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David D Kitts

Publications and source records attributed to David D Kitts.

At least 19 recordsLinked to original sources
PubMed2006

Chemistry and genotoxicity of caramelized sucrose.

Caramelization of a 1% sucrose solution at 180 degrees C accompanied characteristic changes in pH, Mr, UV-absorbance, and fluorescence values as well as increased reducing power activity after 40-60 min. Similar changes occurred to sucrose heated at 150 degrees C, after 150-240 min. Bioactivity of caramelized sucrose samples was tested for mutagenic activity, using Salmonella typhimurium strains TA-98 and TA-100, respectively, as well as the Saccharomyces D7 yeast strain for mitotic recombination and Chinese hamster ovary cells (CHO) to assess clastogenicity. Caramelized sucrose expressed no mutagenicity in the TA-98 strain, but gave positive (p < 0.05) results with the TA-100, base-pair substitution strain. Similarly, mitotic recombination in the Saccharomyces D7 yeast strain and clastogenic activity in CHO cells were induced when exposed to caramelized sucrose. In the all cases, preincubation with S-9 reduced (p < 0.05) the mutagenic activities of caramelized sucrose. Fractionation of the caramelized sucrose into volatile and nonvolatile compounds was performed and tested for clastogenicity using CHO cells. Volatile components contributed approximately 10% to total clastogenicity, which was enhanced by the presence of S-9. Nonvolatile components recovered, consisting of relatively lower Mr, gave highest (p < 0.05) clastogenic activity, denoting that higher Mr caramel colors are relatively free of this property.

Animals↗
PubMed2005

Biological and chemical assessment of antioxidant activity of sugar-lysine model maillard reaction products.

The antioxidant activity of Maillard reaction products (MRPs) is often associated with increased stability and shelf life of food systems vulnerable to oxidation reactions. In this study, nondialyzed, high-molecular weight (HMW = >3500 Da) MRPs were recovered from three model sugar-lysine (glucose-lysine, Glc-Lys; fructose-lysine, Fru-Lys; and ribose-lysine, Rib-Lys) reactions, heated at 121 degrees C for one hour. Samples were characterized by UV and fluorescence spectra and assessed for antioxidant activity using both standard chemical methods (1,1-diphenyl-2-picryl-hydrazyl [DPPH] and oxygen radical absorbing capacity [ORAC]). In addition, biochemical (e.g., cell culture for intracellular oxidation in RAW264.7 cells and protection against metal ion-induced cytotoxicity in C3H/10T1/2 mouse embryo fibroblast cells) assays were used. Patterns of change for fluorescence and multiple colorimetric parameters corresponded to the recovery yield of HMW MRPs and indicated that Rib was more (P < 0.05) reactive than Glc, which in turn was greater (P < 0.05) than Fru. These characteristics of rate of browning did not parallel the significant (P < 0.05) antioxidant activity noted for different sugar-derived HMW MRPs to scavenge DPPH radical, or exhibit total antioxidant activity using the ORAC (e.g., 800-1000 micromol Trolox/gm MRP) method. Antioxidant activity of Glc-, Fru-, and Rib-Lys HMW-MRPs (50 microg/mL) produced protection (P < 0.05) against both H2O2- and AAPH-induced intracellular oxidation reactions in cultured RAW 264.7 cells. Metal chelating activity of all three sugar-derived HMW MRPs (0.01% w/v) was attributed to similar protection (P < 0.05) against Fe2+ and Cu2+-induced cytotoxicity in cultured mouse embryonic fibroblasts. The reducing activity of all three HMW-MRPs indicated the potential for prooxidant activity that could explain enhanced cytotoxicity of Fe3+ in cultured cells.

Animals↗
PubMed2004

Antioxidant activity of sugar-lysine Maillard reaction products in cell free and cell culture systems.

Model Maillard reaction (MR) products (MRPs) employing lysine with an aldohexose (e.g., glucose), ketohexose (e.g., fructose), and aldopentose (e.g., ribose) sugars were generated (e.g., pH 9.0; over 2h heating at 120 degrees ) and fractionated with ethanol into low (LMW) and high (HMW) molecular weight fractions. Characteristically different temporal patterns of fluorescence and ultraviolet/visible absorption spectra were obtained from the three distinct sugar-lysine MRPs, and corresponded to different yields of total and dialyzable carbon, indicating that relative reaction rates and degree of polymerization favored the Rib-Lys MRP, compared to Glu-Lys and Fru-Lys MRPs, respectively (p<0.05). Further characterization of antioxidant activity of the sugar specific-lysine MRPs in chemical (e.g., hydrophobic (1,1,-diphenyl-2-picryl-hydrazyl radical (DPPH) and hydrophilic (Fenton reaction-induced hydroxyl radical) in vitro scavenging assays showed that Rib-Lys HMW MRPs had the highest (p<0.05) affinity to scavenge free radicals. All sugar-Lys MRPs, however, displayed similar protection of cultured Caco-2 cells from exposure to H(2)O(2)-, 2,2'-azobis-(2-amidinopropane) dihydrochloride (AAPH)-, ferrous (Fe(2+))-, and cupric (Cu(2+))-induced cytotoxicity, evaluated both from redox (e.g., MTT response) and cell membrane integrity (e.g., LDH secretion). HMW-MRPs exhibited stronger (p<0.05) antioxidant activity to scavenge hydroxyl and DPPH radicals, and a greater (p<0.05) protective effect against both Fe(2+)- and Cu(2+)-induced cytotoxicity in Caco-2 cells than corresponding LMW-MRPs. We conclude that HMW MRPs possess affective antioxidant protection against oxidizable substrates; however, the degree of polymerization of this product, characteristic to the source of monosaccharide used in the reaction, is not a distinguishable factor for this bioactivity.

Antioxidants↗
PubMed2004

Redox-related cytotoxic responses to different casein glycation products in Caco-2 and int-407 cells.

Sugar-casein glycation products (GPs) were generated by Maillard reaction (MR) with different monosaccharide sources [e.g., glucose (Glc), fructose (Fru), and ribose (Rib)] and prolonged heating (e.g., 27 days at 55 degrees C) to produce Maillard reaction products (MRPs) that varied in opponent (L, a, b) color measurement and changes in pH, available lysine, and amino-sugar ratio. Theses results signified different rates of three sugar and casein glycation. Sugar-casein GPs from aldohexose, ketohexose, and aldopentose sugar sources were recovered on day 18 of heating and compared for bioactive properties using human embryonic intestinal cell (Int-407) and adenocarcinoma cell (Caco-2) lines. Glu- and Fru-casein GPs produced significant (p < 0.05) decreases in antioxidant superoxide dismutase (SOD), glutathione peroxidase, and glutathione reductase enzyme activities in the Int-407 cell line, whereas no effect on antioxidant enzymes was obtained from Rib-casein GP. Moreover, the Caco-2 cell antioxidant enzyme status was not affected by the presence of sugar-casein GPs, regardless of sugar source. The reduction in antioxidant enzyme activity of Int-407 cells by Glu and Fru- casein GPs corresponded to a significant (p < 0.05) reduction in Int-407 cell viability. In contrast, no change in Caco-2 cell viability was observed with sugar-casein GP. This finding demonstrates that the noted variable cytotoxic, sugar specific effects of casein GP were related to reductions in critical antioxidant enzyme activities. Moreover, the source of intestinal cell line was an important factor to show the effect of sugar-casein GPs on redox-related cytotoxicity.

Antioxidants↗
PubMed2004

Mechanistic studies on protopanaxadiol, Rh2, and ginseng (Panax quinquefolius) extract induced cytotoxicity in intestinal Caco-2 cells.

Certain ginsenosides, also known as triterpene glycosides, have been recently reported to have a characteristic effect on cultured intestinal and leukemia cell growth. Ginsenoside aglycones 20(S)-protopanaxadiol (PD), 20(S)-protopanaxatriol (PT), and ginsenoside Rh2 have been identified as having a strong effect on reducing cell viability. Furthermore, ginsenoside Rh2 is thought to be a rare ginsenoside not found in all ginseng products. Rather, Rh2 has been recently reported to be a breakdown product of thermal processing of North American ginseng. In this study, pure ginsenosides PD, PT, Rh2 standards and an enriched Rh2 fraction derived from ginseng leaf were tested in cultured Caco-2 cells for relative cytotoxic potency. PD and Rh2 LC50 were similar after 24 to 72 h, whereas a drop in PT LC50 occurred later at 48 and 72 h. Furthermore, PD and Rh2 affected membrane integrity as indicated by LDH secretion earlier than PT and the enriched Rh2 fraction (P < or = 0.05). Ginsenoside Rh2 showed the greatest (P < or = 0.05) build up of necrotic cells (18.3 +/- 0.1%) at the respective LC50 after 24 h and PD (21.3 +/- 0.3%) showed the largest effect after 44 h of exposure. The effect on apoptotic cells at 44 h of treatment were significantly different (P < or = 0.05) for Rh2 (21 +/- 0.4%), PD (14.6 +/- 0.1%), enriched Rh2 leaf fraction (9.9 +/- 0.6%), and PT (2.3 +/- 0.1%) treatments. Caco-2 caspase-3 activity was different between ginsenoside exposure; Rh2 (10.6 +/- 0.3 nM pNA) had the greatest (P < or = 0.05) activity followed by the enriched Rh2 leaf fraction (8.3 +/- 0.2 nM pNA), PT (7.3 +/- 0.3 nM pNA). The PD (4.8 +/- 0.04 nM pNA) treatment was similar to untreated cells (4.3 +/- 0.05 nM pNA) in caspase-3 activity. These results show variable bioactive response in cultured intestinal cell to specific ginsenosides and an enriched Rh2 North American ginseng extract which may be explained on basis of hydrophobic/hydrophilic balance.

Annexin A5↗
PubMed2004

Chemical characterization of different sugar-casein Maillard reaction products and protective effects on chemical-induced cytotoxicity of Caco-2 cells.

This study examined the chemical modification of casein with three monosaccharides [e.g., glucose (Glc), fructose (fru), and ribose (Rib)], following prolonged gentle heating to product the Maillard reaction (MR). Changes in chemical modification of casein in different sugar-casein MR was monitored using temporal patters of change in fluorescence development, UV absorbance and casein molecular mass, which was studied using SDS-PAGE and MALDI-TOF mass spectrometry. Rib-casein MRP exhibited significantly (p<0.05) advanced fluorescence development at three days, compared to Glc- and Fru-casein MRPs, which corresponded to marked (p<0.05) differences in greater UV absorption of Rib-casein MRPs later on after 15 days of processing. These results were associated with the generation of different high molecular weight complexes generated from the Rib-casein MR, compared to Glu- and Fru-casein MRPs, respectively. Antioxidant activity of all three sugar-modified caseins was also assessed when cultured with Caco-2 cells. A significant, but similar protective effect against 2,2'-azobis-(2-amidinopropane)dihydrochloride (AAPH) radical-induced cytotoxicity, and ferrous- and cupric-induced toxicity of Caco-2 cells was observed for all three sugar-casein MRPs. However, these protective effects were not significantly different among the sugar-modified caseins and native casein. The results suggest that protection of Caco-2 cells from free radical-ferrous- and cupric-induced cytotoxicity by casein was not altered by modification by MR, regardless of source of monosaccharide involved in the reaction.

Amidines↗
PubMed2004

Generation of ginsenosides Rg3 and Rh2 from North American ginseng.

Rg3 and Rh2 ginsenosides are primarily found in Korean red ginseng root (Panax ginseng C.A. Meyer) and valued for their bioactive properties. We quantified both Rh2 and Rg3 ginseng leaf and Rg3 from root extracts derived from North American ginseng (Panax quinquefolius). Quantification was obtained by application of HPLC with ion fragments detected using ESI-MS. Ginseng leaf contained 11.3+/-0.5 mg/g Rh2 and 7.5+/-0.9 mg/g Rg3 in concentrated extracts compared to 10.6+/-0.4 mg/g Rg3 in ginseng root. No detectable Rh2 was found in root extracts by HPLC, although it was detectable by ESI-MS analysis. Ginsenosides Rg3 and Rh2 were detected following hot water reflux extraction, but not from tissues extracted with 80% aqueous ethanol at room temperature. Therefore ginsenosides Rg3 and Rh2 are not naturally present in North American ginseng, but are products of a thermal process. Using ESI-MS analysis, it was found that formation of Rg3 and Rh2, among other compounds, were a function of heating time and were breakdown products of the more abundant ginsenosides Rb1 and Rc. Our findings that heat processed North American ginseng leaf is an excellent source of Rh2 ginsenoside is an important discovery considering that ginseng leaf material is obtainable throughout the entire plant cycle for recovery of valuable ginsenosides for pharmaceutical use.

Chromatography, High Pressure Liquid↗
PubMed2004

Luteolin and luteolin-7-O-glucoside from dandelion flower suppress iNOS and COX-2 in RAW264.7 cells.

Both reactive oxygen- and nitrogen-derived reactive species play important roles in physiological and pathophysiological conditions. Flavones, luteolin and luteolin-7-O-glucoside along with a rich plant source of both flavones, namely dandelion (Taraxacum officinale) flower extract were studied for antioxidant activity in different in vitro model systems. In this current study, luteolin and luteolin-7-O-glucoside at concentrations lower than 20 microM, significantly (p < 0.05) suppressed the productions of nitric oxide and prostaglandin E2 (PGE2) in bacterial lipopolysaccharide activated-mouse macrophage RAW264.7 cells without introducing cytotoxicity. The inhibitory effects were further attributed to the suppression of both inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) protein expression, and not reduced enzymatic activity. Similar suppression for both inducible enzymes was also found with the presence of dandelion flower extract, specifically, the ethyl acetate fraction of dandelion flower extract which contained 10% luteolin and luteolin-7-O-glucoside.

Animals↗
PubMed2004

Ginsenosides 20(S)-protopanaxadiol and Rh2 reduce cell proliferation and increase sub-G1 cells in two cultured intestinal cell lines, Int-407 and Caco-2.

Ginsenosides derived from 20(S)-protopanaxatriol (PT) and 20(S)-protopanaxadiol (PD) groups had similar characteristic cytotoxic effects on the growth of two intestinal cells lines, Int-407 and Caco-2. Pure Rh2, a ginsenoside structurally related to PD, inhibited intestinal cell growth at greater than twice the concentration of PD, while Rh1, a ginsenoside structurally related to aglycone PT, had no cytotoxic effect. Concentrations causing growth inhibition of 50% of cells (LC50) for the compounds PD, PT, and Rh2 were 23, 26, and 53 microg/mL, respectively, for Int-407 cells. In comparison, the LC50 for PD and PT was determined to be 24 microg/mL, and that for Rh2 was 55 microg/mL in Caco-2 cells. A standardized North American ginseng extract with a known ginsenosides composition did not induce cytotoxicity in either of the intestinal cell lines. Cell cycle analysis showed characteristically different (P = 0.05) effects of ginsenosides PD, Rh2, and PT in both cell lines. Rh2 treatment of Int-407 caused a significantly (P = 0.05) higher production of sub-G1 (apoptotic) cells (35% +/- 1%) compared with untreated cells (14% +/- 0.3%) after 24 h. PD and Rh2 treatments were both significantly (P < 0.05) higher in apoptotic cells than in untreated cells after 48 and 72 h. Similar results were obtained for treatment of Caco-2 cells. Lactate dehydrogenase (LDH) activity in both cell lines was similar for PD and Rh2 and higher (P = 0.05) than for PT treatment at most time periods. These results show a specific structure-function relationship for bioactive ginsenosides in two contrasting intestinal cell types.

Apoptosis↗
PubMed2003

Black rice (Oryza sativa L. indica) pigmented fraction suppresses both reactive oxygen species and nitric oxide in chemical and biological model systems.

Anthocyanins, present in fruits and vegetables as natural colorants, have been well characterized to possess bioactive properties. Anthocyanin components extracted from black rice (Oryza sativa L. indica) separated by gel filtration and identified using LC-MS were cyanidin 3-glucoside and peonidin 3-glucoside. A standardized extract of black rice pigmented fraction (BRE) containing known proportions of cyanidin 3-glucoside and peonidin 3-glucoside exhibited marked antioxidant activities and free radical scavenging capacities in a battery of in vitro model systems. Significant (p < 0.05) prevention of supercoiled DNA strand scission induced by reactive oxygen species (specifically, peroxyl radical and hydroxyl radicals) and suppression of the oxidative modification of human low-density lipoprotein was obtained with BRE. In addition, BRE reduced (p < 0.05) the formation of nitric oxide by suppressing inducible nitric oxide synthase expression in murine macrophage RAW264.7 cells, without introducing cell toxicity. The results of this study show that black rice contains anthocyanin pigments with notable antioxidant and anti-inflammatory properties for potential use in nutraceutical or functional food formulations.

Anthocyanins↗
PubMed2003

Antioxidant, prooxidant, and cytotoxic activities of solvent-fractionated dandelion (Taraxacum officinale) flower extracts in vitro.

This study was conducted to investigate the chemical antioxidant and bioactive properties of the water (WF) and ethyl acetate fractions (EAF) derived from dandelion (Taraxacum officinale) flower extract (DFE). HPLC analysis showed the presence of both luteolin and luteolin 7-glucoside in the DFE, which contributed to noted in vitro antioxidant and Caco-2 cell cytotoxic activities. Both WF and EAF of DFE exhibited free radical scavenging activities in a stable 2,2-diphenyl-1-picrylhydrazyl radical model and reduced the breakage of supercoiled DNA strand induced by both non-site-specific and site-specific hydroxyl radical. Oxidation of structured phosphatidylcholine liposome induced by peroxyl radical was reduced in the presence of both EAF and WF. EAF had greater (p < 0.05) affinity to scavenge peroxyl radical than WF, as measured by the formation of conjugated diene. At low concentration, prooxidant activity of both fractions was observed in Cu(2+)-induced structured liposome and hLDL oxidation models, thus indicating that the reducing power of the DFE had resulted in generation of reactive cuprous ion. However, at high concentrations the EAF did not promote oxidation in the presence of Cu(2+), suggesting that the free radical scavenging activity of this fraction was sufficient to minimize the potential oxidative mechanism attributed to the metal ion reducing activity associated with prooxidant activity.

Antineoplastic Agents↗
PubMed2003

Dietary G-rutin suppresses glycation in tissue proteins of streptozotocin-induced diabetic rats.

The present study focused on examining the efficacy of feeding a rutin-glucose derivative (G-rutin) to inhibit glycation reactions that can occur in muscle, kidney and plasma proteins of diabetic rats. Both thiobarbituric acid-reactive substance levels and protein carbonyl contents in muscle and kidney were significantly (p < 0.05) reduced in streptozotocin-induced diabetic rats fed G-rutin supplemented diet, compared to diabetic rats fed control diet. The N(epsilon)-fructoselysine content in muscle and kidney, a biomarker of early glycation reaction, was markedly (p < 0.05) increased by diabetes, but significantly (p < 0.05) reduced in diabetic rats fed G-rutin. Advanced glycation end-products (AGEs) in serum and kidney protein were measured by immunoblot using anti-AGE antibody, and were also reduced in diabetic rats fed dietary G-rutin. Feeding G-rutin also slightly inhibited aldose reductase activity in these animals. These results demonstrate for the first time that dietary G-rutin consumption can provide potential health benefits that are related to the inhibition of tissue glycation reactions common to diabetes.

Animals↗
PubMed2003

In vitro anti-cancer activities in Caco-2 and HCT-116 cells of recombinant cystatin C prepared by a Pichia expression system.

Caco-2 and HCT-116 cells were used to access growth-inhibition and anti-invasion activity of recombinant cystatin C expressed in Pichia pastoris X33, G12W/H86V. The mutant G12W/H86V prepared by a pilot plant production system showed more than 10% growth inhibition of Caco-2 cells at 0.56-56 nM concentrations. Growth-inhibited cells had lower cathepsin L activity than the control cells that were not treated with the inhibitor. Conversely, the cathepsin B activity was not changed by treatment with G12W/H86V. The in vitro anti-invasion test using HCT-116 cells showed that G12W/H86V suppressed the cell invasion by 15%, while its wild-type cystatin, aspartic protease inhibitor pepstatin A, and matrix metalloproteinase (MMP) inhibitor MMP-2/MMP-9 inhibitor III did not suppress cell invasion. These results indicate that the recombinant cystatin C with higher protease inhibitory activity effectively retards the growth and invasiveness of human colon carcinoma cells.

Antineoplastic Agents, Phytogenic↗
PubMed2003

Dietary (n-3) fat and cholesterol alter tissue antioxidant enzymes and susceptibility to oxidation in SHR and WKY rats.

Previously, 8% fish oil blend diets, compared to butter and soybean oil blend diets, reduced specific antioxidant enzyme activities and tissue susceptibility to in vitro oxidative stress in spontaneously hypertensive (SHR) and Wistar Kyoto (WKY) rats. Moreover, high cholesterol (5.0 g/kg diet) diets protected against in vitro tissue lipid oxidation. In this study, we hypothesized that 160 g fat/kg diet as blends of (n-6) or (n-3) oils and cholesterol would alter antioxidant enzyme activities and thus increase tissue susceptibility to oxidation. The effects of diet blends of saturated (butter, B), (n-6) (soybean oil, SBO) or (n-3) (menhaden oil, MO) oils with cholesterol (0.5 or 5.0 g/kg) on systolic blood pressure (SBP), plasma lipids, antioxidant enzymes and susceptibility to oxidation were examined in SHR and WKY rats. SBP at 13 wk of age was greater (P < 0.001) in SHR than in WKY rats, but was not affected by diets. Plasma cholesterol and triacylglycerols were decreased (P < 0.001) by MO diets. Hepatic glutathione reductase activities were reduced (P < 0.001) in SBO-fed SHR and enhanced in SBO- and MO-fed WKY rats. Glutathione levels were reduced (P < 0.001) in RBC and enhanced (P < 0.001) in livers of MO-fed rats. Lipid oxidation was enhanced (P < 0.001) in red blood cells (RBC) from SBO groups, and hearts and livers of MO groups. High cholesterol diets reduced (P < or = 0.001) susceptibility to lipid peroxidation in RBC and liver of SHR and WKY rats. Greater amounts of dietary (n-3) fat enhance tissue susceptibility to oxidation, which can be modulated by increased dietary cholesterol in SHR and WKY rats.

Animals↗
PubMed2003

Supplementation of diets with the black rice pigment fraction attenuates atherosclerotic plaque formation in apolipoprotein e deficient mice.

Apolipoprotein (apo)E-deficient mice were used to study the antiatherogenic effect of black rice pigment fraction (BRF) and the possible mechanisms by which it inhibits atherogenesis. The apoE-deficient mice (n = 45) were randomly divided into three groups and received AIN-93G diet (positive group), AIN-93G with 5 g of black rice pigment fraction/100 g (BRF group) and AIN-93G with 5 g of white rice outer layer fraction/100 g (WRF group) for 16 wk. C57BL/6J mice (n = 15) received AIN-93G and were used as a control group. Blood samples were collected for measurement of lipid concentration, antioxidized LDL antibody and nitric oxide concentration. Livers were extracted for determination of cholesterol concentrations, and aortas were used to determine cholesterol concentrations and inducible nitric oxide synthase protein and mRNA expression. Hearts were used to assess atherosclerotic plaque formation. The apoE-deficient mice fed the black rice pigment fraction diet had 48% (P < 0.01) less atherosclerotic lesion area compared with apoE-deficient mice fed only the AIN-93G diet and 46% (P < 0.01) less lesion area compared with mice fed the white rice outer layer fraction diet. This observation corresponded with significantly (P < 0.05) lower total serum cholesterol, lower liver and aorta cholesterol (P < 0.01) and higher HDL cholesterol (P < 0.05) concentrations and lower (P < 0.05) antioxidized LDL antibody titer in apoE-deficient mice fed the black rice pigment fraction diet compared with positive and WRF groups. Notwithstanding this, mice fed the black rice pigment fraction diet also had lower CD4(+) T lymphocyte expression (P < 0.05) and weaker inducible nitric oxide synthase expression (P < 0.05) compared with mice fed the AIN-93G diet and the white rice outer layer fraction diet, respectively. We concluded that the inhibition of atherosclerotic lesions of the black rice pigment fraction is attributed to the improvement in cholesterol accumulation and reduction in oxidative stress and inflammation.

Animals↗
PubMed2003

Bioactive proteins and peptides from food sources. Applications of bioprocesses used in isolation and recovery.

There are many examples of biologically active food proteins, with physiological significance beyond the pure nutritional requirements that concern available nitrogen for normal growth and maintenance. Moreover, there are many physiologically active peptides, derived by protease activity from various food protein sources; however, relationships between structural properties and functional activities have not been completely elucidated. Many bioactive peptides have in common structural properties that include a relatively short peptide residue length (e.g. 2-9 amino acids), possessing hydrophobic amino acid residues in addition to proline, lysine or arginine groups. Bioactive peptides are also resistant to the action of digestion peptidases. Antihypertensive peptides, known as Angiotensin I converting enzyme (ACE) inhibitors have been derived from milk, corn and fish protein sources. Peptides with opioid activities are derived from wheat gluten or casein, following digestion with pepsin. Exorphins, or opioid peptides derived from food proteins such as wheat and milk (e.g. exogenous sources) have similar structure to endogenous opioid peptides, with a tyrosine residue located at the amino terminal or bioactive site. Immunomodulatory peptides derived from tryptic hydrolysates of rice and soybean proteins act to stimulate superoxide anions (reactive oxygen species-ROS), which triggers non-specific immune defense systems. Antioxidant properties that prevent peroxidation of essential fatty acids have also been shown for peptides derived from milk proteins. The addition of a Leu or Pro residue to the N-terminus of a His-His, dipeptide will enhance antioxidant activity and facilitate further synergy with non-peptide antioxidants (e.g. BHT). We also show herein, that the tryptic digests of casein yielding caseinophosphopeptides exhibits both hydrophilic and lipophilic antioxidant activity due to both metal ion sequestering and quenching of ROS. The separation and purification of bioactive peptides which will involve development of automated and continuous systems is an important field for Food chemists. Much effort has been given to develop selective column chromatography methods that can replace batch methods of salting out, or using solvent extraction to isolate and purify bioactive peptides. Advances here will enable recovery of bioactive peptides with minimal destruction thus enabling utilization by returning these active peptides to functional food or specific nutraceutical applications.

Adjuvants, Immunologic↗