucosidase, pancreatic lipase and angiotensin converting enzyme) and inhibited the proliferation of colon (HT29; IC₅₀ of 1.06 ± 0.02 mg mL^?1) and gastric (AGS IC₅₀ of 1.29 ± 0.03 mg mL^?1) adenocarcinoma cells, without affecting the proliferation of their nontransformed counterparts (IC₅₀ > 2.0 mg mL^?1). This case study demonstrates that locally produced and commercially available dry ginger powder from Brahmaputra valley, India, retains numerous food components that may enhance human health.     

Effect of angiotensin I converting enzyme inhibitory peptide purified from skate skin hydrolysate

Our objective was to evaluate the angiotensin I converting enzyme (ACE) inhibitory activity of skate skin protein hydrolysates and its corresponding fractions. The skate skin hydrolysates were obtained by enzymatic hydrolysis using alcalase, α-chymotrypsin, neutrase, pepsin, papain, and trypsin. Amongst the six hydrolysates, the α-chymotrypsin hydrolysate had the highest ACE inhibitory activity compared to other hydrolysates. The amino acid sequences of the purified peptides were identified to be Pro–Gly–Pro–Leu–Gly–Leu–Thr–Gly–Pro (975.38 Da), and Gln–Leu–Gly–Phe–Leu–Gly–Pro–Arg (874.45 Da). The purified peptides from skate skin had an IC₅₀ value of 95 μM and 148 μM, respectively, and the Lineweaver–Burk plots suggest that they act as a non-competitive inhibitor against ACE. Our study suggested that novel ACE inhibitory peptides derived from skate skin protein may be beneficial as anti-hypertension compounds in functional foods.     

Purification and characterisation of angiotensin I converting enzyme inhibitory peptides from lysozyme hydrolysates

Hen egg white lysozyme (HEWL) was hydrolysed with trypsin, papain and a combination of the two. The prepared hydrolysates exhibited ACE inhibitory activity. The hydrolysates were fractionated using ultrafiltration and reverse phase-high performance liquid chromatography (RP-HPLC). Three fractions, which showed the highest ACE inhibitory activities, were purified by RP-HPLC. They were the F₇ (from papain-trypsin hydrolysate), F₈ (from papain hydrolysate) and F₃ (from trypsin hydrolysate) fractions. The IC₅₀ values were 0.03, 0.155 and 0.23 mg/ml for F₇, F₈ and F₃, respectively. The F₇ fraction was the most potent ACE inhibitor peptide, and was composed of 12 amino acids, Phe-Glu-Ser-Asn-Phe-Asn-Thr-Gln-Ala-Thr-Asn-Arg (MW: 1428.6 Da). Lineweaver-Burk plots suggest that the F₇ peptide acts as an uncompetitive inhibitor against ACE. The kinetic parameters (K_m, V_max, and K_i) for the F₇ peptide were measured and compared to the control.     

Enhancement of angiotensin I converting enzyme inhibitory activity and improvement of the emulsifying and foaming properties of corn gluten hydrolysate using ultrafiltration membranes

In this study, we attempted to enhance angiotensin I converting enzyme (ACE) inhibitory activity using an ultrafiltration (UF) membrane and to improve the emulsifying and foaming properties of fractions. ACE inhibitory activities of the corn gluten hydrolysate prepared by Flavourzyme had the same trend as protein contents and the IC₅₀ value was 0.18 mg solid after 8 h hydrolysis. The hydrolysate was separated by using two kinds of UF membrane (10 and 5 kDa cut-off membranes) and three fractions, >10 kDa, 5–10 kDa, and <5 kDa, were obtained. The yields of these three fractions were 58.3%, 27.2% and 14.5% as dry matter, respectively. The IC₅₀ value (the concentration of ACE inhibitor required to inhibit 50% of the ACE activity under specific conditions) of the <5 kDa fraction was 0.05 mg solid and was approximately fourfold that of the original, 5–10, and >10 kDa fractions. The average hydrophobicity of the <5 kDa fraction was slightly lower than that of the others according to the hydrophobicity index of Nozaki and Tanford, but according to the Krigbaum and Meirovitch index, that of the <5 kDa fraction was slightly higher than those of the others, showing there might be no significant differences among the fractions. The emulsifying activity and emulsion stability in the <5 kDa fraction was higher than those in the other fractions. Two fractions, <5 kDa and >10 kDa, showed poor foaming capacity at below pH 6.0. The foam stabilities of two fractions (<5 kDa and >10 kDa) increased with increasing pH, but that of 5–10 kDa decreased with increasing pH. The UF treatment was an effective method for the enhancement of ACE inhibitory activity with improvement of functional properties.     

Antioxidant and angiotensin converting enzyme (ACE) inhibitory activities of cocoa (Theobroma cacao L.) autolysates

The present study investigated antioxidant and angiotensin converting enzyme (ACE) inhibitory activities of cocoa autolysates. After removal of cocoa fat, alkaloids and polyphenols, the remaining proteinous powder was autolyzed at pH 3.5 and 5.2. At similar concentrations, autolysates produced at pH 3.5 indicated the highest reducing power and ACE inhibition activity. However, those generated at pH 5.2 showed the highest antioxidant activity based on ??-carotene bleaching assay. The results displayed a dose-dependent trend. Based on amino acids composition, slight differences were detected between autolysates, and as it was found, they were rich in hydrophobic amino acids. Qualitative and quantitative tests were applied to assure that the results from the assays were not due to the polyphenols of cocoa autolysates. Based on the results no polyphenols could be detected from cocoa autolysates. It can be indicated that among other useful substances of cocoa, its peptides and amino acids could contribute to its health-promoting properties. Furthermore, these bioactive substances can be exploited into functional foods or used as a source of nutraceuticals.     

Studies on the inhibitory effect of Graptopetalum paraguayense E. Walther extracts on the angiotensin converting enzyme

This study was aimed at evaluating the kinetic properties and capacities of water (GWE), 50% ethanolic (GE50) and 95% ethanolic (GE95) extracts from Graptopetalum paraguayense for the potential to inhibit angiotensin converting enzyme (ACE). The results showed that GWE, GE50 and GE95 showed potent inhibitory effects on ACE. It was found that the ACE inhibitory activities of all the tested extracts increased with the increase of their concentrations. In addition, the ACE inhibition of the tested extracts of G. paraguayense were significantly reduced after the addition of 1.5 mM ZnCl₂, suggesting the inhibitory action of the extracts may have resulted from the chelation of the ACE zinc cofactor. The inhibition kinetics, analyzed by Lineweaver–Burk plots, revealed that G. paraguayense extracts showed a mixed-type inhibition. A comparison of the 50% inhibition concentration (IC₅₀) and K_i values showed that the ethanolic extracts, including GE50 and GE95 exhibited the more effective ACE inhibitory activity than the water extracts of G. paraguayense.     

Free radical scavenging capacity and antioxidant enzyme activity in deerberry (Vaccinium stamineum L.)

Fruit from three genotypes (‘B-76’, ‘B-59’ and ‘SHF-3A’) of deerberry [Vaccinium stamineum L.] were evaluated for fruit quality, total anthocyanin and phenolic contents, antioxidants, antioxidant capacity, and antioxidant enzyme activity. The fruit soluble solids, titratable acids, total anthocyanins, and total phenolic contents varied with genotypes. Cyanidin 3-galactoside and cyanidin 3-arabinoside were the two predominant anthocyanins. Resveratrol was also found in deerberries. Among the three genotypes, ‘B-76’ had higher amount of anthocyanins, phenolic compounds and resveratrol than ‘B-59’ and ‘SHF-3A’. Deerberries contained potent free radical scavenging activities for 2,2-Di (4-tert-octylphenyl)-1-picrylhydrazyl (DPPH), 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS⁺), peroxyl radical (ROO), superoxide radicals (), hydrogen peroxide (H₂O₂), hydroxyl radicals (OH), and singlet oxygen (¹O₂) radicals and also had high activities of antioxidant enzymes including glutathione-peroxidase (GSH-POD), glutathione reductase (GR), superoxide dismutase (SOD), ascorbate peroxidase (AsA-POD), guaiacol peroxidase (G-POD), monodehydroascorbate radical reductase (MDAR), dehydroascorbate reductase (DHAR), glutathione reductase (GR)] and non-enzyme antioxidants [ascorbic acid (ASA) and reduced glutathione (GSH)]. Antioxidant capacities were highly correlated to antioxidant enzymes activities. Among the three genotypes, ‘B-76’ had the highest level of antioxidants and antioxidant enzyme activity.     

The antioxidant, angiotensin converting enzyme inhibition activity, and phenolic compounds of bamboo shoot extracts

This study was undertaken to evaluate the functional properties of two of the most popular species of edible bamboo shoots in Korea (Phyllostachys pubescens and Phyllostachys nigra). Powdered bamboo shoots were extracted with methanol and an aqueous suspension of the obtained methanol extract was partitioned successively with chloroform, ethyl acetate, and butanol, leaving a residual water extract. All obtained extracts were evaluated for their antioxidant capacity and antimicrobial activity, angiotensin converting enzyme (ACE) inhibition activity, and ascorbic acid and phenolic compound content. Methanol and water fractions showed a particularly high ascorbic acid contents. The ethyl acetate fraction contained a high concentration of phenolic compounds. Among all extracts, the ethyl acetate and butanol fractions showed particularly high antioxidant activity. Methanol extract had a significantly higher ACE inhibitory activity than other extracts. None of the extracts inhibited the tested bacteria.     

Effect of enzyme type and hydrolysis conditions on the in vitro angiotensin I‐converting enzyme inhibitory activity and ash content of hydrolysed whey protein isolate

Removal of salts from protein hydrolysate mixture on large scale is very difficult and relatively inefficient. Selecting practical proteinase system and hydrolysis conditions for the production of whey protein isolate (WPI) enzymatic hydrolysates with high angiotensin I‐converting enzyme (ACE) inhibitory activity and low ash content is very useful. The effect of alcalase, neutrase, trypsin and their combined system, i.e. alcalase‐neutrase and trypsin‐neutrase, under two different hydrolysis conditions, i.e. pH‐controlled and pH‐spontaneous drop, on the formation of ACE‐inhibitory peptides and the characteristics of WPI hydrolysate was investigated. Results showed that the ACE‐inhibitory activity of WPI hydrolysate obtained with alcalase was significantly higher than that of its trypsin or neutrase hydrolysate obtained at the same hydrolysis time by both pH‐controlled and pH‐spontaneous drop method (P < 0.05). The WPI hydrolysate obtained after 3 h incubation with alcalase plus 2 h with neutrase under pH‐spontaneous drop condition possessed the highest ACE‐inhibitory activity of 54.30% and the lowest ash content of 2.95%. This is practical as a functional ingredient in the food industry because of its high ACE‐inhibitory capability, commercial availability in large supply of alcalase and neutrase and no needing for additional desalting process.     

Angiotensin converting enzyme inhibitory activity of proteolytic digests of peanut (Arachis hypogaea L.) flour

Defatted raw and roasted peanut flour were hydrolyzed with alcalase or sequentially with pepsin and pancreatin, and then the hydrolyzates were fractionated by RP-HPLC and tested for hypotensive potential. This research revealed that proteolytic peanut digests have an inhibitory effect on the activity of angiotensin converting enzyme (ACE). Three fractions from the hydrophobic end of the chromatogram of each hydrolyzate were the most potent for inhibiting ACE activity in comparison to seven other fractions. These potentially potent fractions were then assayed for IC₅₀. Fractions from the alcalase digestion of raw peanut exhibited IC₅₀ values of 8.7-122 μg/ml, and those from roasted flour exhibited values of 12-235 μg/ml. IC₅₀ values of 7.9-65.9 μg/ml, and 11-36 μg/ml for raw and roasted peanut, respectively, from the pepsin-pancreatin system were observed. These values compare to the IC₅₀ value of 0.36 μg/ml of a known commercial ACE inhibitor (pGlu-Trp-Pro-Arg-Pro-Gln-Ile-Pro-Pro).     

Fermentation with Bacillus spp. as a bioprocess to enhance anthocyanin content,the angiotensin converting enzyme inhibitory effect,and the reducing activity of black soybeans

Food possessing anthocyanins, angiotensin converting enzyme (ACE) inhibitory activity or reducing activity show beneficial effect on human health. To develop healthy food, black soybeans were fermented with either Bacillus subtilis BCRC 14715 or Bacillus sp. CN11, or a mixture of both Bacillus spp. in the present study. The anthocyanin content, the ACE inhibitory activity and the reducing power of the fermented black soybean were then examined. It was found that the ACE inhibitory activity of the extracts of bean and viscous material from the fermented black soybeans varied with extraction solvents and starter organism, yet increased as the fermentation period was extended, regardless of starter organism. After 18 h of fermentation, the water extract of bean showed less ACE inhibitory activity than did the respective 80% ethanol extract. While the water extract of viscous material showed a higher ACE inhibitory activity than the respective ethanol extract. With respect to extraction yield, it was found that the ACE inhibitor in the fermented black soybean could be extracted more efficiently with water than 80% ethanol. Fermentation with B. subtilis BCRC 14715 was also found to increase the anthocyanin content of black soybean and the reducing activity of the extracts. Finally, the 80% ethanol extract showed a higher reducing activity than the water extract.     

Chymotryptic hydrolysates of α-kafirin,the storage protein of sorghum (Sorghum bicolor) exhibited angiotensin converting enzyme inhibitory activity

Kafirin is the main storage protein (prolamin) in sorghum grains. α-Kafirin, the alcohol soluble fraction, was isolated from sorghum flour. Treatment of α-kafirin with chymotrypsin yielded a hydrolysate which on fractionation, using Sephadex G-25 column, yielded four fractions with significant angiotensin converting enzyme (ACE) inhibitory activity in vitro. The IC₅₀ values of these fractions ranged from 1.3 to 24.3 μg/ml. Two of the fractions were found to be competitively inhibiting the enzyme, while two other fractions were non-competitive inhibitors. These results demonstrate that chymotryptic hydrolysates of sorghum prolamin could serve as a good source of peptides with angiotensin I converting enzyme inhibitory activity.     

Hypotensive effect of a sweetpotato protein digest in spontaneously hypertensive rats and purification of angiotensin I-converting enzyme inhibitory peptides

We have investigated angiotensin I-converting enzyme (ACE) inhibitory activity in an enzyme digest of sweetpotato protein, the antihypertensive effect of the digest in spontaneously hypertensive rats (SHR), and the identification of an ACE inhibitory peptide. Protein was prepared from squeezed juice of sweetpotato by isoelectric focusing precipitation. Three kinds of proteases were selected for effective protein digestion. The digest, sweetpotato peptide (SPP), exhibited strong ACE inhibitory activity (IC₅₀: 18.2 μg/ml). SPP was orally administered by gavage to SHR at a dose of 100 mg/kg or 500 mg/kg. The systolic blood pressure and the diastolic blood pressure were measured at 0 (before administration), 2, 4, 8, and 24 h after administration. A dose-dependent decrease in systolic blood pressure in SHR was observed after oral administration of SPP. Significant differences between SPP-administered rats and control rats were observed 4 and 8 h after administration in the 500 mg/kg-administered group and 8 h after administration in the 100 mg/kg-administered group. Diastolic blood pressure also decreased in the SPP-administered groups, although the difference between SPP-administered rats and control rats was not significant. These results suggest that SPP may be useful in the prevention or treatment of hypertension. Peptides with ACE inhibitory activity were purified from SPP by absorption chromatography and preparative HPLC using an ODS column. The amino acid sequences of isolated peptides were I-T-P, I-I-P, G-Q-Y and S-T-Y-Q-T; their ACE inhibitory activities (IC₅₀) were 9.5 μM, 80.8 μM, 52.3 μM and 300.4 μM, respectively. In conclusion, I-T-P is a novel, strong ACE inhibitory peptide.     

Isolation and characterisation of a novel angiotensin I-converting enzyme (ACE) inhibitory peptide from the algae protein waste

A hendeca-peptide with angiotensin I-converting enzyme (ACE) inhibitory activity was isolated from the pepsin hydrolysate of algae protein waste, a mass-produced industrial by-product of an algae essence from microalgae, Chlorella vulgaris. Edman degradation revealed its amino acid sequence to be Val-Glu-Cys-Tyr-Gly-Pro-Asn-Arg-Pro-Gln-Phe. Inhibitory kinetics revealed a non-competitive binding mode with IC₅₀ value against ACE of 29.6 μM, suggesting a potent amount of ACE inhibitory activity compared with other peptides from the microalgae protein hydrolysates which have a reported range between 11.4 and 315.3 μM. In addition, the purified hendeca-peptide completely retained its ACE inhibitory activity at a pH range of 2–10, temperatures of 40–100 °C, as well as after treatments in vitro by a gastrointestinal enzyme, thus indicating its heat- and pH-stability. The combination of the biochemical properties of this isolated hendeca-peptide and a cheap algae protein resource make an attractive alternative for producing a high value product for blood pressure regulation as well as water and fluid balance.     

Phenolic content and antioxidant capacity of supercritical carbon dioxide-treated and air-classified oat bran concentrate microwave-irradiated in water or ethanol at varying temperatures

Oat bran concentrate (OBC) was defatted with supercritical carbon dioxide (SCD), then microwave-irradiated (MI) at 50, 100 or 150 °C for 10 min in water, 50% or 100% ethanol, and extract pH, soluble solids, phenolic content (PC) and antioxidant capacity (AC) were analysed. OBC was air-classified into five fractions and MI in water at 150 °C. OBC without SCD and microwave irradiation was extracted at 22 °C. Most effective temperature during microwave irradiation for maximising extraction of PC and AC was 150 °C. Defatted OBC in 50% ethanol and MI at 150 °C extracted greatest PC and AC. SCD treatment slightly reduced PC and AC. OBC extracted in water or 50% ethanol at 22 °C without microwave irradiation had similar PC and AC than OBC MI at 150 °C, but much higher levels were observed for latter heat treatment using absolute ethanol. Air-classification shows potential to enhance PC and AC.     

Lamiaceae often used in Portuguese folk medicine as a source of powerful antioxidants: Vitamins and phenolics

Three Lamiaceae often used in Portuguese folk medicine: Ground ivy (Glechoma hederaceae L.), oregano (Origanum vulgare subsp. virens (Hoffmanns. & Link) Ietswaart) and mastic thyme (Thymus mastichina L.), revealed to be good sources of powerful antioxidants such as vitamins (ascorbic acid and tocopherols) and phenolics. The HPLC methodology developed for tocopherols analysis proved to be, after validation assays, sensitive and accurate. Ground ivy showed the highest levels of vitamins: ascorbic acid (168 ± 2 μg/g dry weight) and tocopherols (3692 ± 57 μg/g dry weight). The phenolics extraction was optimized using mastic tyme, and different conditions (water and ethanol:water 50% v/v, 30 min at 25 °C and boiling temperature; ethanol and methanol, 24 h at 25 °C). The best methodology (25 °C, 50 ml of methanol, 24 h) was further applied to the other Lamiaceae. Oregano proved to have the highest radical scavenging and lipid peroxidation inhibition capacity. Particularly, the very low EC₅₀ value (0.01 mg/ml) obtained for TBARS inhibition in brain homogenates is very promising, considering that brain is highly sensitive to oxidative damage. Significantly negative linear correlations were observed between phenolics, including flavonoids, and antioxidant activity EC₅₀ values of the three Lamiaceae.     

The variation of superoxide dismutase (SOD) and xanthine oxidase (XO) activities in milk using an improved method to quantitate SOD activity

An improved method for determination of superoxide dismutase (SOD) in milk has been developed. The interference of endogenously occurring xanthine oxidase (XO) has been subs'antially reduced by addition of an ultrafiltration step, which removed 61 ± 10 (mean ± SD) % of the XO activity. This method was used to determine the SOD activity in milk serum from 15 Swedish Red and White (SRW) cows and 18 Swedish Friesian (SF) cows at various stages of lactation. The XO activity in raw milk was also determined. The milk from these cows had a mean SOD activity of 0.83 ± 1.14 U ml^?1 milk serum and a mean XO activity of 49 ± 22 mU ml^?1 raw milk (n = 127). A difference between breeds could be noted in XO activity, ie milk from SF cows had significantly (P < 0.05) higher mean XO levels compared with milk from SRW cows, 54 ± 23 mU ml^?1 than 44 ± 21 mU ml^?1. A significantly increased level of XO activity in milk from SRW cows during the lactation was found. No significant effect of breed or stage of lactation on SOD activity could be detected. Individual cows with high and low milk SOD levels during the entire lactation have been identified.