Chemical compositions and antioxidant activities of water extracts of Chinese propolis

The present study investigated the chemical composition and antioxidant activity of the water extract of propolis (WEP) collected from 26 locations in China. Spectrophotometry was used to determine the physicochemical properties and the chemical constituents of WEP. Phenolic compounds in WEP were identified by RP-HPLC-DAD with reference standards. The antioxidant activities [characterized by reducing power and 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging ability] of WEP were also measured. Results show that epicatechin, p-coumaric acid, morin, 3,4-dimethoxycinnamic acid, naringenin, ferulic acid, cinnamic acid, pinocembrin, and chrysin are the major functional phenolic compounds in Chinese WEPs. Furthermore, most WEPs show strong antioxidant activities, which are significantly correlated with E(1cm)(1%), an index for the estimation of the quality of WEP. WEPs also contain many more active constituents than ethanol extracts of propolis.     

Sources of antioxidant activity in Australian native fruits. Identification and quantification of anthocyanins

Selected native Australian fruits, muntries (Kunzea pomifera F. Muell., Myrtaceae), Tasmanian pepper berry (Tasmanian lanceolata R. Br., Winteraceae), Illawarra plum (Podocarpus elatus R. Br. ex Endl., Podocarpaceae), Burdekin plum (Pleiogynium timorense DC. Leenh, Anacardiaceae), Cedar Bay cherry (Eugenia carissoides F. Muell., Myrtaceae), Davidson's plum (Davidsonia pruriens F. Muell. var. pruriens, Davidsoniaceae), and Molucca raspberry (Rubus moluccanus var. austropacificus van Royen, Rosaceae), were evaluated as sources of antioxidants by 2,2-diphenyl-1-picrylhydrazyl and ferric reducing antioxidant power assays and compared with blueberry (Vaccinum spp. cv. Biloxi). The total reducing capacity of five fruits was 3.5-5.4-fold higher than that of blueberry, and the radical scavenging activities of muntries and Burdekin plum were 1.5- and 2.6-fold higher, respectively. The total phenolic level by Folin-Ciocalteu assay highly correlated with the antioxidant activity. Therefore, systematic research was undertaken to identify and characterize phenolic complexes. In the present study we report on the levels and composition of anthocyanins. The HPLC-DAD and HPLC/ESI-MS-MS (ESI = electrospray ionization) analyses revealed simple anthocyanin profiles of one to four individual pigments, with cyanidin as the dominating type. This is the first evaluation of selected native Australian fruits aiming at their utilization for the development of novel functional food products.     

Phytochemicals and antioxidant properties in wheat bran

Bran samples of seven wheat varieties from four different countries were examined and compared for their phytochemical compositions and antioxidant activities. Phenolic acid composition, tocopherol content, carotenoid profile, and total phenolic content were examined for the phytochemical composition of wheat bran, whereas the measured antioxidant activities were free radical scavenging properties against 2,2-diphenyl-1-picrylhydrazyl radical, radical cation 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt, peroxide radical anion O(2)(.-), and oxygen radical and chelating capacities. The results showed that the tested wheat bran samples differed in their phytochemical compositions and antioxidant properties. Ferulic acid, with a concentration range of 99-231 microg/g, was the predominant phenolic acid in all of the tested bran samples and accounted for about 46-67% of total phenolic acids on a weight basis. The concentrations for alpha-, delta-, and gamma- tocopherols were 1.28-21.29, 0.23-7.0, and 0.92-6.90 microg/g, respectively. In addition, lutein and cryptoxanthin were detected in all of the tested bran samples with levels of 0.50-1.80 and 0.18-0.64 microg/g, respectively. Zeaxanthin was detected in the six bran samples, and the greatest zeaxanthin concentration of 2.19 microg/g was observed in the Australian general purpose wheat bran. Beta-carotene was detected in four of the tested bran samples at a range of 0.09-0.40 microg/g. These data suggest that wheat and wheat bran from different countries may differ in their potentials for serving as dietary sources of natural antioxidants.     

Color and antioxidant properties of cyanidin-based anthocyanin pigments

A series of cyanidin-based anthocyanin pigments was investigated to determine the effect of structural variation on a number of chemical and physical properties: CIELAB color coordinates, visual detection thresholds, hydration constants (pK(H)), and in vitro antioxidant activities (ORAC). In addition to individual isolated compounds, purified total pigment isolates from blackberry, elderberry, black carrot, red cabbage, and sweet potato were also examined. Acylation with cinnamic acids shifted color tonality (hue angle) to purple, and markedly increased pK(H) and antioxidant activity, but lowered the visual detection threshold. Glycosidic substitution at the 5 position moved tonalities toward purple and decreased pK(H), and tended to lower the ORAC value, but raised the visual detection threshold. Increasing the number of sugar substituents at the 3 position also affected all of these parameters, however, the extent was not predictable. Antioxidant levels of purified anthocyanin extracts were much higher than expected from anthocyanin content indicating synergistic effect of anthocyanin mixtures.     

Antimutagenic and antioxidant properties of milk-kefir and soymilk-kefir

This study was aimed at evaluating the antimutagenic and antioxidant properties of milk-kefir and soymilk-kefir. Such antimutagenic activity was determined by means of the Salmonella mutagenicity assay, whereas the antioxidant properties of kefir were evaluated by assessing the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity, lipid peroxidation inhibition activity, ferrous ion chelating ability, reducing power, and antioxidative enzyme activity. Both milk-kefir and soymilk-kefir demonstrated significantly greater antimutagenic activity than milk and soymilk. Milk-kefir and soymilk-kefir also displayed significantly greater scavenging activity upon DPPH radicals, an inhibition effect upon linoleic acid peroxidation, and more substantial reducing power but displayed a reduced glutathione peroxidase activity than was the case for milk and soymilk. Milk and soymilk fermented by kefir grains did not alter the ferrous ion chelating ability and superoxide dismutase activity of the original materials. These findings have demonstrated that milk-kefir and soymilk-kefir possess significant antimutagenic and antioxidant activity and suggest that milk-kefir and soymilk-kefir may be considered among the more promising food components in terms of preventing mutagenic and oxidative damage.     

Chemical characterization and antioxidant properties of coffee melanoidins

Melanoidins, the brown polymers formed through Maillard reaction during coffee roasting, constitute up to 25% of the coffee beverages' dry matter. In this study chemical characterization of melanoidins obtained from light-, medium-, and dark-roasted coffee beans, manufactured from the same starting material, was performed. Melanoidins were separated by gel filtration chromatography and studied by MALDI-TOF mass spectrometry. Results showed that the amount of melanoidins present in the brews increased as the intensity of the thermal treatment increased, while their molecular weight decreased. The antioxidant activity of melanoidins isolated from the different brews was studied by using different methodologies. Melanoidins antiradical activity determined by ABTS(*)(+) and DMPD(*)(+) assays decreased as the intensity of roasting increased, but the ability to prevent linoleic acid peroxidation was higher in the dark-roasted samples. Data suggest that melanoidins must be carefully considered when the relevance of coffee intake in human health is studied.     

Evaluation of the antioxidant properties of free and bound phenolic acids from native and malted finger millet (ragi, Eleusine coracana Indaf-15)

Free and bound phenolic acids were isolated from native and malted finger millet (ragi, Eleusine coracana Indaf-15), and their antioxidant properties were evaluated. Protocatechuic, gallic, and caffeic acids were found to be the major free phenolic acids. A 3-fold decrease was observed in protocatechuic acid content, whereas the decrease was marginal in the case of caffeic acid upon 96 h of malting. However, the contents of other free phenolic acids such as gallic, vanillic, coumaric, and ferulic acids increased. Ferulic, caffeic, and coumaric acids were found to be the major bound phenolic acids, and a 2-fold decrease was observed in their contents upon 96 h of malting. The antioxidant activity of a free phenolic acid mixture was found to be higher compared to that of a bound phenolic acid mixture. An increase in antioxidant activity coefficient was observed in the case of free phenolic acids from 770.0 +/- 7.8 to 1686.0 +/- 16.0, whereas the same was decreased from 570.0 +/- 6.0 to 448.0 +/- 4.5 in bound phenolic acids upon 96 h of malting. Therefore, the antioxidant capacity of phenolic acids changes during the malting of ragi.     

Importance of insoluble-bound phenolics to antioxidant properties of wheat

Two commercial samples of soft (70% Canadian Eastern soft red spring and 30% Canadian Eastern soft white winter) and hard (90% Canadian western hard red spring and 10% Canadian Eastern hard red winter) wheats were used to obtain different milling fractions. Phenolics extracted belonged to free, soluble esters and insoluble-bound fractions. Soluble esters of phenolics and insoluble-bound phenolics were extracted into diethyl ether after alkaline hydrolysis of samples. The content of phenolics was determined using Folin-Ciocalteu's reagent and expressed as ferulic acid equivalents (FAE). The antioxidant activity of phenolic fractions was evaluated using Trolox equivalent antioxidant capacity, 2,2-diphenyl-1-picrylhydrazyl radical scavenging, reducing power, oxygen radical absorbance capacity, inhibition of oxidation of human low-density lipoprotein cholesterol and DNA, Rancimat, inhibition of photochemilumenescence, and iron(II) chelation activity. The bound phenolic content in the bran fraction was 11.3 +/- 0.13 and 12.2 +/- 0.15 mg FAE/g defatted material for hard and soft wheats, respectively. The corresponding values for flour were 0.33 +/- 0.01 and 0.46 +/- 0.02 mg FAE/g defatted sample. The bound phenolic content of hard and soft whole wheats was 2.1 (+/-0.004 or +/-0.005) mg FAE/g defatted material. The free phenolic content ranged from 0.14 +/- 0.004 to 0.98 +/- 0.05 mg FAE/g defatted milling fractions of hard and soft wheats examined. The contribution of bound phenolics to the total phenolic content was significantly higher than that of free and esterified fractions. In wheat, phenolic compounds were concentrated mainly in the bran tissues. In the numerous in vitro antioxidant assays carried out, the bound phenolic fraction demonstrated a significantly higher antioxidant capacity than free and esterified phenolics. Thus, inclusion of bound phenolics in studies related to quantification and antioxidant activity evaluation of grains and cereals is essential.     

Phenolic constituents and antioxidant properties of Xanthosoma violaceum leaves

An extract of Xanthosoma violaceum leaves was subjected to a polyphenol profile determination, including total polyphenols, and antioxidant activity evaluation. Analysis of the extract resulted in the isolation of a new flavone C-glycoside, apigenin 6-C-beta-D-glucopyranosyl-8-C-beta-D-apiofuranoside (1), as well as known flavone C-glycosides, including vitexin (2), isovitexin (3), isovitexin 4'-O-rhamnopyranoside (4), apigenin 6-C-[beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranoside] (5), and apigenin 6,8-diC-beta-D-glucopyranoside (6). The antioxidant activity of the extract was assessed by means of two different in vitro tests: bleaching of the stable 1,1-diphenyl-2-picrylhydrazyl radical (DPPH test) and peroxidation induced by the water-soluble radical initiator 2,2'-azobis(2-amidinopropane) hydrochloride, on mixed dipalmitoylphosphatidylcholine/linoleic acid unilamellar vesicles (LP-LUV test). In both tests used, the extract and a fraction II showed a significant antioxidant/free-radical scavenging effect (fraction II, EC(50) = 11.6 microg/mL) in comparison to alpha-tocopherol (EC(50) = 10.1 microg/mL).     

Determination of antioxidant properties of aroma extracts from various beans

Aroma extracts from fresh soybeans, mung beans, kidney beans, and azuki beans were prepared using simultaneous steam distillation and solvent extraction (SDE) under mild conditions (55 degrees C and 95 mmHg). Extracts were examined for antioxidative activities in two different assays. The aroma extracts isolated from all beans inhibited the oxidation of hexanal for nearly one month at a level of 250 microL/mL. Mung bean and soybean extracts inhibited malonaldehyde (MA) formation from cod-liver oil by 86% and 88%, respectively, at the 250 microL/mL level. Azuki and kidney bean extracts inhibited MA formation from cod-liver oil by 76% and 53%, respectively, at the 250 microL/mL level. The antioxidative activities of mung bean and soybean extracts were comparable with that of the natural antioxidant, alpha-tocopherol (vitamin E).     

Effect of caffeic acid phenethyl ester, an antioxidant from propolis, on inducing apoptosis in human leukemic HL-60 cells.

Caffeic acid phenethyl ester (CAPE) is an active component isolated from propolis. The aim of this study was to investigate the mechanism of CAPE-induced apoptosis in human leukemic HL-60 cells. It was found that CAPE entered HL-60 cells very quickly and then inhibited their survival in a concentration- and time-dependent manner. CAPE induced characteristic DNA fragmentation and morphological changes typical of apoptosis in these cells. Estimation of the apoptotic percentage showed a time-dependent increase after CAPE (6 microg/mL) treatment (up to 66.7 +/- 2.0% at 72 h). Treatment with CAPE caused rapid activation of caspase-3 after 4 h, down-regulation of Bcl-2 expression after 6 h, and up-regulation of Bax expression after 16 h. These results suggest that CAPE is a potent apoptosis-inducing agent; its action is accompanied by activation of caspase-3, down-regulation of Bcl-2, and up-regulation of Bax in human leukemic HL-60 cells.     

Chemical composition and antioxidant properties of clove leaf essential oil

The antioxidant activity of a commercial rectified clove leaf essential oil (Eugenia caryophyllus) and its main constituent eugenol was tested. This essential oil comprises in total 23 identified constituents, among them eugenol (76.8%), followed by beta-caryophyllene (17.4%), alpha-humulene (2.1%), and eugenyl acetate (1.2%) as the main components. The essential oil from clove demonstrated scavenging activity against the 2,2-diphenyl-1-picryl hydracyl (DPPH) radical at concentrations lower than the concentrations of eugenol, butylated hydroxytoluene (BHT), and butylated hydroxyanisole (BHA). This essential oil also showed a significant inhibitory effect against hydroxyl radicals and acted as an iron chelator. With respect to the lipid peroxidation, the inhibitory activity of clove oil determined using a linoleic acid emulsion system indicated a higher antioxidant activity than the standard BHT.     

Total antioxidant capacity of teas by the ferric reducing/antioxidant power assay

This study aimed to compare in vitro antioxidant power of different types of tea (Camellia sinensis). The ferric reducing/antioxidant power (FRAP) assay was used to measure the total antioxidant power of freshly prepared infusions of 25 types of teas. Results showed that different teas had widely different in vitro antioxidant power and that the antioxidant capacity was strongly correlated (r = 0. 956) with the total phenolics content of the tea. Expressed as micromol of antioxidant power/g of dried tea leaves, values ranged as 132-654 micromol/g for black ("fermented") teas, 233-532 micromol/g for Oolong ("semifermented") teas, and 272-1144 micromol/g for green ("nonfermented") teas. One cup of tea of usual strength (1-2%), therefore, can provide the same potential for improving antioxidant status as around 150 mg of pure ascorbic acid (vitamin C).     

Surface functional properties of native, acid-treated, and reduced soy glycinin. 2. Emulsifying properties

Emulsifying properties of native and chemically modified soy glycinins were studied. The influence of ionic strength, protein sample composition and concentration, and assay conditions on the flocculation-creaming process and coalescence resistance was analyzed. Differences in these emulsifying properties were exhibited by native glycinins, which have a variable content of 4S, 11S, and 15S forms. Structure and functionality of native glycinin were modified by means of combined treatments: mild acidic treatments without heating or with heating at variable time and with or without disulfide bonds reduction. Modified glycinins presented different degrees of deamidation, surface hydrophobicity, and molecular mass. A slight enhancement of emulsifying stability at moderated deamidation degrees was observed. In different protein samples, a positive relationship between the flocculation-creaming rate constant and equilibrium oil volume fraction of emulsions with surface hydrophobicity was detected. A remarkable difference was observed between reduced and nonreduced samples, mainly with respect to behavior at low or high ionic strength.     

Surface functional properties of native, acid-treated, and reduced soy glycinin. 1. Foaming properties

Foaming properties of native and chemically modified glycinin were evaluated. Effects of ionic strength and glycinin composition and concentration on foam formation and stabilization were studied. Glycinin was modified by means of combined treatments: cold or hot acidic treatments, with or without later disulfide bridges reduction. Modified proteins obtained from glycinin present different degrees of dissociation, deamidation, and as consequence, varied surface hydrophobicity and molecular size. Parameters of forming and stabilizing of foam were correlated with both deamidation and dissociation degrees of modified and native glycinin samples. A positive relationship was observed between surface behavior and foaming properties of different protein species. Results show that dissociation, deamidation, and reduction have produced structural changes on glycinin (increased surface hydrophobicity, increased net charge, decreased molecular size) which enhance the adsorption and anchorage of proteins at the air-water interface and, consequently, improve the foam forming and stabilizing capacities.     

Studies of the constituents of Uruguayan propolis

Eighteen flavonoids including two new compounds, four aromatic carboxylic acids, and eleven phenolic acid esters including one new compound were isolated and identified from the ethyl acetate soluble fraction of the 70% ethanol extract of Uruguayan propolis. The new compounds were elucidated as pinobanksin 3-(2-methyl)butyrate (1; recently reported in Usia, T.; Banskota, A. H.; Tezuka, Y.; Midorikawa, K.; Matsushige, K.; Kadota, S. J. Nat. Prod. 2002, 65, 673-676) pinobanksin 3-isobutyrate (2), and 2-methyl-2-butenyl ferulate (24). The constituents isolated from Uruguayan propolis in this study were similar to those of propolis of European and Chinese origin. Thus, it is suggested that the Uruguayan propolis has a plant origin similar to those of propolis from Europe and China.     

New C-deoxyhexosyl flavones and antioxidant properties of Passiflora edulis leaf extract

The flavonoids present in passion fruit (Passiflora edulis) leaves were identified by a high-performance liquid chromatography-diode array detection-tandem mass spectrometry (HPLC-DAD-MS/MS) method. Sixteen apigenin or luteolin derivatives were characterized, which included four mono-C-glycosyl, eight O-glycosyl- C-glycosyl, and four O-glycosyl derivatives. With the exceptions of C-hexosyl luteolin and C-hexosyl apigenin, all the compounds exhibited a deoxyhexose moiety. Moreover, the uncommon C-deoxyhexosyl derivatives of luteolin and apigenin have been identified for first time in P. edulis by HPLC-DAD-MS/MS. The antioxidative capacity of passion fruit leaves was checked against DPPH radical and several reactive oxygen species (superoxide radical, hydroxyl radical, and hypochlorous acid), revealing it to be concentration-dependent, although a pro-oxidant effect was noticed for hydroxyl radical.     

水溶性蜂胶的酶解制备工艺优化

为提高蜂胶在水中的溶解性而制备水溶性蜂胶。以水溶液中黄酮提取率为指标,研究了酶的种类、酶反应温度、pH值和酶用量对促进蜂胶水溶性的影响,通过单因素和正交试验优化脂酶制备水溶性蜂胶的工艺条件。以蜂胶醇提液和维生素C为参照,采用N,N-二苯基三硝基苯肼（DPPH）自由基清除率测定方法评价水溶性蜂胶抗氧化能力。正交试验结果表明,影响脂酶水解蜂胶效果的因素从高到低依次为酶用量、酶反应时间、pH值、酶反应温度。脂酶对蜂胶水解的优化条件为,脂酶用量11%,反应时间为2.25 h,酶解液初始pH5.5,酶反应温度为40     

Effects of solid-state enzymatic treatments on the antioxidant properties of wheat bran

This study evaluated the potential of solid-state enzyme treatments to release insoluble bound antioxidants such as phenolic acids from wheat bran, thereby improving its extractable and potentially bioaccessible antioxidant properties including scavenging capacities against peroxyl (ORAC), ABTS cation, DPPH and hydroxyl radicals, total phenolic contents, and phenolic acid compositions. Investigated enzyme preparations included Viscozyme L, Pectinex 3XL, Ultraflo L, Flavourzyme 500L, Celluclast 1.5L, and porcine liver esterase. Results showed significant dose-dependent increases in extractable antioxidant properties for some enzyme preparations, and Ultraflo L was found to be the most efficient enzyme, able to convert as much as 50% of the insoluble bound ferulic acid in wheat bran to the soluble free form. The effect of moisture content on these solid-state enzyme reactions was also evaluated and found to be dependent on enzyme concentration. These data suggest that solid-state enzyme treatments of wheat bran may be a commercially viable post-harvest procedure for improving the bioaccessibility of wheat antioxidants.     

香椿叶抗脂质过氧化物的分离及抗氧化特性

为寻求有应用前景的油脂抗氧化剂,分离纯化香椿叶中抗脂质过氧化物（FTAP）,研究pH值、热处理及贮藏对FTAP抗氧化活性的影响及FTAP在油脂中的应用。FTAP的抗氧化活性用亚油酸过氧化法测定。采用大孔树脂分离纯化FTAP,比色法测定FTAP中的黄酮类含量。以FTAP对亚油酸过氧化抑制率反映其在不同pH值介质、热处理以及贮藏期的抗氧化性。用过氧化值评价FTAP在油脂中的抗氧化作用。结果表明,LSA-10树脂适于FTAP的分离纯化,FTAP抗脂质过氧化作用与其黄酮含量有关;FTAP在pH 7、pH 4时抗氧化活性较强,185℃下加热60 min抗氧化性无显著变化,5℃下贮存30 d抗氧化性稳定,而后逐渐降低;FTAP能抑制猪油和菜籽油的氧化,且呈量效关系,0.02%FTAP与0.02%BHT抗氧化活性相当。FTAP是具有潜力的天然抗氧化剂,可用于油脂或含油脂食品中。