Human Low-density Lipoprotein Oxidation Research Articles

Free radical scavenging and anti-isolated human LDL oxidation activities of Butea superba Roxb. extract

BackgroundButea superba Roxb. (B. superba), is an herbal plant traditionally used for rejuvenation. Additionally, there have been reports on its antioxidant properties. Low-density lipoproteins (LDL) oxidation is the leading cause of cardiovascular diseases (CVDs). Natural products with antioxidant properties have the potential to inhibit LDL oxidation. However, no work has been done about the anti-isolated human LDL oxidation of B. superba extract (BSE). This study aimed to investigate the antioxidant potential of BSE and its ability to prevent isolated human (LDL) oxidation induced by free radical agents.MethodsThe antioxidant properties were investigated by antioxidant assays, including 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2-azinobis-(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS), ferric reducing ability power (FRAP), nitric oxide (NO) and peroxynitrite scavenging assay. More so, anti-isolated human LDL oxidation activities were evaluated by 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH) and 3-morpholinosydnonimine hydrochloride (SIN-1) induced LDL oxidation assay.ResultsBSE exhibited a significant (p < 0.05) antioxidant activity in all the test systems, demonstrating its potential as a potent free radical scavenger. It displayed scavenging effects on DPPH (p < 0.05; IC50 = 487.67 ± 21.94 µg/ml), ABTS (p < 0.05; IC50 = 30.83 ± 1.29 µg/ml). Furthermore, it generated significantly (p < 0.05) increased antioxidant capacity in a dose-dependent manner in FRAP assay and exhibited significantly (p < 0.01) higher percent NO scavenging activity than gallic acid. Besides, BSE at 62.5 µg/ml exhibited a considerable percent peroxynitrite scavenging of 71.40 ± 6.59% after a 2 h period. Moreover, BSE demonstrated anti-isolated human LDL oxidation activity induced by AAPH and SIN-1 (p < 0.05) and revealed scavenging activity similar to ascorbic acid (p > 0.05). Identifying the main constituents of BSE revealed the presence of genistein, daidzein, and biochanin A through Liquid Chromatography-Mass Spectrometer/Mass Spectrometer (LC–MS/MS) analysis.ConclusionThis is the first report that the presence of isoflavones in BSE could play an important role in its antioxidation and isolated human LDL oxidation scavenging properties. These findings suggest the potential for developing antioxidant herbal supplements. However, further studies must be investigated, including efficacious and safe human dosages.

Effect of alkyl‐chain unsaturation on the antioxidant potential of chlorogenic acid derivatives in food and biological systems

SummaryChlorogenic acid (CGA) was modified using acyl chlorides with different levels of unsaturation (C18:0–C18:3) to enhance the lipophilicity and promote its application. The antioxidant activity of CGA derivatives in food and biological models was evaluated. All CGA derivatives had significantly greater antioxidative activity than CGA in fish oil and β‐carotene/linoleic acid emulsions (P &lt; 0.05), but there was no linear relationship between antioxidative activity and unsaturation. The effectiveness of CGA‐C18:0 was significantly greater than that of CGA in scavenging H2O2 and reducing copper‐induced human low‐density lipoprotein (LDL) oxidation (P &lt; 0.05). Furthermore, the H2O2 scavenging activity, inhibitions of copper‐induced human LDL oxidation and hydroxyl or peroxyl radical‐induced DNA oxidation were all linearly related to the unsaturation of the alkyl chains, mainly with the free radical chain reactions of the unsaturated bonds. Our findings showed that CGA derivatives could potentially be used as antioxidants in food and biological systems.

The anti-ischemic and antioxidant activity of the pharmacological agonist of galanin receptor GalR2 and carnosine in in vitro and in vivo model systems

Antioxidant and anti-ischemic properties of the pharmacological agonist of galanin receptor GalR2 WTLNSAGYLLGPβAH (Gal) and its C-terminal fragment, dipeptide carnosine (βAH), were studied in the model of regional ischemia and reperfusion of the rat heart in vivo in the dose range of 0.5-5.0 mg/kg and Cu²⁺-induced free radical oxidation of low density lipoproteins (LDL) of human plasma in vitro for peptide concentrations of 0.01 mM and 0.1 mM. Gal was obtained by automatic solid phase synthesis using the Fmoc methodology; its structure was characterized by 1H-NMR spectroscopy and MALDI-TOF mass spectrometry. Intravenous administration of the optimal dose of Gal (1 mg/kg) to rats after ischemia was more effective than carnosine in reducing of the myocardial infarct size and the activity of creatine kinase-MB and lactate dehydrogenase in blood plasma at the end of reperfusion. It also improved the metabolic state of the reperfused myocardium and reduced the formation of peroxidation products during reperfusion. Gal reduced more effectively the formation of adducts of hydroxyl radicals in the interstitium of the area at risk (AAR) of the rat heart than carnosine. Carnosine at a dose of 1 mg/kg more effectively increased the activity of catalase and glutathione peroxidase in the AAR by the end of reperfusion compared to Gal. In a model of Cu²⁺-initiated oxidation of human plasma LDL 0.1 mM carnosine demonstrated a significantly more pronounced reduction in the formation of lipid radicals compared to Gal. The results show that Gal can be considered as a promising agent that reduces myocardial injury during reperfusion and oxidative stress.

Antioxidant Properties of Galanin and Its N-Terminal Fragments in in vitro and in vivo Oxidative Stress Modeling.

Antioxidant properties of rat galanin GWTLNSAGYLLGPHAIDNHRSFSDKHGLT-NH2 (Gal), N-terminal fragment of galanin (2-15 aa) WTLNSAGYLLGPHA (G1), and its modified analogue WTLNSAGYLLGPβAH (G2) were studied in vivo in the rat model of regional myocardial ischemia and reperfusion and in vitro in the process of Cu2+-induced free radical oxidation of human blood plasma low-density lipoproteins. Intravenous administration of G1, G2, and Gal to rats after ischemia induction reduced the infarction size and activities of the necrosis markers, creatine kinase-MB and lactate dehydrogenase, in blood plasma at the end of reperfusion. G1, G2, and Gal reduced formation of the spin adducts of hydroxyl radicals in the interstitium of the area at risk during reperfusion, moreover, G2 and Gal also reduced formation of the secondary products of lipid peroxidation in the reperfused myocardium. It was shown in the in vivo experiments and in the in vitro model system that the ability of galanin peptides to reduce formation of ROS and attenuate lipid peroxidation during myocardial reperfusion injury was not associated directly with their effects on activities of the antioxidant enzymes of the heart: Cu,Zn-superoxide dismutase, catalase, and glutathione peroxidase. The peptides G1, G2, and Gal at concentrations of 0.01 and 0.1 mM inhibited Cu2+-induced free radical oxidation of human low-density lipoproteins in vitro. The results of oxidative stress modeling demonstrated that the natural and synthetic agonists of galanin receptors reduced formation of the short-lived ROS in the reperfused myocardium, as well as of lipid radicals in blood plasma. Thus, galanin receptors could be a promising therapeutic target for cardiovascular diseases.

Assessment of genetic diversity of Turkish maize landraces for phytic acid and total phenolic contents

Assessment of genetic diversity of Turkish maize landraces for phytic acid and total phenolic contents

Inhibition of low-density lipoprotein oxidation, antioxidative and bile acid-binding capacities of hydrolyzed proteins from carbohydrase-treated oat bran.

This study investigated the valorization of oat bran and the use of its proteins to generate polypeptides with antioxidant and bile acid-binding properties. Ten protein hydrolysates were prepared by treating cellulase (CPI) or Viscozyme (VPI) protein isolates with five proteases. VPI-pepsin was the best peroxyl radical scavenger (497±6-μM Trolox equivalents [TE]/g) while VPI-Flavourzyme quenched hydroxyl radicals (28±0.6) and VPI-pepsin superoxide anion radicals (45.3±6.6%). Hydrolysates, except those produced with pepsin, dose-dependently chelated iron whereas VPI-Protamex had the best copper-chelating capacity (59.83±1.40%). These antioxidative capacities were important in preventing by 50% in vitro copper-induced oxidation of human low-density lipoprotein. Furthermore, due to their aromatic amino acid contents and hydrophobicity, the hydrolysates bound up to 46.3% the bile acids taurodeoxycholate and taurocholate. PRACTICAL APPLICATIONS: The presence of oxidants in foods can damage food molecules and decrease their quality. They are also known to increase the risk of developing chronic conditions like cardiovascular disease. Finding new antioxidant molecules are therefore useful in the management of chronic diseases. Data from this work showed that hydrolyzed oat bran proteins can be useful in stabilizing commercial oil as they reduced the oxidation of peanut oil. Additionally, the protein hydrolysates not only prevented the oxidation of linoleic, a common component of both vegetable oils and biological cell membranes, they also inhibited the oxidation of human LDL cholesterol and chelated bile acids. These hydrolysates can then be further explored as multifunctional ingredients for the development of stable functional food products with potential beneficial effects on the cardiovascular system.

Effect of Traditional Preparation Processing on the Total Phenol Content and Antioxidant Activity of Fallopia multiflora Thunb.

This study evaluates the effects of traditional preparation on the total phenol content and in vitro antioxidant activity of Fallopia multiflora Thunb.. The experimental results show that the total phenol content calculated with gallic acid (GAE) of Fallopia multiflora Thunb. increased during preparation processing. The Fallopia multiflora Thunb. after preparation had a total phenol content of 22.73 ± 0.21 mg GAE/g, about 3% higher than the raw sample (22.03 ± 0.40 mg GAE/g). The preparation processing also significantly increased the antioxidant activity of Fallopia multiflora Thunb.. The concentration of extract, which could neutralize 50% of the free radicals generated from 2.2-diphenyl-1-picrylhydrazyl of medicinal materials, after processing was 53.71 ± 0.44 µg/ml, about 2.3 times lower when compared to raw pharmaceutical materials (124,38 ± 0,56 µg/ml).&#x0D; Keywords&#x0D; Fallopia multilflora Thunb., processing, antioxidant, total phenol, neutralized free radicals.&#x0D; References&#x0D; [1] P.X. Sinh, Traditional pharmacology, Medical Publishing House, Ha Noi, 2014, pp. 352-353 (in Vietnamese).[2] L. Lin, C. Qu, J. Ni, A novel method to analyze hepatotoxic components in Polygonum multiflorum using ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry, Journal of hazardous materials 299 (2015) 249-259. https://doi.org/10.1016/j.jhazmat.2015.06.014[3] Y. Liu, Q. Wang, J. Yang, X. Guo, W. Liu, S. Ma, S. Li, Polygonum multiflorum Thunb.: a review on chemical analysis, processing mechanism, quality evaluation, and hepatotoxicity, Frontiers in pharmacology 9 (2018) 364. http://doi.org/10.3389 / fphar.2018.00364.[4] J. Huang, J.P. Zhang, J.Q. Bai, M.J. Wei, J. Zhang, Z.H. Huang, G.H. Qu, W. Xu, X.H. Qiu, Chemical profiles and metabolite study of raw and processed Polygoni Multiflori Radix in rats by UPLC-LTQ-Orbitrap MSn spectrometry, Chinese journal of natural medicines 16 (5) (2018) 375-400. http://doi.org/10.1016 / S1875-5364 (18) 30070-0.[5] L. Liang, J. Xu, W.W. Zhou, E. Brand, H.B. Chen, Z.Z. Zhao, Integrating targeted and untargeted metabolomics to investigate the processing chemistry of Polygoni Multiflori Radix, Frontiers in pharmacology 9 (2018) 934. http://doi.org/10.3389/fphar.2018.00934.[6] Ministry of Health, Vietnamese Pharmacopoeia V, Medical Publishing House, Ha Noi, part 2, 2018, pp 1180-1181 (in Vietnamese).[7] N.T.H. Ly, T.T. Thao, P.V. Truong, P.T. Thuong, Quality Evaluation of Fallopia multiflora in Vietnam Based on HPLC-FLD and Chemometrics, Natural Products Chemistry &amp; Research 6(6) (2018) 1-7. http://doi.org/10.4172/2329-6836.1000346.[8] L. Lin, B. Ni, H. Lin, M. Zhang, X. Li, Xi. Yin, C. Qu, J. Ni, Traditional usages, botany, phytochemistry, pharmacology and toxicology of Polygonum multiflorum Thunb.: a review, Journal of Ethnopharmacology 159 (2015) 158-183. https://doi.org/10.1016/j.jep.2014.11.009.[9] G.A. Bounda, Y.U. Feng, Review of clinical studies of Polygonum multiflorum Thunb. and its isolated bioactive compounds, Pharmacognosy research 7 (3) (2015) 225. http://doi.org/10.4103 / 0974-8490.157957.[10] M.P. Kähkönen, A.I. Hopia, H.J. Vuorela, J.P. Rauha, K. Pihlaja, T. S. Kujala, M.Heinonen, Antioxidant activity of plant extracts containing phenolic compounds, Journal of agricultural and food chemistry 47 (10) (1999) 3954-3962. http://doi.org/10.1021 / jf990146l.[11] H.H. Lin, A. L. Charles, C.W. Hsieh, Y. ChiLee, J.Y. Ciou, Antioxidant effects of 14 Chinese traditional medicinal herbs against human low-density lipoprotein oxidation, Journal of traditional and complementary medicine 5 (1) (2015) 51-55. https://doi.org/10.1016/j.jtcme.2014.10.001.&#x0D; &#x0D;

Механізми кардіо- та вазопротекторної дії ресвератролу

У статті наведено огляд сучасних даних щодо механізмів реалізації кардіо- та вазопротекторної дії ресвератролу. Наведені результати експериментальних і клінічних досліджень, що підтверджують можливість включення ресвератролу в фармакотерапію серцево-судинних захворювань. Вплив ресвератролу на серцево-судинну систему полягає в підвищенні продукції NO, зниженні синтезу ендотеліну-1, проявів оксидативного стресу, запобіганні проліферації клітин гладеньких м’язів, ремоделюванні судин та посиленні жорсткості артерій. Крім того, ресвератрол знижує інфільтрацію імунних клітин у судинну стінку та зменшує запалення судинної стінки. Ресвератрол має значну біологічну активність та може застосовуватися не тільки як кардіопротекторний, але й як протизапальний, антидіабетичний, нейротропний, протипухлинний засіб.

Effect of roasting condition on the antioxidative activity of the methanolic extract from defatted sesame meal

Sesame seeds are usually roasted prior to expelling oil. The defatted sesame meal contains lignan glycosides in its methanolic extract. The objective of this study was to investigate the antioxidative activity of methanolic extract from defatted black sesame meal roasted at three different temperatures (180, 200, 220°C) for different durations (5-30 min). The antioxidative activities were evaluated by the 2,2-diphenyl-1-picrylhydrazyl hydrate (DPPH) radical scavenging ability and the inhibition of Cu2+ induced oxidation of human low-density lipoprotein (LDL). The effects of roasting condition on the browning index of sesame meal and the total phenolic content of the methanolic extract were also investigated. Results showed that as roasting temperature and time increased, the DPPH radical scavenging ability and the inhibition of Cu2+ induced oxidation of human LDL also increased. Meanwhile, the total phenolic content in the methanolic extract from defatted sesame meal and the browning level of sesame meal also increased with roasting temperature and time. These results suggested that the enhancement of antioxidative activity would probably be due to total phenolic compounds and Maillard reaction products formed during roasting process.

Chromium and human low-density lipoprotein oxidation

Chromium is a catalytic metal able to foster oxidant damage, albeit its capacity to induce human LDL oxidation is to date unkown. Thus, we have investigated whether trivalent and hexavalent chromium, namely Cr(III) and Cr(VI), can induce human LDL oxidation. Cr(III) as CrCl3 is incapable of inducing LDL oxidation at pH 7.4 or 4.5. However, Cr(III), specifically at physiological pH of 7.4 and in the presence of phosphates, causes an absorbance increase at 234 resembling a spectrophotometric kinetics of LDL oxidation with a lag- and propagation-like phase. In this regard, it is conceivable that peculiar Cr(III) forms such as Cr(III) hydroxide and, especially, Cr(III) polynuclear hydroxocomplexes formed at pH 7.4 interact with phosphates generating species with an intrinsic absorbance at 234 nm, which increases over time resembling a spectrophotometric kinetics of LDL oxidation. Cr(VI), as K2Cr2O7, can instead induce substantial human LDL oxidation at acidic pH such as 4.5, which is typical of the intracellular lysosomal compartment. LDL oxidation is related to binding of Cr(VI) to LDL particles with quenching of the LDL tryptophan fluorescence, and it is inhibited by the metal chelators EDTA and deferoxamine, as well as by the chain-breaking antioxidants butylated hydroxytoluene and probucol. Moreover, Cr(VI)-induced LDL oxidation is inhibited by mannitol conceivably by binding Cr(V) formed from LDL-dependent Cr(VI) reduction and not by scavenging hydroxyl radicals (OH); indeed, the OH scavengers sodium formate and ethanol are ineffective against Cr(VI)-induced LDL oxidation. Notably, heightened LDL lipid hydroperoxide levels and decreased LDL tryptophan fluorescence occur in Cr plating workers, indicating Cr-induced human LDL oxidation in vivo. The biochemical, pathophysiological and clinical implications of these novel findings on chromium and human LDL oxidation are discussed.

Anti-Atherosclerotic Effects of Fruits of Vitex rotundifolia and Their Isolated Compounds via Inhibition of Human LDL and HDL Oxidation.

Low-density lipoprotein (LDL) and high-density lipoprotein (HDL) oxidation are well known to increase the risk for atherosclerosis. In our ongoing research on natural products with inhibitory activities against oxidation of lipoproteins, fruits of Vitex rotundifolia were found to be highly active. There is no report on the effects on LDL and HDL oxidation. Herein, we investigated the inhibitory effects of V. rotundifolia fruit extract and its six compounds, which are: (1) artemetin, (2) casticin, (3) hesperidin, (4) luteolin, (5) vitexin, and (6) vanillic acid, against LDL and HDL oxidation. The LDL and HDL oxidations were determined by measuring production of conjugated dienes and thiobarbituric acid reactive substances, amount of hyperchromicity and carbonyl content, change in electrical charge, and apoA-I aggregation. In addition, the contents of the compounds in the extracts were analyzed using HPLC-DAD. Consequently, extracts of Vitex rotundifolia fruits and compounds 2 and 4 suppressed oxidation of LDL and HDL, showing inhibition of lipid peroxidation, decrease of negative charges in lipoproteins, reduction of hyperchromicity, decrease in carbonyl contents, and prevention of apoA-I aggregation. In particular, compounds 2 and 4 exhibited more potent inhibitory effect on oxidation of LDL and HDL than the extracts, suggesting their protective role against atherosclerosis via inhibition of LDL and HDL oxidation. The contents of artemetin, casticin, and vanillic acid in the extracts were 1.838 ± 0.007, 8.629 ± 0.078, and 1.717 ± 0.006 mg/g, respectively.

Inhibitory effects of compounds isolated from roots of Cynanchum wilfordii on oxidation and glycation of human low-density lipoprotein (LDL)

Abstract Low-density lipoprotein (LDL) modification such as oxidation and glycation has been known to play a significant role in the initiation and progression of atherosclerosis. The inhibitors on LDL modification have been emerged as a new strategy to be a supplement for prevention of atherosclerosis. In an effort to discover inhibitors on LDL modification from natural products, phytochemical investigation on Cynanchum wilfordii roots were performed, leading to isolation of acetophenones (1–6) including a new one (1) and nine pregnane-type steroids (7–15). The structure of the compound 1 was determined by analysis of 1D and 2D NMR spectral data analysis. All the isolated compounds were evaluated for their inhibitory activities against LDL modification. Among them, compounds 2 and 5 strongly inhibited LDL oxidation and glycation. These results suggest that compounds 2 and 5 from C. wilfordii may provide potential protective effects against atherosclerosis via inhibition of LDL oxidation and glycation.

Inhibition of Human Platelet Aggregation and Low-Density Lipoprotein Oxidation by Premna foetida Extract and Its Major Compounds

Many Premna species have been used in traditional medicine to treat hypertension and cardiac insufficiency, and as a tonic for cardiac-related problems. Some have been reported to possess cardiovascular protective activity through several possible mechanisms, but not Premna foetida. In the present study, the methanol extract of P. foetida leaves (PFM) and its isolated compounds were evaluated for their ability to inhibit copper-mediated human low-density lipoprotein (LDL) oxidation and arachidonic acid (AA)- and adenosine diphosphate (ADP)-induced platelet aggregation. Six flavonoids, three triterpenoids, vanillic acid and stigmasterol were successfully isolated from PFM. Of the isolated compounds, quercetin was the most active against LDL oxidation (IC50 4.25 µM). The flavonols were more active than the flavones against LDL oxidation, suggesting that hydroxyl group at C-3 and the catechol moiety at B-ring may play important roles in protecting LDL from oxidation. Most tested flavonoids showed stronger inhibition towards AA-induced than the ADP-induced platelet aggregation with apigenin exhibiting the strongest effect (IC50 52.3 and 127.4 µM, respectively) while quercetin and kaempferol showed moderate activity. The results suggested that flavonoids, especially quercetin, apigenin and kaempferol were among the major constituents of P. foetida responsible for anti-LDL oxidation and anti-platelet aggregation.

Evaluation of the Antioxidative and Hypo-cholesterolemic Effects of Lingzhi or Reishi Medicinal Mushroom, Ganoderma lucidum (Agaricomycetes), in Ameliorating Cardiovascular Disease.

Oxidative stress (OS) and hypercholesterolemia have been linked with a heightened risk of cardiovascular disease (CVD). Because of the numerous drawbacks of synthetic antioxidants and cholesterol-lowering drugs, natural antioxidative and hypocholesterolemic agents are of immense importance. This study was designed to determine both the OS-attenuating and cholesterol-lowering capacities of the hot water extract (HWE) and of five solvent-solvent-partitioned fractions of Ganoderma lucidum. In vitro antioxidative performance of G. lucidum HWE and fractions was measured through DPPH free radical scavenging, Folin-Ciocalteu assay, lipid peroxidation inhibition, and human low-density lipoprotein (LDL) oxidation inhibition. In vivo antioxidative performance of G. lucidum was assessed by measuring the plasma and liver antioxidative enzymatic activities (catalase, glutathione peroxidase, and superoxide dismutase) in G. lucidum HWE-fed rats. In the CVD tests, the HWE at 200 mg/kg b.w. lowered plasma levels of total cholesterol, triacylglycerol, and LDL cholesterol and increased high-density lipoprotein cholesterol. The current findings indicate the therapeutic potentiality of G. lucidum as an OS-attenuating and hypocholesterolemic agent en route to withstanding CVD complications.

Anti-Helicobacter pylori effect of various extracts of ixeris chinensis on inflammatory markers in human gastric epithelial AGS cells

Ixeris chinensis (Thunb.) Nakai (Taiwan) is a traditional herbal medicine used for treating various ailments, such as stomach ache, common cold and diarrhoea. The objective of the present study was to evaluate the antioxidative, anti-inflammatory and anti-adhesive effect of I. chinensis on Helicobacter pylori (H. pylori)-induced gastric adenocarcinoma in an AGS cell model. Three types of I. chinensis extract were used: boiling water extract (BWE), ethanol extract (EE) and chloroform extract (CE) to check anti-H. pylori activity on the AGS cell line. Phytochemical and HPLC analysis were performed. In vitro antioxidant activity, including TEAC, DPPH and H2O2 scavenging abilities, was evaluated. In addition, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined, and an MTT assay determined survival rate. Furthermore, interleukin-8 (IL-8), tumor necrosis factor (TNF-α) and nitric oxide (NO) levels were measured. The BWE showed better antioxidative activity than the EE and CE. The lag time of human low-density lipoprotein (LDL) oxidation was significantly increased by BWE, EE and CE. However, CE showed maximum antibacterial (MIC, MBC), anti-adhesive (urease test) and anti-inflammatory (IL-8, NO, TNF-α) activities. Based on the above findings, I. chinensis extract (BWE and CE) clearly shows antioxidative, anti-inflammatory and anti-adhesive effects on H. pylori-induced gastric adenocarcinoma in the AGS cell model. Hence, I. chinensis might be used to combat against H. pylori-induced gastric cancer with standard chemotherapeutic agents.

Preparation and antioxidant activity of tyrosol and hydroxytyrosol esters

A series of lipophilic esters of tyrosol and hydroxytyrosol, two naturally occurring phenols with interesting biological properties, have been prepared by an enzymatic synthesis and saponification procedure, using lipase from Candida antarctica as the catalyst. Their antioxidant activities were evaluated by the 2,2-diphenyl-1-picrylhydrazyl (DPPH), human low-density lipoprotein (LDL) oxidation, and DNA strand scission assays. All methods used for evaluating antioxidant activity revealed that tyrosol and its derivatives were less active than hydroxytyrosol and its analogues due to the influence of the catechol structure of the latter. For hydroxytyrosol, the introduction of the lipid moiety decreased its antioxidant activity. Meanwhile, an unsaturation-dependent antioxidant trend was observed for tyrosol and hydroxytyrosol esters in DNA strand scission assay, and for tyrosol esters in DPPH procedure. However, in LDL oxidation assay, possible oxidation of the polyunsaturated fatty acid moiety of tyrosol esters should also be considered.

Composition of phenolic compounds and antioxidant attributes of Cyclea gracillima Diels extracts

Cyclea gracillima Diels is a Taiwanese native medicinal herb. However, there are currently few relevant reports on its biochemical activity. In this study, the antioxidant attributes of the ethanol and hot water extracts of this herb were assayed using in vitro models, including the following: 2,2-diphenyl-1-(2,4,6-trinitrophenyl)-hydrazyl radical scavenging, Trolox equivalent antioxidant capacity, reducing power, and chelating ferrous ions. The following biochemical models were also assayed: inhibition of human low density lipoprotein oxidation, inhibition of human erythrocyte hemolysis, and scavenging oxygen radicals in human blood. The composition and content of flavonoids and phenolic acids in these extracts were also analyzed. The results showed that these extracts with high polyphenol levels presented remarkable antioxidant effects in all assays, especially when extracted with ethanol. Six phenolic acids (mainly ferulic acid, sinapic acid, and syringic acid) and 12 flavonoids (mainly narigenin, myricetin, naringin, and apigenin) were found in these extracts.

Iron as a catalyst of human low-density lipoprotein oxidation: Critical factors involved in its oxidant properties

Iron-induced human LDL oxidation, which is relevant to atherosclerosis, has not yet been properly investigated. We addressed such issue using iron(II) and (III) basically in the presence of phosphates, which are present in vivo and influence iron oxidative properties, at pH 4.5 and 7.4, representative, respectively, of the lysosomal and plasma environment. In 10mM phosphate buffered saline (PBS), iron(II) induces substantial LDL oxidation at pH 4.5 at low micromolar concentrations, while at pH 7.4 has low oxidative effects; iron(III) promotes small LDL oxidation only at pH 4.5. In 10mM sodium acetate/NaCl buffer, pH 4.5, iron-induced LDL oxidation is far higher than in PBS, highlighting the relevance of phosphates in the inhibitory modulation of iron-induced LDL oxidation. LDL oxidation is related to iron binding to the protein and lipid moiety of LDL, and requires the presence of iron(II) bound to LDL together with iron(III). Chemical modification of LDL carboxyl groups, which could bind iron especially at pH 4.5, decreases significantly iron binding to LDL and iron-induced LDL oxidation. Hydroxyl radical scavengers are ineffective on iron-induced LDL oxidation, which is inhibited by metal chelation, scavengers of alkoxyl/peroxyl radicals, or removal of LDL lipid hydroperoxides (LOOH). Overall, substantial human LDL oxidation is induced LOOH-dependently by iron(II) at pH 4.5 even in the presence of phosphates, suggesting the occurrence of iron(II)-induced LDL oxidation in vivo within lysosomes, where pH is about 4.5, iron(II) and phosphates coexist, plasma with its antioxidants is absent, and glutathione peroxidase is poorly expressed resulting in LOOH accumulation.

Protective Effect of Antioxidant Extracts from Grey Oyster Mushroom, Pleurotus pulmonarius (Agaricomycetes), Against Human Low-Density Lipoprotein Oxidation and Aortic Endothelial Cell Damage.

This study evaluated the in vitro antioxidant capacities of extracts from Pleurotus pulmonarius via Folin-Ciocalteu, 1,1-diphenyl-2-picrylhydrazyl free radical scavenging, metal chelating, cupric ion reducing antioxidant capacity, and lipid peroxidation inhibition assays. Extract compositions were determined by phenol-sulfuric acid; Coomassie Plus (Bradford) protein; Spectroquant zinc, copper, and manganese test assays; and liquid chromatography-tandem mass spectrometry (LC/MS/MS) and gas chromatography-mass spectrometry (GC/MS). Methanol-dichloromethane extract, water fraction, hot water, aqueous extract and hexane fraction exhibited the most potent extracts in the antioxidant activities. LC/MS/MS and GC/MS showed that the extracts contained ergothioneine, ergosterol, flavonoid, and phenolic compounds. The selected potent extracts were evaluated for their inhibitory effect against oxidation of human low-density lipoproteins and protective effects against hydrogen peroxide-induced cytotoxic injury in human aortic endothelial cells. The crude aqueous extract was deemed most potent for the prevention of human low-density lipoprotein oxidation and endothelial membrane damage. Ergothioneine might be the compound responsible for the activities, as supported by previous reports. Thus, P. pulmonarius may be a valuable antioxidant ingredient in functional foods or nutraceuticals.

Synthesis of phenolic amides and evaluation of their antioxidant and anti-inflammatory activity in vitro and in vivo

15 phenolic amides (PAs) have been synthesized and examinedin vitrousing four tests: (1) prevention of Cu2+-induced human low-density lipoprotein oxidation, (2) scavenging of stable radicals, (3) anti-inflammatory activity, and (4) scavenging of superoxide radicals.