Antioxidant activity of two phloroglucinol derivatives from Dryopteris crassirhizoma

The rhizome of Dryopteris crassirhizoma NAKAI exhibited significant antioxidant activity, as assessed by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity in vitro. Two phloroglucinol derivatives, flavaspidic acids PB (1) and AB (2), were isolated from the rhizome of D. crassirhizoma by a bioassay-guided fractionation. 1H-, 13C-NMR, and UV analysis were used to determine the structures. Furthermore, the two compounds were tested for their antioxidant activities, such as their DPPH radical scavenging, superoxide radical scavenging, and lipid peroxidation (LPO) inhibitory activities. Compounds 1 and 2 exhibited potent antioxidant activity against the LPO inhibitory test with IC(50) values of 12.9 and 13.1 microM, respectively, compared with alpha-tocopherol (IC(50); 15.6 microM) and butylated hydroxy anisole (BHA, IC(50); 10.8 microM), while the two compounds had a moderated effect on the DPPH radical scavenging activity (IC(50); 71.7, 76.3 microM) as well as superoxide radical scavenging activity (IC(50); 58.6, 64.4 microM). The potent activity of the flavaspidic acids (1, 2) on inhibiting LPO might be due to possible stabilization as a result of chelating with iron.     

Neuroprotective and free radical scavenging activities of phenolic compounds fromHovenia dulcis

The EtOAc-soluble fraction from a methanolic extract of Hovenia dulcis Thunb. exhibited neuroprotective activity against glutamate-induced neurotoxicity in mouse hippocampal HT22 cells. The neuroprotective activity-guided isolation resulted in 8 phenolic compounds (1-8), such as vanillic acid (1), ferulic acid (2), 3,5-dihydroxystilbene (3), (+)-aromadendrin (4), methyl vanillate (5), (-)-catechin (6), 2,3,4-trihydrobenzoic acid (7), and (+)-afzelechin (8). Among these, compounds 6 and 8 had a neuroprotective effect on the glutamate-induced neurotoxicity in HT22 cells. Furthermore, compound 6 had a DPPH free radical scavenging effect with an IC50 value of 57.7 microM, and a superoxide anion radical scavenging effect with an IC50 value of 8.0 microM. Both compounds 6 and 8 had ABTS cation radical scavenging effects with IC50 values of 7.8 microM and 23.7 microM, respectively. These results suggest that compounds 6 and 8 could be neuroprotectants owing to their free radical scavenging activities.     

Antioxidant constituents and a new triterpenoid glycoside from<Emphasis Type="Italic">Flos Lonicerae</Emphasis>

As a component of our continuing investigations into herb-derived antioxidant agents, we have evaluated the antioxidant effects of Flos Lonicerae (Lonicera japonica flowers), via 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, total reactive oxygen species (ROS), hydroxyl radical (*OH), and peroxynitrite (ONOO-) assays. Among the methanolic extract and the dichloromethane, ethyl acetate, n-butanol, and water fractions, the EtOAc fraction of Flos Lonicerae exhibited marked scavenging/inhibitory activities, as follows: IC50 values of 4.37, 27.58 +/- 0.71, 0.47 +/- 0.05, and 12.13 +/- 0.79 microg/mL in the DPPH, total ROS, ONOO-, and *OH assays, respectively. Via a bioactivity-guided fractionation approach, a new triterpenoid glycoside, oleanolic acid 28-O-alpha-L-rhamnopyranosyl-(1-->2)-[beta-D-xylopyranosyl(1-->6)]-beta-D-glucopyranosyl ester (12), along with eleven known compounds, including chrysoeriol (1), luteolin (2), 5-hydroxymethyl-2-furfural (3), caffeic acid (4), protocatechuic acid (5), chrysoeriol 7-O-beta-D-glucopyranoside (6), isorhamnetin 3-O-beta-D-glucopyranoside (7), kaempferol 3-O-beta-D-glucopyranoside (8), quercetin 3-O-beta-D-glucopyranoside (9), hederagenin 3-O-alpha-L-arabinopyranoside (10), and luteolin 7-O-beta-D-glucopyranoside (11), were isolated from the EtOAc fraction. The structures of isolated compounds 1-12 were elucidated via spectroscopic analyses. Compound 12 was isolated from a natural source for the first time. Compounds 2, 4, 5, 7, 9, and 11 evidenced marked scavenging activities, with IC50 values of 2.08-11.76 microM for DPPH radicals, and 1.47-6.98 microM for ONOO-.     

Antimycobacterial and antioxidant flavones from<Emphasis Type="Italic">Limnophila geoffrayi</Emphasis>

The chloroform extract of the aerial part of Limnophila geoffrayi showed antimycobacterial and antioxidant activities. Bioassay-guided fractionation has led to the isolation of the flavones nevadensin (5,7-dihydroxy-6,8,4'-trimethoxyflavone, 1) and isothymusin (6,7-dimethoxy-5,8,4'-trihydroxyflavone, 2). Both compounds 1 and 2 exhibited inhibition activity against Mycobacterium tuberculosis, with equal MIC value of 200 microg/mL. Only compound 2 exhibited antioxidant activity against the radical scavenging ability of DPPH, with the IC50 value of 7.7 microg/mL. The crude hexane, chloroform and methanol extracts as well as the pure compounds 1 and 2 did not exhibit mutagenic activity in the Bacillus subtilis recassay.     

Further isolation of peroxynitrite and 1,1-diphenyl-2-picrylhydrazyl radical scavenging isorhamnetin 7-O-glucoside from the leaves of Brassica juncea L

From the leaves of Brassica juncea, an radical scavenging isorhamnetin 7-O-glucoside on peroxynitrite and 1,1-diphenyl-2-picrylhydrazyl (DPPH) was isolated and characterized based on the spectroscopic evidence. The compound showed the peroxynitrite and DPPH scavenging activities with IC50 values of 2.07 +/- 0.17 and 13.3 microM, respectively. Penicillamine and L-ascorbic acid as positive control exhibited radical scavenging activities with IC50 values of 3.17 +/- 0.39 and 12.78 microM, respectively.     

Antioxidant activity from the stem bark of<Emphasis Type="Italic">Albizzia julibrissin</Emphasis>

The antioxidant activity of the stem bark from Albizzia julibrissin was evaluated for its potential to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, to inhibit the generation of the hydroxyl radical (*OH), total reactive oxygen species (ROS) and to scavenge authentic peroxynitrites (ONOO-). The methanol extract of A. julibrissin exhibited strong antioxidant activity in the tested model systems. Therefore, it was further fractionated using several solvents. The antioxidant activity of the individual fractions were in the order of ethyl acetate (EtOAc) > n-butanol (n-BuOH) > dichloromethane (CH2Cl2) > and water (H2O). The ethyl acetate soluble fraction, which exhibited strong antioxidant activity, was further purified by repeated silicagel, Sephadex LH-20 and RP-18 gel column chromatography. Sulfuretin (1) and 3',4',7-trihydroxyflavone (2) were isolated as the active principles. Compounds 1 and 2 exhibited good activity in all tested model systems. Compound 1 exhibited five times more inhibitory activity on the total ROS than Trolox. Compound 2 showed six times stronger DPPH radical scavenging activity than L-ascorbic acid. These results show the possible antioxidant activity of the A. julibrissin crude extract and its major constituents.     

Flavonoids from the flower ofRhododendron yedoense var.Poukhanense and their antioxidant activities

Antioxidant flavonoids have been isolated from the flower of Rhododendron yedoense var. poukhanense. One new flavonoid and three known flavonoids, quercetin-5-O-beta-D-glucopyranoside (1), quercetin (3), and quercitrin (4), were isolated from the butanol and ethyl acetate extracts of the plant. The new flavonoid was identified as myricitrin-5-methyl ether (2). The isolation of these flavonoids from this plant, for the first time, is a valuable finding. The flavonoids were evaluated for their antioxidant activities using 1,1-diphenyl-2-picrylhydrazyl free radical (DPPH), TBARS (thiobarbituric acid reactive substance) and superoxide anion radical (O2-) in the xanthine/xanthine oxidase assay system. In the DPPH scavenging assay, the IC50 values were 4.5 +/- 0.48 microM for compound 2 and 9.7 +/- 0.29 microM for compound 3, which showed an antioxidant activity approximately 1.5-2 times higher than the antioxidant activity of alpha-tocopherol (9.8 +/- 0.94 microM). Additionally, the antioxidant activities of myricitrin-5-methyl ether (2) (IC50 = 1.7 +/- 0.22 microM) and quercetrin (4) (IC50 = 1.9 +/- 0.63 microM) were higher than that of L-ascorbic acid (IC50 = 7.4 +/- 0.63 microM) when evaluated using a TBARS assay. Compound 2 showed high activity in both the inhibition of xanthine oxidase (1.1 +/- 0.21 mM) and in the activation of superoxide scavenging.     

金丝梅石油醚超声提取物GC-MS分析及其体外抗氧化作用

目的采用GC-MS分析金丝梅(HypericumpatalumThumb.)石油醚超声提取物中的化学成分,并研究该提取物的抗氧化作用。方法以石油醚为溶剂,采用超声提取法提取金丝梅中的化学成分,并采用GC-MS分析石油醚超声提取物中的化学成分;采用DPPH和ABTS2种方法研究金丝梅石油醚超声提取物的抗氧化活性。结果从金丝梅石油醚超声提取物中共鉴定了24个化合物。其中,3-甲基庚烷含量最高,达26.329%,检测出的化合物类型为烷烃类(57.99%)、萜类(17.22%)、芳烃(7.78%)和其他类型(17.01%)化合物。该提取物对DPPH自由基和ABTS^·+自由基的清除作用在一定浓度范围内成对数关系,对DPPH自由基清除作用的IC50值>20mg·mL^-1,对ABTS^·+自由基的清除作用TEAC值为(3.71±0.1)μmol·L^-1。结论金丝梅石油醚超声提取物中脂溶性成分较多,具有一定的抗氧化活性。该研究结果为金丝梅化学成分的研究及进一步利用提供了科学依据。     

乌梅抗氧化作用的实验考察

目的:研究乌梅提取物抗氧化作用。方法:通过检测还原力和清除DPPH、ABTS和超氧阴离子自由基的能力,分析和评价乌梅提取物的抗氧化活性。结果:乌梅醇提物对DPPH、ABTS自由基的IC50分别为0.500 mg.mL-1及0.253 mg.mL-1;乌梅水提物对DPPH、ABTS自由基的IC50分别0.510 mg.mL-1及0.500 mg.mL-1;乌梅醇提物还原能力大于乌梅水提物,且乌梅醇提物对超氧阴离子自由基的清除作用显著,其清除作用优于乌梅水提物及对照品BHT。结论:乌梅提取物有不同程度的抗氧化活性,其中以醇提物抗氧化作用最强。     

Free-radical scavenging activity of <Emphasis Type="Italic">Bergia suffruticosa</Emphasis> (Delile) Fenzl

Bergia suffruticosa (Family Elatinaceae) is an important Indian medicinal plant, traditionally used to repair bones and applied on sores. The plant has not been studied much. Preliminary phytochemical screening of the plant showed the presence of high amount of phenolics, tannins and flavonoids. Subsequent quantification showed the presence of 8.8% w/w phenolics (calculated as gallic acid), and 7.5% w/w tannins. This high amount of tannins and phenolics prompted us to evaluate its antioxidant activity. We studied the antioxidant activity of B. suffruticosa whole plant in three in vitro models: DPPH radical scavenging activity, superoxide scavenging activity and measurement of reducing power. Methanolic extract of whole plant of B. suffruticosa showed a very good DPPH radical scavenging activity (EC₅₀ of 13.1 μg) and superoxide scavenging activity (EC₅₀ of 139.4 μg) in a dose-dependent manner. The extract showed dose-dependent reduction ability (Fe³⁺ to Fe²⁺ transformation) with a maximum absorbance of 1.195 at a concentration of 300 μg of the extract.     

Tungtungmadic acid, a novel antioxidant, fromSalicornia herbacea

Tungtungmadic acid (3-caffeoyl-4-dihydrocaffeoyl quinic acid) is a new chlorogenic acid derivative that was isolated from the Salicornia herbacea. The structure of tungtungmadic acid was determined using chemical and spectral analysis. The antioxidant activity of tungtungmadic acid was evaluated using various antioxidant assays, including free radical scavenging, lipid peroxidation and hydroxyl radical-induced DNA strand breaks assays. Tungtungmadic acid (IC50 = 5.1 microM and 9.3 microM) was found to have higher antioxidant activity in the DPPH scavenging assay as well as in the iron-induced liver microsomal lipid peroxidation system. In addition, the tungtungmadic acid was also effective in protecting the plasmid DNA against strand breakage induced by hydroxyl radicals.     

Cytotoxic and antioxidant activity of Achillea alexandri-regis

The cytotoxicity and antioxidant properties of herb extracts of Achillea alexandri-regis were studied. Combined chloroform and ethylacetate extracts exhibited a pronounced cytotoxic effect against HeLa cancer cells (IC50 = 25.92 +/- 4.96 microg/ml), and lower cytotoxicity against K562 leukemia cells (IC50 = 48.59 +/- 18.31 microg/ml). The methanol extract was found to be a moderately cytotoxic in vitro agent against HeLa and K562 cells. No suppressive activity was detected on non-malignant peripheral blood mononuclear cells (PBMC). The antioxidant activity of the methanol extract was assessed by DPPH radical scavenging. The methanol extract of A. alexandri-regis showed concentration dependent DPPH radical scavenging activity with IC50 = 36.14 +/- 0.05 microg/ml.     

Antioxidative components from the aerial Parts ofLactuca scariola L

The antioxidant activity of Lactuca scariola (Compositae) was investigated by measuring the radical scavenging effect on DPPH (1,1-diphenyl-2-picrylhydrazyl) radical. The methanolic extract of the aerial parts of Lactuca scariola showed strong radical scavenging activity. The EtOAc soluble fraction exhibited a stronger activity than the others, and was purified by silica gel and Sephadex LH-20 column chromatography. Quercetin-3-O-beta-D-glucopyranoside, luteolin-7-O-beta-D-glucopyranoside, luteolin, quercetin and kaempferol, together with 1beta,13-dihydrolactucin were isolated from the EtOAc soluble fraction as active ingredients.     

Hepatoprotective and free radical scavenging activities of prenylflavonoids,coumarin, and stilbene from Morus alba

Chemical investigation of the EtOH extract of Morus alba L. (Moraceae), as guided by free radical scavenging activity, furnished 5,7-dihydroxycoumarin 7-methyl ether (1), two prenylflavones, cudraflavone B (2) and cudraflavone C (3), and oxyresveratrol (4). Compounds 1 and 4 showed superoxide scavenging effects with the IC(50) values of 19.1 +/- 3.6 and 3.81 +/- 0.5 microM, respectively. Compound 4 exhibited a DPPH free radical scavenging effect (IC(50) = 23.4 +/- 1.5 microM). Compounds 2 and 4 showed hepatoprotective effects with EC(50) values of 10.3 +/- 0.42 and 32.3 +/- 2.62 micro, respectively, on tacrine-induced cytotoxicity in human liver-derived Hep G2 cells.     

Antioxidant effect ofSalvia miltiorrhiza

A strong antioxidant activity, which was measured by the radical scavenging effect on 1,1-diphenyl-2-picrylhydrazyl(DPPH) radical, was detected in the methanol extract ofSalvia miltiorrhiza Bunge (Labiatae). By activity-directed fractionation, compounds 1 and 2 were isolated as antioxidant principles ofS. miltiorrhiza. Compounds 1 and 2 were identified as dimethyl lithospermate and 3-(3,4-dihydroxyphenyl)lactamide, respectively, on the basis of spectral data. The radical scavenging effect of compounds 1 and 2 on DPPH radical exceeded that of L-ascorbic acid which is a well known antioxidant. These two compounds also showed prominent inhibitory activity against free radical generation in dichlorofluorescein (DCF) method and cytoprotective effect againstt-BHP in cultured liver cell.     

Antioxidant effects of quinoline alkaloids and 2,4-di-tert-butylphenol isolated from Scolopendra subspinipes

The oxidized low-density lipoprotein (ox-LDL) plays a critical role at the early stages of atherosclerosis. Thus, the prevention of LDL-oxidation by antioxidants may arrest the progression of atherosclerosis. Two quinoline alkaloids, 3,8-dihydroxyquinoline (1) and 2,8-dihydroxy-3,4-dimethoxyquinoline (3), and 2,4-di-tert-butylphenol (2) were isolated from the dried body of Scolopendra subspinipes. Compounds 1-3 exhibited antioxidant activities on copper-mediated (1: IC50=2.6 microM, 2: IC50=8.2 microM, 3: IC50=63.0 microM), AAPH-mediated oxidation (1: IC50=3.9 microM, 2: IC50=9.9 microM, 3: IC50=71.8 microM), and SIN-1-mediated oxidation (1: 70%, 2: 52%, 3: 29% at 5.0 microM) in the TBARS assay. The antioxidant activities of compounds 1-3 were tested with respect to other parameters, such as the lag time of conjugated diene fromation, relative electrophoretic mobility (REM) of ox-LDL, and apoB-100 fragmentation on copper-mediated LDL-oxidation. In addition, compounds 1-3 showed 1,1-diphenyl-2-picrylhydrasyl (DPPH) radical scavenging activity and compound 1 also exhibited metal chelating activity.     

A radical scavenging Farnesylhydroquinone from a marine-derived fungusPenicillium sp.

Farnesylhydroquinone (1) has been isolated from the mycelium of a marine-derived fungus of the genus Penicillium. The structure of the compound (1) has been elucidated by spectral method. The compound 1 exhibits potent radical scavenging activity (IC50 12.5 microM) against the DPPH.     

Anti-oxidant activities of<Emphasis Type="Italic">acanthopanax senticosus</Emphasis> stems and their lignan components

The antioxidant activities of Acanthopanax senticosus stems were evaluated in CCl4-intoxicated rats. The n-butanol fraction from the water extract of the stems, when pretreated orally at 200 mg/kg/day for 7 consecutive days in rats, was demonstrated to exhibit significant increases in antioxidant enzyme activities such as hepatic cytosolic superoxide dismutase, catalase and glutathione peroxidase by 30.31, 19.82 and 155%, respectively. The n-butanol fraction whereas showed a significant inhibition of serum GPT activity (65.79% inhibition) elevated with hepatic damage induced by CCl4-intoxication. Eleutheroside B, a lignan component, isolated from the n-butanol fraction was found to cause a moderate free radical scavenging effect on DPPH, its scavenging potency as indicated in IC50 value, being 58.5 microM. These results suggested that the stems of A. senticosus possess not only antioxidant but also hepatoprotective activities.     

野牡丹提取液的抗氧化活性研究

目的 研究野牡丹提取液的抗氧化活性。方法 采用二苯代苦味肼基自由基（DPPH•）和铁离子还原/抗氧化能力（FRAP）测定法,测定其抗氧化活性,并将其与芦丁和维生素C（Vc）的抗氧化能力进行比较研究。结果 野牡丹提取液具有较强的抗氧化能力,对DPPH自由基有较好的清除率,半数清除浓度（IC₅₀）为23 μg/mL;对Fe³⁺也具有较好的还原能力,0.5 mol/L FeSO₄当量对应野牡丹提取液质量浓度为55 μg/mL。结论 野牡丹的抗氧化能力与芦丁相近,低于Vc。野牡丹的抗氧化活性在一定浓度范围内与黄酮的含量有较好的相关性。     

茉莉花挥发油清除自由基活性的研究

目的：从清除1,1－二苯基－2－苦苯肼自由基（DPPH?）、羟自由基（? OH）、超氧阴离子自由基（O2?－）3个方面,研究茉莉花挥发油清除自由基活性。方法采用水蒸气蒸馏法提取茉莉花挥发油,从其清除DPPH?、? OH和O2?－能力3个方面进行考察,并以常用抗氧化剂L－抗坏血酸为对照作比较,通过计算半数抑制浓度（ IC50）评价茉莉花挥发油清除,在供试质量浓度范围内,呈一定量效关系,其 IC50分别为153．548μg?mL －1、56．481μg? mL －1和133．586μg? mL －1。结论茉莉花挥发油具有良好的清除自由基活性,是一种新型天然抗氧化物质来源。