Comparative study of eight well-known polyphenolic antioxidants

Eight antioxidants from five different polyphenolic classes (cinnamic acids, benzoic acids, flavonoids, proanthocyanidins and stilbenes), and the water-soluble vitamin E derivative trolox were examined for their antioxidant activity in-vitro. In addition, the compounds were tested for their cytotoxicity on growing fibroblasts and their inhibition of the classical pathway of the complement system. Procyanidin C1 was shown to be a good scavenger of both DPPH(*) and HO(*), and a strong inhibitor of lipid peroxidation and the classical pathway of the complement system. Consequently, procyanidin C1 was classified as the most promising antioxidant in-vitro of all compounds tested. In contrast, genistein exhibited a very low antioxidant activity in both the lipid peroxidation and the DPPH(*) scavenging assay, a high cytotoxicity and a low complement-inhibiting activity.     

A-type procyanidin derivatives with antioxidant and much enhanced α-glucosidase inhibitor activities

Procyanidins are natural compounds with good biological activity. However, due to a large number of phenolic hydroxyl groups in the structure, they have high polarity and low bioavailability. The preparation of A-type proanthocyanidin derivatives is an effective way to change their polarity and biological activity. In this paper, a series of A-type procyanidin derivatives were designed and synthesized by two practical and safe methods, and two new dimeric A-type procyanidin derivatives, procyanidin A1-acetone conjugate (6) and procyanidin A2-cystein conjugate (9) were obtained and reported for the first time. Their structures were characterized and confirmed by ¹H NMR, ¹³C NMR, HMBC, ¹H-¹H COSY and MS. All the compounds showed strong DPPH scavenging activities. Compound 6 showed inhibitory effects on α-glucosidase with an IC₅₀ value of 8.7 μg/mL, while its parental compound, procyanidin A1, had no inhibitory effects. Degradation of procyanidins from peanut skin by L-cystein was studied. The results showed that the main structural unit of procyanidins in peanut skin was A-type proanthocyanidins dimer.     

山葡萄籽多酚类化合物体外抗氧化活性的研究(英文)

目的:本文对分自山葡萄籽中的五种多酚类化合物( )-儿茶素、原花青素B_2、原花青素B_5、原花青素B_5-3′-O-gallate和山葡萄素进行抗脂质过氧化研究。方法:采用体外抗小鼠肝匀浆脂质过氧化的方法对这些化合物的抗氧化活性进行评价。结果:( )-儿茶素,原花青素B_2,原花青素B_5,原花青素B_5-3′-O-gallate和山葡萄素等五种化合物对小鼠肝匀浆过氧化脂质生成的半数抑制浓度(IC_(50))分别为0.47、0.25、0.10、0.02及0.03mmol/L,阳性对照维生素E的IC_(50)为0.13mmol/L。对这些化合物的构效关系进行的初步分析表明:带有没食子酰基的多酚具有更强的抗氧化活性,二聚体的抗氧化活性均比单体( )-儿茶素的活性强。另外,4→6连接的二聚体比4→8连接的二聚体具有更强的抗氧化活性。结论:原花青素B_5、原花青素B_5-3′-O-gallate及山葡萄素的抗氧化活性都比维生素E强,且这类多酚的抗氧化活性强弱与取代类型及聚合方式密切相关。     

Analysis of major antioxidants from extracts of Myrmecodia pendans by UV/visible spectrophotometer,liquid chromatography/tandem mass spectrometry,and high-performance liquid chromatography/UV techniques

In the present work, heat reflux extraction with ethanol/water (80:20; v/v) as the solvent was used to extract antioxidants from Myrmecodia pendans. The crude extract (CE) was fractionated using hexane and ethyl acetate. Ethyl acetate fraction (EAF) and aqueous fraction were collected. Antioxidant activity against 1,1-diphenyl-2-picrylhydrazyl-radical radical and ferric reducing power of the CE, EAF, and aqueous fraction were evaluated. EAF showed comparable antioxidant activity against 1,1-diphenyl-2-picrylhydrazyl-radical radical and ferric reducing power to those of the CE. UV/visible, liquid chromatography/electrospray ionization/tandem mass spectrometry, and high-performance liquid chromatography were employed for identifying the major antioxidant compounds in the EAF. Three major phenolic compounds (rosmarinic acid, procyanidin B1, and polymer of procyanidin B1) were identified. The first two compounds were confirmed and quantified by high-performance liquid chromatography using authentic standards, but confirmation of the third compound was hampered by a lack of commercial standard. Concentrations of rosmarinic acid and procyanidin B1 in the EAF were found to be 20.688 ±1.573 mg/g dry sample and 3.236 ±0.280 mg/g dry sample, respectively. All these three compounds are reported for the first time in sarang semut.     

Extracts of Agrimonia eupatoria L. as sources of biologically active compounds and evaluation of their antioxidant,antimicrobial, and antibiofilm activities

In this study, we determined the concentration of total phenols, flavonoids, tannins, and proanthocyanidins in the water, diethyl ether, acetone, and ethanol extracts of Agrimonia eupatoria L. We also investigated the antioxidant activity of these extracts using two methods [2,2-diphenyl-1-picrylhydrazyl (DPPH) and reducing power] and their in vitro antimicrobial (antibacterial and antifungal) activity on some selected species of bacteria and fungi. In addition, the effects of the acetone and water extracts on the inhibition of biofilm formation of Proteus mirabilis and Pseudomonas aeruginosa were investigated using the crystal violet method. The concentration of total phenols was measured according to the Folin–Ciocalteu method and the values obtained ranged from 19.61 mgGA/g to 220.31 mgGA/g. The concentration of flavonoids was examined by the aluminum chloride method and the values obtained ranged from 20.58 mgRU/g to 97.06 mgRU/g. The total tannins concentration was measured by the polyvinylpolypyrrolidone method and the values obtained ranged from 3.06 mgGA/g to 207.27 mgGA/g. The concentration of proanthocyanidins was determined by the butanol–HCl method and the values obtained ranged from 4.15 CChE/g to 103.72 CChE/g. Among the various extracts studied, the acetone extract exhibited good antioxidant activity (97.13%, as determined by the DPPH method). The acetone extract was active in the absorbance value range from 2.2665 to 0.2495 (as determined by the reducing power method). The strongest antimicrobial activity was detected on G⁺ bacteria, especially on probiotic species, and the acetone extract demonstrated the highest activity. Biofilm inhibitory concentration required to reduce biofilm coverage by 50% values for acetone extract was 4315 μg/mL for P. mirabilis and 4469.5 μg/mL for P. aeruginosa. The results provide a basis for further research of this plant species.     

Comparative effects of flavonoids on oxidant scavenging and ischemia-reperfusion injury in cardiomyocytes

Since flavonoids scavenge reactive oxygen species, they may potentially protect against ischemia/reperfusion injury. This study compared the scavenging capacity of specific flavonoids towards different reactive oxygen species. Whether the differential oxidant scavenging capacity correlated with their protective efficacy in ischemia/reperfusion injury of cardiomyocytes was determined. The free radical scavenging capacity of five flavonoids (wogonin, baicalin, baicalein, catechin and procyanidin B2) was analyzed using electron spin resonance spectrometry for 3 radicals: 1,1-diphenyl-2picrylhydrazyl (DPPH), superoxide and hydroxyl radical. A well-established chick cardiomyocyte model of ischemia (1 h)/reperfusion (3 h) was used to evaluate flavonoid-induced protection against ischemia/reperfusion injury in chronic treatment (pretreated 72 h and treated through ischemia/reperfusion) and acute treatment protocols (during ischemia/reperfusion or only at reperfusion). The cell viability was assessed by propidium iodide. The DPPH scavenging was most significant with catechin, followed by procyanidin B2, baicalein, baicalin, and wogonin. The superoxide scavenging was, similarly, most significant with catechin, followed by baicalein, procyanidin B2, and baicalin. For hydroxyl radical, only baicalein showed a significant scavenging capacity (>50% reduction in ESR signal). For the cardiomyocyte studies, all flavonoids but wogonin showed protection against ischemia/reperfusion injury in the chronic treatment protocol. When flavonoids were administered only during ischemia/reperfusion, baicalein, procyanidin B2, and catechin significantly reduced cell death. If flavonoids were administered just at reperfusion, only baicalein and procyanidin B2 had protective effects, and the efficacy was less. Flavonoids possess specific but differential radical scavenging capacity, which, in conjunction with the timing of treatment, affects their protective efficacy in cardiomyocytes exposed to ischemia/reperfusion.     

莲房原花青素提取纯化工艺研究与抗氧化活性评价

目的 优化莲房原花青素提取纯化工艺并评价抗氧化活性。方法 以正交设计L₉(3⁴)优化莲房原花青素提取工艺参数,用大孔吸附树脂进行纯化,而后通过1,1-二苯基-2-苦肼基(DPPH)和羟基自由基(·OH)清除率评价其体外抗氧化活性。结果 在最佳提取工艺条件下(8倍量50%乙醇回流提取2次,每次3 h),提取率达91.3%,进一步通过大孔树脂AB-8纯化,最终提取物中原花青素纯度为80.7%。莲房原花青素抗氧化活性与葡萄籽原花青素无显著性差异,均明显优于维生素C。结论 该提取纯化方法简单、高效,可用于莲房原花青素提取物的制备。莲房原花青素具有较强的抗氧化活性,值得进一步开发利用。     

Characterization of myrtle seed (Myrtus communis var. baetica) as a source of lipids,phenolics, and antioxidant activities

This study aimed to characterize the chemical composition and antioxidant activity of the oil and the methanolic extract of Myrtus communis var. baetica seed. The oil yield of myrtle seed was 8.90%, with the amount of neutral lipid, especially triacylglycerol, being the highest, followed by phospholipids and glycolipids. Total lipids and all lipid classes were rich in linoleic acid. The content of total phenols, flavonoids, tannins, and proanthocyanidins of the methanolic extract and the oil from myrtle seed was determined using spectrophotometric methods. Antioxidant activities of the oil and the methanolic extract from myrtle seed were evaluated using 1,1-diphenyl-2-picrylhydrazyl radical scavenging, β-carotene–linoleic acid bleaching, and reducing power and metal chelating activity assays. In all tests, the methanolic extract of myrtle seed showed better antioxidant activity than oil. This investigation could suggest the use of myrtle seed in food, industrial, and biomedical applications for its potential metabolites and antioxidant abilities.     

Inhibitory effects of condensed tannins on angiotensin converting enzyme

Effects of condensed tannins isolated from Rhei Rhizoma on the activities of angiotensin converting enzyme (ACE) and various proteases were examined in vitro. Among the various condensed tannins tested, procyanidin B-5 3,3'-di-O-gallate and procyanidin C-1 3,3',3"-tri-O-gallate strongly inhibited the activity of ACE. The concentration of procyanidin B-5 3,3'-di-O-gallate required for 50% inhibition of ACE was 1.3 X 10(-6) M. The inhibition of ACE by condensed tannins was reversible and non-competitive, according to dialysis and to Dixon plots. However, over one hundred times the concentration was required to inhibit activities of other proteases such as trypsin, chymotrypsin, leucine aminopeptidase, carboxypeptidase A and urinary kallikrein. These results suggest that the inhibitory effects of condensed tannins on the activities of ACE are specific.     

山楂原花青素和葡萄籽原花青素活性比较

目的比较山楂原花青素(OPC)与葡萄籽OPC的生物活性。方法体外将肝癌细胞Hep-S、小鼠肉瘤S-180、小鼠胸腺、脾淋巴细胞、肾细胞和肝细胞分别与不同浓度的山楂OPC或葡萄籽OPC共同培养,用MTT法检测抑制Hep-S和S-180增殖的影响以及促进T细胞、B细胞、肾细胞和肝细胞增殖的影响。提取与山楂OPC或葡萄籽OPC共同培养的Hep-S细胞的DNA,检测Hep-S细胞的凋亡程度。结果山楂OPC比葡萄籽OPC抑制Hep-S和S-180增殖作用更好;其促进T细胞、B细胞、肾细胞和肝细胞增殖效果也更强;与葡萄籽OPC相比,山楂OPC使Hep-S细胞中的DNA发生更明显的凋亡,产生更多的DNA片段。结论山楂OPC具有比葡萄籽OPC更强的生物活性。     

低功率超声醇提薄荷总黄酮工艺优化及抗氧化活性研究

目的 优选乙醇提取薄荷总黄酮的最佳工艺,并考察薄荷总黄酮的抗氧化活性.方法 采用低功率超声法(50℃,100 W)提取薄荷总黄酮,在单因素试验基础上,采用响应面分析法优选最佳薄荷总黄酮醇提工艺;采用Fetion反应考察薄荷总黄酮的抗氧化活性.结果 最佳提取工艺为乙醇体积分数41.14％,液料比21.57:1(mL/g)...     

Tannin Producing Dimeric Proanthocyanidins in Juniperus communis.

From bark extracts of JUNIPERUS COMMUNIS L. (Cupressaceae) some dimeric proanthocyanidins have been isolated and their structures elucidated. They belong to the procyanidin typs B1, B2, B3 and B4, what means that there is a C4 to C8' linkage.     

Tannins from Hamamelis virginiana: Identification of Proanthocyanidins and Hamamelitannin Quantification in Leaf, Bark, and Stem Extracts.

The tannins in leaf, bark, and stem extracts of HAMAMELIS VIRGINIANA were analyzed. Four proanthocyanidins were isolated by HPLC. One was a procyanidin polymer containing only one type of flavanol unit; the other three were polymers of procyanidin and prodelphinidin containing two types of flavanol units. A method of assay of hamamelitannin showed the bark extract to be 31 times richer in hamamelitannin than the leaf extract and 87 times richer than the stem extract.     

Isolation and structure elucidation of phenolic antioxidants from Tamarind (Tamarindus indica L.) seeds and pericarp.

Although it is already known that Tamarind (Tamarindus indica L.) seeds contain phenolic substances, the individual components of the seeds have not been fully identified and quantitated, and in the case of Tamarind pericarp not reported. Therefore, major polyphenolic compounds were extracted using organic solvents and the metabolites were isolated by semi-preparative high performance liquid chromatography. Their structures were elucidated by liquid chromatography-electrospray-ionisation-mass spectrometry (LC-ESI-MS), nano-electrospray-ionisation mass spectrometry (ESI-MS), and where possible by gas chromatography-mass spectrometry (GC-MS) and 1H and 13C NMR. Quantitative analysis of polyphenolic compounds in Tamarind seeds and pericarp was conducted by analytical high performance liquid chromatography (HPLC), calculated against standard curves of authentic compounds. The yields of total phenolic compounds after Soxhlet extraction with methanol were 6.54 and 2.82 g/kg (dry weight) in the seeds and pericarp respectively. The profile (%) of polyphenolics in Tamarind pericarp was dominated by proanthcyanidins (73.4) in various forms (+)-catechin (2.0), procyanidin B2 (8.2), (-)-epicatechin (9.4), procyanidin trimer (11.3), procyanidin tetramer (22.2), procyanidin pentamer (11.6), procyanidin hexamer (12.8) along with taxifolin (7.4), apigenin (2.0), eriodictyol (6.9), luteolin (5.0) and naringenin (1.4) of total phenols, respectively. The content of Tamarind seeds comprised only procyanidins, represented (%) mainly by oligomeric procyanidin tetramer (30.2), procyanidin hexamer (23.8), procyanidin trimer (18.1), procyanidin pentamer (17.6) with lower amounts of procyanidin B2 (5.5) and (-)-epicatechin (4.8). Extraction of Tamarind pericarp and seeds using acetone:methanol:acetic acid gave only procyanidin oligomers, but in much higher yield and variety. The antioxidant capacities of the Soxhlet methanolic extracts were determined, and indicates that Tamarind may be an important source of cancer chemopreventive natural products in tropical regions.     

樱桃叶中黄酮类成分的定性定量研究及体外抗氧化活性初步评价

目的:建立樱桃叶中黄酮类成分的定性定量方法,并初步评价其体外抗氧化活性。方法:药材经水解后提取总黄酮;紫外分光光度(UV)法测定总黄酮含量;薄层色谱(TLC)法检测槲皮素和山柰酚的存在与否;高效液相色谱(HPLC)法测定槲皮素与山柰酚的含量;Fenton反应法评价抗氧化活性。结果:UV法芦丁的检测浓度在11.0～110.0μg·mL-1范围内与吸光度呈良好线性关系(r=0.9998),平均加样回收率为98.3%(RSD=1.3%,n=6);TLC可清晰检出槲皮素与山柰酚;HPLC法槲皮素与山柰酚的检测浓度分别在37.5～1200.0ng·mL-(1r=0.9997)、62.5～2000.0ng·mL-(1r=0.9994)范围内与各自峰面积积分值呈良好线性关系,平均加样回收率分别为99.8%(RSD=3.4%,n=9)、100.0%(RSD=1.9%,n=9);樱桃叶总黄酮提取液具有一定抗氧化能力,并呈量-效关系。结论:该方法准确、可靠、重复性好,可作为樱桃叶的质量控制方法。     

响应面法优化土人参根中总黄酮提取及其抗氧化活性研究

目的 采用超声波辅助提取苗药用的土人参根中总黄酮,比较不同提法所得总黄酮的抗氧化活性。方法 在单因素试验基础上采用响应面法优化超声波处理后固液比、乙醇体积分数、浸提温度及其交互作用对总黄酮得率的影响,DPPH.、超氧阴离子与羟基自由基清除法考查水浴、超声波辅助和酶辅助提取的苗药土人参根中总黄酮的抗氧化活性。结果 苗药用土人参根中总黄酮的最佳工艺为固液比1:26、乙醇体积分数65%、浸提温度70℃,在此条件下,总黄酮得率为 2.62% ,与回归方程预测值 2.603% 符合良好。结论 该优化工艺实现了土人参根中黄酮类化合物的高效提取,所得总黄酮以酶法提取的抗氧化性能力最强。目的 采用超声波辅助提取苗药用的土人参根中总黄酮,比较不同提取方法所得总黄酮的抗氧化活性。方法 在单因素试验基础上采用响应面法优化超声波处理后固液比、乙醇体积分数、浸提温度及其交互作用对总黄酮得率的影响,DPPH?、超氧阴离子与羟基自由基清除法考查水浴、超声波辅助和酶辅助提取的苗药土人参根中总黄酮的抗氧化活性。结果 苗药用土人参根中总黄酮的最佳工艺为固液比1:26、乙醇体积分数65%、浸提温度70℃,在此条件下,总黄酮得率为 2.620% ,与回归方程预测值 2.603% 符合良好。三种提取方法所得总黄酮的抗氧化活性以酶法提取的最强且均好于Vc。结论 该优化工艺实现了土人参根中黄酮类化合物的高效提取,不同提取方法得到的总黄酮抗氧化活性差异明显。     

Comparative effects of gamma and electron beam irradiation on the antioxidant potential of Portuguese chestnuts (Castanea sativa Mill.)

Chestnuts (Castanea sativa Mill.) are widely consumed all over the world, and have been recently studied for their antioxidant potential. The present study reports the effect of e-beam and gamma radiation (doses of 0, 0.5, 1 and 3 kGy) on the antioxidant potential of Portuguese chestnuts. Irradiation might be an alternative preservation method, since Methyl Bromide, a widely used fumigant, was banished by the European Union in 2010 due to its toxicity. The antioxidant activity was evaluated through 2,2-diphenyl-1-pycrylhydrazyl (DPPH) free radical scavenging activity assay, reducing power by the Ferricyanide/Prussian blue assay, and lipid peroxidation inhibition by β-carotene/linoleate and thiobarbituric acid reactive substances (TBARS) assays. The analysis of total phenolics and flavonoids was performed by spectrophotometric assays. Irradiated samples preserved total phenolics content (but not flavonoids) and revealed higher antioxidant activity (lower EC₅₀ values) than the control samples. The most indicated doses to maintain antioxidants content, and to increase antioxidant activity were 1 and 3 kGy for electron beam and gamma radiation, respectively.     

LC-MS identification and preparative HPLC isolation of Frankenia pulverulenta phenolics with antioxidant and neuroprotective capacities in PC12 cell line

Context: Frankenia pulverulenta L. (Frankeniaceae) is a medicinal species with carminative, analgesic and antiviral properties. However, phytochemical investigations, antioxidant and neuroprotective capacities of this plant remain unclear.

Objective: This work assesses the phenolic composition of F. pulverulenta shoot and root and evaluates their antioxidant and neuroprotective capacities.

Materials and methods: Successive fractionation of F. pulverulenta shoot and root using 6 solvents were used. Antioxidant capacity of these fractions was assessed through four in vitro tests (DPPH, ABTS, Fe-chelating activity and ORAC). Phenolic identification, purification as well as neuroprotective activity of ethyl acetate (EtOAc) fraction and purified molecules were assessed.

Results: Among the tested fractions, EtOAc shoot and root fractions possessed considerable phenolic contents (383 and 374?mg GAE/g E, respectively) because of their important ORAC (821 and 1054?mg of TE/g E), DPPH (586 and 750?mg of TE/g) and ABTS (1453 and 1319?mg of TE/g) results. Moreover, gallic acid, quercetin, quercetin galloyl glucoside, trigalloyl hexoside, procyanidin dimers and sulfated flavonoids were identified by LC-DAD-ESI-MS for the first time in this species. The relevant cytoprotective capacity (at 300?μg/mL) against β-amyloid peptide induced toxicity in PC12 cells of EtOAc fractions were corroborated with the chemical composition. In addition, purified molecules were tested for their ORAC and neuroprotective activity. Quercetin showed the best ORAC value (33.55?mmol TE/g polyphenols); nevertheless, procyanidin dimer exhibited an exceptionally efficient neuroprotective activity (100% of viability at 50?μg/mL).

Discussion and conclusions: These findings suggest that this halophyte is a promising source of antioxidant and neuroprotective molecules for pharmaceutical purposes.     

Variation in the phenolic content and in vitro antioxidant activity of Sorbus aucuparia leaf extracts during vegetation

Seasonal variation in the antioxidant activity and content of phenolic compounds was studied for the 70% methanol extracts of Sorbus aucuparia leaves harvested monthly over the full course of the growing season. The antioxidant potential of the extracts was evaluated using two complementary in vitro tests: the DPPH (2,2-diphenyl-1-picrylhydrazyl) radical-scavenging assay and the AAPH [2,2'-azobis-(2-amidinopropane)dihydrochloride]-induced [corrected] linoleic acid (LA) peroxidation test. The radical-scavenging capacities of the extracts towards the DPPH radical were in the range of 0.40 to 0.57 millimolar Trolox equivalents/g dry weight of the leaves. They were significantly correlated (r = -0.8480, p < 0.05) with the results of the LA-peroxidation test, indicating the S. aucuparia leaf extracts to be universal antioxidants. Significant linear correlations were also found between the different antioxidant potentials and total phenolic contents as estimated by the Folin-Ciocalteu method and further verified by serial determinations of proanthocyanidins, chlorogenic acid isomers and flavonoids ([r] in the range of 0.81-0.97, p < 0.05). As the best antioxidant capacities and the highest phenolic contents were found for the leaf samples harvested during the three summer months (June, July and August), this period could be considered to be optimal for cost-effective production of natural health products. For the leaf samples collected in July, the values of EC50 and IC50 for the two antioxidant tests were 2.02 and 93.45 μg [corrected] phenolics/mL, respectively. These antioxidant capacities were found to be higher or comparable to those of synthetic and natural phenolic antioxidants, such as BHT (butylated hydroxytoluene), BHA (butylated hydroxyanisole), TBHQ (tert-butylhydroquinone), quercetin and Trolox.