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。     

胭脂红酸体外清除自由基作用

以DPPH 自由基、ABTS+·及O2 －·3 种自由基为实验对象,通过比较特定波长下自由基溶液吸光度的变化,评估胭脂红酸清除自由基的能力,并与抗坏血酸清除3 种自由基的能力做比较。结果显示：胭脂红酸与抗坏血酸对3 种自由基：DPPH 自由基、ABTS+·及O2 －·均具有清除活性;当胭脂红酸达到一定质量浓度时,对DPPH 自由基、ABTS+·及O2 －·的清除率分别可达83%、85% 及46.84% 左右。结果表明胭脂红酸是一种对自由基具有一定清除活性的食品添加剂。     

Radical Scavenging Capacity and Antioxidant Activity of the E Vitamer Fraction in Rice Bran

ABSTRACT: Radical scavenging capacity and antioxidant activity of an E vitamer fraction from rice bran were investigated. The E vitamer fraction was prepared by a liquid-liquid extraction method. The free radical scavenging capacity of the E vitamer fraction was measured by the 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) method at the concentration range of 2.5 to 640 ppm, whereas the antioxidant activities were measured by both the reducing power and ferric thiocyanate (FTC) methods at different concentrations (0, 2.5, 10, 40, and 160 ppm). Radical scavenging capacity of the fraction was effective up to 160 ppm, then remained stable. Also, at a concentration of 160 ppm, it was highly effective in inhibiting linoleic acid peroxidation. Similarly, superoxide scavenging and antioxidant activities of the E vitamer fraction were compared with those of the synthetic phenol compounds. Results showed that with a concentration of the E vitamer fraction at 160 ppm, the antioxidant activity was comparable to both butylated hydroxytoluene (BHT, 160 ppm) and butylated hydroxyanisole (BHA, 160 ppm). No significant differences (P > 0.05) were found among them. The E vitamer fraction may be a good substitute for the synthetic phenol antioxidants currently used in industry because the former is more natural and comparatively effective in its radical scavenging capacity and antioxidant activity.     

酿酒葡萄皮渣中多酚物质的提取及其对羟基自由基的清除研究

本文以酿酒葡萄皮渣为研究对象,通过单因素试验以及正交试验研究了超声波辅助提取对葡萄皮渣多酚得率的影响,并对工艺条件进行优化,确定了提取葡萄皮渣多酚的最佳工艺参数为:超声时间30 min,温度60℃,料液比1:20(g/mL),超声功率200 W,在该条件下葡萄皮渣多酚得率为6.72 mg/g。并研究了葡萄皮渣多酚粗提物对羟基自由基的清除能力,结果表明:在实验浓度范围内,当添加的葡萄皮渣多酚的质量浓度为0.79 mg/mL时,对羟自由基的清除率可达78.64%。     

阴香果实花色苷的体外抗氧化活性

以半制备HPLC纯化的阴香果实花色苷为供试样品,研究其体外抗氧化活性。结果表明： 阴香果实花色苷对DPPH自由基、超氧阴离子自由基、羟自由基、脂质过氧化的半抑制剂量(IC50)分别为：5.46、7.60、78.25、173.74μg/mL,总抗氧化活力和还原力明显高于VC,金属离子螯合力与EDTA相当。研究表明阴香花色苷具有较强的清除自由基与抗氧化活性。     

Total Phenolic Compounds, Flavonoids, and Radical Scavenging Activity of 21 Selected Tropical Plants

ABSTRACT:  Free radical scavenging activity of 21 tropical plant extracts was evaluated using 1,1-diphenyl-2-picrylhydrazyl assay (DPPH). Total phenolic compounds and flavonoids were determined using Folin–Ciocalteu and HPLC, respectively. Results of the study revealed that all the plants tested exhibited excellent antioxidant activity with IC₅₀ in the range of 21.3 to 89.6 μg/mL. The most potent activity was demonstrated by  Cosmos caudatus  (21.3 μg/mL) and  Piper betle  (23.0 μg/mL) that are not significantly different than that of     -tocopherol or BHA.  L. inermis  extract was found to consist of the highest concentration of phenolics, catechin, epicatechin, and naringenin. High content of quercetin, myricetin, and kaempferol were identified in  Vitex negundo ,  Centella asiatica , and  Sesbania grandiflora  extracts, respectively. Luteolin and apigenin, on the other hand, were found in  Premna cordifolia  and  Kaempferia galanga  extracts. Strong correlation ( R  = 0.8613) between total phenolic compounds and total flavonoids ( R  = 0.8430) and that of antioxidant activity of the extracts were observed. The study revealed that phenolic, in particular flavonoids, may be the main contributors to the antioxidant activity exhibited by the plants.
Practical Application: Potent antioxidant from natural sources is of great interest to replace the use of synthetic antioxidants. In addition, some of the plants have great potential to be used in the development of functional ingredients/foods that are currently in demand for the health benefits associated with their use.     

不同品种石榴花色苷、总多酚含量及抗氧化活性比较研究

石榴中含有丰富的花色苷和多酚类物质,具有良好的抗氧化活性。以5个石榴品种(大叶天红蛋、大红酸、净皮甜、御石榴和喀什红子酸石榴)为实验材料,分析其总花色苷、总多酚含量,并用DPPH、FRAP、ABTS、螯合亚铁离子法测定抗氧化活性,比较不同石榴品种总花色苷、总多酚含量及抗氧化活性。结果表明:不同石榴品种总花色苷含量范围为3.54～13.89mg/100g,总多酚含量范围为38.89～68.28mg/100g;清除DPPH自由基范围为24.30%～45.73%;FRAP法测得的还原力范围为0.38～0.78;清除ABTS+.能力范围为58.02%～83.40%;螯合亚铁离子能力范围为14.73%～70.60%。相对而言,喀什红子酸石榴抗氧化活性较好,其次为御石榴。     

黑果腺肋花楸多酚稳定性的研究

通过测定黑果腺肋花楸多酚在不同条件下多酚保留率的变化,分别研究在不同pH值、糖类、温度、光照强度、氧化还原剂和防腐剂条件下对黑果腺肋花楸多酚稳定性影响。结果表明：在pH 2～3的条件下多酚保留率可达96.12%以上;糖类对多酚稳定性具有一定增强作用,多酚保留率与糖分添加量呈正相关;随着光照强度的增加,多酚保留率显著下降,在避光条件下多酚最为稳定;当温度超过50 ℃时,温度对多酚保留率影响显著;氧化还原剂对多酚具有显著的破坏作用,而氧化剂对多酚的影响明显大于还原剂;防腐剂可有效减少多酚的降解,但随防腐剂添加量的增加,多酚保留率并无显著增高,低添加量的防腐剂可有效提高多酚稳定性。     

芹菜多酚的抗氧化性及其稳定性研究

以芹菜多酚为研究对象,采用DPPH自由基清除率法和铁离子还原能力(FRAP)法对其抗氧化性进行评价,并分析温度、光照、pH值、Na_2SO_3、H_2O_2、山梨酸钾等对其稳定性的影响。结果表明:pH值在2~6范围时DPPH自由基清除率从92.99%到84.88%;100℃,在40~60 min范围时清除率从91.32%降低到87.5%;Na_2SO_3浓度大于0.2%时,DPPH自由基清除率低于10.04%;防腐剂浓度与芹菜多酚DPPH自由基清除率呈负相关;光照和氧化剂对芹菜多酚的稳定性影响较小。研究认为芹菜多酚具有较好的抗氧化性,但需注意控制外界环境对其的影响,增强使用效果。     

Determination of Anthocyanins, Total Phenolic Content, and Antioxidant Activity in Andes Berry (Rubus glaucus Benth)

ABSTRACT:  Anthocyanins, total phenolic content, ascorbic acid content, and the antioxidant activity were determined in extracts of Andes berry fruit ( Rubus glaucus Benth). Anthocyanis (ACNs) were isolated and characterized by means of high-performance liquid chromatography (HPLC) with photodiode array detection and electro spray ionization/mass spectrometry (PDA-ESI/MS/MS) analysis. The anthocyanin (ACN) content was 45 mg/100 g FW. The isolated anthocyanins were characterized as cyanidin 3-sambubioside, cyanidin 3-glucoside, cyanidin 3-xylorutinoside, cyanidin 3-rutinoside, pelargonidin 3-glucoside, and pelargonidin 3-rutinoside. The ascorbic acid content was 10.1 mg/100 g FW. The total phenolic content as determined by the Folin–Ciocalteau method was 294 mg GAE/100 g FW while the antioxidant activity as measured by ABTS ^{· +} radical scavenging capacity and ferric reducing antioxidant power (FRAP) was 2.01 and 4.50 mmol TE/100 g FW or 8.22 mmoles ferric iron reduced/100 g FW, respectively. The high phenolic content and antioxidant capacity of Andes berry suggest that this fruit could be a rich source of natural pigments, nutraceuticals, and natural antioxidants.     

Ascorbic Acid Fortification Reduces Anthocyanins in Extruded Blueberry-Corn Cereals

ABSTRACT: Corn meal was mixed with ascorbic acid (0%, 0.1%, and 1%, wt/wt) and sucrose (15%) or lowbush blueberry concentrate (17%), and twin-screw extruded to produce ready-to-eat breakfast cereals. Consumers evaluated selected samples using just-right scales. Extrusion decreased anthocyanins in blueberry cereals; ascorbic acid was retained better in cereals containing blueberry concentrate than in the sweetened corn cereals. Blueberry concentrate decreased expansion ratio and increased bulk density. Based on sensory scores, blueberry extrudates with 0.1% ascorbic acid could be acceptable if sweetness is increased.     

金钱草清除自由基活性及其成分研究

用2:1的甲醇:氯仿超声提取金钱草成分,并用石油醚、乙酸乙酯和正丁醇依次进行萃取,利用DPPH法、邻二氮菲-Fe2+氧化法和AP-TEMED法进行清除自由基活性实验,同时与合成抗氧化剂BHT进行对照。结果显示乙酸乙酯提取物(EAF)具有最高的清除自由基活性,大于人工合成抗氧化剂BHT。利用硅胶,RP-18和SephadexLH-20对其进行活性追踪分离,得到3种纯的清除自由基活性成分。利用1D、2DNMR和ESI-MS对其结构进行鉴定。结果显示为槲皮素、槲皮素-3-o-葡萄糖甙和山奈酚-3-o-葡萄糖甙。活性大小顺序为槲皮素>槲皮素-3-o-葡萄糖甙>山奈酚-3-o-葡萄糖甙>EAF>BHT。含酚羟基化合物的清除自由基活性与其结构密切相关。活性大小主要取决于酚羟基的数目。     

Irradiation Effects on Free Radical Scavenging and Antioxidant Activity of Phytic Acid

ABSTRACT: Free radical scavenging and antioxidant activities of irradiated phytic acid at various concentrations were studied. Phytic acid sodium salt dissolved in deionized distilled water was irradiated at 0, 5, 10, 15, and 20 kGy. The degradation of phytic acid by irradiation was observed, and it was found that the concentrations had an effect on the degree of degradation. Stable 2,2-diphenyl-1-picrylhydrazyl radical scavenging ability of phytic acid was significantly increased by irradiation ( P < 0.05) and was positively correlated with irradiation dose ( P < 0.01). Antioxidant activity of phytic acid in lipid model systems was slightly increased by irradiation; however, at higher concentrations, the activity was reduced or was the same compared with nonirradiated phytic acid.     

L-抗坏血酸肉桂酸酯的合成及其抗氧化活性研究

以L-抗坏血酸和肉桂酸为原料,采用酰氯法合成得到了L-抗坏血酸肉桂酸酯。用分光光度法研究了酯化产物的稳定性、清除羟自由基(?OH)和二苯代苦味肼基自由基(DPPH?)的能力,并与Vc和常用的油溶性抗氧化剂叔丁基对苯二酚(TBHQ)进行比较,结果表明：新合成的L-抗坏血酸肉桂酸酯与Vc相比,稳定性得以明显改善,其清除DPPH?的EC50值为63.96 μmol/L,清除能力与Vc相当,清除?OH的EC50值为7.84 mmol/L,在浓度较高时优于TBHQ。     

插田泡花色苷的振荡提取及抗氧化活性

采用乙醇振荡提取插田泡果实花色苷,通过正交试验筛选花色苷提取的最佳条件,同时对插田泡花色苷的抗氧化活性进行研究。结果显示,体积分数85%乙醇溶液（pH 3）按料液比1∶30（g/mL）在50 ℃条件下振荡提取1 h,同样条件下样品再重复提取,振荡时间 1 h,花色苷提取量达211.05 mg/100 g。在实验范围内,花色苷对2,2’-联氮-双（3-乙基苯并噻吡咯啉-6-磺酸）（2,2’-azinobis-(3-ethylbenzthiazoline-6-sulphonate),ABTS）、二苯代苦味肼基（1,1-diphenyl-2-picrylhydrazyl radical 2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl,DPPH）、羟自由基（·OH）均有较强的清除能力,清除率随质量浓度的升高而增大,呈正线性相关;花色苷对不同自由基的抑制能力大小依次为·OH（IC50=1.71 μg/mL）＞ABTS+·（IC50=2.27 μg/mL）＞DPPH自由基（IC50=3.44 μg/mL）,抑制能力均远高于阳性对照VC和二丁基羟基甲苯。结果表明,插田泡花色苷具有显著的抗氧化活性,是一种值得开发的天然抗氧化剂和功能性食品资源。     

反应时间对DPPH·法、ABTS+·法评价抗氧化性结果的影响

由于DPPH·法、ABTS+·法操作简单,不需要特殊的检测设备(通过反应体系颜色的改变评价试样抗氧化性),因此,常被选作抗氧化性能评价方法。用这两种方法进行抗氧化性评价时,通常用固定反应时间下算得的EC50值(自由基清除率为50%时所需试样浓度)表征抗氧化剂的抗氧化性强弱(对于DPPH·法,固定时间为30min;对于ABTS+·法,固定时间为6min),结果表明:不同抗氧化剂因其组成、结构的差异,与DPPH·、ABTS+·反应速率不同,反应到达平衡的时间不同,将反应时间固定在某一值时,可能对抗氧化剂的抗氧化性评价带来错误的判断。     

欧李多酚清除自由基活性研究

采用大豆卵磷脂脂质模型系统、低密度脂蛋白体系和牛血清白蛋白介质三个不同的评价体系考察欧李多酚的清除自由基和抗氧化活性。研究表明,欧李多酚的脂质过氧化和蛋白质氧化抑制呈剂量和时间依赖性方式,总酚与抗氧化能力之间的相关性较好,能完全抑制由过氧自由基和铜离子诱导早期的共轭二烯(CD)的生成,延长脂质氧化诱导期,有效地抑制由过氧自由基诱导的牛血清白蛋白氧化。欧李多酚能通过淬灭自由基的方式抑制因自由基所致的生物膜、脂蛋白和血清白蛋白氧化损伤。     

槲寄生总黄酮微波提取工艺及其抗氧化活性研究

目的：优化提取槲寄生总黄酮的最佳工艺条件及测定其体外抗氧化活性。方法：以产品中总黄酮的质量分数为指标,正交试验L9(34)对槲寄生的微波辅助萃取工艺参数进行优化,并测定其体外抗氧化活性。结果：槲寄生总黄酮的最佳提取工艺为乙醇溶液体积分数70%、微波萃取功率500W、固液比1:40(g/mL)、萃取温度70℃,提取率达1.88%。其体外清除DPPH 自由基及·OH 的IC50 值分别为0.036mg/mL 和0.572mg/mL。结论：槲寄生总黄酮抗氧化活性明显,且最佳工艺操作简单快捷,适用于工业化大批量提取槲寄生总黄酮。     

Phenolic Composition,Radical Scavenging Activity and an Approach for Authentication of Aronia melanocarpa Berries,Juice, and Pomace

Aronia melanocarpa is a rich source of phenolic compounds like anthocyanins, chlorogenic acids, quercetin derivatives, and proanthocyanidins possessing strong antioxidative potential. The consumption of A. melanocarpa is actually increasing because of the known bioactivity of its phenolic constituents. A. melanocarpa extracts are used as natural colorants and nutraceuticals. Several attempts of adulteration of aronia products have already been reported. In this study, we investigated changes in phenolic composition from berry to juice by HPLC‐PDA, and HPLC‐ESI‐MSⁿ analyses as well as fingerprint profiles for authentication of commercially available aronia products in order to detect possible adulteration. Additionally, the radical scavenging activity of aronia products was determined by using the TEAC (Trolox® equivalent antioxidant capacity) assay. Aronia pomace, a valuable by‐product of juice production, showed the highest phenolic content and possessed the highest radical scavenging activity.