Studies on the antioxidative activities of Hsian-tsao (Mesona procumbens Hemsl) leaf gum

This study aimed at evaluating the antioxidative activity of crude hsian-tsao leaf gum extracted by sodium bicarbonate solutions and precipitated by 70% ethanol. The antioxidative activities, including the radical-scavenging effects, Fe(2+)-chelating ability, and reducing power as well as the inhibition of FeSO(4)-H(2)O(2)-induced malondialdehyde formation in rat tissue homogenate were studied in vitro. It was found that the antioxidative effect provided by hsian-tsao leaf gum was strongly concentration dependent. In general, the antioxidative activity increased with increasing gum concentration, to a certain extent, and then leveled off with further increase in gum concentration. A concentrtaion-dependent kinetics for the rate of change in antioxidative activity was proposed. The antioxidative activity constant (k) and the half-inhibition concentration (IC(50)) for each antioxidative reaction studied were calculated. From a comparison of the IC(50) values for different antioxidative reactions, it seemed that hsian-tsao leaf gum was more effective in scavenging superoxide radicals than chelating Fe(2+) or scavenging alpha,alpha-diphenyl-beta-picrylhydrazyl (DPPH) radicals. As compared to the commercial antioxidants, hsian-tsao leaf gum showed less scavenging effect on the DPPH radical and reducing power but better superoxide radical-scavenging effect and Fe(2+)-chelating ability than alpha-tocopherol and BHT.     

Active recombinant thioredoxin h protein with antioxidant activities from sweet potato (Ipomoea batatas [L.] Lam Tainong 57) storage roots

Recombinant thioredoxin h (Trx2) overproduced in Escherichia coli (M15) was purified by Ni2+-chelated affinity chromatography. The molecular mass of Trx2 is approximately 1.4 kDa as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Total antioxidant status, 1,1-diphenyl-2-picrylhydrazyl (DPPH) staining, reducing power method, Fe2+-chelating ability, ferric thiocyanate (FTC) method, and protection of calf thymus DNA against hydroxyl radical-induced damage were studied. The thioredoxin h protein with a concentration of 12.5 mg/mL exhibited the highest activity (expressed as 0.37 +/- 0.012 mM ABTS* radical cation being cleared) in a total antioxidant status test. In the DPPH staining thioredoxin h appeared as white spots when it was diluted to 50 mg/mL (a final amount of 15 microg). Like the total antioxidant status, the reducing power, Fe2+-chelating ability, FTC activity, and protection against hydroxyl radical-induced calf thymus DNA damage were found with the thioredoxin h protein. It was suggested that thioredoxin h might contribute to its antioxidant activities against hydroxyl and peroxyl radicals.     

Antioxidative ability of lactic acid bacteria

Nineteen strains of lactic acid bacteria were investigated for antioxidative activity. These includedLactobacillus acidophilus B, E, N1, 4356, LA-1, and Farr; Lactobacillus bulgaricus 12 278, 448, 449, Lb, 1006, and 11 842; Streptococcus thermophilus 821, MC, 573, 3641, and 19 987; and Bifidobacterium longum B6 and 15 708. Intracellular cell-free extract of all strains demonstrated antioxidative activity with inhibition rates of ascorbate autoxidation in the range of 7-12%. Antioxidative mechanisms including metal ion chelating ability, scavenge of reactive oxygen species, enzyme inhibition, and reducing activity of intracellular cell-free extract of lactic acid bacteria were studied. S. thermophilus 821 had the highest metal ion chelating ability for Fe(2+), and B. longum 15 708 showed the highest Cu(2+) chelating ability among the 19 strains tested. All strains demonstrated reactive oxygen species scavenging ability. L. acidophilus E showed the highest hydroxyl radical scavenging ability, and B. longum B6 had the best hydrogen peroxide scavenging ability. Reducing activity was also found in all strains. Most of the strains tested demonstrated excellent reducing activity. B. longum B6 showed the highest reducing activity among the 19 strains tested. In enzyme inhibition, superoxide dismutase activity was not found in these 19 strains, and the activity of superoxide dismutase was not induced when metal ion Mn(2+), Fe(2+), or Cu(2+)Zn(2+) was present.     

Determination of antioxidant and antimicrobial activities of Rumex crispus L. extracts

The antioxidant activities, reducing powers, 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activities, amount of total phenolic compounds, and antimicrobial activities of ether, ethanol, and hot water extracts of the leaves and seeds of Rumex crispus L. were studied. The antioxidant activities of extracts increase with increasing amount of extracts (50-150 microg). However, the water extracts of both the leaves and seeds have shown the highest antioxidant activities. Thus, addition of 75 microg of each of the above extracts to the linoleic acid emulsion caused the inhibition of peroxide formation by 96 and 94%, respectively. Although the antioxidant activity of the ethanol extract of seed was lower than the water extract, the difference between these was not statistically significant, P > 0.05. Unlike the other extracts, 75 microg of the ether extract of seeds was unable to show statistically significant antioxidant activity, P > 0.05 (between this extract and control in that there is no extract in the test sample). Among all of the extracts, the highest amount of total phenolic compound was found in the ethanol extract of seeds, whereas the lowest amount was found in the ether extract of seeds. Like phenolic compounds, the highest reducing power and the highest DPPH scavenging activity were found in the ethanol extract of seeds. However, the reducing activity of the ethanol extract of seeds was approximately 40% that of ascorbic acid, whereas in the presence of 400 microg of water and ethanol extracts of seeds scavenging activities were about 85 and 90%, respectively. There were statistically significant correlations between amount of phenolic compounds and reducing power and between amount of phenolic compounds and percent DPPH scavenging activities (r = 0.99, P < 0.01, and r = 0.864, P < 0.05, respectively) and also between reducing powers and percent DPPH scavenging activities (r = 0.892, P < 0.05). The ether extracts of both the leaves and seeds and ethanol extract of leaves had shown antimicrobial activities on Staphylococcus aureus and Bacillus subtilis. However, none of the water extracts showed antimicrobial activity on the studied microorganisms.     

广东石豆兰不同溶剂提取物抗氧化及与总黄酮、总酚含量的关系

为明确广东石豆兰的抗氧化能力及抗氧化成分,以鳞茎为材料,以甲醇、乙醇、丙酮和乙酸乙酯为提取剂得到4种提取物,测定了4种提取物中总黄酮、总酚含量及其抗氧化活性,并分析了两者之间的关系。结果表明,石豆兰总酚含量高于总黄酮,乙醇为总酚和总黄酮2种物质的最佳提取溶剂;甲醇提取物对羟基自由基清除力和对Fe²⁺的螯合力最强,对DPPH自由基清除效果最差;丙酮提取物具有最强的总还原力和清除超氧阴离子的能力,而清除羟基自由基能力最弱;乙酸乙酯提取物清除DPPH自由基的能力最强,但总还原力、清除超氧阴离子的能力、Fe²⁺的螯合力最弱。此外,除了DPPH自由基外,其他4个抗氧化指标与总黄酮或总酚含量呈正相关(0.185<r<0.969),总还原力与总黄酮含量呈显著相关。本研究结果为广东石豆兰抗氧化物质的提取及进一步开发利用提供了参考依据。     

Antioxidative activity of protein hydrolysates prepared from alkaline-aided channel catfish protein isolates

Antioxidative activity of hydrolyzed protein prepared from alkali-solubilized catfish protein isolates was studied. The isolates were hydrolyzed to 5, 15, and 30% degree of hydrolysis using the protease enzyme, Protamex. Hydrolyzed protein was separated into hydrolysates and soluble supernatants, and both of these fractions were studied for their metal chelating ability, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging ability, ferric reducing antioxidant power (FRAP), oxygen radical absorbance capacity (ORAC), and their ability to inhibit the formation of thiobarbituric acid reactive substances (TBARS) in washed tilapia muscle containing tilapia hemolysate. Both hydrolysates and supernatants were characterized using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Results showed that DPPH radical scavenging ability and reducing power of catfish protein hydrolysates decreased, whereas the ORAC value, metal chelating ability, and ability to inhibit TBARS increased, with an increase in the degree of hydrolysis. Hydrolysate samples showed higher DPPH radical scavenging ability and Fe(3+) reducing ability, and supernatant samples had higher metal chelating ability. In general, low molecular weight (MW) peptides had high ORAC values and high metal chelating ability, and high MW peptides had a higher reducing power (FRAP) and were more effective in scavenging DPPH radicals. In a washed muscle model system, the ability of catfish protein hydrolysates and their corresponding supernatants to inhibit the formation of TBARS increased with an increase in the degree of hydrolysis.     

Isolation and characterization of antioxidant protein fractions from melinjo (Gnetum gnemon) seeds

The protein from the seeds of melinjo ( Gnetum gnemon ) was purified using a precipitation method and ion exchange chromatographic techniques to identify the potent antioxidant and free radical scavenging activities. Two antioxidant protein fractions were isolated from G. gnemon seed with molecular weights of approximately 30 kDa (Gg-AOPI) and 12 kDa (Gg-AOPII) by SDS-PAGE. The N-terminal amino acid sequence of Gg-AOPII is Gly-Asn-Gly-Lys-Ala-Thr-Val-Ala-Ile-Leu-Val-Lys-Glu-Lys-Val-Glu-Tyr-Gly-Glu-Glu, and the result of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) analysis showed that they were distinct from each other; no protein in database matching was found to both Gg-AOPI and Gg-AOPII. The antioxidant or free radical scavenging activities of Gg-AOPs were investigated by employing in vitro assay systems including the inhibition of linoleic acid autoxidation, scavenging effect on α,α-diphenyl-β-picrylhydrazyl free radical (DPPH), 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), reducing power, chelating abilities of metal ions Cu(2+) and Fe(2+), and protections against hydroxyl radical-mediated DNA damages. The result showed that two protein fractions exhibited significant (p < 0.05) antioxidant activities against free radicals such as DPPH, ABTS, and superoxide anion and showed activities similar to those of glutathione (G-SH) and BHT in a linoleic acid emulsion assay system. Moreover, Gg-AOPI and Gg-AOPII also exhibited notable reducing power and strong chelating effect on Fe(2+) and protected hydroxyl radical induced oxidative DNA damage. The data obtained by the in vitro systems obviously established the antioxidant potency of Gg-AOPs.     

Antimutagenic and antioxidant properties of milk-kefir and soymilk-kefir

This study was aimed at evaluating the antimutagenic and antioxidant properties of milk-kefir and soymilk-kefir. Such antimutagenic activity was determined by means of the Salmonella mutagenicity assay, whereas the antioxidant properties of kefir were evaluated by assessing the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity, lipid peroxidation inhibition activity, ferrous ion chelating ability, reducing power, and antioxidative enzyme activity. Both milk-kefir and soymilk-kefir demonstrated significantly greater antimutagenic activity than milk and soymilk. Milk-kefir and soymilk-kefir also displayed significantly greater scavenging activity upon DPPH radicals, an inhibition effect upon linoleic acid peroxidation, and more substantial reducing power but displayed a reduced glutathione peroxidase activity than was the case for milk and soymilk. Milk and soymilk fermented by kefir grains did not alter the ferrous ion chelating ability and superoxide dismutase activity of the original materials. These findings have demonstrated that milk-kefir and soymilk-kefir possess significant antimutagenic and antioxidant activity and suggest that milk-kefir and soymilk-kefir may be considered among the more promising food components in terms of preventing mutagenic and oxidative damage.     

Antioxidative activities of oolong tea

While the antioxidative properties of green and black tea have been extensively studied, less attention has been given to these properties in oolong tea. The reducing powers, the 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activities, the amount of total phenolic compounds, the inhibitory effect on FeCl(2)/H(2)O(2) (Fenton reaction system)-induced DNA damage, and the inhibitory effect on erythrocyte hemolysis of an oolong tea water extract (OTE) were evaluated in the present study. The OTE was found to have strong antioxidative activities in all of the model systems tested. When the OTE was separated into different fractions according to molecular weight, it was found that the fractions with higher amounts of phenolic compounds (lower molecular weight) have stronger antioxidative activities. The present results support the concept that oolong tea contains several low molecular weight antioxidants that may have health promotion activities.     

Effects of extraction solvent mixtures on antioxidant activity evaluation and their extraction capacity and selectivity for free phenolic compounds in barley (Hordeum vulgare L.)

Four kinds of solvent extracts from three Chinese barley varieties (Ken-3, KA4B, and Gan-3) were used to examine the effects of extraction solvent mixtures on antioxidant activity evaluation and their extraction capacity and selectivity for free phenolic compounds in barley through free radical scavenging activity, reducing power and metal chelating activity, and individual and total phenolic contents. Results showed that extraction solvent mixtures had significant impacts on antioxidant activity estimation, as well as different extraction capacity and selectivity for free phenolic compounds in barley. The highest DPPH* and ABTS*+ scavenging activities and reducing power were found in 80% acetone extracts, whereas the strongest *OH scavenging activity, O2*- scavenging activity, and metal chelating activity were found in 80% ethanol, 80% methanol, and water extracts, respectively. Additionally, 80% acetone showed the highest extraction capacity for (+)-catechin and ferulic, caffeic, vanillic, and p-coumaric acids, 80% methanol for (-)-epicatechin and syringic acid, and water for protocatechuic and gallic acids. Furthermore, correlations analysis revealed that TPC, reducing power, DPPH* and ABTS*+ scavenging activities were well positively correlated with each other (p < 0.01). Thus, for routine screening of barley varieties with higher antioxidant activity, 80% acetone was recommended to extract free phenolic compounds from barley. DPPH* scavenging activity and ABTS*+ scavenging activity or reducing power could be used to assess barley antioxidant activity.     

菜籽蛋白加工废液中多酚和多糖同步提取工艺优化

为开发利用菜籽蛋白加工废液中的生理活性物质,该研究在单因素试验基础上,采用Box-Behnken响应面试验设计法,对菜籽蛋白加工废液中多酚和多糖提取工艺条件进行优化,同时探究两种物质的体外抗氧化活性。结果表明,影响菜籽蛋白加工废液中多酚和多糖得率的因素大小顺序为:乙醇体积分数浸提温度浸提时间,最佳提取工艺为:浸提温度60℃、乙醇体积分数65%、浸提时间31 min,在此条件下多酚得率为2.19%,多糖得率为8.14%;多酚提取物对DPPH·具有较强清除能力,其半抑制质量浓度为0.20 mg/mL,多糖提取物对DPPH·和·OH均具有较强的清除能力,其半抑制质量浓度分别为1.45、2.38 mg/mL;高效液相色谱法初步检测表明,菜籽蛋白加工废液中含有香豆酸、丁香酸、对香豆酸、芥子酸和苯甲酸。研究结果为菜籽蛋白加工废液的再利用提供参考。     

Solid‐State Bioprocessing with Cordyceps militaris Enhanced Antioxidant Activity and DNA Damage Protection of Red Beans (Phaseolus angularis)

In this study, red beans were bioprocessed by using a novel solid‐state fermentation (SSF) with an edible and medical filamentous fungus Cordyceps militaris . The effect of SSF on the total phenolic content (TPC), antioxidant activity, and DNA damage protection of red beans was determined. Furthermore, solvents with different polarities (80% methanol, 80% ethanol, 80% acetone, and deionized water) were used to extract antioxidant compounds from the red bean samples. The results indicated that SSF significantly enhanced TPC, 2,2‐azinobis(3‐ethylbenzothiazoline‐6‐sulfonic acid) diammonium salt radical cation scavenging activity, reducing power, and chelating ability of red beans. Furthermore, this study also demonstrated that fermented red beans exhibited greater protection against oxidative DNA damage than nonfermented red beans. Besides, the water extract of fermented red beans showed the highest TPC, antioxidant activity, and DNA damage protection among the various extracts examined. For the specific phenolics profile, HPLC analysis was performed, which showed that gallic acid, chlorogenic acid, p‐hydroxybenzoic acid, syringic acid, ferulic acid, daidzein, quercetin, and genistein of red beans were increased during SSF. There was a positive correlation among phenolic compounds, antioxidant activity, and DNA damage protection. Thus, this study demonstrated that SSF with C. militaris is an effective method for the enhancement of phenolic compounds, antioxidant activity, and DNA damage protection of red beans.     

Gastroprotective effect of red pigments in black chokeberry fruit (Aronia melanocarpa Elliot) on acute gastric hemorrhagic lesions in rats

It has been reported that the fruits and leaves of berries such as the blackberry, raspberry, and strawberry contain a high level of scavenging activity for chemically generated active oxygen species. This study investigated the antioxidative activities of black chokeberry fruit (Aronia melanocarpa Elliot) both in vitro and in vivo using the DPPH stable radical and rats with ethanol-induced gastric injury, respectively. The red pigment fraction of the black chokeberry contained three main components, one of which was identified as cyanidin 3-O-beta-glucoside by HPLC analysis and (1)H NMR. The black chokeberry red pigment fraction scavenged >44% of DPPH radicals at a concentration of 25 microg/mL compared to the control solution. The black chokeberry extract and its hydrolysate administrated at 2 g/kg of body weight each had nearly the same protective effect as quercetin administrated at 100 mg/kg of body weight in suppressing the area of gastric mucosal damage caused by the subsequent application of ethanol to <30% compared to the control group. The black chokeberry red pigment fraction had a similarly significant protective effect on gastric mucosa in a dose-dependent manner when administered at 30-300 mg/kg of body weight, and the administration of 30 mg/kg of body weight could suppress ethanol-induced gastric mucosal damage by approximately 50% (ID(50) = 30 mg/kg of body weight).     

枯草芽孢杆菌Y-6产抗菌肽的体外抗氧化效果研究

为研究枯草芽孢杆菌Y-6产抗菌肽的抗氧化活性,通过化学发光法测定抗菌肽清除H2O2、·OH和O2·3种氧自由基的性能,再通过分光光度法测定抗菌肽的还原能力、对DPPH·的清除率以及对肝匀浆丙二醛(MDA)生成的抑制率.结果表明,抗菌肽有一定清除自由基、抑制脂质过氧化的作用,试验范围内抗菌肽浓度越高,抗氧化效果越好.抗菌...     

Antioxidant activity of glyceollins derived from soybean elicited with Aspergillus sojae

The extract of soybean exposed to biotic elicitors such as food-grade fungus is known to have antioxidant activity. Glyceollins were major bioactive compounds present in soybean elicited by fungi and shown to have antifungal and anticancer activities. The purpose of present study was to evaluate the antioxidant activities of glyceollins by measuring ferric reducing antioxidant power (FRAP), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, singlet oxygen quenching, 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging, hydroxyl radical scavenging activity, and lipid peroxidation inhibition. In addition, the antioxidant potential of glyceollins were measured by a fluorescent probe, 2',7'-dichlorofluorescin diacetate (DCFDA), and dihydroethidium (DHE) in mouse hepatoma hepa1c1c7 cells in which they were insulted with H2O2 to generate reactive oxygen species (ROS). Glyceollins showed a strong reducing power and inhibited lipid peroxidation, with significant scavenging activities of radicals including singlet oxygen, superoxide anion, ABTS, and DPPH. We also found that glyceollins significantly suppressed H2O2-induced ROS production in hepa1c1c7 cells. Therefore, glyceollins deserve further study as natural antioxidants and nutraceuticals.     

Evaluation of antioxidant and prooxidant activities of bamboo Phyllostachys nigra var. Henonis leaf extract in vitro

Solvent-extracted bamboo leaf extract (BLE) containing chlorogenic acid, caffeic acid, and luteolin 7-glucoside was evaluated in vitro for free radical scavenging and antioxidant activities using a battery of test methods. BLE exhibited a concentration-dependent scavenging activity of DPPH radical. BLE prolonged the lag phase and suppressed the rate of propagation of liposome peroxidation initiated by peroxyl radical induced by 2,2'-azobis(2-amidinopropane dihydrochloride (AAPH) at 37 degrees C. BLE also prevented human low-density lipoprotein oxidation, mediated by Cu(2+), which was monitored by the lower formation of conjugated diene and fluorescence and a reduced negative charge of apo-B protein. Finally, BLE protected supercoiled DNA strand against scission induced by AAPH-mediated peroxyl radical. Prooxidant activity of BLE was seen in a Cu(2+)-induced peroxidation of structured phosphatidylcholine liposome, indicating catalytic peroxidation due to a relatively high reducing power of BLE. It was concluded that the BLE has both antioxidant activity and prooxidant activity; the antioxidant activity was attributed to free radical scavenging activity, and the prooxidant activity, albeit minor, resulted from the reducing power of plant phenolics in the presence of transitional metal ions.     

Reducing, radical scavenging, and chelation properties of in vitro digests of alcalase-treated zein hydrolysate

The objective of the study was to assess the antioxidant potential of alcalase-treated zein hydrolysate (ZH) during a two-stage (1 h of pepsin --> 0.5-2 h of pancreatin, 37 degrees C) in vitro digestion. Sephadex gel filtration and high-performance size exclusion chromatography were used to separate ZH into fractions. The amino acid composition, 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS(+*)) and 1,1-diphenyl-2-picrylhydrazyl (DPPH*) free radical scavenging activity, reducing power, and Cu (2+) chelation ability were tested to determine the antioxidant efficacy of ZH. Results showed that in vitro digests of ZH contained up to 16.5% free amino acids, with short peptides (<500 Da) making up the rest of the mass. The ABTS(+*) scavenging activity of ZH was decreased by 27% (P<0.05) after pepsin treatment but was fully recovered upon subsequent pancreatin digestion, while the DPPH* scavenging activity of ZH was substantially less than ABTS(+*) scavenging activity and showed a 7-fold reduction following pancreatin treatment. The reducing power of ZH increased 2-fold (P<0.05) following pancreatin digestion when compared with nondigested ZH. The ability of ZH to sequester Cu (2+) was reduced by pepsin digestion but was reestablished following pancreatin treatment. The antioxidant activity demonstrated by in vitro digests of ZH (1-8 mg/mL) was comparable to or exceeded (P<0.05) that of 0.1 mg/mL of ascorbic acid or BHA. The results suggested that dietary zein alcalase hydrolysate may have the benefit to promote the health of the human digestive tract.     

Effect of foliar application of selenium on the antioxidant activity of aqueous and ethanolic extracts of selenium-enriched rice

Selenium fertilizer was foliar applied to determine the effects of antioxidant activity of selenium-enriched rice assessed by alpha,alpha-diphenyl-beta-picylhydrazyl (DPPH) radical scavenging and the ferric thiocyanate (FTC) method. Results showed that selenium concentration in rice was significantly enhanced dose dependently. Aqueous or ethanolic extracts of rice displayed significantly higher antioxidant activity against lipid peroxidation. The activities of aqueous extracts were significantly higher than those of ethanolic extracts and increased with the increasing selenium concentration in rice. The DPPH assay showed that the kinetic behaviors of aqueous extracts were complex and slow, while ethanolic extracts reacted quickly with DPPH radical. Aqueous extracts of rice exhibited higher antiradical efficiencies than ethanolic extracts, and rice (1.275 mg Se kg(-)(1)) presented the lowest EC(50) values of 533.46 +/- 0.58 microg mL(-)(1). As compared to rice extracts, all of the reference antioxidants showed more than 4-fold antiradical efficiencies than rice extracts. This radical scavenging activity was significantly correlated with selenium concentrations in rice (R = 0.862, p < 0.05), while ethanolic extracts were inversely correlated with selenium concentration in rice.     

Antioxidative activity and active components of longan (Dimocarpus longan Lour.) flower extracts

Three different solvent extracts (methanol, ethyl acetate, and n-hexane) of longan ( Dimocarpus longan Lour.) flowers were assayed with three different antioxidant capacity methods, namely, the DPPH free radical scavenging effect, the oxygen radical absorbance capacity (ORAC) assay, and the inhibition of Cu(2+)-induced oxidation of human low-density lipoprotein (LDL). It was revealed that the methanol extract has the best antioxidative activity, followed by ethyl acetate and n-hexane extracts. The methanol extract was separated by liquid-liquid partition into n-hexane, ethyl acetate, n-butanol, and water fractions. The ethyl acetate fraction was found to have the highest activity of delaying LDL oxidation. After silica gel column chromatography, the fraction having a superior activity was identified as containing two major compounds, (-)-epicatechin and proanthocyanidin A2.     

Suppressive effect of a proanthocyanidin-rich extract from longan (Dimocarpus longan Lour.) flowers on nitric oxide production in LPS-stimulated macrophage cells

Anthocyanidins found in certain flowers have been shown to act as strong antioxidants in various systems, exhibiting multiple biological actions. The antioxidative effects of water extract and ethanolic extract of longan (Dimocarpus longan Lour.) flowers were evaluated by radical scavenging activity and compared to those of gallic acid, myricetin, and epigallocatechin gallate. In this study, the suppressive effects of longan flower extracts on nitric oxide and prostaglandin E2 production were investigated using a lipopolysaccharide-stimulated RAW 264.7 cell model. Abundant levels of phenolic compounds including flavonoids, condensed tannins, and proanthocyanidins were found in water or ethanolic extracts prepared from dried longan flowers. The antioxidative effect of longan flower extract was similar to the effect exhibited by pure antioxidants. Moreover, longan flower extract showed prominent inhibitory effects on prostaglandin E2 production. Significant concentration-dependent inhibition of nitric oxide production was detected when cells were cotreated with lipopolysaccharide and various concentrations of longan flower extracts. These inhibitory effects were further attributed to suppression of inducible nitric oxide synthase protein expression and not to reduced enzymatic activity. These results suggest that longan flower crude extracts, especially ethanolic extract, have antioxidant and anti-inflammatory effects, and the probable mechanism involves inhibition of inflammation by proanthocyanidins. Preliminary observations suggest that longan flower extract, especially alcoholic extract, could be another potential source of natural dietary antioxidant and anti-inflammatory agent.