Isolation and characterization of antioxidant protein fractions from melinjo (Gnetum gnemon) seeds

The protein from the seeds of melinjo ( Gnetum gnemon ) was purified using a precipitation method and ion exchange chromatographic techniques to identify the potent antioxidant and free radical scavenging activities. Two antioxidant protein fractions were isolated from G. gnemon seed with molecular weights of approximately 30 kDa (Gg-AOPI) and 12 kDa (Gg-AOPII) by SDS-PAGE. The N-terminal amino acid sequence of Gg-AOPII is Gly-Asn-Gly-Lys-Ala-Thr-Val-Ala-Ile-Leu-Val-Lys-Glu-Lys-Val-Glu-Tyr-Gly-Glu-Glu, and the result of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) analysis showed that they were distinct from each other; no protein in database matching was found to both Gg-AOPI and Gg-AOPII. The antioxidant or free radical scavenging activities of Gg-AOPs were investigated by employing in vitro assay systems including the inhibition of linoleic acid autoxidation, scavenging effect on α,α-diphenyl-β-picrylhydrazyl free radical (DPPH), 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), reducing power, chelating abilities of metal ions Cu(2+) and Fe(2+), and protections against hydroxyl radical-mediated DNA damages. The result showed that two protein fractions exhibited significant (p < 0.05) antioxidant activities against free radicals such as DPPH, ABTS, and superoxide anion and showed activities similar to those of glutathione (G-SH) and BHT in a linoleic acid emulsion assay system. Moreover, Gg-AOPI and Gg-AOPII also exhibited notable reducing power and strong chelating effect on Fe(2+) and protected hydroxyl radical induced oxidative DNA damage. The data obtained by the in vitro systems obviously established the antioxidant potency of Gg-AOPs.     

Antioxidative activity of protein hydrolysates prepared from alkaline-aided channel catfish protein isolates

Antioxidative activity of hydrolyzed protein prepared from alkali-solubilized catfish protein isolates was studied. The isolates were hydrolyzed to 5, 15, and 30% degree of hydrolysis using the protease enzyme, Protamex. Hydrolyzed protein was separated into hydrolysates and soluble supernatants, and both of these fractions were studied for their metal chelating ability, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging ability, ferric reducing antioxidant power (FRAP), oxygen radical absorbance capacity (ORAC), and their ability to inhibit the formation of thiobarbituric acid reactive substances (TBARS) in washed tilapia muscle containing tilapia hemolysate. Both hydrolysates and supernatants were characterized using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Results showed that DPPH radical scavenging ability and reducing power of catfish protein hydrolysates decreased, whereas the ORAC value, metal chelating ability, and ability to inhibit TBARS increased, with an increase in the degree of hydrolysis. Hydrolysate samples showed higher DPPH radical scavenging ability and Fe(3+) reducing ability, and supernatant samples had higher metal chelating ability. In general, low molecular weight (MW) peptides had high ORAC values and high metal chelating ability, and high MW peptides had a higher reducing power (FRAP) and were more effective in scavenging DPPH radicals. In a washed muscle model system, the ability of catfish protein hydrolysates and their corresponding supernatants to inhibit the formation of TBARS increased with an increase in the degree of hydrolysis.     

Antioxidative capacity of extracts and constituents in Cornus capitata adventitious roots

Radical scavenging activities of extracts and constituents in Cornus capitata adventitious root cultures were evaluated by using 1,1-diphenyl-2-pycrylhydrazyl (DPPH) and superoxide anion radicals. Inhibitory activity against peroxidation of linoleic acid was assayed by using the thiobarbituric acid (TBA) method. Ethyl acetate and aqueous fractions were prepared from adventitious roots cultured in Murashige-Skoog liquid medium with 0.1 microM Cu(2+) (0.1CuMS) or 10 microM Cu(2+) (10CuMS). The highest scavenging activities on DPPH and superoxide anion radicals were observed in the ethyl acetate fraction from 0.1CuMS. In the inhibitory activity against linoleic acid oxidation, the ethyl acetate fraction from 10CuMS was highest among the fractions tested. The ethyl acetate fraction of adventitious roots cultured in 0.1CuMS contained mainly galloylglucoses (1,2,3,6-tetragalloylglucose and 1,2,3,4,6-pentagalloylglucose). The ethyl acetate fraction of adventitious roots cultured in 10CuMS contained mainly ellagic acid derivatives [3,3'-di-O-methylellagic acid 4-(5"-acetyl)-alpha-L-arabinofuranoside and stenophyllin H1]. Aqueous fractions prepared from both media contained iridoid glycosides (dihydrocornin and cornin). Tetra- and pentagalloylglucoses showed strong inhibitory activities (61.9 and 85.2%, respectively) against linoleic acid oxidation relative to those of butylated hydroxytoluene (BHT) (91.1%) or alpha-tocopherol (49.5%) at 50 microM concentration. Although both ellagic acid derivatives had weak activities (<50%) on DPPH and superoxide anion radical scavenging, 3,3'-di-O-methylellagic acid 4-(5"-acetyl)-alpha-L-arabinofuranoside was stronger (74.7%) than alpha-tocopherol (49.5%) in inhibiting linoleic acid oxidation at 50 microM concentration. Iridoid glycosides exhibited little activity against DPPH and superoxide anion radicals or against oxidation of linoleic acid.     

Antioxidant activity and emulsion-stabilizing effect of pectic enzyme treated pectin in soy protein isolate-stabilized oil/water emulsion

The antioxidant activity of pectic enzyme treated pectin (PET-pectin) prepared from citrus pectin by enzymatic hydrolysis and its potential use as a stabilizer and an antioxidant for soy protein isolate (SPI)-stabilized oil in water (O/W) emulsion were investigated. Trolox equivalent antioxidant capacity (TEAC) was found to be positively associated with molecular weight (M(w)) of PET-pectin and negatively associated with degree of esterification (DE) of PET-pectin. PET-pectin (1 kDa and 11.6% DE) prepared from citrus pectin after 24 h of hydrolysis by commercial pectic enzyme produced by Aspergillus niger expressed higher α,α-diphenyl-β-picrylhydrazyl (DPPH) radical scavenging activity, TEAC, and reducing power than untreated citrus pectin (353 kDa and 60% DE). The addition of PET-pectin could increase both emulsifying activity (EA) and emulsion stability (ES) of SPI-stabilized O/W emulsion. When the SPI-stabilized lipid droplet was coated with the mixture of PET-pectin and pectin, the EA and ES of the emulsion were improved more than they were when the lipid droplet was coated with either pectin or PET-pectin alone. The amount of secondary oxidation products (thiobarbituric acid reactive substances) produced in the emulsion prepared with the mixture of SPI and PET-pectin was less than the amount produced in the emulsion prepared with either SPI or SPI/pectin. These results suggest that PET-pectin has an emulsion-stabilizing effect and lipid oxidation inhibition ability on SPI-stabilized emulsion. Therefore, PET-pectin can be used as a stabilizer as well as an antioxidant in plant origin in SPI-stabilized O/W emulsion and thus prolong the shelf life of food emulsion.     

Antioxidant activity of peptides obtained from porcine myofibrillar proteins by protease treatment

Hydrolysates obtained from porcine myofibrillar proteins by protease treatment (papain or actinase E) exhibited high antioxidant activity in a linolenic acid peroxidation system induced by Fe(2+). Hydrolysates produced by both papain and actinase E showed higher activities at pH 7.1 than at pH 5.4. The antioxidant activity of the papain hydrolysate was almost the same as that of vitamin E at pH 7.0. These hydrolysates possessed 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity and chelating activity toward metal ions. Antioxidant peptides were separated from the papain hydrolysate by ion exchange chromatography. The acidic fraction obtained by this method exhibited higher activity than the neutral or basic fractions. Antioxidant peptides in the acidic fraction were isolated by high-performance liquid chromatography on an ODS column and shown to possess the structures DSGVT, IEAEGE, DAQEKLE, EELDNALN, and VPSIDDQEELM. The DAQEKLE peptide showed the highest activity among these peptides.     

Caseins and casein hydrolysates. 2. Antioxidative properties and relevance to lipoxygenase inhibition

The antioxidant activity of caseins and casein-derived peptides was evaluated by using three free radical producing reactions-the lipoxygenase- and AAPH-catalyzed oxidation of linoleic acid and the hemoglobin-catalyzed oxidation of linoleic acid hydroperoxide. Caseins and casein-derived peptides were able to inhibit enzymatic and nonenzymatic lipid peroxidation, suggesting they were preferred targets for the free radical intermediates. The antioxidative feature was not lost with the dephosphorylation or the proteolysis of the proteins. The fractionation of the tryptic beta-casein digest yielded peptides with antioxidant activity. A structure-function relationship between the amino acid sequence and the antioxidant capacity and effectiveness is proposed. In addition, indirect evidence suggested that the trapping of free radicals by the proteins/peptides was accompanied by the oxidation of proteins/peptides, according to a sequence-specific mechanism.     

Molecular design of antibrowning agents

Tyrosinase inhibitory and antioxidant activity of gallic acid and its series of alkyl chain esters were investigated. All inhibited the oxidation of L-3,4-dihydroxyphenylalanine (L-DOPA) catalyzed by mushroom tyrosinase. However, gallic acid and its short alkyl chain esters were oxidized as substrates yielding the colored oxidation products. In contrast, the long alkyl chain esters inhibited the enzyme activity without being oxidized. This indicates that the carbon chain length is associated with their tyrosinase inhibitory activity, presumably by interacting with the hydrophobic protein pocket in the enzyme. On the other hand, the esters, regardless their carbon chain length, showed potent scavenging activity on the autoxidation of linoleic acid and 1,1-diphenyl-2-p-picryhydrazyl (DPPH) radical, suggesting that the alkyl chain length is not related to the activity. The effects of side-chain length of gallates in relation to their antibrowning activity are studied.     

Antioxidative efficacy of alkali-treated tilapia protein hydrolysates: a comparative study of five enzymes

The antioxidant activities of alkali-treated tilapia protein hydrolysates were determined by their ability to inhibit the formation of lipid hydroperoxides (PV) and thiobarbituric acid reactive substances (TBARS) in a washed muscle model system and by their ability to inhibit DPPH free radicals and chelate ferrous ion in an aqueous solution. Protein isolates were prepared from tilapia white muscle using alkali solubilization at pH 11.0 and reprecipitation at pH 5.5. Protein hydrolysates were prepared by hydrolyzing the isolates using five different enzymes, Cryotin F, Protease A Amano, Protease N Amano, Flavourzyme, and Neutrase, to 7.5, 15, and 25% degrees of hydrolysis (DH). All of the protein hydrolysates significantly (p<0.05) inhibited the development of TBARS and PV. The antioxidant activity of the hydrolysates increased with the DH. Also, the antioxidant activity of the hydrolysates varied significantly (p<0.05) among the different enzymes. The ability of different enzyme-catalyzed protein hydrolysates to scavenge DPPH radicals was not reflected in their ability to inhibit oxidation in a washed tilapia model system. In a washed muscle model system, the hydrolysates prepared using Cryotin F were most effective and the hydrolysates prepared using Flavourzyme and Neutrase were least effective in inhibiting the development of TBARS and PV, whereas in an aqueous solution, hydrolysates prepared using Flavourzyme were most effective in scavenging DPPH radicals and chelating ferrous ions. Enzymatic hydrolysis decreased the size of tilapia protein hydrolysates and, in general, tilapia protein hydrolysates with low molecular weights were better antioxidants than those with high molecular weights.     

Synthesis of lipophilic clovamide derivatives and their antioxidative potential against lipid peroxidation

Some N-(hydroxycinnamoyl)-L-tyrosine and L-DOPA alkyl esters were synthesized and evaluated as a variation of the clovamide (N-caffeoyl-L-3,4-dihydroxyphenylalanine) structure, a known antioxidant found in red clover. The amides were prepared in good yields starting from methyl and dodecylesters of L-tyrosine and L-DOPA by reacting with the N-hydroxysuccinimidyl esters of ferulic, sinapic, and acetyl-protected caffeic acid, respectively. In the DPPH* (2,2-diphenyl-1-picrylhydrazyl) and superoxide radical quencher assays they showed radical scavenging activity equal to or higher than those of the standard antioxidants ascorbic acid and tocopherol. The antioxidative potentials of the clovamide derivatives against bulk lipid oxidation, as determined by the accelerated autoxidation of oils, were equal to or higher than those of the standard antioxidants; some of the compounds were able to protect an emulsion of linoleic acid/beta-carotene against oxidation. N-Caffeoyl L-tyrosine methyl ester and the N-cinnamoyl L-DOPA alkyl esters especially were potent antioxidants in bulk lipids and moderate protectants in emulsions.     

Antioxidant properties of a radical-scavenging peptide purified from enzymatically prepared fish skin gelatin hydrolysate

Hoki (Johnius belengerii) skin gelatin was hydrolyzed with three commercial enzymes to identify radical-scavenging potencies of derived peptides. Peptides derived from tryptic hydrolysate exhibited the highest scavenging activities on superoxide, carbon-centered 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals assessed by ESR spectroscopy. Following consecutive chromatographic separations of tryptic hydroolysate, the peptide sequence His-Gly-Pro-Leu-Gly-Pro-Leu (797 Da) acted as a strong radical scavenger under studied conditions. Further, this peptide could act as an antioxidant against linoleic acid peroxidation and the activity was closer to the highly active synthetic antioxidant butylated hydroxytoluene (BHT). In addition, antioxidative enzyme levels in cultured human hepatoma cells were increased in the presence of this peptide and it was presumed to be the peptide involved in maintaining the redox balance in the cell environment. Present data indicate that free-radical-scavenging activities of hoki skin gelatin peptides substantially contribute to their antioxidant properties measured in different oxidative systems.     

Evaluation of the antioxidant activity of environmental plants: activity of the leaf extracts from seashore plants

The antioxidant activity of the methanolic extracts of the leaves of 39 plant species was examined. These leaves were collected from the plants growing on subtropical seashores. The activity was evaluated by three kinds of assay methods, which included the DPPH radical scavenging assay, linoleic acid oxidation assay, and oxidative cell death assay. Two extracts from Excoecaria agallocha and Terminalia catappa showed remarkably potent activity in all assay systems. The HPLC analysis of the extracts indicated the presence of the same antioxidant and isolation work for the compound identified ellagic acid. The isolated ellagic acid showed strong antioxidant activity in the assay systems used.     

Antioxidant activity of a combinatorial library of emulsifier-antioxidant bioconjugates

A combinatorial chemistry approach was employed for the design and systematic synthesis of antioxidant-emulsifier bioconjugates to improve antioxidant activity in the interface between oil and water. A combinatorial library of 12 bioconjugates was synthesized from the phenolic antioxidants Trolox (a water-soluble alpha-tocopherol analogue), dihydroferulic acid, dihydrocaffeic acid, and gallic acid in combination with serine ethyl ester, serine lauryl ester, and lauroyl serine by esterification of the serine side chain or amidation, respectively. The bioconjugates were characterized by NMR and mass spectrometry, and each was tested for antioxidant activity by measuring the radical scavenging rate of 2,2-diphenyl-1-picrylhydrazyl (DPPH (*)) in methanol, the radical scavenging rate of DPPH (*) in a heterogeneous solvent system, the rate of oxygen consumption in an oil-in-water emulsion with metmyoglobin initiated oxidation, and the lag phase for diene formation in unilamellar liposomes with free radical initiation in the aqueous phase; each case was compared to the antioxidant activity of the parent antioxidant. In general, the conjugates with longer chain derivatives exhibited improved antioxidative activity in heterogeneous systems, whereas no improvement was observed in homogeneous solution. The rate of oxygen consumption in oil-in-water emulsion was found to decrease with increasing octanol/water partition coefficient, which is suggested to correspond to a saturation of the water/oil interface with antioxidant bioconjugate to approach maximal protection.     

超声辅助竹节虾头酶解及抗氧化肽分离研究

为了实现竹节虾加工副产物的高值化利用,以竹节虾加工废弃物中的虾头副产物为原料,以水解度和DPPH清除率作为评价指标,采用中性蛋白酶酶解,通过响应面法优化超声辅助酶解工艺,并依次通过超滤、凝胶层析色谱和反相高效液相色谱等分离方法,从竹节虾虾头酶解产物中分离制备抗氧化肽,采用超高压液相色谱串联质谱联用技术对肽的结构进行表征。结果表明,在中性蛋白酶添加量为3 000 U·g~(-1)、p H值7.0条件下,最佳超声辅助酶解工艺参数为超声时间41 min,超声温度55℃,超声频率22 k Hz,料液比1∶9(w/v),在此条件下获得的酶解产物DPPH清除率达69.50%。当水解时间为0.5~2.5 h时,超声辅助酶解的酶解产物水解度和DPPH清除率比非超声辅助酶解工艺分别高17.95%和18.83%,该工艺缩短了酶解时间,节约了能耗。酶解产物经超滤初步分离发现,相对分子质量在3k Da(SHP4)的组分具有显著的抗氧化活性。用凝胶层析法进一步分离纯化SHP4组分后得到4个峰,其中SHP4-II的DPPH清除率最高;SHP4-II通过反相高效液相纯化后也得到4个主要肽峰,在多肽含量为1.5 mg·m L~(-1)时,SHP4-II-4的DPPH清除率最高,达到85.69%,并且具有较好的分离度,质谱分析发现,该抗氧化肽的结构为Gly-Asn-Gly-Leu-Pro(455.99 Da)。本研究结果为虾肽抗氧化保健食品的研发提供了一定的科学依据。     

Phenolics composition and antioxidant activity of sweet basil (Ocimum basilicum L.)

The antioxidant activity of a methanolic extract of Ocimum basilicum L. (sweet basil) was examined using different in vitro assay model systems. The crude extract was fractionated on a Sephadex LH-20 column, and six fractions were identified. The DPPH scavenging assay system and the oxidation of the soy phosphotidylcholin liposome model system were used to evaluate the antioxidant activity of each fraction. Fraction IV showed the strongest activity followed by fractions V and VI. Phenolic compounds responsible for the antioxidative activity of the fractions were characterized by atmospheric pressure chemical ionization liquid chromatography-mass spectrometry. The major antioxidant compound in fraction IV was confirmed as rosmarinic acid by (1)H NMR and characteristic fragmentations in the mass spectrum. Moreover, the native of antioxidant activity of rosmarinic acid in the liposome system was examined. The results showed that one rosmarinic acid can capture 1.52 radicals, and furthermore, the existence of a synergistic effect between alpha-tocopherol and rosmarinic acid was revealed.     

Total antioxidant capacity of arginine-conjugated linoleic acid (CLA) complex

Conjugated linoleic acids (CLA) have shown diverse biological activities, including anti-carcinogenic, anti-atherosclerotic, anti-adipogenic, and anti-diabetogenic effects. Recent reports also showed that CLA has free radical scavenging capacity, which may give health benefits to human beings. However, the application of CLA as a bioactive ingredient has been limited due to its insolubility in water. To overcome this problem, we investigated antioxidant activities of arginine (Arg)-CLA, a water-soluble CLA salt, using both 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 2,2'-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assays. CLA, Arg, and Arg-CLA all exerted radical scavenging activities in a dose-dependent manner in both assays. Arg-CLA at 20 mM scavenged 89 and 55% of ABTS and DPPH radicals in 3 h, respectively, whereas CLA alone quenched only 48 and 26% of them under the same conditions. The antioxidant activity of the Arg-CLA complex was found to be synergistic in ABTS assay and comparable to that of vitamin E in DPPH assay.     

Antioxidant and antimelanogenic activities of polyamine conjugates from corn bran and related hydroxycinnamic acids

The antioxidant activity of three major polyamine conjugates, N,N'-dicoumaroyl-putrescine (DCP), N-p-coumaroyl-N'-feruloylputrescine (CFP), and N,N'-diferuloyl-putrescine (DFP) isolated from corn bran, and their related hydroxycinnamic acids, p-coumaric acid and ferulic acid, were evaluated by three antioxidant in vitro assay systems, including 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and superoxide and hydroxyl radicals generated by enzymatic and nonenzymatic reactions. Additionally, five phenolic compounds were evaluated for melanogenesis inhibitory activity using mushroom tyrosinase and B16 melanoma cells. Most of the phenolic compounds significantly scavenged DPPH, superoxide, and hydroxyl radicals in a dose-dependent manner. Particularly, DFP showed potent DPPH (IC50 = 38.46 microM) and superoxide (IC50 = 291.62 microM) radical scavenging activities, while DCP exhibited the strongest hydroxyl radical scavenging activity (IC50 = 120.55 microM). CFP also exerted moderate DPPH, superoxide, and hydroxyl radical scavenging activities. Meanwhile, DCP (IC50 = 181.73 microM) showed potent tyrosinase inhibitory activity toward l-tyrosine as the substrate, whereas DFP (IC50 = 733.64 microM) significantly inhibited melanin synthesis in B16 melanoma cells. These current results indicate that these three polyamine conjugates from corn bran may be useful potential sources of natural antioxidants and skin-whitening agents.     

Antioxidant properties of ferulic acid and its related compounds

Antioxidant activity of 24 ferulic acid related compounds together with 6 gallic acid related compounds was evaluated using several different physical systems as well as their radical scavenging activity. The radical scavenging activity on 1,1-diphenyl-2-picrylhydrazyl (DPPH) decreased in the order caffeic acid > sinapic acid > ferulic acid > ferulic acid esters > p-coumaric acid. In bulk methyl linoleate, test hydroxycinnamic acids and ferulic acid esters showed antioxidant activity in parallel with their radical scavenging activity. In an ethanol-buffer solution of linoleic acid, the activity of test compounds was not always associated with their radical scavenging activity. Ferulic acid was most effective among the tested phenolic acids. Esterification of ferulic acid resulted in increasing activity. The activity of alkyl ferulates was somewhat influenced by the chain length of alcohol moiety. When the inhibitory effects of alkyl ferulates against oxidation of liposome induced by AAPH were tested, hexyl, octyl, and 2-ethyl-1-hexyl ferulates were more active than the other alkyl ferulates. Furthermore, lauryl gallate is most effective among the tested alkyl gallates. These results indicated that not only the radical scavenging activity of antioxidants, but also their affinity with lipid substrates, might be important factors in their activity.     

In vitro antioxidant properties and phenolic composition of Salvia virgata Jacq. from Turkey

Antioxidant activities and phenolic compositions of the active fractions of Salvia virgata Jacq. (Lamiaceae) from Turkey were examined. The aerial part of S. virgata was extracted with different solvents in an order of increasing polarity such as hexane, ethyl acetate, methanol, and 50% aqueous methanol using a Soxhlet apparatus. Water extract was also prepared from S. virgata by reflux. All solvent fractions were investigated for their total phenolic contents, total flavonoids, flavonols, qualitative-quantitative compositions (by HPLC-PDA analysis), iron(III) reductive activities, free radical scavenging activities (using DPPH*), and effect upon linoleic acid peroxidation activities; also, the peroxidation level was determined by the TBA method. The results of activity tests given as IC50 values were estimated from nonlinear algorithm and compared with standards, viz., butylated hydroxytoluene, ascorbic acid, and gallic acid. Polar fractions were found to be more active for free radical activity whereas nonpolar fractions protected the peroxidation of linoleic acid. Rosmarinic acid was the most abundant component in the extracts, followed by caffeic acid and lutelin-7- O-glycoside.     

Scavenging of free radicals, antimicrobial, and cytotoxic activities of the Maillard reaction products of beta-lactoglobulin glycated with several sugars

The Maillard reaction occurs during many industrial and domestic thermal treatments of foods. It is widely used because of its role in creating colors, flavors, textures, and other functional properties in foodstuffs. Proteins glycated without the use of conventional chemical reagents have improved technofunctional properties such as heat stability, emulsifying, and foaming properties. The present study was carried out to determine the extent to which this reaction can convey antioxidant, antimicrobial, or cytotoxic activities to beta-lactoglobulin (BLG) and to its tryptic and peptic hydrolysates. BLG was modified with six different sugars in solution at 60 degrees C. Antiradical properties were estimated using a radical scavenging activity test. Antimicrobial activities against different bacterial strains were studied with a diffusion disk method. Cytotoxic tests were performed using two cell lines and the 3-(4,5-dimethylthiazoyl-2-yl)-2,5-diphenyltetrazolium bromide (MTT) rapid colorimetric assay. Glycation induced a radical scavenging activity to BLG, the intensity of which depended on the sugar used for modification. Proteins modified with ribose and arabinose showed the highest radical scavenging activities depicted by about 80 and 60% of 2,2-diphenyl-1-picrylhydrazyl (DPPH) absorption decrease at 515 nm. No antimicrobial effect of any glycated form of BLG against Escherichia coli, Bacillus subtilis, Listeria innocua, and Streptococcus mutans was observed. The MTT test showed no enhancement of cytotoxicity by modified proteins and peptides against COS-7 and HL-60 cells. Thus, glycated proteins could be used in formulated food as functional ingredients with a radical scavenging activity able to delay deterioration due to oxidation. This use could be even more advisable considering the lack of toxicity to eukaryotic and prokaryotic cell cultures demonstrated in this work.     

Evaluation of antioxidant and prooxidant activities of bamboo Phyllostachys nigra var. Henonis leaf extract in vitro

Solvent-extracted bamboo leaf extract (BLE) containing chlorogenic acid, caffeic acid, and luteolin 7-glucoside was evaluated in vitro for free radical scavenging and antioxidant activities using a battery of test methods. BLE exhibited a concentration-dependent scavenging activity of DPPH radical. BLE prolonged the lag phase and suppressed the rate of propagation of liposome peroxidation initiated by peroxyl radical induced by 2,2'-azobis(2-amidinopropane dihydrochloride (AAPH) at 37 degrees C. BLE also prevented human low-density lipoprotein oxidation, mediated by Cu(2+), which was monitored by the lower formation of conjugated diene and fluorescence and a reduced negative charge of apo-B protein. Finally, BLE protected supercoiled DNA strand against scission induced by AAPH-mediated peroxyl radical. Prooxidant activity of BLE was seen in a Cu(2+)-induced peroxidation of structured phosphatidylcholine liposome, indicating catalytic peroxidation due to a relatively high reducing power of BLE. It was concluded that the BLE has both antioxidant activity and prooxidant activity; the antioxidant activity was attributed to free radical scavenging activity, and the prooxidant activity, albeit minor, resulted from the reducing power of plant phenolics in the presence of transitional metal ions.