山楂原花青素抗氧化、清除亚硝酸盐及阻断亚硝胺合成的研究

目的 探讨山楂原花青素(HPC)抗氧化、清除亚硝酸盐及阻断亚硝胺合成的作用。方法 HPC和维生素C浓度均为20、80、140、200、260、320 mg/L,采用分光光度计法分别测定HPC组对超氧阴离子自由基(O^-_2·)、羟自由基(·OH)和DPPH·的清除能力、总抗氧化能力及清除亚硝酸盐和阻断亚硝胺合成能力,并与维生素C组比较。结果 20～260 mg/L的浓度范围内,HPC对·OH清除率显著高于维生素C(P＜0.05)。在一定浓度范围内,HPC对DPPH·自由基的清除率及总抗氧化能力均高于维生素C组(P＜0.05),且其自由基清除能力与总抗氧化能力均与浓度成正比;HPC能够有效清除体系中的亚硝酸盐,其清除能力在试验浓度范围内随浓度增大而增大,在140～320 mg/L范围内,HPC对亚硝酸盐的清除率均高于维生素C组(P＜0.05)。结论 HPC能够有效清除自由基和亚硝酸并且能够阻断亚硝胺的合成,对机体抗衰老、预防肿瘤有积极作用。     

山楂叶总黄酮含量测定及抗氧化活性研究

目的:评价山西晋南地区采集的山楂叶中总黄酮的含量及体外抗氧化活性。方法:采用显色法测定总黄酮含量;通过对1,1-二苯基-2-苦基肼(1,1-diphenyl-2-picrylhydra-zyl, DPPH)、2,2-联氮-双(3-乙基苯并噻唑-6-磺酸)二铵盐(2,2′-azino-bis[3-ethylbenzothiazoline-6-sulfonic acid]diammonium salt, ABTS)和羟自由基的清除能力评价体外抗氧化活性。结果:山楂叶总黄酮含量为(79.06±2.05)mg/g。总黄酮对DPPH、ABTS自由基清除半数抑制浓度(half maximal inhibitory concentration, IC₅₀)分别为(91.63±1.75)和(64.34±4.53)μg/mL,与抗坏血酸相比,相对抗氧化活性(relative antioxidant activity, RAA)分别为40.71%和76.64%;对羟自由基清除率较低,三者均低于同质量浓度下的抗坏血酸。结论:山西晋南地区采集的山楂叶总黄酮含量较高,有较高的抗氧化活性,可...     

水红花子水提物的抗氧化活性

目的 研究水红花子水提物的抗氧化活性及其机制。方法 用D-半乳糖建立衰老小鼠模型,分别灌胃服用生药量0.8、1.6和3.2g/kg·b.w.的水红花子水提物(n=10),每日1次,共7周。分别用TBA比色法、亚硝酸盐法、DTNB法及Sohal法测定心、肝、肾中丙二醛(MDA)、超氧化物岐化酶(SOD)、谷胱甘肽过氧化物酶(GSH-PX)及脑中脂褐质(LF)含量。结果 衰老小鼠心、肝、肾组织中MDA含量升高,SOD及GSH-PX活性降低,脑组织中LF升高。上述3种剂量的EFPO,能不同程度抑制脑组织中LF升高及心、肝、肾组织中MDA升高,其量效关系均呈负相关,相关系数分别为-0.963(相关性检验P<0.01)、-0.981(P<0.01)、-0.966(P<0.05)及-0.978(P<0.01);能不同程度抑制心、肝、肾组织中SOD活力下降,其量效关系均呈正相关,相关系数分别为0.984(P<0.05)、0.990(P<0.01)、0.985(P<0.01);能不同程度抑制心、肝、肾组织中GSH-PX活力下降,其量效关系均呈正相关,相关系数分别为0.984(P<0.01)、0.956(P<0.01)及0.957(P<0.01)。结论 水红花子水提物可通过清除·OH,提高SOD及GSH-PX活力而发挥抗氧化活性。     

脐血NK细胞改善亚急性衰老大鼠肝脏损伤

目的 探讨脐血NK细胞改善亚急性衰老大鼠模型肝脏损伤的可行性及其分子机制。 方法 采用基因工程改造的K562细胞,从新鲜脐带血获得大量NK细胞。8~10周龄雄性Wistar大鼠随机分为4组:Normal组、Model组、Mod-Con组和Mod-NK组。实验完成1周后观察大鼠体质量及肝脏指数,检测血清和肝脏中超氧化物岐酶(SOD)、丙二醛(MDA)及肝脏中凋亡相关基因的表达,观察肝脏切片组织细胞形态变化。 结果 皮下注射D-半乳糖可成功构建亚急性衰老大鼠模型。输注大量高纯度的脐血NK细胞,可显著改善其肝脏损伤,促进体质量回升(P<0.01)并降低肝脏指数(P<0.05),血清及肝脏中SOD活性增强(P<0.01),MDA水平降低(P<0.01);肝脏切片示肝细胞水肿减轻,Masson染色显示肝组织纤维化减轻;促凋亡基因表达减少(P<0.01),而抗凋亡基因成纤维细胞生长因子表达上升(P<0.01)。 结论 脐血NK细胞输注可有效改善亚急性衰老大鼠的肝脏损伤。     

知母皂苷元对痴呆模型大鼠的影响

目的 建立大鼠β-淀粉样肽[Aβ(25-35)]诱导的痴呆模型,探讨知母总皂苷在阿耳茨海默病(AD)发病机制中的作用。方法 SD大鼠60只,采用脑立体定位技术在大鼠单侧侧脑室一次性注射老化的Aβ(25-35)建立实验性AD模型。手术24h后,大鼠经灌胃分别给予3种剂量的知母总皂苷和EGB761,模型组和空白组给予等剂量的蒸馏水,1次/1d,连续14d。在给予Aβ(25-35)后的第8天,应用Morris水迷宫法测定大鼠的学习记忆功能,造模后第14天断头取脑,测定脑组织超氧化物歧化酶(SOD)、丙二醛(MDA)和总抗氧化能力。结果 与空白对照组相比,模型组大鼠空间学习记忆能力明显减弱,寻找平台潜伏期明显延长(P<0.01);脑组织SOD、总抗氧化能力明显降低(P<0.01),而MDA明显升高(P<0.05)。与模型组比较,给予知母总皂苷治疗后的大鼠学习记忆功能障碍得到明显改善,潜伏期显著缩短(P<0.05),SOD活力显著提高(P<0.05),总抗氧化能力也显著增强(P<0.05),MDA水平明显降低(P<0.05)。结论 知母总皂苷可明显改善AD模型大鼠的学习记忆功能,同时可提高模型大鼠的抗过氧化能力,这有可能是其改善学习记忆的原因之一。     

5-甲基四氢叶酸对大鼠动脉粥样硬化的潜在干预作用

目的 探讨5-甲基四氢叶酸(5-MTHF)对大鼠动脉粥样硬化的潜在干预特性和可能机制。 方法 高脂饮食联合维生素D2建立大鼠动脉粥样硬化模型,将48只雄性Wister大鼠随机分为对照组、模型组、5-MTHF低剂量组(0.5 mg/kg)和5-MTHF高剂量组(2 mg/kg),每组12只。6周后处死大鼠,检测各组大鼠血清活性叶酸、同型半胱氨酸、血脂、氧化应激、炎症因子和内皮因子含量,采用苏木精-伊红染色法观察大鼠主动脉病理变化,采用qRT-PCR法检测大鼠主动脉中核因子-κB p65(NF-κB p65)和凝集素样氧化型低密度脂蛋白受体-1(LOX-1)mRNA表达。 结果 与对照组比较,模型组大鼠体质量下降(P<0.05),血清总胆固醇(TC)、甘油三酯(TG)、低密度脂蛋白(LDC-C)含量增加(P<0.001),高密度脂蛋白(HDL-C)含量降低(P<0.001),主动脉中有平滑肌细胞增生和脂质斑块弥漫,提示大鼠动脉粥样硬化造模成功。模型组血清活性叶酸含量较对照组差异无统计学意义(P>0.05),同型半胱氨酸浓度增加77.47%(P<0.001)。与模型组相比,5-MTHF低剂量组、5-MTHF高剂量组血清活性叶酸水平升高(P=0.042,P<0.001),同型半胱氨酸浓度降低(P=0.046,P<0.001);5-MTHF低剂量组大鼠的血脂异常、一氧化氮(NO)和一氧化氮合酶(NOS)活力、超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GSH-Px)、丙二醛(MDA)、炎症肿瘤坏死因子α(TNF-α)、白介素1β(IL-1β)、白介素6(IL-6)、内皮素1(ET-1)、可溶性细胞间黏附分子1(sICAM-1)、NF-κB p65和LOX-1 mRNA表达水平均无明显改善(P>0.05);5-MTHF高剂量组大鼠血清TC和LDC-C含量降低(P=0.023,P=0.036),HDL-C含量升高(P=0.035);NO浓度、NOS和SOD活力增加(P=0.035,P=0.022,P=0.04);MDA、TNF-α、IL-6、ET-1含量降低(P=0.022,P=0.045,P=0.024,P=0.045),GSH-Px活力明显增强(P=0.007);LOX-1 mRNA表达下调(P=0.038),NF-κB p65 mRNA表达下调差异无统计学意义(P>0.05)。5-MTHF对动脉粥样硬化大鼠斑块无消退作用,但高剂量5-MTHF可减少平滑肌细胞增生和斑块中泡沫细胞聚集。 结论 5-MTHF可以改善动脉粥样硬化大鼠的血脂异常、氧化应激和炎症反应,减少泡沫细胞聚集和平滑肌细胞增生,但未减轻动脉粥样硬化斑块,其作用机制可能是降低同型半胱氨酸水平,抑制氧化应激和下调LOX-1 mRNA表达。     

星状神经节阻滞对自发性高血压大鼠心肌细胞凋亡与Bcl-2，Bax蛋白表达的影响

目的: 研究自发性高血压大鼠(SHR) 心肌细胞凋亡与Bcl-1/Bax蛋白表达的关系,探讨星状神经节阻滞对SHR心肌细胞凋亡的保护作用。方法: 将32只10周龄雄性SHR随机分为4组(n=8)：左侧星状神经节阻滞组(LS组)、右侧星状节阻滞组(RS组)、药物卡托普利组(D组)、手术对照组(C组)。用ALC-NIBP无创血压测量系统测定大鼠血压,第10周实验结束后用3%戊巴比妥钠腹腔注射(45 mg/kg)麻醉SHR,取出心脏用TUNEL法测定左室心肌细胞凋亡指数,免疫组织化学检测心肌Bcl-2和Bax表达的含量。结果: 与C组和LS组比较,RS组SHR凋亡指数明显降低(P<0.05); 心肌Bcl-2表达明显增强(P<0.05), Bax表达明显减弱(P<0.05), Bcl-2/Bax比值增高(P<0.05)。结论: Bcl-2抗凋亡及Bax促凋亡蛋白表达参与SHR心肌细胞凋亡; 右侧星状神经节阻滞能够影响凋亡相关基因蛋白的表达,降低心肌细胞凋亡指数,减轻左心室肥厚。     

野菊花提取液中总黄酮含量测定分析

目的 测定野菊花提取液经聚酰胺色谱柱分离后不同洗脱层总黄酮含量。方法 采用60%浓度乙醇水加热回流提取野菊花供试品,经聚酰胺色谱柱分离纯化得到不同浓度乙醇洗脱层。采用紫外可见分光光度法对不同洗脱层总黄酮含量进行测定。结果 野菊花提取液50%乙醇洗脱液干膏得率为0.975 3%,干膏得率最高。70%乙醇洗脱层黄酮类化合物含量为46.51%,含量最高。结论 聚酰胺色谱柱分离纯化法准确、灵敏、简便、重复性好,为野菊花黄酮类化合物富集纯化提供了科学基础。     

脂肪源性干细胞对内源性皮肤老化的治疗作用

目的 研究脂肪源性干细胞(ADSCs)对内源性皮肤老化的抗衰老作用及机制。 方法 分离培养小鼠皮肤成纤维细胞(MSFCs)及人ADSCs。将MSFCs 分为对照组、模型组、ADSCs条件培养基组。D-半乳糖(D-gal)制备MSFCs衰老模型,ADSCs条件培养基培养。镜下及流式检测ROS、β-半乳糖苷酶活性的变化,RT-PCR 检测caspase3、p53、sirt1基因的表达情况,Western blotting检测Sirt1蛋白表达。 结果 模型组较对照组ROS水平上升(P<0.001)、β-半乳糖苷酶着色增深,而ADSCs条件培养基组较模型组ROS水平降低(P<0.001)、β-半乳糖苷酶着色变浅。RT-PCR检测结果显示模型组较对照组caspase3(P<0.001)、p53(P=0.001)表达升高,sirt1表达下降(P<0.001);而ADSCs条件培养基组较模型组caspase3(P<0.001)、p53(P=0.001)表达下降,sirt1表达升高(P<0.001)。 Western blotting结果显示模型组较对照组Sirt1表达下降(P<0.001),而ADSCs条件培养基组较模型组Sirt1表达升高(P=0.006)。 结论 ADSCs可通过Sirt1通路改善D-gal引起的内源性皮肤老化。     

Scavenging Effects of Total Flavonoids from Leaves of Ficus Microcarpa L.f.in Fuzhou on DPPH Free Radical

目的 分析福州小叶榕叶总黄酮对DPPH自由基的清除作用. 方法 采用醇提取小叶榕叶总黄酮,亚硝酸钠-硝酸铝-氢氧化钠显色法测定提取物总黄酮含量,DPPH法评价总黄酮的抗氧化活性. 结果 小叶榕叶干膏得率22.2％.以芦丁为标准品,小叶榕叶中总黄酮线性范围10.44～62.64 μ9/mL(r=0.9998),平均回收率94.63％,RSD 0.852％,测得总黄酮含量为68.24 mg/g.小叶榕叶总黄酮提取物浓度为0.0445mg/mL时,对DPPH自由基清除率达到85.86％. 结论 福州小叶榕叶总黄酮是潜在抗氧化天然药物资源.     

茯砖茶不同溶剂提取物抗氧化活性研究

目的 研究茯砖茶不同溶剂提取物体外抗氧化活性,并测定其总多酚、黄酮含量.方法 以抗坏血酸为阳性对照,采用二苯代苦味酰基（DPPH）、[2,2＇-连氨-（3-乙基苯并噻唑啉-6-磺酸）二氨盐]（ABTS）及铁离子还原/抗氧化能力（FRAP）三种抗氧化模型,评价茯砖茶80％乙醇（总提物）、石油醚、乙酸乙酯、正丁醇和水5种不同溶剂提取物体外清除DPPH、ABTS＋自由基能力和对铁离子的还原/抗氧化能力.结果 茯砖茶乙酸乙酯提取物总多酚含量最高,正丁醇提取物黄酮含量最高,分别为（291.38±5.24）、（222.86±6.12）mg/g.茯砖茶不同溶剂提取物均具有一定的抗氧化活性,清除ABTS＋自由基和铁离子还原/抗氧化能力为：总提物＞乙酸乙酯提取物＞正丁醇提取物＞水提物＞石油醚提取物;清除DPPH自由基的能力为：乙酸乙酯提取物＞总提物＞正丁醇提取物＞水提物＞石油醚提取物.茯砖茶总提物和乙酸乙酯提取物均具有良好的抗氧化活性,清除DPPH自由基能力的半清除率浓度（IC50）分别为0.048、0.043 g/L,清除ABTS＋自由基能力的IC50分别为0.025、0.027 g/L.茯砖茶抗氧化能力与总多酚含量呈正相关.结论 茯砖茶提取物具有良好的抗氧化能力,为开发功能性抗氧化剂提供科学依据.     

西青果丙酮及水提取物体外抗氧化活性初步研究

目的 探讨西青果丙酮提取物和水提取物在3种评价体系下的体外抗氧化活性.方法 采用福林酚比色法测定西青果丙酮提取物和水提取物的总酚含量;利用清除1,1-二.苯基-2-苦肼基自由基(DPPH·)、2,2-联氮基-双-(3-乙基苯并噻唑啉-6-磺酸)二铵盐自由基(ABTS+·)评价法、还原法测定西青果两种溶剂提取物的抗氧化活性.结果 西青果丙酮提取物和水提取物总酚含量分别为(622.19±1.35)mg/g和(457.43±0.96) mg/g;两种溶剂提取物均表现出良好的抗氧化活性,对DPPH、ABTS自由基清除率的IC50值分别为8.427、19.575 μg/mL和20.273、33.064 μg/mL;对Fe3+均有一定的还原能力,其结果与浓度呈良好的量效关系,丙酮提取物还原效果最为明显.结论 西青果丙酮提取物和水提取物具有较强的抗氧化活性.     

Phytochemical investigation and in vitro antioxidant activity of an indigenous medicinal plant Alpinia nigra B.L. Burtt

Objective

To investigate antioxidant potential of methanol extract of Alpinia nigra leaves.

Methods

The study was done by using various in vitro methods such as 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS), nitric oxide and hydrogen peroxide radical scavenging assays. Phytochemical constituents, total phenolic content and total flavonoid content of the extract at different concentrations (10-500 µg/mL) were determined.

Results

Alpinia nigra leaves showed high free radical scavenging activity as evidenced by the low IC₅₀ values in DPPH (64.51 µg/mL), in ABTS (28.32 µg/mL), in nitric oxide (80.02 µg/mL) and in H₂O₂ (77.45 µg/mL) scavenging assays. Furthermore the TPC and TFC of the extract were found to be 69.25 mg gallic acid equivalent per gram of extract and 78.84 mg quercetin equivalent per gram of extract respectively.

Conclusions

The results of present comprehensive analysis demonstrated that Alpinia nigra leaves possess high phenolic, flavonoid contents and potential antioxidant activity, and could be used as a viable source of natural antioxidants and might be exploited for functional foods and neutraceutical applications.     

中药桑叶固体发酵前后抗氧化活性的研究

目的 探讨桑叶固体发酵前后70％乙醇提取物的体外抗氧化活性.方法 应用“药用真菌固体发酵工程”的原理和方法,以桑叶为药性基质,冠突散囊菌为发酵菌种,在一定条件下进行固体发酵,对发酵物用70％乙醇进行提取.并以维生素C（Vc）和乙二胺四乙酸（EDTA）为阳性对照,以清除1,1-二苯基-2-三硝基苯肼（DPPH）、2,2-联氮-二（3-乙基-苯并噻唑-6-磺酸）二铵盐（ABTS）、＆#183;OH自由基、铁还原能力及与Fe2＋螯合能力5个指标对发酵前后桑叶体外抗氧化活性进行评价;同时对发酵前后总黄酮、总酚酸含量进行测定.结果 未发酵桑叶70％乙醇提取物清除自由基能力及铁还原能力优于固体发酵7d后桑叶的70％乙醇提取物,但对于Fe2＋螯合能力而言,发酵后的桑叶70％乙醇提取物较未发酵前有所升高.其中未发酵桑叶70％乙醇提取物DPPH、ABTS、Fe2＋螯合能力的IC50值分别为：4.69、2.03、20.89 mg/mL,而固体发酵7d后的桑叶70％乙醇提取物三者的IC50值分别为：17.63、1.87、9.20 mg/mL;同时含量测定结果显示,发酵后桑叶中总多酚含量较发酵前明显下降,而发酵后桑叶中总黄酮含量却高于发酵前总黄酮含量.其中发酵前桑叶中总黄酮、总酚酸含量分别为4.39、3.95 mg/mL,而发酵后桑叶中总黄酮含量上升至5.37 mg/g,总酚酸下降为1.55 mg/g.结论 固体发酵7d,能够降低桑叶清除自由基的能力及铁还原能力,但却能升高其螯合能力.     

Antioxidant potential of phenolic extracts of Mimusops elengi

Objective

To evaluate the antioxidant potential of the phenolic extracts of Mimusops elengi (M. elengi) L. (Sapotaceae).

Methods

The extract of stem bark and seeds of M. elengi were prepared in methanol and acetone:water (7:3). The acetone: water was further partitioned with ethyl acetate and n-butanol. Antioxidant activity of the extracts and partitioned fractions of M. elengi was evaluated in terms of radical scavenging potential (DPPH), inhibition of lipid peroxidation [ferric thiocyanate (FTC)], and total antioxidant activity (phosphomolybdate method). Total phenolics content were calculated using Folin-Ciocalteu reagent.

Results

The stem bark extract partitioned with ethyl acetate exhibited highest amount of total phenols (98.0 mg GAE/g dry weight), among all other extracts, with 92.0% DPPH radical scavenging activity at concentration of 0.5 mg/mL, while methanol extract (stem bark) had maximum inhibition of lipid peroxidation (62.0%) and total antioxidant activity (771.0 mg/g GAE/g). A positive correlation occurred between total phenols and radical scavenging activity (R² = 0.922 9) and total antioxidant activity (R² = 0.945 1).

Conclusions

Our study suggested that antioxidant activity of stembark extract of M. elengi is due the presence of phenolic compounds. Furthermore, the bark extract is a valuable source of natural antioxidants.     

Antioxidant activities of Indigofera cassioides Rottl. Ex. DC. using various in vitro assay models

Objective

To evaluate the antioxidant potential of methanolic leaf extract of Indigofera cassioides (MEIC) using various in vitro antioxidant assay systems.

Methods

Antioxidant and free radical scavenging activity of MEIC was assayed by using different in vitro models like ABTS, DPPH, nitric oxide, superoxide, hydrogen peroxide and hydroxyl radical. Reductive ability of the extract was tested by the complex formation with potassium ferricyanide. Further total phenol and flavonoid contents of the crude extract were also determined. Rutin and ascorbic acid were used as standards.

Results

MEIC exhibited potent and concentration dependent free radical scavenging activity in all the tested models. Reductive ability was also found to increase with increase in MEIC concentration. Total phenol and flavonoid content determination showed that the extract is rich in phenols and flavonoids.

Conclusions

All the results of the in vitro antioxidant assays reveal potent antioxidant and free radical scavenging activity of the leaves of Indigofera cassioides, equivalent to that of standard ascorbic acid and rutin. This potent antioxidant activity may be attributed to its high phenolic and flavonoid contents.     

Analysis of phytochemical profile of Terminalia arjuna bark extract with antioxidative and antimicrobial properties

Objective

To investigate phytochemical screening, antimicrobial activity and qualitative thin layer chromatographic separation of flavonoid components, antioxidant activity and total flavonoid compound of Terminalia arjuna.

Methods

For phytochemical screening, some common and available standard tests were done. Antimicrobial bioassay was done through agar well diffusion method. Detection of antioxidant activity and flavonoid compounds were done through thin layer chromatography. Total antioxidant activity was measured by 2, 2-diphenyl-1-picrylhydrazyl (DPPH) in colorimetric method. Aluminum chloride colorimetric method was used for total flavonoid determination.

Results

Phytochemical screening showed the active compounds presence in high concentration, such as phytosterol, lactones, flavonoids, phenolic compounds and tannins and glycosides. The antimicrobial activity of extract showed that greater inhibition zone against Gram negative bacteria than Gram positive bacteria. This methanolic extract showed a promising antioxidant activity, as absorption of DPPH redicles decreased in DPPH free radical scavenging assay. Flavonoids components having antioxidant property present in the methanol extract at a level of 199.00 mg quercetin equivalent/g of dried methanol extract in colorimetric method.

Conclusions

The Terminalia arjuna bark extract revealed the presence of bio-active constituents which are known to exhibit medicinal as well as physiological activities.     

Chemical composition and antioxidant activity of a Lebanese plant Euphorbia macroclada schyzoceras

Objective

To determine the chemical composition, total phenolic and total flavonoid contents of the crude extracts from leaves and stems of a Lebanese plant Euphorbia macroclada schyzoceras (E. macroclada), and to evaluate their antioxidant potential using DPPH, H₂O₂, and chelating of ferrous ions tests.

Methods

Quantification of the total phenolic and total flavonoid contents of the crude extracts from leaves and stems and the antioxidant activities were evaluated using spectrophotometric analyses. The chemical composition has been estimated using different techniques such as IR, LC/MS and NMR.

Results

Ethanolic extract from leaves of E. macroclada was better than aqueous extract and showed higher content in total phenolic and total flavonoid than found in the stems. On the other hand, using DPPH and H₂O₂ tests, this extract from leaves showed higher antioxidant capacity than aqueous extract. However, using the chelating of ferrous ions test, the antioxidant activity of the aqueous extract of both stems and leaves was stronger than that of ethanolic once. The chemical composition of the whole plant showed the presence of some aromatic compounds and fatty acids.

Conclusions

Both ethanolic and water extracts from both parts of this plant are effective and have good antioxidant power. So, this plant can be used in the prevention of a number of diseases related to oxidative stress.