Lycopene-rich fractions derived from pink guava by-product and their potential activity towards hydrogen peroxide-induced cellular and DNA damage

Effects of solvent and supercritical carbon dioxide (SC-CO₂) extraction on antioxidant and cytotoxic activities of lycopene-rich fractions of decanted pink guava by-product (decanter) were determined with lycopene-equivalent antioxidant capacity, β-carotene bleaching and MTT (3-(4,5-dimethylthiazol-2yl)-2,5-diphenyl tetrazolium bromide) assays. Extraction with SC-CO₂ gave a higher yield than solvent extraction (3.15 vs. 0.68 mg/100 g dried decanter, corresponding to 42.99 and 33.63 mg of lycopene). No cytotoxicity was found in Chang liver cells supplemented with either extracts (6.25–200 μg/ml). Solvent extract at 25 μg/ml (2.32 μM lycopene) and SC-CO₂ extract at 200 μg/ml (5.09 μM lycopene) had protective effect against hydrogen peroxide-induced cytotoxicity. However, only high concentrations of solvent extract (200 μg/ml; lycopene = 18.65 μM) or lycopene standard (10 μM) protected cells against DNA damage. Supercritical fluid extraction demonstrated a higher yield in lycopene-rich fraction from decanter. These fractions have the potential to be developed as a functional ingredient to prevent oxidative stress and other related diseases.     

牡荆素保护DNA氧化损伤的活性评价及机制分析

采用DNA保护能力分析法,测定牡荆素保护DNA的能力;运用Ferrozine法和紫外可见光谱(UV-Vis)分析牡荆素Fe2+络合反应;运用Cu2+还原法,测定牡荆素的电子转移(Electron-transfer,ET)能力。在此基础上,探讨牡荆素保护DNA氧化损伤的可能化学机制。结果表明:牡荆素在DNA保护能力分析法、Ferrozine法和Cu~(2+)还原法中均表现出剂量相关性,其IC50值分别为(919.6±23.6),(9.3±1.2),(421.7±29.2)μmol/L。UV-Vis光谱分析表明,牡荆素与Fe2+混合后,在波长554nm处出现新的吸收峰[摩尔吸光系数ε=2 680.74L/(mol·cm)]。总之,牡荆素能保护DNA免受羟基自由基(·OH)诱导的氧化损伤。其保护机制可能与电子转移ET和Fe2+络合有关,络合位点可能在4-羰基-5-羟基之间。     

Effects of phleomycin-induced DNA damage on the fission yeast Schizosaccharomyces pombe cell cycle

The effect of phleomycin, a bleomycin-like antibiotic, has been investigated in the fission yeast, Schizosaccharomyces pombe. We report that in response to phleomycin-induced DNA damage, growth was inhibited and S. pombe cells arrested in the G2-phase of the cell cycle. DNA repair mutants rad9 and rad17 did not arrest and were hypersensitive to phleomycin. Cell cycle mutants that entered mitosis without monitoring the completion of DNA replication also displayed an increased sensitivity to this DNA-damaging agent. Thus, phleomycin could be used as a tool in the fission yeast S. pombe model system for the study of DNA damage and cell cycle checkpoints, or as a new selective agent.     

Genotoxicological Assessment of Nebuloside-A a Triterpenoid Saponin Compound on Whole Blood DNA

We investigated the genotoxic effect of nebuloside-A on whole blood DNA by using alkaline Single Cell Gel Electrophoresis Comet assay. Saponins are a widespread class of bioactive compounds produced by many plant species. Nebuloside A was isolated from baby’s-breath (Gypsophila arrostii) by high performance liquid chromatography method. Mass spectra obtained by electrospray ionization-time of flight-mass spectrometry in a negative ion mode to reduce the protonation. Complete nuclear magnetic resonance spectroscopy assignments of nebuloside A was achieved by using 2D-nuclear magnetic resonance spectroscopy techniques, such as double-quantum filtered correlation spectroscopy, heteronuclear single quanthum correlation, heteronuclear multiple-bond correlation, and total correlation spectroscopy. DNA damage was measured in total arbitrary units by visual scoring of comets in different concentrations of nebuloside A and H₂O₂ treatments. We found that significant dose dependent relationship between nebuloside A and its genotoxic effect.     

芡实多糖的提取、抗氧化活性及对质粒DNA氧化损伤防护作用的研究

采用纤维素酶超声辅助法提取芡实多糖,由正交实验获得芡实多糖的最佳提取条件,并探究其体外抗氧化活性及对H2O2光解反应诱导质粒p BR322 DNA损伤的保护作用。结果表明芡实多糖的最佳提取条件为:料液比1∶20(g/m L)、p H3、纤维素酶用量为原料质量的2.0%、超声时间5min、提取时间3h、提取温度40℃,多糖得率为17.04%。芡实多糖清除DPPH·、羟基自由基的能力较好,IC50分别为1.78、6.96mg/m L,清除过氧化氢、超氧阴离子自由基的能力较弱,浓度为10mg/m L时,清除率分别为48.00%、20.32%。芡实多糖对抑制DNA损伤具有显著作用,在多糖水溶液质量浓度为0.08mg/m L时,具有最佳保护作用;在质量浓度大于1.0mg/m L时,对质粒DNA没有保护作用,甚至促进了DNA的损伤。综上所述,芡实多糖具有抗氧化及抑制DNA氧化损伤的能力。      

咖啡酸衍生物对自由基致DNA氧化损伤的联合保护作用

目的:探讨咖啡酸衍生物（CADs）:绿原酸（Chlorogenic acid,ChA）、阿魏酸（Ferulic acid,FeA）、迷迭香酸（Rosmarinic acid,RoA）对自由基致DNA损伤的联合抑制保护效果。方法:运用DPPH自由基及羟自由基反应模型观察不同组成的CADs对自由基的淬灭效应,以CuSO₄-Phen-VitC-H₂O₂-DNA化学发光体系测定不同成分的多酚类物质对·OH致DNA损伤的抑制作用。结果:在30min时间内,三种CADs联合组在浓度为25、50、100、200μg/mL时,对DPPH·清除率分别为28.93%、58.39%、83.93%和84.09%;对·OH清除率分别为33.43%、55.27%、71.23%、77.49%。在DNA化学发光体系中,在25～200μg/mL范围内,三种CADs联合组对DNA损伤产物发光抑制率为12.49%～81.09%。结论:CADs能有效清除DPPH自由基和羟自由基,抑制羟自由基引发的DNA损伤程度,并延迟其受损伤的时间。在各实验组中三种CADs联用组在对DPPH自由基清除率、DNA损伤产物发光抑制率以及保护DNA损伤的能力均最强,体现出协同作用。      

大孔树脂纯化废酒花黄腐酚及其抗DNA氧化损伤的活性

采用大孔树脂从酿造废酒花中分离纯化黄腐酚,并且检测了黄腐酚抗DNA氧化损伤的活性。结果表明:HPD100A树脂对黄腐酚的吸附率为100%,解吸率为77.69%,适合于废酒花黄腐酚的纯化。最佳工艺条件为:上样液黄腐酚质量浓度0.25mg/m L、上样量15BV、上样液p H5.5、上样流速2BV/h,洗脱剂为95%乙醇,洗脱流速2BV/h,洗脱剂用量3BV。在此条件下,可将黄腐酚纯度由纯化前的4.95%提高为51.50%,回收率为72.56%。结果表明,分离得到的黄腐酚纯化物对Phen-Cu SO4-VC诱导DNA氧化损伤的抑制作用（EC50为0.22mg/m L）显著优于抗坏血酸（EC50为0.51mg/m L）和芦丁（EC50为0.93mg/m L）,具有显著地抗DNA氧化损伤活性。      

DNA damage, a biomarker of carcinogenesis: its measurement and modulation by diet and environment

Free radicals and other reactive oxygen or nitrogen species are constantly generated in vivo and can cause oxidative damage to DNA. This damage has been implicated to be important in many diseases, including cancer. The assessment of damage in various biological matrices, such as tissues, cells, and urine, is vital to understanding this role and subsequently devising intervention strategies. During the last 20 years, many analytical techniques have been developed to monitor oxidative DNA base damage. High-performance liquid chromatography-electrochemical detection and gas chromatography-mass spectrometry are the two pioneering contributions to the field. Currently, the arsenal of methods available include the promising high-performance liquid chromatography-tandem mass spectrometry technique, capillary electrophoresis, 32P-postlabeling, antibody-base immunoassays, and assays involving the use of DNA repair glycosylases such as the comet assay. The objective of this review is to discuss the biological significance of oxidative DNA damage, evaluate the effectiveness of several techniques for measurement of oxidative DNA damage in various biological samples and review current research on factors (dietary and non-dietary) that influence DNA oxidative damage using these techniques.     

玉米蛋白粉中叶黄素和玉米黄素对口腔癌细胞DNA的损伤作用

研究玉米蛋白粉中叶黄素和玉米黄素对人口腔癌KB细胞的作用机制。在人口腔癌KB细胞的细胞培养液中分别加入40μL/L、60μL/L叶黄素和30μL/L、40μL/L玉米黄素,分别培养48h、72h。用单细胞凝胶电泳(SCGE)检测叶黄素和玉米黄素对人口腔癌KB细胞DNA损伤程度。玉米蛋白粉中叶黄素和玉米黄素可引起KB细胞DNA链断裂,细胞尾长、尾DNA百分含量和尾矩显著高于对照组,差异有统计学意义(P<0.01)。叶黄素和玉米黄素能导致人口腔癌细胞KB的DNA损伤,抑制肿瘤细胞生长。     

Ochratoxin A induces oxidative DNA damage in liver and kidney after oral dosing to rats

The nephrotoxic/carcinogenic mycotoxin ochratoxin A (OTA) occurs as a contaminant in food and feed and may be linked to human endemic Balkan nephropathy. The mechanism of OTA-derived carcinogenicity is still under debate, since reactive metabolites of OTA and DNA adducts have not been unambiguously identified. Oxidative DNA damage, however, has been observed in vitro after incubation of mammalian cells with OTA. In this study, we investigated whether OTA induces oxidative DNA damage in vivo as well. Male F344 rats were dosed with 0, 0.03, 0.1, 0.3 mg/kg bw per day OTA for 4 wk (gavage, 7 days/wk, five animals per dose group). Subsequently, oxidative DNA damage was determined in liver and kidney by the comet assay (single cell gel electrophoresis) with/without use of the repair enzyme formamido-pyrimidine-DNA-glycosylase (FPG). The administration of OTA had no effect on basic DNA damage (determined without FPG); however, OTA-mediated oxidative damage was detected with FPG treatment in kidney and liver DNA of all dose groups. Since the doses were in a range that had caused kidney tumors in a 2-year carcinogenicity study with rats, the oxidative DNA damage induced by OTA may help to explain its mechanism of carcinogenicity. For the selective induction of tumors in the kidney, increased oxidative stress in connection with severe cytotoxicity and increased cell proliferation might represent driving factors.     

Synergistic effect of green tea polyphenols with trolox on free radical-induced oxidative DNA damage

The antioxidant effect of the principal polyphenolic components extracted from green tea leaves, namely (−)-epicatechin (EC), (−)-epigallocatechin (EGC), (−)-epicatechin gallate (ECG) and (−)-epigallocatechin gallate (EGCG), and their synergistic antioxidant effects with trolox against oxidative DNA damage were studied. The oxidative DNA damage was initiated by a water-soluble azo initiator, 2,2′-azobis (2-amidinopropane hydrochloride) (AAPH) and the ability of green tea polyphenols and/or trolox (a water-soluble analogue of α-tocopherol) to inhibit the oxidative damage of DNA was assessed, in vitro, by measuring the conversion of supercoiled pBR322 plasmid DNA to the open circular and linear forms. It was found that these green tea polyphenols could significantly inhibit the oxidative damage of DNA synergistically with trolox, with an activity sequence of EC = ECG > EGCG > EGC.     

黄蜀葵花黄酮抗氧化性及对DNA氧化损伤的保护作用

采用石油醚、乙酸乙酯和正丁醇对黄蜀葵花乙醇提取物进行分级萃取,得到石油醚相、乙酸乙酯相、正丁醇相和水相4个不同极性成分。采用DPPH·清除、·OH清除和H_2O_2清除试验考察了其抗氧化活性,研究了正丁醇相对·OH和H_2O_2诱导DNA氧化损伤的保护作用,并利用HPLC—MS对正丁醇中黄酮类物质进行了鉴定。结果表明:黄蜀葵花黄酮主要富集于乙酸乙酯相和正丁醇相;乙酸乙酯相对DPPH·的清除能力最好,IC_(50)值为0.038 6 mg/mL,而正丁醇相对·OH和H_2O_2的清除能力较好,IC_(50)值分别为0.225 0,0.575 7mg/mL;正丁醇相对·OH和H_2O_2诱导的DNA氧化损伤都有保护作用;正丁醇相中含有11种黄酮类化合物。     

Sweet potato protein hydrolysates: antioxidant activity and protective effects on oxidative DNA damage

In this study, sweet potato protein (SPP) hydrolysates were prepared by six enzymes (alcalase, proleather FG‐F, AS1.398, neutrase, papain and pepsin). The antioxidant activities and protective effect against oxidative DNA damage of SPP hydrolysates were investigated. Alcalase hydrolysates exhibited the highest hydroxyl radical‐scavenging activity (IC₅₀ 1.74 mg mL^?1) and Fe²⁺‐chelating ability (IC₅₀ 1.54 mg mL^?1) (P < 0.05). Compared with other five hydrolysates, the hydrolysates obtained by alcalase had the most abundant <3‐kDa fractions. In addition, below 3‐kDa fractions of alcalase hydrolysates showed the highest antioxidant activities and protective effects against DNA damage through both scavenging hydroxyl radicals and chelating Fe²⁺, which was probably because of the increase in several antioxidant amino acids, such as His, Met, Cys, Tyr and Phe, as well as the hydrophobic amino acids. The results suggested that enzymatic hydrolysis could be used as an effective technique to produce high value‐added peptides products from SPP.