Free radical scavenging and antioxidant activity of 5,7,3′,4′-hydroxy-substituted flavonoids

The antioxidant efficiencies of 5,7,3′,4′-hydroxy-substituted flavonoids were examined. The tested compounds (quercetin, luteolin, taxifolin, (+)-catechin and eriodictyol) were selected with a view to their C-ring differentiated pattern. Each one was added in cottonseed oil at equimolar amounts and the retardation of lipid peroxidation was estimated by means of peroxide value. Furthermore, their ability to scavenge DPPH radical was studied in two solvents (methanol and ethyl acetate) and the DPPH method proved a satisfactory prediction test for the antioxidant action of flavonoids in oils when methanol was used as the reaction media. Furthermore, the comparison of the C-ring structural element contribution to the antioxidant action revealed the full substitution to be the most important followed by the 3-OH and 2,3-double bond in the presence of the 4-carbonyl. Concerning the monosubstituted flavonoids, the 4-carbonyl group induced minor activity, whereas the 3-OH increased significantly the antiradical and antioxidant action.     

Crystallization kinetics of polymorphic forms of a molecular compound constructed by SOS (1,3-distearoyl-2-oleoyl-sn-glycerol) and SSO (1,2-distearoyl-3-oleoyl-rac-glycerol)

Crystallization kinetics of binary mixture phases of SOS (1,3-distearoyl-2-oleoyl-sn-glycerol) and SSO (1,2-distearoyl-3-oleoyl-rac-glycerol) were examined with time-resolved X-ray diffraction (XRD) and DSC methods. Formation of three polymorphic forms, named _c, β′_c and β_c, of a molecular compound was observed at a SOS/SSO=50/50 concentration ratio. The XRD data showed that all three polymorphs were arranged in a double chain-length structure, although a triple chain-length structure is formed in and β′ forms of SSO, and β′ and β forms of SOS. The time-resolved XRD studies showed that _c and β_c forms of the molecular compound crystallized more rapidly than the corresponding polymorphic forms of SOS and SSO. The results were discussed in terms of molecular chain–chain interactions of SOS and SSO, by assuming that kinetic processes of nucleation may prefer the formation of the _c and β_c forms arranged in the double chain-length structure.     

Degradation of chlorfenvinphos in carrots during storage

In order to investigate the degradation products of chlorfenvinphos, organically grown carrots were treated with the pesticide. After storage at 5 °C for 3 months, the following compounds were detected by gas chromatography-mass spectrometric (GC-MS) analysis: 1-(2′,4′-dichlorophenyl)ethan-1-ol, 2,4-dichlorobenzoic acid, and 2,2-dichloro-1-(2′,4′-dichlorophenyl) vinyl alcohol. The metabolic fate of the pesticide was also investigated by use of ¹⁴C-ring-labelled chlorfenvinphos which was prepared using o-[¹⁴C]dichlorobenzene as a starting material. After a month of storage at room temperature, the following compounds were determined in carrots and in sand in which the carrots were buried after treatment with [¹⁴C]chlorfenvinphos: 2,2′,4′-trichloroacetophenone, 2,4-dichloroacetophenone and 2-chloro-1-(2′,4′-dichlorophenyl)vinyl alcohol. Separation of radioactive compounds was performed using high-performance liquid chromatography and a radioactivity flow detector. The identification of compounds was carried out by GC-MS.     

Stability and antioxidant activity of phenolic compounds during in vitro digestion

The impact of phenolic compounds on the human body depended on the type, content, bioavailability, and antioxidant activity. After digestion, different phenolic compounds had different changes of bioavailability and antioxidant activity, which needed to be considered in the application. In this experiment, the structural stability and antioxidant activity of 27 phenolic compounds (phenolic acids, flavonols, flavonoids, and flavanones) were investigated during the in vitro simulated digestion. This experiment eliminated the influence of food matrix, provide a basis for regularity for the changes of phenolic substances in different materials. Results showed that the bioaccessibility of phenolic compounds with different structures varied, and there was a conformational relationship between the structure and stability. After oral digestion, most of the phenolic compounds underwent degradation and the cellular antioxidant activity (CAA) values decreased to a large extent (p < 0.05). After gastric digestion, the content (p > 0.05) and CAA values (p < 0.05) of most phenolic compounds increased. However, after intestinal digestion, the phenolic compounds were degraded to a greater extent, and different structures of phenolic compounds had different changes in CAA values (p < 0.05). In general, the CAA values of most phenolic compounds after in vitro digestion were lower than the initial value. The 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2′-azino-bis (3-ehylbenzthiazoline-6-sulfonic acid) (ABTS), and ferric reducing antioxidant power (FRAP) values of phenolic acids and flavonols decreased after in vitro simulated digestion (p < 0.05), while the values of DPPH, ABTS, and FRAP of most flavonoids (p < 0.05) increased. The increased oxygen radical absorption capacity (ORAC) values were found in most phenolic acids, flavonols, and flavonoids (p < 0.05), and most flavanones showed unremarkable changes in ORAC values (p > 0.05). In general, the changing trend of chemical-based antioxidant activity was consistent with the content of phenolic compounds.     

Radical scavenging compounds in onion skin

Two major flavonols (F_I and F_II) in onion skin were isolated. According to the ultraviolet–visible absorption spectra, F_I and F_II fractions were thought to be 3,5,7,3′-OH and 3 (5),7,3′,4′-OH of flavonol, respectively. After acid hydrolysis of the two fractions, F_I was found to consist of quercetin and glucose, but F_II only contained quercetin. F_I and F_II were confirmed by fast atom bombardment as quercetin 4′-glucoside and quercetin, respectively. The F_I and F_II fractions exhibited potent radical scavenging activity against DPPH, superoxide anion (O₂·^-) , and hydroxyl (·OH) radicals.     

APPLICATION OF THE OXIDATIVE STABILITY INDEX FOR ASSESSING THE ANTIOXIDANT PROPERTIES OF FLAVONOIDS1

The antioxidant activities of representative flavonoid classes (flavonols, flavones, flavanones, isoflavones and flavanols) relative to dl‐α‐tocopherol were evaluated using the Oxidative Stability Index (OSI) value. At 5 mM concentrations in tocopherol stripped corn oil (TSCO), antioxidant activity was determined as follows: (+) catechin > quercetin > (+,?) taxifolin > dl‐α‐tocopherol > THI (3′, 4′, 7‐trihydroxyisoflavone) > luteolin. Intra‐assay and inter‐assay coefficients of variation were 1.43% and 2.73%. Peroxide Induction (PI) values were utilizéd as a comparison method using compounds and conditions identical to those in OSI experiments. Relative values for OSI and PI of the flavonoids tested showed a 0.98 correlation. This method also revealed differences in antioxidant activity of catechins due to stereochemistry. The OSI offers a simple, reproducible method for the evaluation of flavonoid antioxidant activities in a lipid environment.     

The effects of Ca ions, EGTA and storage time on myofibrillar protein degradation, levels of Ca(2+)-dependent proteases and cathepsins B, H, L and D of ostrich skeletal muscle

The effect of Ca ions and ethylene glycol-bis(β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid (EGTA) on myofibrillar protein degradation showed that when ostrich iliotibialis lateralis muscle was incubated with 10 mM EGTA at 2–4 °C for 24 hr, the activity of extracted cathepsin H was unchanged compared with a buffer-incubated sample. Ca⁺⁺ had no effect on extracted cathepsin H activity, while that of Ca²⁺-dependent protease (CDP) decreased significantly (p < 0.05). Ca²⁺-treatment enhanced post-mortem changes observed in myofibrillar protein patterns (production of fragments around 30 K) that were not observed in EGTA-incubated myofibrils. The effect of storage time on shear force, CDP activity, cathepsin B, D, H and L activities and the SDS-PAGE pattern of myofibrils showed a time-dependent reduction in CDP activity. Of the cathepsins studied only cathepsin H showed a reduction (40%) in activity. The most prominent component appearing on storage at 2–4 °C had a M_r of 27 K. The incubation of myofibrils with CDP mimicked the post-mortem changes. CDP may be responsible for some of the post-mortem changes observed, although shear force measurements suggest these changes do not lead to significant tenderisation.     

Bioactive and Antioxidant Activity from Citrus bergamia Risso (Bergamot) Juice Collected in Different Areas of Reggio Calabria Province,Italy

The chemical composition and antioxidant activity of juice extracted from seven samples of bergamot (Citrus bergamia Risso) collected in different areas of Reggio Calabria Province were investigated. The ascorbic acid, total polyphenol, and flavonoid contents were determined. Total flavonoids and polyphenols were analyzed by ultraviolet spectra, while flavanone content was analyzed by high-performance liquid chromatography. The antioxidant activity of the fractions was assessed using three representative assays: 2,2′-azinobis(3-ethylbenzothiazoline 6-sulfonic acid), 1,1-Diphenyl-2-picryl-hydrazyl radical quenching and β-carotene bleaching test. The main flavanones were naringin, neohesperedin, and neoeriocitrin, and their average content 242.4 ± 1.8, 183.0 ± 0.6, and 247.0 ± 1.4 mg mL^–1, respectively. The results showed that bergamot juice possessed a good quality and a valuable source of health promoting constituents. In fact it contained eriocitrin, naringin, neoeriocitrin, and neohesperedin, which may contribute differentially to the antioxidant capacity.     

Polyphenols contents and antioxidant capacity of 68 Chinese herbals suitable for medical or food uses

The present study estimated in vitro antioxidant activities of 68 common Chinese herbals both for medical and food uses, using Folin–Ciocalteu, ferric-reducing/antioxidant power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging assays. The results showed different extraction had various antioxidant properties. Six plant materials including Chinese White Olive, Clove, Pricklyash Peel, Villous Amomum Fruit, Chinese Star Anise and Pagodatree Flower appeared highest total phenolics (>45 mg gallic acid equivalents (GAE)/g) and flavonoids content (>45 mg rutin equivalents (RE)/g), which also showed highest antioxidant activity (FRAP value > 2.5 mmol/g, DPPH radical-scavenging capacity > 85%), indicating they have potentials for use as natural sources of antioxidant foods. The total phenolics content of these 68 plant extracts was significantly positively correlated (r² = 0.9467) with their antioxidant capacity. Therefore, the content of phenolic compounds could be used as an important indicator of its antioxidant capacity.     

6种黄酮协同抗氧化作用及构效关系研究

以ABTS~+·清除能力为指标,采用Chou-Talalay中效原理设计试验,研究6种结构不同的小分子黄酮协同抗氧化作用及构效关系。结果表明:6种黄酮化合物对ABTS~+·清除能力依次为:5,6,7-三羟基黄酮6-羟基黄酮3,7-二羟基黄酮5-羟基黄酮3-羟基黄酮7-羟基黄酮抗坏血酸,其中5,6,7-三羟基黄酮、6-羟基黄酮和3,7-二羟基黄酮氧化作用效果显著;在不同浓度下,两种黄酮复配物对ABTS+·清除能力的联合作用指数CI值有较大差异;3,7-二羟基黄酮和其它5种黄酮都有明显的协同作用。充分说明6种黄酮化合物之间的协同抗氧化作用与化合物的羟基位置和数量有关,具有C_(3,7)-二羟基是协同抗氧化作用的主要结构特点。     

Antioxidant properties of anthocyanidins,anthocyanidin-3-glucosides and respective portisins

The study of the antioxidants properties of three classes of pigments, namely anthocyanidins (cyanidin-Cy, delphinidin-Dp and malvidin-Mv), anthocyanidin-3-glucosides (Cy-3-gluc, Dp-3-gluc and Mv-3-gluc), and portisins (Cy-pt, Dp-pt and Mv-pt) was carried out. The aim was to evaluate the relationship between the structure antioxidant properties of individual anthocyanins and respective derivative pigments. The ability of these compounds to inhibit lipid peroxidation in a liposome membrane system was examined by monitoring oxygen consumption and the antiradical and reducing capacities were determined using the DPPH and FRAP assay, respectively. All compounds tested showed antiradical and reducing properties. These features seemed to increase with the presence of catechol and pyrogallol groups in ring B of anthocyanidin-3-glucosides and respective aglycones. The results obtained for portisins are very likely to be related with their unique structural features. The flavanol moiety of the compounds structure seems to be crucial for the antiradical properties, whilst their reducing ability was only evident for the portisin derived from malvidin. This outcome could be due to some of the structural features of these pigments as they are complex structures and may have several different conformations in solution. The antioxidant protection towards lipid peroxidation increased with the overall hydrophobicity of the compounds. This feature is related to the location of the antioxidant on the liposome surface vs. water phase. Among the pigments tested, portisins showed the higher effect in preventing lipid peroxidation of soybean phosphatidylcholine liposomes, especially the portisin derived from Cy. This outcome could be due to the presence of two o-catechol groups in the structure of this compound.     

Antioxidant properties of major metabolites of quercetin

Dietary flavonoids have been related to health promotion, which has been attributed in part to their antioxidant properties as demonstrated in many in vitro studies. However, in the human organism most flavonoids are little bioavailable and largely transformed to different metabolites that are crucial to explain the health effects associated with their dietary intake, although little is known about their biological activities. Quercetin is a majority flavonoid in the human diet that has been commonly used in studies on the flavonoid and health relationships. In this study, the antioxidant activity of different conjugated metabolites of quercetin (quercetin 3′-O-sulphate, quercetin 4′-O-sulphate, quercetin 3-O-glucuronide and isorhamnetin 3-O-sulphate) prepared in the laboratory, and of some phenolic acids that may result from its colonic degradation, was investigated by two in vitro assays (ABTS and FRAP assays). As expected, substitution of the hydroxyl groups of quercetin by the conjugating substituents resulted in a decrease in the antioxidant activity with regard to the parent compound. Despite this, the conjugated metabolites still retained significant antioxidant activity and behave as significantly better radical scavengers and reducing compounds than usually recognized antioxidants like α-tocopherol. Greater antioxidant activity of the metabolites was found in the ABTS assay, conducted at pH 7.4, suggesting that quercetin derivatives could act as potential radical scavengers in physiological conditions. Similarly, antioxidant activity significantly higher than α-tocopherol was also found in the ABTS assay for 3,4-dihydroxyphenylacetic, 3-methoxy-4-hydroxyphenylacetic and 3-(3,4-dihydroxyphenyl)propionic acids, described as products of the colonic degradation of quercetin. Phenylacetic acids were more active than benzoic and phenylpropionic acids, and the activity increased with the number of phenolic hydroxyls in the molecule; methoxylated derivatives showed, in general, lower activity than the equivalent O-dihydroxylated forms but greater than that of the monohydroxylated precursor. The results obtained are expected to contribute to the understanding of the mechanisms involved in the biological effects associated with the intake of flavonoid-rich diets.     

Genotype and gender differences in carnosine extracts and antioxidant activities of chicken breast and thigh meats

The aim of this work was to investigate the effects of genotypes and gender of chickens on carnosine contents and their antioxidant activities. The carnosine content of fresh meat from Thai indigenous and hybrid native chickens differed between breeds (p < 0.01) and genders (p < 0.01). Regardless of these differences, breast meat contained 2–4-fold higher carnosine than thigh meat. After water and heat extraction at 80 °C and ultrafiltration, the carnosine content of meat extracts had the same distribution as in fresh meat. No relationship between total iron and carnosine content on antioxidant activity of the extract was detected. However, when compared in the extracts on the basis of mM carnosine in oxidation system, the extracts of chicken meat showed greater antioxidant activity than pure carnosine (p < 0.05). Furthermore, at equal concentrations, thigh meat extract had higher effective inhibiting ability than breast extract.     

Characterization of the phytochemicals and antioxidant properties of extracts from Teaw (Cratoxylum formosum Dyer)

The leaves of the Thai vegetable, Teaw (Cratoxylum formosum Dyer) were extracted with ethanol to provide an extract that had antioxidant properties. The composition of the extract was studied by high-performance liquid chromatography with a diode array detector, and by electrospray ionization mass spectrometry. The main antioxidant component (peak 1) was chlorogenic acid, which was present at 60% of the extract. Three minor components were present at 7%, 3% and 2%, and other components that were present at lower concentrations were also observed. Treatment of the Teaw extract with 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) caused a similar reduction in peak area of 55.2–58.1% for chlorogenic acid and the three minor components, indicating that these components had common structural features. Component 2 was identified as dicaffeoylquinic acid, and compounds 3 and 4 were identified as ferulic acid derivatives. The radical-scavenging activity of the Teaw extract was compared with -tocopherol, BHT and chlorogenic acid, using the DPPH and 2,2′-azinobis (3-ethylbenzothialozinesulfonic acid) radical cation (ABTS⁺) assays. The Teaw extract scavenged both free radicals more strongly than did -tocopherol and BHT, and the activity of the extract was consistent with the concentration of chlorogenic acid that was present, confirming that this component is a major contributor to the antioxidant activity. The acute toxicity of the Teaw leaf extract was investigated in mice, and it was found that the LD₅₀ of the extract was >32 g/kg. Consequently, this plant is a promising source of a natural food antioxidant.     

木贼醇提物不同萃取部位总酚酸、黄酮含量测定及抗氧化活性研究

目的:对木贼的乙醇提取物不同萃取部位进行总酚酸、黄酮含量测定及抗氧化活性比较,以探知木贼抗氧化活性物质基础。方法:木贼经70%乙醇超声提取浓缩后,采用有机溶剂萃取法依次得到石油醚、乙酸乙酯、正丁醇、水相4个部位萃取物;利用紫外-分光光度法比较各萃取部位总黄酮、酚酸含量差异;以抗坏血酸为阳性对照,比较不同萃取部位还原能力、羟自由基(·OH)、1,1-二苯基-2-三硝基苯肼(DPPH·)、2,2'-联氮-双(3-乙基苯并噻唑-6-磺酸)二铵盐(ABTS+·)清除率的差异,评价各部位抗氧化能力强弱。结果:木贼各萃取物总黄酮含量在5.70~61.55 mg/g 范围内,总酚酸含量在4.07~19.10 mg/g 范围内,乙酸乙酯萃取物总黄酮与酚酸含量明显高于其他萃取物,其还原能力、羟自由基、DPPH·、ABTS+·清除率也明显高于正丁醇、石油醚和水相萃取物,乙酸乙酯萃取物对羟自由基、ABTS+·、DPPH·清除能力IC₅₀值分别为:(0.321±0.0026)、(0.213±0.0010)和(0.169±0.0014) mg/mL。结论:经各相溶剂萃取后木贼有效成分得到初步分离,乙酸乙酯相萃取部位总黄酮和酚酸相对含量及抗氧化活性明显强于总提物和其他萃取部位,且其抗氧化能力呈量效关系。实验发现木贼中黄酮和酚酸类成分与其抗氧化能力密切相关。     

木犀草素与槲皮素抗氧化性能差异的电化学研究

黄酮醇的抗氧化活性通常显著强于与之对应的黄酮,而两者的分子结构仅在C环3-位上相差一个羟基。为了揭示黄酮醇3-OH增强抗氧化活性的反应机理,选取槲皮素和木犀草素,对两者的氧化过程进行循环伏安法和现场薄层长光程紫外可见光谱电化学测试。结果表明,两者在发生2e－/2H+反应氧化为对应的邻醌之后,只有槲皮素邻醌能够进一步转化为更稳定的单一共轭结构,带动失电子步骤的进行,从而增强了槲皮素的抗氧化活性。这个后行转化反应必须以3-位羟基的存在为前提。     

Evaluation of antioxidant and inhibitory activities for different subclasses flavonoids on enzymes for rheumatoid arthritis

Antioxidant activities of flavonoids were decreased in the order of flavonols > flavanones > flavones. Inhibitory intensities for hyaluronidase and collagenase reaction differed clearly according to flavonoid subclasses. Kaempferol, quercetin, myricetin, and rutin in flavonols inhibited hyaluronidase reaction specifically, while apigenin, luteolin, baicalin, and baicalein in flavones showed specific inhibition to collagenase reaction. In addition, the flavonoids, except baicalin and catechin, inhibited potently LPS-induced nitrite production in a dose-dependent manner, which might be mainly due to the suppression of inducible nitric oxide (NO) synthase. Quercetin and luteolin showed the strongest inhibitory activities on 15-lipoxygenase (LOX), and quercetin showed relatively potent inhibition on cyclooxygenase-1 (COX-1) reaction. Otherwise, all tested flavonoids possessed the inhibitory activity to COX-2 reaction, and especially luteolin, kaempferol, hesperetin, and naringin showed relatively the potent inhibition on COX-2 reaction. This report elucidated the anti-inflammatory activities, such as the antioxidant property, inhibition of NO production, and inhibition of inflammatory enzymes (hyaluronidase, collagenase, LOX, and COXs) of several subclass flavonoids.     

不同品种甘薯叶提取物抗氧化及对α-葡萄糖苷酶抑制活性的研究

本研究旨在通过比较7个品种甘薯叶提取物的抗氧化活性和α-葡萄糖苷酶抑制活性,探讨甘薯叶抗氧化和降血糖的潜力。以甘薯叶为研究对象,测定其总多酚和总黄酮含量,体外实验评价其抗氧化活性(DPPH·清除能力、ABTS+·清除能力、·OH清除能力和还原能力)及对α-葡萄糖苷酶的抑制活性。结果表明7个品种甘薯叶提取物总多酚和总黄酮含量、抗氧化活性以及α-葡萄糖苷酶抑制活性具有明显差异。甘薯叶总多酚含量介于15.02~33.33 mg GAE/g DW,总黄酮含量介于1.06~3.11 mg RE/g DW。徐薯18、济薯18和龙薯9甘薯叶总多酚和总黄酮含量最高,品种间无统计学差异(P>0.05)。龙薯9自由基(DPPH·、ABTS+·、·OH)清除能力最强;济薯18还原能力最强;商薯19抑制α-葡萄糖苷酶活性最强。总多酚和总黄酮含量与抗氧化活性之间具有极显著的正相关性(P<0.01),而与α-葡萄糖苷酶抑制活性之间没有显著的相关性(P>0.05)。本研究表明甘薯叶是潜在抗氧化剂和α-葡萄糖苷酶抑制剂的优质来源,为甘薯种植和生产品种的选择提供理论依据。     

基于UPLC-QTOF-MS和HPLC-QQQ-MS技术的鹰嘴豆酚类化合物定性、定量分析及其抗氧化能力研究

鹰嘴豆为一种高营养豆类植物。为深入了解其营养价值,用80%甲醇溶液提取酚类物质,对提取物中不同存在形态的酚类化合物及其抗氧化活性进行测定,并对其提取物进行酚类的定性及定量分析。结果表明,酚酸含量最高部分为糖苷键合态酚类物质(0.81 mg/g),黄酮含量最高部分为游离态酚类物质(0.26 mg/g),不同存在形式酚类物质含量及抗氧化能力不同;80%甲醇提取物通过UPLC-QTOF-MS定性分析,对其24种化合物进行鉴定,包括12种黄酮、4种酚酸;HPLC-QQQ-MS定量分析表明:对羟基苯甲酸、香豆酸、原儿茶酸类化合物含量丰富。     

基于量子化学分析的类黄酮抗氧化功能区划分

本研究采用量子化学方法对常见类黄酮的最高占有轨道组成、最活泼羟基位置与其抗氧化活性的关系进行研究。结果表明：类黄酮的分子结构可分为3 个功能域：抗氧化能力决定域(B 环)、抗氧化能力加强域(C 环)、溶解性及亲和力调节域(A 环)。 该功能域划分表明,可通过在类黄酮分子的A 环上引入亲油或亲水性的基团来提高其在水相或油相中的溶解性,充分发挥其抗氧化作用。