C-phycocyanin, a very potent and novel platelet aggregation inhibitor from Spirulina platensis

The aim of this study was to systematically examine the inhibitory mechanisms of C-phycocyanin (C-PC), one of the major phycobiliproteins of Spirulina platensis (a blue-green alga), in platelet activation. In this study, C-PC concentration-dependently (0.5-10 nM) inhibited platelet aggregation stimulated by agonists. C-PC (4 and 8 nM) inhibited intracellular Ca2+ mobilization and thromboxane A2 formation but not phosphoinositide breakdown stimulated by collagen (1 microg/mL) in human platelets. In addition, C-PC (4 and 8 nM) markedly increased levels of cyclic GMP and cyclic GMP-induced vasodilator-stimulated phosphoprotein (VASP) Ser(157) phosphorylation. Rapid phosphorylation of a platelet protein of Mw 47,000 (P47), a marker of protein kinase C activation, was triggered by phorbol-12,13-dibutyrate (150 nM). This phosphorylation was markedly inhibited by C-PC (4 and 8 nM). In addition, C-PC (4 and 8 nM) markedly reduced the electron spin resonance (ESR) signal intensity of hydroxyl radicals in collagen (1 microg/mL)-activated platelets. The present study reports on a novel and very potent (in nanomolar concentrations) antiplatelet agent, C-PC, which is involved in the following inhibitory pathways: (1) C-phycocyanin increases cyclic GMP/VASP Ser157 phosphorylation and subsequently inhibits protein kinase C activity, resulting in inhibition of both P47 phosphorylation and intracellular Ca2+ mobilization, and (2) C-PC may inhibit free radicals (such as hydroxyl radicals) released from activated platelets, which ultimately inhibits platelet aggregation. These results strongly indicate that C-PC appears to represent a novel and potential antiplatelet agent for treatment of arterial thromboembolism.     

Inhibitory effect of α-lipoic acid on platelet aggregation is mediated by PPARs

Peroxisome proliferator-activated receptors (PPARs) isoforms (α, β/δ, and γ are present in human platelets, and activation of PPARs inhibits platelet aggregation. α-Lipoic acid (ALA), occurring naturally in human food, has been reported to exhibit an antiplatelet activity. However, the mechanisms underlying ALA-mediated inhibition of platelet aggregation remain unknown. The aim of this study was to investigate whether the antiplatelet activity of ALA is mediated by PPARs. ALA itself significantly induced PPARα/γ activation in platelets and increased intracellular amounts of PPARα/γ by blocking PPARα/γ secretion from arachidonic acid (AA)-activated platelets. Moreover, ALA significantly inhibited AA-induced platelet aggregation, Ca(2+) mobilization, and cyclooxygenase-1 (COX-1) activity, but increased cyclic AMP production in rabbit washed platelets. Importantly, ALA also enhanced interaction of PPARα/γ with protein kinase Cα (PKCα) and COX-1 accompanied by an inhibition of PKCα activity in resting and AA-activated platelets. However, the above effects of ALA on platelets were markedly reversed by simultaneous addition of selective PPARα antagonist (GW6471) or PPARγ antagonist (GW9662). Taken together, the present study provides a novel mechanism by which ALA inhibition of platelet aggregation is mediated by PPARα/γ-dependent processes, which involve interaction with PKCα and COX-1, increase of cyclic AMP formation, and inhibition of intracellular Ca(2+) mobilization.     

Synthesis and biological evaluation of novel C(6) modified baicalein derivatives as antioxidative agents

Baicalein, one of the major flavones, was found to be responsible for the antioxidative activity of the traditional Chinese medicinal herb Huang-Qin ( Scutellaria baicalensis Georgi), which is widely used as an antioxidative, anti-inflammatory, and antitumor agent. The hydroxyl group of the A ring of the baicalein was alkylated at position 6 with terpenoids such as prenyl, geranyl, and farnesyl groups, and their free radical scavenging activities and glutathione (GSH) depletion capacities were examined. Their free radical scavenging activity was measured according to the 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS(*+)) scavenging method. Baicalein and newly synthesized baicalein derivatives were found to be good free radical scavengers. Flow cytometrical method was employed to measure the intracellular antioxidative activity and GSH depletion capacity of these derivatives in human acute monocytic leukemia cell line (THP-1). It was also found that baicalein and its derivatives could decrease the levels of exogenous cumene hydroperoxide and H2O2 in THP-1 cells. These compounds also could significantly inhibit the intracellular GSH depletion induced by cumene hydroperoxide in THP-1 cells. The production of cumene hydroperoxide-induced Bax, a pro-apoptotic related protein, could also be inhibited by baicalein and its derivatives. These results suggested that baicalein and its derivatives could be beneficial to human health.     

Evaluation of free radical scavenging activities of antioxidants with an H(2)O(2)/NaOH/DMSO system by electron spin resonance.

An H(2)O(2)/NaOH/DMSO system has been developed for the formation of three free radicals, and the application of the system was examined with the antioxidants ascorbic acid and tocopherol. Superoxide anion, hydroxyl radical,and methyl radical are simultaneously generated in this system. The scavenging activity of ascorbic acid and tocopherol for these radicals was estimated by 5, 5'-dimethyl-1-pyrroline-N-oxide spin trapping electron spin resonance. Both water-soluble and oil-soluble antioxidants could be evaluated by using this system. Ascorbic acid specifically inhibited the superoxide anion and hydroxyl radical, whereas tocopherol suppressed the methyl radical.     

alpha-Naphthoflavone, a potent antiplatelet flavonoid, is mediated through inhibition of phospholipase C activity and stimulation of cyclic GMP formation

The aim of this study was to systematically examine the inhibitory mechanisms of the flavonoid alpha-naphthoflavone (alpha-NF) in platelet activation. In this study, alpha-NF concentration dependently (5-20 microM) inhibited platelet aggregation stimulated by agonists. alpha-NF (5 and 10 microM) inhibited intracellular Ca(2+) mobilization, phosphoinositide breakdown, and thromboxane A(2) formation stimulated by collagen (1 microg/mL) in human platelets. In addition, alpha-NF (5 and 10 microM) markedly increased levels of cyclic GMP and cyclic GMP-induced vasodilator-stimulated phosphoprotein (VASP) Ser(157) phosphorylation. Rapid phosphorylation of a platelet protein of Mr 47,000 (P47), a marker of protein kinase C activation, was triggered by phorbol-12,13-dibutyrate (60 nM). This phosphorylation was markedly inhibited by alpha-NF (5 and 10 microM). However, alpha-NF (5 and 10 microM) did not reduce the electron spin resonance (ESR) signal intensity of hydroxyl radicals in collagen (1 microg/mL)-activated platelets. These results indicate that the antiplatelet activity of alpha-NF may be involved in the following pathways. (1) alpha-NF may inhibit the activation of phospholipase C, followed by inhibition of phosphoinositide breakdown, protein kinase C activation, and thromboxane A(2) formation, thereby leading to inhibition of intracellular Ca(2+) mobilization. (2) alpha-NF also activated the formation of cyclic GMP, resulting in inhibition of platelet aggregation. These results strongly indicate that alpha-NF appears to represent a novel and potent antiplatelet agent for treatment of arterial thromboembolism.     

Antioxidative and antiplatelet effects of aqueous inflorescence Piper betle extract

Piper betle, belonging to the Piperaceae family, is a tropical plant, and its leaf and inflorescence are popularly consumed by betel quid (BQ) chewers in Taiwan and many other South and Southeast Asian countries. However, little is known about the biochemical properties of inflorescence Piper betle (IPB) toward reactive oxygen species (ROS) and platelet functions. In the present work, aqueous IPB extract was shown to be a scavenger of H(2)O(2), superoxide radical, and hydroxyl radical with a 50% inhibitory concentration (IC(50)) of about 80, 28, and 73 microg/mL, respectively. IPB extract also prevented the hydroxyl radical induced PUC18 plasmid DNA breaks at concentrations higher than 40 microg/mL. Since ROS are crucial for platelet aggregation, we further found that IPB extract also inhibited the arachidonic acid (AA) induced and collagen-induced platelet aggregation, with an IC(50) of 207 and 335 microg/mL, respectively. IPB extract also inhibited the AA-, collagen- (>100 microg/mL of IPB), and thrombin (>250 microg/mL of IPB)-induced thromboxane B(2) (TXB(2)) production by more than 90%. However, IPB extract showed little effect on thrombin-induced aggregation. These results indicated that aqueous components of IPB are potential ROS scavengers and may prevent the platelet aggregation possibly via scavenging ROS or inhibition of TXB(2) production.     

Antioxidant and antimelanogenic activities of polyamine conjugates from corn bran and related hydroxycinnamic acids

The antioxidant activity of three major polyamine conjugates, N,N'-dicoumaroyl-putrescine (DCP), N-p-coumaroyl-N'-feruloylputrescine (CFP), and N,N'-diferuloyl-putrescine (DFP) isolated from corn bran, and their related hydroxycinnamic acids, p-coumaric acid and ferulic acid, were evaluated by three antioxidant in vitro assay systems, including 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and superoxide and hydroxyl radicals generated by enzymatic and nonenzymatic reactions. Additionally, five phenolic compounds were evaluated for melanogenesis inhibitory activity using mushroom tyrosinase and B16 melanoma cells. Most of the phenolic compounds significantly scavenged DPPH, superoxide, and hydroxyl radicals in a dose-dependent manner. Particularly, DFP showed potent DPPH (IC50 = 38.46 microM) and superoxide (IC50 = 291.62 microM) radical scavenging activities, while DCP exhibited the strongest hydroxyl radical scavenging activity (IC50 = 120.55 microM). CFP also exerted moderate DPPH, superoxide, and hydroxyl radical scavenging activities. Meanwhile, DCP (IC50 = 181.73 microM) showed potent tyrosinase inhibitory activity toward l-tyrosine as the substrate, whereas DFP (IC50 = 733.64 microM) significantly inhibited melanin synthesis in B16 melanoma cells. These current results indicate that these three polyamine conjugates from corn bran may be useful potential sources of natural antioxidants and skin-whitening agents.     

Kinetic study of flavonoid reactions with stable radicals

The antiradical activities of some flavonols (kaempferol, quercetin, robinetin, quercetagetin, and myricetin), flavones (apigenin, baicalein, and luteolin), flavanones (naringenin and dihydroquercetin), and flavanols [(+)-catechin and (-)-epicatechin] were determined by measuring the reaction kinetics with 2,2-diphenyl-1-picrylhydrazyl (DPPH) and alpha,gamma-bisdiphenylene-beta-phenylallyl (BDPA) radicals. The reactions, which follow the mixed second-order rate law, were investigated under pseudo-first-order conditions by use of a large excess of flavonoids, and their stoichiometry was determined by spectrophotometric titration. The results confirm stoichiometric factors of 1, 2, and 3 for flavonoids with one, two, and three hydroxyl groups in the B-ring, respectively, excluding kaempferol, which, despite a single OH group in the B-ring, has a factor of 2, which is explained by the 3-OH group supporting the reaction with free radicals. Structure-activity considerations indicate for the present series of flavonoids the importance of multiple OH substitutions and conjugation. The logarithms of reaction rate constants with the OH, DPPH, and BDPA radicals correlate well with the reduction potential of the flavonoids.     

Mechanisms involved in the antiplatelet activity of rutin, a glycoside of the flavonol quercetin, in human platelets

The aim of this study was to systematically examine the inhibitory mechanisms of rutin, a well-known flavonoid in platelet aggregation. In this study, rutin concentration-dependently (250 and 290 microM) inhibited platelet aggregation in human platelets stimulated by agonists (i.e., collagen). Rutin (250 and 290 microM) did not significantly interfere with the binding of FITC-triflavin to the glycoprotein IIb/IIIa complex in human platelets. Rutin (250 and 290 microM) markedly inhibited intracellular Ca(2+) mobilization and thromboxane A(2) formation in human platelets stimulated by collagen. Rapid phosphorylation of a platelet protein of M(r) 47000 (P47), a marker of protein kinase C activation, was triggered by collagen (1 microg/mL). This phosphorylation was markedly inhibited by rutin (250 and 290 microM). On the other hand, rutin (250 and 290 microM) did not significantly increase the formations of cyclic AMP and nitric oxide/cyclic GMP in platelets. In conclusion, these results indicate that the antiplatelet activity of rutin may involve the following pathways: rutin inhibited the activation of phospholipase C, followed by inhibition of protein kinase C activity and thromboxane A(2) formation, thereby leading to inhibition of the phosphorylation of P47 and intracellular Ca(2+) mobilization, finally resulting in inhibition of platelet aggregation.     

Free radical scavenging activity of grape seed extract and antioxidants by electron spin resonance spectrometry in an H(2)O(2)/NaOH/DMSO system.

The scavenging effects of grape seed extract (GSE) on free radicals formed in an H(2)O(2)/NaOH/DMSO system were examined using a spin-trapping electron spin resonance (ESR) method and compared with other natural antioxidants, ascorbic acid, dl-alpha-tocopherol, and beta-carotene. GSE reduced greatly the ESR signal intensity of superoxide radical-5,5-dimethyl-1-pyrroline-N-oxide (DMPO) adducts. GSE also exhibited weak scavenging activity on hydroxyl radical and a little scavenging activity on methyl radical. Ascorbic acid exhibited strong superoxide and hydroxyl radical scavenging activities, but it increased the amount of methyl radical at high concentration. dl-alpha-Tocopherol reduced the amount of superoxide anion, especially the amount of methyl radical. However, it slightly reduced the amount of hydroxyl radical. beta-Carotene reduced the amount of hydroxyl radical and methyl radical, but it also slightly reduced superoxide anion. In the case of combination use of beta-carotene and dl-alpha-tocopherol, all radical species were suppressed. Combination of GSE and dl-alpha-tocopherol also could reduce all radical species. beta-Carotene and dl-alpha-tocopherol could reduce the methyl radical formation induced by ascorbic acid.     

Factors influencing benzene formation from the decarboxylation of benzoate in liquid model systems

Benzene may occur in foods due to the oxidative decarboxylation of benzoate in the presence of hydroxyl radicals. This study investigated factors influencing benzene formation in liquid model systems. The type of buffer, other sources of hydroxyl radical formation in food (photo oxidation of riboflavin and lipid oxidation), transition metal ion concentrations, and the inhibitory effect of antioxidants were tested in benzoate containing model systems. Regarding the hydroxyl radical sources tested, the highest benzene formation was observed in light exposed model systems containing ascorbic acid, Cu(2+), and riboflavin in Na-citrate buffer (1250 ± 131 μg kg(-1)). In practice, it seems that the combination ascorbic acid/transition metal ion remains the biggest contributor to benzene formation in food. However, the concentration of Cu(2+) influences significantly benzene formation in such a system with highest benzene yields observed for Cu(2+) 50 μM (1400 μg kg(-1)). The presence of antioxidants with metal chelation or reduction properties could prevent completely benzene formation.     

Inhibitory effects of green tea polyphenols on the production of a virulence factor of the periodontal-disease-causing anaerobic bacterium Porphyromonas gingivalis

The effect of polyphenolic compounds isolated from green tea (Camellia sinensis) on the production of toxic end metabolites of Porphyromonas gingivalis was investigated. Green tea polyphenols completely inhibited the production of n-butyric acid and propionic acid at a concentration of 1.0-2.0 mg/mL in general anaerobic medium (GAM). (-)-Epigallocatechin gallate (EGCg), which is a major component of tea polyphenols also inhibited the production of phenylacetic acid at 0.5 mg/mL in GAM broth. In the experiment using resting cells of P. gingivalis, phenylacetic acid was produced from l-phenylalanine and phenylpyruvic acid, but this reaction was also inhibited by EGCg, (-)-epicatechin gallate, and (-)-gallocatechin gallate. However, (+)-catechin, (+)-gallocatechin, (-)-epicatechin, and (-)-epigallocatechin did not inhibit those reactions. These results indicate that the inhibitory effect on the production of toxic end metabolites of P. gingivalis can be attributed to the presence of the galloyl moiety, which is ester-linked with the 3-OH of the catechin moiety in the polyphenolic compounds. This study shows that continuous application of tea polyphenols on a daily basis can be considered as a useful and practical method for the prevention of periodontal diseases.     

Ultraviolet-induced oxidation of ascorbic acid in a model juice system: identification of degradation products

Degradation products of ultraviolet (UV-C, 254 nm) treated ascorbic acid (AA) are reported. Analysis by high-performance liquid chromatography-mass spectroscopy (HPLC-MS) conducted in a 0.5% malic acid model juice system (pH 3.3) demonstrated increased degradation of AA above untreated controls with concomitant increases in dehydroascorbic acid (DHA) and 2,3-diketogulonic acid (DKGA) levels. Electron spin resonance (ESR) spectroscopy studies, conducted in phosphate buffer (pH 7.0) to increase detection sensitivity, demonstrated that ascorbyl radical (AA?) formation occurs simultaneously with AA degradation. Consistent with a previous study in which UV treatments were shown to accelerate dark storage degradation, AA? radicals continued to form for up to 200 min after an initial UV treatment. Results from this study suggest that the mechanism for UV-induced degradation is the same as the general mechanism for metal-catalyzed oxidation of AA in juice.     

Involvement of Ca2+ in the inhibition by crocetin of platelet activity and thrombosis formation

Crocetin, a unique carotenoid with potent antioxidative and anti-inflammatory activities, is a major ingredient of saffron used as an important spice and food colorant in various parts of the world. In the present study, the effects of crocetin on platelet activity and thrombosis formation were systematically investigated. Crocetin showed a dose-dependent inhibition of platelet aggregation induced by ADP, collagen, but not by arachidonic acid (AA). Crocetin significantly attenuated dense granule release, while neither platelets adhesion to collagen nor cyclic AMP level was altered by crocetin. Pretreatment with crocetin was confirmed to partially inhibit Ca (2+) mobilization via reducing both intracellular Ca (2+) release and extracellular Ca (2+) influx. Besides that, crocetin prolonged the occlusive time in electrical stimulation-induced carotid arterial thrombosis. These findings suggest that the favorable impacts of crocetin on platelet activity and thrombosis formation may be related to the inhibition of Ca (2+) elevation in stimulated platelets.     

Neuroprotective effects of xanthohumol, a prenylated flavonoid from hops (Humulus lupulus), in ischemic stroke of rats

Xanthohumol is the principal prenylated flavonoid in hops (Humulus lupulus L.), an ingredient of beer. Xanthohumol was found to be a potent chemopreventive agent; however, no data are available concerning its neuroprotective effects. In the present study, the neuroprotective activity and mechanisms of xanthohumol in rats with middle cerebral artery occlusion (MCAO)-induced cerebral ischemia were examined. Treatment with xanthohumol (0.2 and 0.4 mg/kg; intraperitoneally) 10 min before MCAO dose-dependently attenuated focal cerebral ischemia and improved neurobehavioral deficits in cerebral ischemic rats. Xanthohumol treatment produced a marked reduction in infarct size compared to that in control rats. MCAO-induced focal cerebral ischemia was associated with increases in hypoxia-inducible factor (HIF)-1α, tumor necrosis factor (TNF)-α, inducible nitric oxide synthase (iNOS), and active caspase-3 protein expressions in ischemic regions. These expressions were obviously inhibited by treatment with xanthohumol. In addition, xanthohumol (3-70 μM) concentration-dependently inhibited platelet aggregation stimulated by collagen (1 μg/mL) in human platelet-rich plasma. An electron spin resonance (ESR) method was used to examine the scavenging activity of xanthohumol on free radicals which had formed. Xanthohumol (1.5 and 3 μM) markedly reduced the ESR signal intensity of hydroxyl radical (OH?) formation in the H?O?/NaOH/DMSO system. In conclusion, this study demonstrates for the first time that in addition to its originally being considered an agent preventing tumor growth, xanthohumol possesses potent neuroprotective activity. This activity is mediated, at least in part, by inhibition of inflammatory responses (i.e., HIF-1α, iNOS expression, and free radical formation), apoptosis (i.e., TNF-α, active caspase-3), and platelet activation, resulting in a reduction of infarct volume and improvement in neurobehavior in rats with cerebral ischemia. Therefore, this novel role of xanthohumol may represent high therapeutic potential for treatment or prevention of ischemia-reperfusion injury-related disorders.     

Free radical studies of ellagic acid, a natural phenolic antioxidant

Ellagic acid, a plant-derived polyphenol, inhibits gamma-radiation (hydroxyl radical) induced lipid peroxidation in rat liver microsomes in a dose- and concentration-dependent manner. Its antioxidant capacity has been estimated using the 1,1-diphenyl-2-picrylhydrazyl radical assay. To understand the actual mechanisms involved in antioxidant activity and the free radical scavenging ability,a nanosecond pulse radiolysis technique has been employed. The rate constants for the reactions of several reactive oxygen species and reactive nitrogen species such as hydroxyl, peroxyl, and nitrogen dioxide radicals have been found to be in the range of 10(6)-10(9) M(-1) s(-1). The ellagic acid radicals have been characterized by the absorption spectra and decay kinetics. Studies on the reactions of ellagic acid with the 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate) radical and the radicals of ellagic acid with ascorbate have been used to estimate its one-electron reduction potential. Ellagic acid has also been found to be a good scavenger of peroxynitrite. Using stopped-flow reaction analyzer with absorption detection, the rate constant for this reaction has been determined to be 3.7 x 10(3) M(-1) s (-1). The electron spin resonance spectra of the oxidized ellagic acid radicals have been recorded by horseradish peroxidase and hydrogen peroxide method.     

抗氧化剂对辐照猪肉理化和感官品质的影响

为减少猪肉辐照灭菌后产生的异味和脂肪氧化,研究了叔丁基对苯二酚、虾青素、维生素E、茶多酚4种抗氧化剂对辐照猪肉理化和感官品质的影响。采用2 g/L抗氧化剂浸泡处理,透氧包装,辐照剂量2.6 kGy,冷藏10 d。分析测定辐照猪肉感官品质、过氧化值、硫代巴比妥酸反应物、挥发性物质、抗氧化剂对羟自由基清除能力,筛选出适合猪肉辐照的高效抗氧化剂。结果表明：叔丁基对苯二酚在储藏期可以很好地减轻辐照异味并抑制脂肪氧化,效果优于虾青素、维生素E、茶多酚。叔丁基对苯二酚和维生素E可以有效地降低脂肪辐照后产生的挥发性物质含量。叔丁基对苯二酚（0.5 g/L）对羟自由基的清除率为52.5%,高于其他抗氧化剂,可抑制猪肉辐照过程中羟自由基参与的反应。     

Crystal and molecular structure of piceatannol; scavenging features of resveratrol and piceatannol on hydroxyl and peroxyl radicals and docking with transthyretin

The mechanism by which the naturally occurring polyphenolic compounds resveratrol (RES), C(14)H(12)O(3), and its metabolite piceatannol (PIC), C(14)H(12)O(4), scavenge free radicals is studied using experimental and density functional theory (DFT) methods. PIC's crystal structure shows a strong intermolecular hydrogen bond network, which, through a concerted motion of the hydroxyl hydrogen atoms, can produce a second hydrogen bond chain. This reorganization offers a low-energy pathway for the transfer of hydrogen atoms and is a contributing factor to PIC's biological activity. Additionally, DFT calculations describing the entire reaction mechanism of RES, PIC, and 3,3',4',5,5'-pentahydroxystilbene with hydroxyl and peroxyl radicals agree with experimental results, showing that increased hydroxylation aids in scavenging activity. PIC is more efficient than RES because (i) by sharing its 3'-OH hydrogen atom with its adjacent neighbor, O-4', the abstraction and transfer of the 4'-H atom to the free radical becomes easier and (ii) the resulting PIC semiquinone radical is more stable. As a result of the reaction with OH(*), both RES and PIC form water; with the peroxyl radical, both RES and PIC form hydrogen peroxide. Also, docking of PIC onto the protein transthyretin suggests better performance than RES and confirms its possible application in neurodegenerative conditions such as Alzheimer's disease.     

Potent Inhibitory effect of flavonoids in Scutellaria baicalensis on amyloid beta protein-induced neurotoxicity

The free radical scavenging activities of two major flavonoids (baicalein and baicalin) in Scutellaria baicalensis were determined. The antioxidant capacities of baicalein and baicalin were determined by the 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)(*)(-) scavenging assay and showed about 110 and 70% vitamin C equivalent antioxidant capacity, respectively. Because amyloid beta (Abeta) protein is known to increase free radical production and lipid peroxidation in PC12 nerve cells, leading to apoptosis and cell death, treatment with baicalein and baicalin may result in the prevention of cellular damage by the Abeta-induced reactive oxygen species. We found that baicalein and baicalin resulted in a dose-dependent anti-Abeta toxicity by means of three different assays [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction, lactate dehydrogenase release, and trypan blue exclusion assays]. These results suggest that baicalein as well as baicalin can reduce the cytotoxicity of Abeta protein in PC12 cells, possibly by a reduction of oxidative stress, and these flavonoids may be useful in the chemoprevention of Alzheimer's disease.     

Antagonism of free-radical-induced damage of adlay seed and its antiproliferative effect in human histolytic lymphoma U937 monocytic cells

The goal of our current research was to investigate the antioxidative effects of methanolic extracts from different parts of adlay seed and their antiproliferative activity in malignant human cells. The methanolic extracts from different parts of adlay seeds were from the hull (AHM), testa (ATM), bran (ABM), and polished adlay (PAM). AHM exhibited greater capacity to scavenge superoxide anion radicals in the PMS-NADH system than ATM, ABM, or PAM. The scavenging capacities of AHM and ATM on hydrogen peroxides were about 20% at a dose of 250 microg/mL. Using the method of deoxyribose degradation to assess damage caused by hydroxyl radicals, AHM was found to inhibit damage in deoxyribose at a higher concentration. However, ATM, ABM, and PAM exhibited prooxidative activity at the same concentration. The inhibitory effect on enzymatic oxidation of xanthine to uric acid was found to follow the order AHM > ATM =. ABM. However, PAM was inactive. All test samples were positive for inhibition of TPA-induced free radical formation on neutrophil-like leukocytes and were found to follow the order AHM > ATM > ABM > PAM. When human histolytic lymphoma U937 monocytic cells were exposed to tert-butyl hydroperoxide, AHM protected the cells against the cytotoxicity caused by tert-butyl hydroperoxide. In addition, AHM exhibited antiproliferative activity against human histolytic lymphoma U937 monocytic cells in a dose-dependent manner. The antiproliferative properties of AHM appear to be attributable to its induction of apoptotic cell death as determined by flow cytometry. These results show that AHM displays multiple antioxidant effects and induces apoptosis of malignant human cells.