ESR Study of the Singlet Oxygen Quenching and Protective Activity of Trolox on the Photodecomposition of Riboflavin and Lumiflavin in Aqueous Buffer Solutions

ABSTRACT:  Singlet oxygen quenching activity of Trolox, a water-soluble derivative of tocopherol, was studied by electron spin resonance (ESR) spectroscopy in a buffer solution (pH 7.4) containing methylene blue (MB), 2,2,6,6-tetramethyl-4-piperidone (TMPD) after light illumination for 30 min. Trolox at the concentration of 125 μM quenched 89.1% singlet oxygen in the system. Trolox showed significantly higher singlet oxygen quenching activity than ascorbic acid in the buffer solution ( P  < 0.05). Riboflavin in phosphate buffer solutions was degraded very fast under fluorescent light illumination. The photodegradation rate of riboflavin at pH 8.5 was significantly higher than pHs 4.5 and 6.5 ( P  < 0.05). Lumiflavin was also degraded under the fluorescent light illumination, but its degradation rate was much lower than that of riboflavin under the same light intensity. Unlike riboflavin, the rate of lumiflavin photodegradation was the greatest at pH 4.5 and followed by pHs 6.5 and 8.5, in a decreasing order. Trolox greatly protected the photodegradation of riboflavin and lumiflavin. The protective activities of Trolox against the photodegradation of riboflavin and lumiflavin were also pH dependent. The treatments of 5 mM Trolox in the buffer solutions of pHs 8.5 and 6.5 exhibited 56.1% and 31.7% protection of riboflavin against degradation during 120 min light illumination, respectively. The treatments of Trolox at the concentrations of 1, 3, and 5 mM in the buffer of 6.5 exhibited 14.8%, 58.4%, and 81.4% protection of lumiflavin against degradation during 24 h light illumination, respectively.     

Electron Donation Mechanisms of β-Carotene as a Free Radical Scavenger

ABSTRACT The free radical scavenging ability of β-carotene was studied using free radical 2,2-diphenyl-1-picryl-hydrazyl (DPPH). As the concentration of β-carotene in acetone increased, the absorbance of DPPH at 517 nm decreased, which indicates that β-carotene scavenges free radicals. It was shown that β-carotene does not work as an antioxidant in soybean oil. The NMR spectrum of DPPH with BHA in CDCl₃ showed a new peak at 5.0(d) was formed and the peak at 6.6(d) from BHA was split into 2 peaks, which may be due to the hydrogen atom donation from BHA to DPPH. The NMR spectra of DPPH with p-carotene did not change during reaction and no peak was formed.     

抗坏血酸清除DPPH 自由基的作用机理

采用光谱、电化学和质谱分析方法研究抗坏血酸对DPPH 自由基清除机理,发现DPPH 在溶液中是以自由基形态和含氮- 氮双键的高度共轭结构的正离子态(DPPH+)存在且抗坏血酸对上述两种形态都有清除作用。由于DPPH 自由基与DPPH+ 在溶液中处于平衡态,故同种抗氧化剂用 517nm 波长处DPPH+ 的吸收强度变化可间接评价对DPPH 自由基的清除作用,但对不同抗氧化剂而言,因抗氧化剂对DPPH 的不同形态相对清除作用的不同会带来较大的误差或误判。本研究对准确评价抗氧化剂的自由基清除作用具有一定指导意义。     

pH值对乳清蛋白糖基化产物体外抗氧化特性的影响

选择6种不同的糖基配体,通过湿热糖基化反应,研究乳清蛋白不同糖基化复合物在不同pH值下的反应特性及抗氧化特性。结果表明:在pH值3～9的条件下,6种乳清蛋白糖基化复合物与乳清蛋白420nm和294nm处的吸光值差异显著(P<0.05);且6种乳清蛋白糖基化复合物的游离氧基酸含量均显著降低(P<0.05)。除了乳清蛋白-蔗糖复合物外,其他5种乳清蛋白糖基化复合物的还原能力、DPPH自由基清除能、·OH自由基清除能力和抗脂质过氧化能力随pH值的升高都有所提高。乳清蛋白-木糖复合物的抗氧化能力提高最大,而且在pH值7～9的反应条件下,具有比V_c更高的还原能力。     

Optimization of phenolic compound recovery and antioxidant activity of light and dark dried fig (Ficus carica L.) varieties

The optimum conditions for extraction of total phenolic contents (TPC) and for enhancing the antioxidant activity from light and dark dried figs were determined. The effects of the solvent nature (acetone, ethanol, methanol, or water), solvent concentration (20–80%), acetic acid concentration (0–2%), extraction temperature (25–70°C), extraction time (0.5–4 h), sample to solvent ratio (1/25–1/100), and number of extractions (1, 2, and 3) were determined. The TPC was used to identify antioxidant compounds. 2,2-diphenyl-1-picrylhydrazyl (DPPH) was used to evaluate antioxidant activity. All extraction parameters had significant effects (p<0.05) on the TPC and the antioxidant activities. The best conditions were obtained with double extraction using 60% acetone without acidification, at 40°C for 120 min, and with a 1/75 solid to solvent ratio. These conditions resulted in TPC concentrations of 469.46 (light variety) and 399.79 mg of gallic acid (GAE)/100 g (dark variety), and antioxidant activities of 96.47 and 102.28 mg of GAE/100 g, respectively.     

沙苑子提取物中多酚含量的测定

研究Folin-Ciocalteu 比色法测定沙苑子中多酚含量的优化条件,并以优化的条件测定沙苑子不同溶剂提取物中多酚的含量。结果表明：Folin-Ciocalteu 显色剂(经稀释10 倍)用量1.00mL、7.5g/100mL Na2CO3 用量3.00mL、反应温度25℃、反应时间120min、测定波长647nm 为沙苑子中多酚含量测定的最佳条件,所用没食子酸标准品在10～100μg/mL 范围内与吸光度呈良好的线性关系(y=0.0081x － 0.0249,R2=0.9996);沙苑子甲醇、乙醇和丙酮溶液提取物的质量浓度为1g/100mL 左右时较适合测定其多酚的含量。     

葡萄糖-牡蛎酶解液美拉德反应体系的抗氧化活性

以牡蛎酶解液与葡萄糖建立美拉德反应体系,以1,1-二苯基-2-三硝基苯肼（1,1-diphenyl-2-picrylhydrazyl, DPPH）自由基清除率、金属离子螯合能力和还原能力为指标,通过葡萄糖质量分数、反应温度、pH值以及反应时 间4 个因素的单因素试验和正交试验优化得到具有强抗氧化活性的美拉德反应产物适宜反应条件。结果表明,葡萄 糖-牡蛎酶解液美拉德反应产物具有较强抗氧化活性的反应条件为葡萄糖质量分数4%、反应温度120 ℃、pH 7.0、 反应时间120 min。在此组合条件下,牡蛎酶解液美拉德反应得到的反应液的DPPH自由基清除率为93.2%,金属离 子螯合能力为22.5%,还原能力为1.436。     

黄色洋葱皮不同溶剂多酚提取物的总酚、总黄酮含量及抗氧化活性

以黄色洋葱皮为原料,分别利用70%甲醇、70%乙醇和70%丙酮作为提取溶剂进行多酚类物质提取。测定提取物中的总酚含量、总黄酮含量并研究其抗氧化活性(DPPH自由基清除能力、ABTS自由基清除能力以及铁还原能力)。研究结果显示:利用甲醇作为提取剂所得的多酚类物质提取率最高(12.35%),并且提取物中总酚和总黄酮含量最高,分别为83.17、34.31 mg/g。同时,甲醇提取物对DPPH自由基和ABTS自由基的半抑制浓度IC₅₀分别为0.059和0.031 mg/mL,低于抗坏血酸而高于乙醇提取物和丙酮提取物。     

Antioxidant formation by γ-irradiation of glucose–amino acid model systems

The efficacy of γ-irradiation for the formation of Maillard reaction products (MRPs) from glucose and lysine/glycine and the antioxidant potential of MRPs thus formed were examined. Formation of MRPs was observed by monitoring absorbance at 284 nm and 420 nm. Upon irradiation, there was a dose-dependent increase in absorbance (r² = 0.99) at both the wavelengths. Irradiation of glucose/lysine solution resulted in higher absorbance at 284 nm than did that of glucose/glycine solution. Similarly, increase in absorbance at 420 nm was observed upon irradiation in both the systems. No significant absorbance was observed with unirradiated solution of glucose and lysine/glycine. These findings thus clearly revealed the formation of intermediate products and brown complexes (of Maillard reaction) upon irradiation of glucose/amino acid solution. A fluorescence was also observed in irradiated glucose/amino acid solution, whereas, none was seen in non-irradiated solution. These observations further confirmed the formation of MRPs, as fluorescent compounds are known to be precursors of brown pigments formed during the Maillard reaction. These MRPs exhibited excellent antioxidant activity, as measured by 1,1-diphenyl-2-picrylhydrazyl (DPPH) and β-carotene bleaching assays. MRPs, formed at a 40 kGy dose, scavenged up to 62% of DPPH radical and 82% of β-carotene was protected from bleaching. Reducing power of MRPs, estimated using the ferricyanide, method was also increased as compared to non-irradiated solutions. Further, these MRPs were able to scavenge hydroxyl radical and superoxide anion radical to the extents of 33% and 58%, respectively. These MRPs could chelate iron to an extent of 32% under in vitro conditions. Thus, these studies clearly demonstrated that radiation technology could be employed for obtaining novel antioxidants from sugar and amino acid combinations.     

石榴皮提取物的抗氧化作用研究

分别以水、甲醇、丙酮和乙酸乙酯为溶剂,对石榴皮中的多酚进行了提取,得到4种提取物。采用油脂过氧化值(POV)法和二苯三硝基苯肼(DPPH)自由基法研究了提取物的抗氧化活性。结果显示,4种提取物均具有抗油脂过氧化和清除DPPH自由基的能力,其抗氧化活性随添加量的增加而增加。4种提取物中,丙酮提取物的抗油脂过氧化作用最大,其次为水提取物和甲醇提取物,乙酸乙酯提取物的抗油脂过氧化作用最小。当丙酮提取物添加量为猪油质量的0.1%时,其抗油脂过氧化活性接近添加量为0.02%茶多酚或BHT。4种提取物对DPPH自由基的清除能力大小顺序依次为:水提取物、丙酮提取物、甲醇提取物和乙酸乙酯提取物。浓度为0.0175 mg/mL的水提取物对DPPH自由基的清除率高达85.2%,高于BHT,但略低于茶多酚。石榴皮多酚是一种有效的天然抗氧化剂。     

Total phenolic compounds,radical scavenging and metal chelation of extracts from Icelandic seaweeds

Screening of potential antioxidant activities of water and 70% acetone extracts from ten species of Icelandic seaweeds was performed using three antioxidant assays. Significant differences were observed both in total phenolic contents (TPC) and antioxidant activities of extracts from the various species evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, oxygen radical absorbance capacity (ORAC) and ferrous ion-chelating ability assays. Acetone extracts from three Fucoid species had the highest TPC and consequently exhibited the strongest radical scavenging activities. High correlation was found between TPC of seaweed extracts and their scavenging capacity against DPPH and peroxyl radicals, indicating an important role of algal polyphenols as chain-breaking antioxidants. However, water extracts generally had higher ferrous ion-chelating activity than 70% acetone extracts and no correlation was found with their TPC, suggesting that other components such as polysaccharides, proteins or peptides in the extracts were more effective chelators of ferrous ions than phenolic compounds.     

西式发酵火腿粗肽的制备及抗氧化活性和氨基酸组成分析

采用磷酸盐缓冲液和盐酸溶液提取西式发酵火腿的粗肽,测定并比较2种溶液提取的粗肽1,1-二苯基-2-三硝基苯肼(1,1-diphenyl-2-picrylhydrazyl,DPPH)自由基、羟自由基清除能力、Fe2+螯合能力及总抗氧化能力,同时对氨基酸组成进行分析.结果表明:磷酸盐法提取得到的粗肽粉A的质量和肽含量显著高...     

蓝莓花青素的抗氧化活性对比及其稳定性分析

本文研究不同提取工艺对蓝莓花青素抗氧化活性的影响,以及对微波波辅助提取得到的蓝莓花青素的稳定性进行了分析。通过1,1-二苯基-2-苦肼基(DPPH·)、羟基自由基(·OH)、超氧自由基(O2-·)等体外抗氧化实验评价不同提取工艺所提取的蓝莓花青素抗氧化活性,并分析光照、pH、温度、葡萄糖以及有机酸对蓝莓花青素保存率的影响。结果显示,乙醇浸取法、丙酮浸取法和微波辅助提取法的蓝莓花青素的得率分别为4.46%、4.41%和4.92%。蓝莓花青素的体外抗氧化活性在0.25~4.0 mg/mL范围内有浓度依赖性,微波辅助提取法获得的蓝莓花青素浓度为4.0 mg/mL时,DPPH·清除率、·OH清除率和O2-·清除率分别为86.59%、56.85%和88.65%,均显著高于乙醇浸提法、丙酮浸提法(p<0.05)。蓝莓花青素在强光、碱性、高温及抗坏血酸存在的环境下较为不稳定,而葡萄糖和柠檬酸则对蓝莓花青素的稳定性有一定的保护作用。     

Enhancement of antioxidant activity,total phenolic and flavonoid content of black soybeans by solid state fermentation with Bacillus subtilis BCRC 14715

In the present study, a solid state fermentation of black soybeans with Bacillus subtilis BCRC 14715 was performed. The effect of fermentation on the changes of total phenolic and flavonoid content and antioxidant activities including 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging effect, and Fe²⁺-chelating ability exerted by various solvent (water, 80% methanol, 80% ethanol, 80% acetone) extracts of black soybeans was examined. It was found that fermentation enhanced the total phenolic and flavonoid content as well as antioxidant activity of the black soybean extract. Among the various extracts examined, the acetone extract of fermented black soybeans showed the highest total phenolic and flavonoid content. The acetone extract and the methanol extract of fermented black soybeans showed the highest DPPH free radical-scavenging effect and Fe²⁺-chelating ability, respectively. Analysis of extraction yields showed that the active principle associated with the DPPH radical-scavenging effect was most efficiently extracted from black soybeans using water, regardless of fermentation. Water and methanol effectively extract the Fe²⁺-chelating principles from non-fermented and fermented black soybeans, respectively.     

金耳、银耳、木耳多酚提取及其抗氧化活性

以金耳、银耳、木耳为原料,分别用80%丙酮、80%甲醇、乙酸乙酯、石油醚对3种食用菌多酚类物质进行提取。通过高效液相色谱法和体外清除自由基方法(DPPH法、O-2.清除能力和.OH清除能力),对3种食用菌多酚类物质的主要组成及体外抗氧化能力进行初步研究。结果表明,80%丙酮提取效果最好,3种食用菌中槲皮素含量相当,金耳和银耳中芦丁和表儿茶素含量较高,木耳中儿茶素和绿原酸含量较高;体外抗氧化结果显示3种食用菌提取液具有较强的自由基清除能力和Fe3+还原能力,其中对DPPH.与O-2.的清除能力较强,对.OH的清除能力较弱。     

模拟胃肠液环境下Mozzarella干酪提取液抗氧化活性

为评价干酪成熟过程中形成的活性肽及存活的发酵剂菌种对人体的抗氧化作用,对不同菌种组合Mozzarella干酪的蒸馏水、pH4.6醋酸缓冲液和12%三氯乙酸（TCA）提取液在模拟胃肠液环境下对DPPH自由基的清除率以及还原力进行测定。结果表明,所有不同菌种组合Mozzarella干酪的不同溶剂提取液在模拟胃肠液的环境下具有一定的抗氧化活性,并且模拟肠液的抗氧化活性大大低于模拟胃液环境,活性下降最高达88.35%。添加干酪乳杆菌（Lactobacillus casei）LPC-37的3号Mozzarella干酪提取液在模拟胃肠液环境下的抗氧化活性高于其他Mozzarella干酪,其水、pH4.6醋酸缓冲液、12%TCA提取液在模拟肠液环境下对DPPH清除率分别为73.96%、30.28%、70.27%,还原力分别为0.37、0.18、0.18。     

金银花不同溶剂提取物多酚含量及抗氧化活性

分别以水、70%甲醇、70%乙醇和70%丙酮为提取剂,超声辅助提取金银花中多酚,采用Folin-Ciocalteu法测定提取液中多酚量,并利用清除DPPH·、·OH和ABTS+·法评价其抗氧化活性。结果表明,金银花不同溶剂水、70%甲醇、70%乙醇和70%丙酮提取物中多酚含量分别为18.97、46.56、46.63、48.49 mg/g,以水为溶剂与以有机溶液为溶剂,金银花多酚提取量有极显著差异(p<0.01)。不同溶剂金银花多酚均具有一定的清除DPPH·、·OH和ABTS+·能力,即抗氧化活性,但其清除DPPH·和ABTS+·的能力弱于2,6-二叔丁基-4-甲基苯酚(butylated hydroxytoluene,BHT),清除·OH的能力强于BHT。不同溶剂提取的金银花多酚种类不同,对自由基的清除能力不同。     

温度、光照及p H 值对阴香花色苷清除D P P H自由基活性的影响

以大孔吸附树脂精制及半制备HPLC 纯化的阴香果实花色苷样品,研究阴香花色苷清除DPPH 自由基的活性及温度、光照、pH 值对花色苷清除DPPH 自由基的影响。结果表明：阴香花色苷对DPPH 自由基半清除剂量IC50 ＝ 4.6μg/ml;花色苷溶液100℃处理5h 及130℃处理30min 对DPPH 自由基清除率显著下降,pH 9 处理3d 及pH10 处理2d 自由基清除率,625 ～3418 lx 光照8d 自由基清除率与处理1d 无显著差异,14～70.8klx 太阳光对花色苷清除DPPH 自由基活性的稳定性有显著影响。     

不同提取方法对蓝莓色素得率及抗氧化活力的 影响研究

目的 研究不同提取方法对蓝莓色素得率、抗氧化活力的影响及得率与抗氧化活力间的关系。方法 分别以乙醇、甲醇、丙酮为浸提溶剂,常规溶剂浸提、超声辅助浸提、微波辅助浸提3种提取方式,测定浸提液色素得率及其清除DPPH.、 、.OH的能力;分析色素得率与抗氧化活力的关系。结果 不同提取溶剂对蓝莓色素得率的影响差异不显著(P>0.05),但不同提取方式对蓝莓色素得率的影响差异显著(P＜0.05);不同提取方法的蓝莓色素清除DPPH.、 、和.OH的能力存在显著差异(P<0.05);蓝莓色素得率与其清除DPPH.与.OH能力间存在显著的正相关。结论 提取方式对蓝莓色素的得率及抗氧化活力有显著影响;蓝莓色素得率与其清除DPPH.和.OH能力呈显著的正相关性;超声辅助乙醇浸提更有助于获取高得率、高抗氧化活性的蓝莓色素。     

Effect of gamma irradiation on the extraction yield, total phenolic content and free radical-scavenging activity of Nigella staiva seed

In the present study, the radiation processing of Nigella sativa seed samples was carried out at dose levels of 2, 4, 8, 10, 12 and 16 kGy. The extraction yield, total phenolic content and 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical-scavenging activity of both control and irradiated samples extracted in acetone, methanol and water were assessed. The results showed that the extraction yields increased with an increase in radiation dose for all the test solvents. At 16 kGy the increases were 3.7%, 4.2%, 5.6% and 9.0% for hexane, acetone, water and methanol extracts, respectively. The phenolic content in the acetone extract was found to be increased from 3.7 for the control sample to 3.8 mg/g for the 16 kGy radiation-processed sample. No significant change was observed for the phenolic content of the methanolic extract, while the aqueous extract showed a decrease at dose levels of 12 and 16 kGy. In the control samples, the DPPH radical-scavenging activity was 79.4%, 79.1% and 92.0% for water, acetone and methanol extracts, respectively, at 5 mg/ml concentration. Gamma irradiation enhanced the scavenging activity in acetone and methanol extracts by 10.6% and 5.4%, respectively, at 16 kGy. In summary, gamma irradiation increased the extraction yield and total phenolic content, as well as enhancing the free radical-scavenging activity. In addition, the type of solvent used for extraction also affected the impact of irradiation on antioxidant activity and total phenolic content of N. sativa seed.