Characterization and antioxidant evaluation of phenolic compounds extracted from the protein concentrate and protein isolate produced from pawpaw (Carica papaya Linn.) seeds

In this study, the qualitative and quantitative analysis of the absolute (100%) and aqueous (80%) methanolic extract of Carica papaya Linn processed seed flour samples in terms of their antioxidant properties and their phenolic compounds was investigated. The antioxidant properties were determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power, and metal chelating assay methods. The protein isolate exhibited higher radical scavenging activity power as compared to other samples. Ferulic acid, caffeic acid, p-coumaric acid, kaempferol-3-glucoside, p-hydroxybenzoic acid, and quercetin-3-galactoside were phenolic compounds isolated with ferulic acid as high as 0.62 mg/DWg. Carica papaya seed isolates and concentrate demonstrated potent antioxidant activity and could be of nutraceutical importance in the pharmaceutical and food industry.     

Acidic degradation and enhanced antioxidant activities of exopolysaccharides from Cordyceps sinensis mycelial culture

An exopolysaccharide (EPS) fraction isolated from mycelial culture of a Cordyceps sinensis fungus, designated EPS-1 with an average molecular weight (MW) of 38 kDa, was hydrolysed in dilute sulphuric acid solution at pH 1 and 90 °C, yielding two major MW fractions, 3.0 kDa and 30 kDa, respectively. While the proportion of lower MW fraction increased with the hydrolysis period (18% in 0.5 h and 92% in 10 h), the polydispersity (M_w/M_n) of EPS decreased steadily (from 1.47 initially to 1.10 in 10 h). The IR spectra of hydrolysed EPS fractions showed changes only in the C–O–C and C–O–H band peaks from that of EPS-1. These results suggest that the hydrolysis of EPS in the acidic solution caused the EPS degradation mainly by cleaving the glycosidic linkage but no change in the primary molecular structure. The hydrolysed EPS fractions had much higher (30–80%) antioxidant and radical-scavenging activities.     

微波辅助水酶法提取番茄籽油工艺优化及理化特性研究

以番茄籽为原料提取番茄籽油,通过响应面法优化微波辅助复合酶法提取番茄籽油(MEOs)工艺,并建立回归模型;同时研究了MEOs的理化特性、脂肪酸组成和抗氧化活性,并与传统索氏提取番茄籽油(SEOs)进行比较。结果表明,采用复合酶(纤维素酶∶果胶酶∶蛋白酶=1∶1∶1)的最佳提取工艺为酶添加量1.5%、温度35℃、时间40 min、微波功率500 W,在此条件下MEOs得率为29.65%;MEOs与SEOs在理化特性方面没有显著区别,但MEOs含有较高的生育酚,同时具有较高的氧化稳定性。MEOs表现出较强的抗氧化活性,在DPPH·和β-胡萝卜素-亚油酸测试体系中其IC50分别为9.52和10.64 mg/m L。MEOs是一种理想的天然保健食品原料,具有较好的开发利用前景。     

Antioxidative Potential of the Polyphenolics of Stephania japonica var. Discolor (Blume) Forman: A Chromatographic (High-Performance Liquid Chromatography) and Spectrophotometric Measure

This study investigated the quantitative phytochemical contents, total phenolics, total flavonoids, total carotenoids, antioxidative capacity, tannin, proanthocyanidins, lycopene, chlorophyll a, and chlorophyll b of the Stephania japonica extract. Comprehensive antioxidative effects of the extract were also investigated. Quantitative assays were conducted through both spectrophotometric and high-performance liquid chromatographic methods. Antioxidative effects were measured through FeCl₃ reducing power, metal chelating power, reducing power, 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS) scavenging activity, N, N-dimethyl-1,4-diaminobenzene free radical scavenging activity, superoxide radical scavenging activity, and nitric oxide scavenging effect. The contents of total phenolics, total flavonoids, total carotenoids, total antioxidative capacity, tannin, proanthocyanidins, lycopene, chlorophyll a, and chlorophyll b were found to be 47.32 ± 0.75 mg tannic acid equivalent, 61.41 ± 1.58 mg catechin equivalent, 63.29 ± 2.21 mg, 22.85 ± 0.70 mg ascorbic acid equivalent, 76.17 ± 0.97 mg tannic acid equivalent, 94.96 ± 4.49 mg catechin equivalent, 22.19 ± 0.79 µg, 22.19 ± 0.79 µg, 7.52 ± 1.24 mg, and 10.43 ± 2.11 mg, respectively, in 1 g of ethanol extract. A high concentration of epicatechin, p-coumaric acid, and rutin hydrate and moderate concentration of caffeic acid and quercetin was detected in the extract. The IC₅₀ value for ferric reducing power assay, metal chelating assay, reducing power assay, ABTS scavenging assay, N, N-dimethyl-1,4-diaminobenzene scavenging assay, superoxide scavenging assay and nitric oxide (NO) assay were 465.06 ± 7.32 µmol ascorbic acid/g, 1656.52, 270.55, 457.27, 632.74, 217.5, and 464.00 µg/mL, respectively. No beta carotene was detected in the extract. The extract was demonstrated to be a very potential source of antioxidative metabolites.     

Antioxidant evaluation of polyhydroxylated nerolidols from redroot pigweed (Amaranthus retroflexus) leaves

Amaranthus retroflexus L., also known as redroot pigweed, is an invasive and cosmopolite plant belonging to Amaranthus genus, anciently used as food sources. From the methanolic extract of the redroot pigweed leaves, several new polyhydroxylated terpenes with a nerolidol skeleton have been isolated and characterized. In this study the antioxidant activity of the methanolic extract of the plant, as well as of its terpene constituents, has been evaluated. The antioxidant properties of each metabolite were evidenced by evaluating their ability to scavenge the DPPH radical and the pro-oxidant hydrogen peroxide as well as by assessing their capacity to inhibit the formation of thiobarbituric acid reactive species (TBARS), and to induce the formation of a phosphomolybdenum complex. The methanolic extract of the plant showed a strong dose-response antioxidant activity, while the pure nerolidol derivatives showed antioxidant capacities comparable to those exercised by the standard α-tocopherol.     

Angiotensin I-converting enzyme-inhibitory peptide fractions from albumin 1 and globulin as obtained of amaranth grain

A number of biopeptides promoting health benefits have been isolated from food-protein hydrolysates and can be released during enzymatic digestion. Antihypertensive peptides can be part of protein fractions from amaranth grain. The objective of this work was to obtain ACE-inhibitory peptide fractions from albumin 1 and the globulin of amaranth (Amaranthus hypochondriacus) grain. Albumin 1 and globulin were hydrolysed with alcalase; hydrolysis was monitored by proteolytic degradation and by ACE-inhibitory activity. The highest ACE-inhibitory activity was 40% and 35% as obtained after 18 and 15 h hydrolysis for albumin 1 and globulin, respectively. Further separation and purification of the ACE-inhibitory peptide fractions were carried out by gel filtration and C₁₈ RP–HPLC. The IC₅₀ was 0.35 ± 0.02 mg/ml for albumin 1 peptide fraction and 0.15 ± 0.03 mg/ml for globulin peptide fraction. Albumin 1 peptide fraction showed an competitive mode of ACE inhibition, whereas the globulin peptide fraction was competitive. The globulin peptide fraction may have one of the most active naturally-occurring ACE-inhibitory peptides.     

New nitrogen-containing bromophenols from the marine red alga Rhodomela confervoides and their radical scavenging activity

In addition to nine known bromophenol derivatives, five new nitrogen-containing bromophenols were isolated from an ethyl acetate extract of the marine red alga Rhodomela confervoides. By using spectroscopic methods, the structures of the new compounds were identified as 3-(2,3-dibromo-4,5-dihydroxybenzyl)pyrrolidine-2,5-dione (1), methyl 4-(2,3-dibromo-4,5-dihydroxybenzylamino)-4-oxobutanoate (2), 4-(2,3-dibromo-4,5-dihydroxybenzylamino)-4-oxobutanoic acid (3), 3-bromo-5-hydroxy-4-methoxybenzamide (4), and 2-(3-bromo-5-hydroxy-4-methoxyphenyl)acetamide (5). All of these bromophenols showed potent scavenging activity against DPPH (1,1-diphenyl-2-picrylhydrazyl) radicals, with IC(50) values ranging from 5.22 to 23.60μM. These compounds also displayed moderate activity against ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonate) radicals, with Trolox Equivalent Antioxidant Capacity values (TEAC) ranging from 2.11 to 3.58mM. The results obtained in this study demonstrate that the bromophenols obtained from R. confervoides may have potential application in food and/or pharmaceutical fields as natural antioxidants.     

稻壳基磁性介孔SiO2的改性及其性质表征

以稻壳为硅源,γ-氨丙基三乙氧基硅烷(APTES)为改性剂,制备改性磁性介孔SiO_2(NMMS),研究了搅拌时间、温度及料液比对氨基接枝率的影响;同时,对NMMS的结构进行表征,并初步测定了其对AFB1的吸附效果。结果表明,搅拌时间、温度及料液比对氨基接枝率的影响均显著,制备NMMS的最优工艺条件为:搅拌时间10 h,温度80℃,料液比1∶3,氨基接枝率最高为(13.3±0.2)%;NMMS具有良好的磁分离特性,且氨基嫁接成功;其孔道有序,孔径和比表面积分别为2.03 nm和205.88 m2/g,对AFB1的脱除率可达(83.96±2.74)%,约为未改性的磁性介孔SiO_2(MMS)的2倍。因此,氨基改性有利于NMMS对AFB1的吸附,达到有效脱除AFB1的目的。     

Antioxidant properties of water and ethanol extracts from hot air-dried and freeze-dried daylily flowers

Daylily (Hemerocallis fulva Linn.) flowers were hot air-dried and freeze-dried after harvest. Water and ethanol extracts were prepared from these dried flowers and their antioxidant properties were evaluated using total antioxidant activity, reducing capacity, metal chelating activity, and DPPH and superoxide anion radical scavenging activities, comparing with standards. Extracts from daylily flowers exhibited strong antioxidant activity. Ethanol was more efficienct to extract antioxidants than water and that freeze-drying preserved higher activities than air-drying. Ethanol extract from freeze-dried daylily flowers showed the highest antioxidant activity and phenol content.     

Phenolic profile and antioxidant activities of olive mill wastewater

Olive trees play an important role in the Moroccan agro-economy, providing both employment and export revenue. However, the olive oil industry generates large amounts of wastes and wastewaters. The disposal of these polluting by-products is a significant environmental problem that needs an adequate solution. On one hand, the phytotoxic and antimicrobial effects of olive mill wastewaters are mainly due to their phenolic content. The hydrophilic character of the polyphenols results in the major proportion of natural phenols being separated into the water phase during the olive processing. On other hand, the health benefits arising from a diet containing olive oil have been attributed to its richness in phenolic compounds that act as natural antioxidants and are thought to contribute to the prevention of heart diseases and cancers. Olive mill wastewater (OMW) samples have been analysed in terms of their phenolic constituents and antioxidant activities. The total phenolic content, flavonoids, flavanols, and proanthocyanidins were determined. The antioxidant and radical scavenging activity of phenolic extracts and microfiltred samples was evaluated using different tests (iron(II) chelating activity, total antioxidant capacity, DPPH assays and lipid peroxidation test). The obtained results reveal the considerable antioxidant capacity of the OMW, that can be considered as an inexpensive potential source of high added value powerful natural antioxidants comparable to some synthetic antioxidants commonly used in the food industry.     

Purification of angiotensin I-converting enzyme-inhibitory peptides from the enzymatic hydrolysate of defatted canola meal

Defatted canola meals from seeds of different processing origins were hydrolyzed by Alcalase to give hydrolysates that inhibited angiotensin converting enzyme (ACE) activity. Heat treated meals yielded protein hydrolysates with 50% ACE-inhibitory concentrations of 27.1 and 28.6 μg protein/ml compared with 35.7 and 44.3 μg protein/ml for the none-heat treated meals. Separation of the hydrolysate on a Sephadex G-15 gel permeation column (GPC) yielded a fraction with an IC₅₀ value of 2.3 μg protein/ml. Amino acid analysis showed that the GPC fraction contained 45% content of aromatic amino acids in comparison to 8.5% of the hydrolysate. Two peptides, Val-Ser-Val (IC₅₀ = 0.15 μM) and Phe-Leu (IC₅₀ = 1.33 μM) were purified, and located in the primary structure of canola napin and cruciferin native proteins. The results suggest that canola protein hydrolysate is a potential ingredient for the formulation of hypotensive functional foods.     

Physico-chemical and bioactive properties of different floral origin honeys from Romania

In this study, we investigated and compared the physico-chemical properties (moisture, colour, ash, and sugars content) as well as total phenols, total flavonoids and antioxidant activity of several honey samples (24) collected from different regions of Romania. The physico-chemical values were in the range of approved limits (conforming to EU legislation); excepting the monosaccharide values for one sample (T2). For this sample, the other values were within legislation limits. The results obtained showed that the most valuable honey is the honeydew one. Correlation between RSA and total phenols and total flavonoids, respectively, was determined, and a positive correlation was found. This study demonstrates remarkable variation in antioxidant properties and content of total phenols in honey, depending on its botanic or geographic source.     

Inhibitory effects of salicylic acid family compounds on the diphenolase activity of mushroom tyrosinase

Mushroom tyrosinase (EC 1.14.18.1) catalyzes both the hydroxylation of tyrosine into o-diphenols and the oxidation of o-diphenols into o-quinones that form brown or black pigments. In the present paper, inhibitory effects on the diphenolase activity of 10 compounds of the salicylic acid-family on the diphenolase activity of mushroom tyrosinase have been studied. The results show that some of these compounds behave as reversible inhibitors. Salicylic acid is a competitive inhibitor while 4-methoxysalicylic acid is non-competitive, 5-methoxysalicylic acid is mixed-I type and 4-methylsalicylic acid and 5-methylsalicylic acid are mixed-II type. The inhibition constants of these five compounds were evaluated. The inhibition strength follows the order: 4-methylsalicylic acid > 5-methylsalicylic acid > 4-methoxysalicylic acid > salicylic acid > 5-methoxysalicylic acid. Models of the interaction between the enzyme and the inhibitors are further discussed and compared.     

Highly active metallocarboxypeptidase from newly isolated Geobacillus strain SBS-4S: cloning and characterization

The carboxypeptidase gene from Geobacillus SBS-4S was cloned and sequenced. The sequence analysis displayed the gene consists of an open reading frame of 1503 nucleotides encoding a protein of 500 amino acids (CBP(SBS)). The amino acid sequence comparison revealed that CBP(SBS) exhibited a highest homology of 41.6% (identity) with carboxypeptidase Taq from Thermus aquaticus among the characterized proteases. CBP(SBS) contained an active site motif (265)HEXXH(269) which is conserved in family-M32 of carboxypeptidases. The gene was expressed with His-Tag utilizing Escherichia coli expression system and purified to apparent homogeneity. The purified CBP(SBS) showed highest activity at pH 7.5 and 70°C. The enzyme activity was metal ion dependent. Among metal ions highest activity was found in the presence of Co(2+). Thermostability studies of CBP(SBS) by circular dichroism spectroscopy demonstrated the melting temperature of the protein around 77°C. The enzyme exhibited K(m) and V(max) values of 14 mM and 10526 μmol min(-1) mg(-1) when carbobenzoxy-alanine-arginine was used as substrate. k(cat) and k(cat)/K(m) valves were 10175 s(-1) and 726 mM(-1) s(-1). To our knowledge this is the highest ever reported enzyme activity of a metallocarboxypeptidase and the first characterization of a metallocarboxypeptidase from genus Geobacillus.     

Structural characterization of globulin from common buckwheat (Fagopyrum esculentum Moench) using circular dichroism and Raman spectroscopy

Raman and far-UV circular dichroism (CD) spectroscopy was used to study the conformation of globulin from common buckwheat (Fagopyrum esculentum Moench) (BWG) under the influence of various buffer environments and heat treatments. Secondary structural analysis of BWG by CD spectroscopy yielded 15.0% α-helical, 25.8% β-sheet, 28.9% β-turn and 30.3% random coil contents. Raman spectrum also showed β-sheets as the major secondary structure in native BWG. Chaotropic salts caused band shifts and intensity changes in Raman amide III vibration, indicating transitions from β-sheet to disordered structure following the lyotropic series of anions. Extreme pHs and several protein structure perturbants led to changes in CD and Raman spectral characteristics, demonstrating protein unfolding and denaturation. Increasing heating time at 100 °C induced the appearance of anti-parallel β-sheet (1235–1237 cm⁻¹) and caused a progressive increase in random coil content, suggesting protein denaturation and aggregation. Both non-covalent and covalent interactions play important roles in stabilizing the conformation of BWG.     

Antioxidant activity of protein extracts from heat-treated or thermally processed chickpeas and white beans

In this study, antioxidant activities of water-soluble protein extracts from chickpeas and white beans were investigated. The area under the curve (AUC) values of lyophilized crude protein extracts (dialyzed or undialyzed) from thermally processed (121 °C for 20 min) or heat-treated (90 °C for 20 min) chickpeas (73–91 μmol trolox/g) and white beans (39–67 μmol trolox/g) indicated a higher free radical-scavenging capacity and thermostability for chickpea proteins than for white bean proteins. The thermal processing also increased the Fe⁺²-chelating capacity of lyophilized chickpea crude protein extracts 1.8-fold whereas it caused a 2.3-fold reduction in the Fe⁺²-chelating capacity of lyophilized white bean crude protein extracts. Dialysis increased the protein content of lyophilized chickpea extracts 1.5–2-fold but it did not affect the protein content of lyophilized white bean extracts significantly. Ammonium sulfate precipitation was not effective for selective precipitation of antioxidant proteins. However, it improved the free radical-scavenging capacity of lyophilized protein extracts from thermally processed chickpeas and white beans by almost 25% and 100%, respectively. DEAE-cellulose chromatography, indicated the presence of five (A₁–A₅) and three (B₁–B₃) antioxidant protein fractions in heat-treated and thermally processed chickpea protein extracts, respectively, and can be used for the partial purification of antioxidant proteins. The results of this study showed the good potential of chickpea proteins as thermostable natural food antioxidants.     

Effect of methylation on the structure and radical scavenging activity of polysaccharides from longan (Dimocarpus longan Lour.) fruit pericarp

Polysaccharides of longan fruit pericarp (PLFP) were purified by gel filtration chromatography and methylated by methyl iodide. The structure of methylated PLFP was identified by gas chromatography/mass spectrometry. The results indicated that the percentages of methylated Ara, Glc and Gal increased gradually to a maximal value with increasing volume of methyl iodide. Methylation resulted in a decrease in the DPPH radical scavenging activity of PLFP, while the superoxide anion radical scavenging activity of PLFP decreased with increasing the degree of methylation. When the degree of methylation reached up to 47.4% or a higher value, a promoted effect on the generation of superoxide anion was observed. Furthermore, a high correlation coefficient between degree of methylation and superoxide anion radical scavenging activity of PLFP was determined, which indicated the important role of hydroxyl groups of monosaccharide units in the radical scavenging activity of PLFP.     

Antioxidative activities and chemical characterization of polysaccharides extracted from the basidiomycete Schizophyllum commune

Antioxidant properties of hot water extract (HWE), hot water extracted polysaccharides (HWP) and hot alkali extracted polysaccharides (HWAE) were obtained from fruiting bodies of the wild basidiomycete Schizophyllum commune. All extracts contained both α- and β-glucans as determined by Megazyme β-glucan assay kit. Glucose was found by TLC and NMR to be the prevalent monosaccharide in all extracts. Total phenol contents were in descending order of HWP ≈ HWE > HWAE. Median effective concentrations (EC₅₀ values) of antioxidant activities were 8.3 ± 0.1, 6.9 ± 0.0 and 8.9 ± 0.1 mg/mL, and of the DPPH scavenging activity 0.8 ± 0.0, 0.6 ± 0.0 and 1.8 ± 0.0 mg/mL, for HWE, HWP and HWAE, respectively. EC₅₀ values of reducing power were 7.6 ± 0.1, 7.9 ± 0.0 and 12.5 ± 0.1 mg/mL, whereas those of the chelating abilities on ferrous ions were 3.1 ± 0.0, 4.6 ± 0.1 and 4.9 ± 0.1 mg/mL. The EC₅₀ values of the antioxidant activity, of the DPPH scavenging, and of the reducing power were correlated with total polysaccharide as well as with total phenol content. The antioxidant activities of all the extracts may be caused by both polysaccharides and polyphenols or by a complex of both.