Niacin protects against abdominal aortic aneurysm formation via GPR109A independent mechanisms: role of NAD+/nicotinamide.

AIMS: Chronic adventitial and medial infiltration of immune cells play an important role in the pathogenesis of abdominal aortic aneurysms (AAAs). Nicotinic acid (niacin) was shown to inhibit atherosclerosis by activating the anti-inflammatory G protein-coupled receptor GPR109A [also known as hydroxycarboxylic acid receptor 2 (HCA2)] expressed on immune cells, blunting immune activation and adventitial inflammatory cell infiltration. Here, we investigated the role of niacin and GPR109A in regulating AAA formation. METHODS AND RESULTS: Mice were supplemented with niacin or nicotinamide, and AAA was induced by angiotensin II (AngII) infusion or calcium chloride (CaCl2) application. Niacin markedly reduced AAA formation in both AngII and CaCl2 models, diminishing adventitial immune cell infiltration, concomitant inflammatory responses, and matrix degradation. Unexpectedly, GPR109A gene deletion did not abrogate the protective effects of niacin against AAA formation, suggesting GPR109A-independent mechanisms. Interestingly, nicotinamide, which does not activate GPR109A, also inhibited AAA formation and phenocopied the effects of niacin. Mechanistically, both niacin and nicotinamide supplementation increased nicotinamide adenine dinucleotide (NAD+) levels and NAD+-dependent Sirt1 activity, which were reduced in AAA tissues. Furthermore, pharmacological inhibition of Sirt1 abrogated the protective effect of nicotinamide against AAA formation. CONCLUSION: Niacin protects against AAA formation independent of GPR109A, most likely by serving as an NAD+ precursor. Supplementation of NAD+ using nicotinamide-related biomolecules may represent an effective and well-tolerated approach to preventing or treating AAA.

Effects of Taurine on Eusociality of Ants.

The effects of taurine have been characterized primarily in mammals, and insects are not generally used to study taurine. In this study, ants were used to examine the effect of taurine on eusociality. Ants are the principal models for studying eusociality and superorganisms. Japanese carpenter ants (Camponotus japonicus) were fed a taurine-supplemented diet and tested using ant eusocial indexes. Ant farm structures were constructed using transparent PET bottles containing autoclaved soil. Three categories of vital index were used to study the effect of taurine on group activity: creation of formicaries (residence chambers), cooperative defense efforts, and population density (or group size and composition). Control, low-, and high-taurine diets were prepared using three different levels of taurine in sucrose powder: 0, 5, and 20% (g/g), respectively. The cooperative defense efforts against exogenous queen ants were recorded daily. The high-taurine group took less time to complete their defense formation than the other groups. At least 16% more formicaries (chambers) were observed in the taurine-fed groups than in the control. There were evident differences between control and taurine-fed groups in the total numbers of ants and eggs. The taurine-fed group sustained higher total numbers of ants, excluding the queen. Taurine-fed groups showed a significant increase both in the number of workers and eggs. When fed with taurine, ants responded positively on the eusocial vitality indexes. These results show that taurine exerts a positive effect on the eusociality of ants at the level of the superorganism.

Role of myeloperoxidase in abdominal aortic aneurysm formation: mitigation by taurine.

Oxidative stress plays a fundamental role in abdominal aortic aneurysm (AAA) formation. Activated polymorphonuclear leukocytes (or neutrophils) are associated with AAA and express myeloperoxidase (MPO), which promotes inflammation, matrix degradation, and other pathological features of AAA, including enhanced oxidative stress through generation of reactive oxygen species. Both plasma and aortic MPO levels are elevated in patients with AAA, but the role of MPO in AAA pathogenesis has, heretofore, never been investigated. Here, we show that MPO gene deletion attenuates AAA formation in two animal models: ANG II infusion in apolipoprotein E-deficient mice and elastase perfusion in C57BL/6 mice. Oral administration of taurine [1% or 4% (wt/vol) in drinking water], an amino acid known to react rapidly with MPO-generated oxidants like hypochlorous acid, also prevented AAA formation in the ANG II and elastase models as well as the CaCl2 application model of AAA formation while reducing aortic peroxidase activity and aortic protein-bound dityrosine levels, an oxidative cross link formed by MPO. Both MPO gene deletion and taurine supplementation blunted aortic macrophage accumulation, elastin fragmentation, and matrix metalloproteinase activation, key features of AAA pathogenesis. Moreover, MPO gene deletion and taurine administration significantly attenuated the induction of serum amyloid A, which promotes ANG II-induced AAAs. These data implicate MPO in AAA pathogenesis and suggest that studies exploring whether taurine can serve as a potential therapeutic for the prevention or treatment of AAA in patients merit consideration.NEW & NOTEWORTHY Neutrophils are abundant in abdominal aortic aneurysm (AAA), and myeloperoxidase (MPO), prominently expressed in neutrophils, is associated with AAA in humans. This study demonstrates that MPO gene deletion or supplementation with the natural product taurine, which can scavenge MPO-generated oxidants, can prevent AAA formation, suggesting an attractive potential therapeutic strategy for AAA.

Tissue Inhibitor of Metalloproteinase-1 (TIMP-1) and IL-23 Induced by Polysaccharide of the Black Hoof Medicinal Mushroom, Phellinus linteus (Agaricomycetes).

Matrix metalloproteinase-9 (MMP-9) has diverse roles associated with cell growth, migration, invasion, and angiogenesis. Tissue inhibitor of metalloproteinase-1 (TIMP-1) is known to inhibit MMP-9 by complexing with it at a 1:1 ratio. Suppressing MMP-9 activity through the overexpression of TIMP-1 allows for regulation of tumor growth and metastasis by blocking invasion and angiogenesis in the tumor microenvironment. We found that TIMP-1 and interleukin (IL)-23 are induced in RAW264.7 macrophage cells, a cell line established by Abelson leukemia virus transformation from the BALB/c mouse strain, in a dose-dependent pattern, at the transcriptional level by treatment with a crude polysaccharide fraction of Phellinus linteus (CPP) at a range of 10 to 1000 µg/mL. We purified CPP into 2 polysaccharide fractions, Fr-I and Fr-II, and one protein fraction, Fr-III. Among the 3 fractions, Fr-II increased TIMP-1 expression 6.8-fold compared with the control, according to quantitative reverse-transcription polymerase chain reaction (qRT-PCR) analysis in the RAW264.7 culture system. On the other hand, all 3 fractions increased IL-23 expression, with the highest increase brought about by Fr-II. qRT-PCR analysis showed that Fr-I and Fr-II increased IL-17 expression in RAW264.7 cells by 13.3-fold and 19.6-fold, respectively. IL-17 expression in lung tissue was increased 2.1-fold compared with the control group, whereas that in liver tissue was unaltered by oral administration of CPP for 7 days. In a mouse model, qRT-PCR analysis showed that CPP induced liver TIMP-1 and lung IL-17 expressions 8.9-fold and 2.1-fold, respectively, without affecting MMP-9 expression. Our in vitro and in vivo data suggest that inducing TIMP-1 without altering MMP-9 expression by administering the polysaccharide fraction of Ph. linteus could be a novel antitumor or antimetastasis mechanism of polysaccharide from the medicinal mushroom Ph. linteus.

Activation of NADPH Oxidase by ß-Glucan from Phellinus baumii (Agaricomycetes) in RAW 264.7 Cells.

Production of oxygen-derived free radicals in phagocytes is important in preventing bacterial and fungal infections. Among free radicals, superoxide anions are a typical reactive oxygen species secreted by macrophages and neutrophils. NADPH oxidase (NOX) is a key producer of superoxide anions in these cells. ß-glucans from mushrooms modulate the immune system by binding with the dectin-1 receptor on macrophages. Dectin-1 functions as a pattern recognition receptor that recognizes the pathogen-associated molecular pattern of ß-glucans. During dectin-1 signaling, NOX functions in the activated macrophages to produce ROS, which are critical in antimicrobial host defense. In this study, NOX activation was measured using a lucigenin chemiluminescence assay in RAW 264.7 murine macrophages treated for 1 hour with a ß-glucan fraction from Phellinus baumii (BGF; 10, 100, 500, and 1000 µg/mL) in the absence or presence of phorbol 12-myristate 13-acetate (PMA) or lipopolysaccharide (LPS). NOX was activated at BGF concentrations exceeding 10 µg/mL. BGF in the presence of PMA or LPS activated the enzyme more than treatment with PMA or LPS alone. In the presence of the NOX inhibitor diphenyleneiodonium, BGF still activated NOX. When macrophages were treated with BGF and Staphylococcus aureus, bacterial viability was reduced in a concentration-dependent manner, possibly as a result of increased phagocytosis and oxygen radical production by the activated NOX. These results demonstrate that BGF is a potent stimulator of NOX in macrophages and augments macrophage-mediated phagocytosis and NOX activity.

Induction of Flavin-Containing Monooxygenase in Mice by Oral Administration of Phellinus baumii (Agaricomycetes) Extract.

Phellinus baumii is a yellow mushroom long used in alternative medicine in Korea and other central Asian countries. To identify genes affected by a single or 7-day oral administration of a water extract of Ph. Baumii, mouse liver tissue was analyzed using microarrays. The results showed that 8 and 23 genes were upregulated and 3 and 11 genes downregulated more than 3-fold by single and multiple oral administrations of 100 mg/kg PBE, respectively. Among the upregulated genes, the expression of 3 flavin-containing monooxygenase (Fmo) family genes, Fmo2-4, was upregulated in a concentration-dependent manner. The microarray analysis also showed that single and multiple administrations of PBE increased Fmo3 expression in the mouse liver by 5.1- and 17.6-fold, respectively. To validate the Fmo expression microarray data, polymerase chain reaction was used to confirm the induction of Fmo subclass genes. Mice were orally administered Ph. Baumii extract (PBE), Ph. Baumii water, or Ph. Baumii ß-glucan fraction (PBG) for 7 days, and induction of the expression of the Fmo subclasses in the liver, lung, and kidney was investigated. Fmo2, Fmo3, and Fmo4 expression was induced by both PBE and PBG in the lung, liver, and kidney, respectively. However, no induction of Fmo1 and Fmo5 was detected. To investigate the metabolic acceleration of xenobiotic by PBE, carbendazim was orally administered to mice and its clearance from the blood analyzed. High-performance liquid chromatography analysis showed accelerated clearance of serum carbendazim by oral administration of PBE for 7 days, as evidenced by the reduced peak plasma concentration, time to reach the peak plasma concentration, and area under the curve values. Moreover, PBE increased the carbendazim clearance rate at the higher concentration. These data indicate that oral administration of PBE resulted in modulation of gene expression: PBE was responsible for the induction of Fmo2, Fmo3, and Fmo4 expression. PBE also accelerated the metabolic clearance of carbendazim in vivo and so could be applied to the detoxification of xenobiotics such as drugs, pesticides, and nicotine.

Innate immunity induced by fungal ß-glucans via dectin-1 signaling pathway.

Mushrooms are a highly valuable source of substances that possess unique biological properties and medicinal efficacy. Medicinal mushrooms traditionally have been used to treat cancer, fungal infections, hypertension, diabetes, inflammation, and renal disorders. Medicinal mushrooms produce high-molecular-weight ß-glucans, which have antitumor and antifungal activities that stimulate innate immunity. Innate immune cells express pattern recognition receptors (PRRs) such as dectin-1, Toll-like receptors, and mannose receptors on their cell surfaces. These PRRs recognize pathogens by binding to highly conserved pathogen-associated molecular patterns such as ß-glucan, mannan, and lipopolysaccharide. The immunomodulating activities of innate immune cells are augmented by the binding of ß-glucans to dectin-1 that is expressed by macrophages or dendritic cells. Upon binding ß-glucan, innate immune cells activate adaptive immune cells such as B and T lymphocytes or natural killer cells by secreting various cytokines such as interleukins (IL-4, IL-6) and tumor necrosis factor-α. Water-insoluble ß-glucans have stronger immunostimulating activities than their water-soluble counterparts. ß-glucans have antifungal activity that is similar to their anticancer activities and is mediated by binding to dectin-1, albeit by an unknown mechanism. In this review we discuss recent progress in understanding the mechanisms responsible for the antitumor activities of fungal ß-glucans that act through pathogen-associated molecular patterns and PRRs.

Cardiac stem cells with electrical stimulation improve ischaemic heart function through regulation of connective tissue growth factor and miR-378.

AIMS: In this study, we investigated whether pre-conditioning (PC) by electrical stimulation (EleS) induces cytoprotective effect on cardiac stem cells (CSCs) and determined its underlying molecular mechanisms. METHODS AND RESULTS: Sca-1(+) CSCs were isolated from male C57BL6 mice (12 weeks) hearts. PC of CSCs with EleS ((EleS)CSCs) was carried out for 3 h at 1.5 V followed by exposure to 300 µM H2O2 for 5 h. Cytoprotective effects and cell adhesion ability were significantly increased by EleS as evaluated by transferase-mediated dUTP nick-end labelling (TUNEL), lactate dehydrogenase (LDH) release assay, and adhesion assay. EleS increased phosphorylation of AKT, focal adhesion kinase (FAK), and glycogen synthase kinase (GSK3ß), as well as decreased caspase-3 cleavage. Interestingly, inhibition of AKT or FAK abolished the pro-survival effects of EleS. We found that connective tissue growth factor (Ctgf) was responsible for EleS-induced CSC survival and adhesion.The survival rate of (EleS)CSCs after transplantation in the infarcted myocardium was significantly increased together with improvement in cardiac function. Importantly, knockdown of Ctgf abolished EleS-induced cytoprotective effects and recovery of cardiac function. Furthermore, we identified miR-378 as a potential Ctgf regulator in (EleS)CSCs. CONCLUSION: EleS enhanced CSC survival in vitro and in vivo as well as functional recovery of the ischaemic heart through an AKT/FAK/CTGF signalling pathway. It is suggested that Ctgf and miR-378 are novel therapeutic targets for stem cell-based therapy.

Medicinal mushroom Lingzhi or Reishi, Ganoderma lucidum (W.Curt.:Fr.) P. Karst., beta-glucan induces Toll-like receptors and fails to induce inflammatory cytokines in NF-kappaB inhibitor-treated macrophages.

Beta-Glucan of medicinal Lingzhi or Reishi mushroom, Ganoderma lucidum (BGG), possesses immunostimulatory and anti-tumor activities. Innate immune cells are activated by the binding of beta-glucan to the dectin-1 receptor. The present study investigated the immunostimulating activities of BGG, including binding to dectin-1, secretion of cytokines and reactive oxygen species, and induction of Toll-like receptors (TLRs) in RAW264.7 mouse macrophages. Reverse transcription-polymerase chain reaction and flow cytometry were used for the cytokine and TLR analyses. A mouse inflammation antibody array was used for protein-level cytokine analysis. BGG bound to dectin-1 and induced RAW264.7 cell secretion of several cytokines, including granulocyte colony-stimulating factor, interleukin (IL)-6, regulated upon activation normal T cell expressed and secreted (RANTES), tissue inhibitor of metalloproteinase-1, and tumor necrosis factor-alpha. The secretion of these cytokines was further increased by the addition of lipopolysaccharide (LPS). BGG also induced both nitric oxide and inducible nitric oxide synthase (iNOS). Treatment with an inhibitor of nuclear factor-kappa B (NF-kappaB) reduced the induction of IL-1, IL-6, and iNOS in a concentration-dependent manner. Expressions of TLR2, TLR4, and TLR6 were increased by BGG treatment, and addition of LPS induced further induction of TLR4 and TLR6. Our result indicates that BGG induces macrophage secretion of inflammatory cytokines, which can be potentiated by the presence of LPS, likely by binding to dectin-1 and TLR-2/6 receptors, which activate NF-kappaB and prompt the secretion of cytokines.

Taurine normalizes blood levels and urinary loss of selenium, chromium, and manganese in rats chronically consuming alcohol.

The present study was undertaken to evaluate effects of dietary taurine supplementation on the homeostasis of trace elements, including Se, Cu, Mn and Cr, in rats chronically consuming alcohol. Male SD rats were fed for 8 wk a liquid form of a control diet (CD), an ethanol diet (ED), or a taurine-supplemented ethanol diet (TED). Plasma Se and Mn concentrations were significantly lower in the ED rats than in the CD rats; dietary taurine supplementation corrected alcohol-induced decreases in plasma Se and Mn levels. Chronic alcohol consumption significantly increased urinary excretion of Se (a 53% increase, p < 0.05), Cr (a 62% increase, p < 0.05), Mn (a 45% increase, p < 0.05) and Cu (a 30% increase, p < 0.05) in rats. Urinary losses of these trace elements induced by chronic alcohol consumption in rats were abolished by taurine supplementation. These results suggest that taurine supplementation in rats may protect against Se, Cr and Mn insufficiency caused by chronic alcohol-mediated loss of the trace elements in the urine.

Anti-obesity effects of Juniperus chinensis extract are associated with increased AMP-activated protein kinase expression and phosphorylation in the visceral adipose tissue of rats.

This study evaluates the protective effect of Juniperus chinensis hot water extract (JCE) against high-fat-diet (HFD)-induced obesity and its molecular mechanisms in the visceral adipose tissue of rats. JCE supplementation significantly lowered body weight gain, visceral fat-pad weights, blood lipid levels, and blood insulin and leptin levels of rats rendered obese by an HFD. Feeding with JCE significantly reversed the HFD-induced down-regulation of the epididymal adipose tissue genes implicated in adipogenesis, such as the peroxisome proliferator-activated receptors gamma2 (PPARgamma2), adipocyte protein 2 (aP2), sterol regulatory element binding protein 1c (SREBP1c), fatty acid synthase (FAS), and HMG-CoA reductase (HMGR), as well as those involved in uncoupled respiration, such as the uncoupling protein 2 (UCP2) and uncoupling protein 3 (UCP3). Dietary supplementation with JCE also reversed the HFD-induced decreases in the AMP-activated protein kinase (AMPK) and the acetyl-CoA carboxylase 2 (ACC2) expressions at both the mRNA and protein levels and restored the HFD-induced inhibitions in the AMPK and ACC2 phosphorylation, which are related to fatty acid beta-oxidation, in the epididymal adipose tissue. This study reports, for the first time, that the JCE can have an anti-obesity effect in a rodent model with HFD-induced obesity through an enhanced gene transcription of the uncoupling protein as well as an elevated AMPK protein expression and phosphorylation in the visceral adipose tissue.

Characterization of taurine as inhibitor of sodium glucose transporter.

The most characterized roles of taurine include osmoregulator and membrane-stabilizing activities. However, much remains to be understood about its role in human physiology concerning its anti-hyperglycemic effect. Studies indicate that taurine-supplemented diet helps alleviate hyperglycemia or insulin resistance. This hypoglycemic effect has been postulated as taurine helping to increase the excretion of cholesterol. Alternatively, this study investigated the effect of taurine on glucose transporter using heterologous expression of sodium-glucose transporter-1 (SGLT-1). SGLT-1 was expressed in Xenopus oocytes and the effect of taurine on the expressed SGLT-1 was analyzed utilizing 2-deoxy-D-glucose (2-DOG) uptake and voltage clamp studies. In the oocytes expressing SGLT-1, taurine was shown to inhibit SGLT-1 activity compared to the non-treated controls in a dose-dependent manner. In the presence of taurine, the glucose uptake was greatly inhibited and the glucose-generated current was significantly inhibited. Synthetic taurine analogs were also shown to be effective in inhibiting SGLT-1 activity in a manner comparable to taurine. These effects might offer a promising opportunity in designing functional foods with anti-hyperglycemic potential by supplementing taurine and its analogs to the diet.

Taurine-responsive genes related to signal transduction as identified by cDNA microarray analyses of HepG2 cells.

Taurine-induced changes in the expression profiles of HepG2 cells were assessed using a cDNA microarray technology, and confirmed by real-time reverse transcription-polymerase chain reaction (RT-PCR) analyses. Of 8,298 human genes on the microarray, 128 genes (87 known genes) were up-regulated, and 349 (206 known genes) were down-regulated more than 2.0-fold by taurine. Among the 293 known genes regulated by taurine, a total of 44 genes were involved in signal transduction; 16 genes were up-regulated greater than 2.0-fold, and 28 genes were down-regulated more than 2.0-fold by taurine. The results of RT-PCR analyses for the five genes selected were consistent with our microarray data, although the fold changes in the expression level differed somewhat between the two analytical methods. Among signal transduction-related genes affected by taurine, four genes--mitogen-activated protein kinase (MAPK) kinase kinase 7, p21-activated kinase 4, sprouty homolog 2, and MAPK kinase 1--are implicated in the MAPK signaling pathway. Taurine also regulated the expression of signal transducer and activator of transcription (STAT) 3 gene involved in the Janus kinase-STAT pathway, and diacylglycerol kinase, zeta 104 kDa, the downstream mediator of the protein kinase C transmembrane signaling pathway. In conclusion, gene expression profiling of HepG2 cells treated with taurine provided us with new insights into the novel aspects of taurine as a possible regulator of MAPK signaling cascades and protein kinase C signaling pathways involved in cellular processes such as cell growth, differentiation, and apoptosis.

Suppressive effects of mioga ginger and ginger constituents on reactive oxygen and nitrogen species generation, and the expression of inducible pro-inflammatory genes in macrophages.

We previously conducted screening tests of the chloroform extracts from a total of 89 species of Japanese plant food items for their suppressive effects on superoxide (O(2) ()) generation through both NADPH oxidase and xanthine oxidase, and reported that mioga ginger (Zingiber mioga Roscoe) indicated the strongest suppressive activities. In this study, the suppressive effects of mioga ginger constituents, aframodial, and galanal B, together with [6]-gingerol and galanolactone occurring in ginger, on free radical generation and inducible proinflammatory gene expressions were investigated. Of these constituents, aframodial (20 microM) exhibited marked suppressive effects on 12-O-tetradecanoylphorbol-13-acetate-induced O(2) () generation in HL-60 cells and lipopolysaccharide (LPS)/interferon-gamma-induced nitric oxide (NO) generation in RAW264.7 cells (inhibition rates [IRs]=84.6% and 95.9%, respectively). Aframodial also strongly suppressed the stimulated HL-60 cell-induced mutagenicity in AS52 cells (IR=95.9%). The LPS-induced expression of inducible proinflammatory genes such as inducible NO synthase, interleukin (IL)-1beta, IL-6, and granulocyte-macrophage colony-stimulating factor was significantly abolished (IRs=99.1%, 74.6%, 74.0%, and 64.4%, respectively) by aframodial. In addition, degradation of the inhibitor of nuclear factor kappaB was suppressed by this compound (IR=100%), suggesting that the suppression of nuclear factor kappaB activation, at least in part, is involved. Taken together, these results suggest that aframodial has potent antioxidative and anti-inflammatory potentials, and may be a promising candidate in prevention and/or therapy for chronic inflammationassociated carcinogenesis.

Suppressive effects of selected antioxidants on the activated leukocytes-induced mutagenesis in the co-culture assay systems.

We recently established a novel co-culture assay system using activated inflammatory cells and AS52 Chinese hamster ovary cells, and demonstrated that reactive oxygen and nitrogen species (RONS) generated from activated inflammatory leukocytes induce mutations in the gpt recorder gene in AS52 cells. In this study, we examined the inhibitory effects of 19 agents with antioxidative properties on RONS generation in cultured inflammatory cells and on mutagenesis in AS52 cells co-cultured with activated inflammatory cells. The results demonstrate that there is a linear correlation between the ability of these agents to suppress RONS production in activated inflammatory cells and to inhibit mutation in AS52 cells.

Screening of edible Japanese plants for suppressive effects on phorbol ester-induced superoxide generation in differentiated HL-60 cells and AS52 cells.

Epithelial xanthine oxidase (XOD) is one of the major enzymes responsible for superoxide (O(2)(-)) generation, which is involved in oxidative stress. However, there are few known reports of a convenient bioassay to detect cellular XOD activity. We tested several cell lines, and found that AS52, from Chinese hamster ovary cells, produced a significant level of O(2)(-) in response to 12-O-tetradecanoylphorbol 13-acetate (TPA), and this activity was markedly inhibited by allopurinol, an XOD inhibitor. Using AS52 cells and differentiated HL-60 cells, we conducted screening tests of edible Japanese plant extracts for their inhibitory activities toward TPA-induced O(2)(-) generation from both reduced nicotinamide adenine dinucleotide oxidase (HL-60) and XOD (AS52). Notably, the extracts from mioga ginger, rape, avocado, carrot, turnip, taro, and shimeji showed potent inhibition of O(2)(-) generation in both cell lines. These results suggest that several edible Japanese plants carry a significant antioxidative and cancer preventive potential.

Suppressive Effects of Edible Thai Plants on Superoxide and Nitric Oxide Generation.

We screened ethanol extracts from a total of 134 species of edible Thai plants for their suppressive effects on superoxide (O2(-)) generation using a xanthine (XA)-xanthine oxidase (XOD) assay system. When the extracts were tested at a concentration of 500 &mgr;/g/ml, 28.4% significantly suppressed O2(-) generation. Of these active extracts, it was found that in 17.9% of cases the action was due to XOD inhibition, in 1.5% due to O2(-) scavenging activity, and in 9% due to both XOD inhibition and O2(-) scavenging. In addition, some plant extracts (25 species) which had been known to possibly possess anti-tumor promoting activity were tested for O2(-) and NO generation in cellular systems. In this test, 13 species exhibited strong inhibitory activity toward both O2(-) and NO generation. From the fruit pods of Oroxylum indicum (Bignoniaceae), a traditional vegetable in Thailand, two flavones, oroxylin A and chrysin, and a triterpene carboxylic acid, ursolic acid (UA), were identified as inhibitors of O2(-) generation in XA/XOD system. These compounds also showed marked inhibitory effects on the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced O2(-) generation in dimethylsulfoxide (DMSO)-differentiated HL-60 cells. Our results suggest that, as we have reported earlier, edible Thai plants are promising sources of antioxidants with chemopreventive potential.