• Journal of the Mineralogical Society of Korea
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• v.9 no.1
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• pp.1-6
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• 1996

Woolastonite from Susan occurs as intercalations in limestone beds of Lower Paleozoic Joseon Supergroup. It is a thermal metamorphic product of impure limestone. Electron microprobe analysis shows that it is considerably pure wollastonite. It has triclinic cell with a=7.932$\AA$, b=7.328$\AA$, c=7.069$\AA$, $\alpha$=89.995$^{\circ}$, $\beta$=$95.255^{\circ}$, and $ \Upsilon=103.367^{\circ}$.Dissolution behaviors of wollastonite have been studied conducting three different dissolution experiments; two different reactions with HC1 (one batch and one re-initialization experiment) and one traction with distilled water. In the batch type powder wollastonite-HCl reaction, pH of solution rapidly increases in the early stage and then its rate of increase slows down to reach plateau resulting in parabolic relationship with time. It is represented by the early rapid rise and fall in pH giving a sharp pH-edge and succeeding slow rise in the re-initialization experiment. The early rapid rise in pH is due to the rapid sorption of H- in solution to oxygens on the reactive surface of wollastonite and the fall in pH means that all reactive surface sites are occupied by H- ions and no more H- adsorption occurs. The slow rise in pH following the pH- edge is due to the dissolution of wollastonite as evidenced by the correlation of pH variation and cation concentration. Dissolution of powder wollastonite in HCl shows linear trend with time. Si is dissolved predominantly over Ca at a constant rate. Ca is dissolved predominantly in the very early stage. Dissolution rate of coarse-grained wollastonite fragments in distilled water is parabolic with times howing a rapid reaction in the early stage and a slow reaction in the advanced stage. The Ca/Si ratio in solution is high in the case of coarse-grained wollastonite fragment as compared with powder wollastonite. The coarse-grained wollastonite fragment-water (acid) reaction resulted in the solution with an elevated constant pH value (alkaline) giving an important significance on the environmental view point.

• Natural Product Sciences
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• v.15 no.1
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• pp.37-43
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• 2009

Oxidative stress is caused by an imbalance between the production of reactive oxygen and an ability of a biological system, to readily detoxify the reactive intermediates or easily repair the resulting damage. It has been suggested that developmental alloxan-induced liver damage is mediated through increases in oxidative stress. The anti-diabetic effect and antioxidant activity of Phaleria macrocarpa (PM) fractions were investigated in alloxan-induced diabetic rats. After two weeks administration of PM, the liver antioxidant enzyme and hyperglycemic state were evaluated. The results showed that oral administration of PM treatments reduced blood glucose levels in diabetic rats by oral administration (P < 0.05). Serum glutamic-oxaloacetic transaminase (sGOT) and serum glutamic-pyruvate-transaminase (sGPT) were also diminished by PM supplementation. The superoxide dismutase (SOD), catalase (CAT) and glutathione-peroxidase (GPx) activities, and glutathione (GSH) level in the alloxan-induced diabetic rats were significantly decreased (P < 0.05) compared to those in the normal rats but were restored by PM treatments. PM fractions also repressed the level of malondialdehyde (MDA) in the liver. Glutathione reductase (GR), glutathione-S-transferase (GST) and $\gamma$-glutamylcysteine synthase (GCS) were also reduced in alloxan-induced diabetic rats. PM fractions could restore the GR and GST activities, but the GCS activity was not affected in rat livers. From the results of the present study, the diabetic effect of the butanol fraction of PM against alloxan-induced diabetic rats was concluded to be mediated either by preventing the decline of hepatic antioxidant status or due to its indirect radical scavenging capacity.

• Natural Product Sciences
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• v.9 no.2
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• pp.68-72
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• 2003

Quercetin and its sugar conjugates are the most abundantly distributed bioflavonoids and represent the largest proportion of flavonols in the plant kingdom. The present study was undertaken to demonstrate the effect of quercetin on the role of reactive oxygen species (ROS) in the development of gastric ulcers in rats. Administration of quercetin in doses of 50, 100 and $200\;mg\;kg^{-1}$ twice daily for 5 days, showed dose dependent significant protection against ethanol (EtOH), aspirin (ASP), cold-restraint stress (CRS) and pylorus ligation (PL) -induced gastric ulcer models and the results were comparable with those elicited by sucralfate. The thiobarbituric acid reactive substances in the stomach mucosa, an index of lipid peroxidation and regulation of plasma corticosterone were significantly increased in CRS-induced gastric ulceration. The queroetin $(100\;mg\;kg^{-1})$ and reduced glutathione effectively inhibited gastric lesions induced by CRS with a significant decrease in the lipid peroxidation and plasma corticosterone. These results indicate that quercetin a bioflavonoid exerts its antiulcer effect in light of free radical scavenging and plasma corticosterone in cold restraint stress ulcers.

• Natural Product Sciences
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• v.17 no.2
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• pp.65-79
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• 2011

Reactive oxygen species potentially cause damage to cellular components including lipids, protein and DNA; this oxidative damage plays a key role in the pathogenesis of neurodegenerative disease, cardiovascular disease, metabolic disease and cancer. On the basis of the oxidative stress hypothesis, a number of studies have been performed to search for an efficient and safe antioxidant. Although in vitro studies have provided promising results, only a limited number of natural and synthetic antioxidants have been developed for clinical application due to their low efficacy and side-effects. Thus, the discovery of new antioxidants with marked efficacy and safety has attracted worldwide attention in recent decades. Since plants are recognized as important sources of natural antioxidants, our research has focused on the discovery of new naturally occurring antioxidants from medicinal plants. The purpose of this review is to open a new prospect in the field of search for natural antioxidants from medicinal plants by summarizing our recent findings. Using in vitro bioassay systems such as 2,2-diphenyl-1-picrylhydrazyl, superoxide radical scavenging tests and lipid peroxidation models, we have tested over than 350 species of medicinal plants for their antioxidant activity and selected several of them for further investigation. During the research on the discovery of effective natural antioxidants from the medicinal plants selected, we have isolated several new and known antioxidant compounds that include stilbene glycosides, phenolic glycosides, flavonoids, oligostilbenes, and coumarins. Our results suggest that the presence of antioxidant compounds in the medicinal plants might be associated with the traditional use to treat inflammation, cardiovascular disease and various chronic diseases.

• Microbiology and Biotechnology Letters
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• v.33 no.3
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• pp.231-235
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• 2005

Histamine-releasing factors (HRFs) are soluble mediators that can release histamine and other mediators from basophils and mast cells and their activity can vary, depending on the type of IgE. The activity of HRFs is affected by the presence of IgE, although HRF is thought to bind to a specific receptor other than IgE. Until now, HRF signaling pathway including its receptor remains unclear in spite of numerous studies. Since there had been many reports about reactive oxygen species (ROS) as a signaling molecule rather than as a by-product of metabolism, we investigated the possibility of ROS as an intracellular messenger involved in HRF-mediated histamine degranulation. In RBL-2H3 cells, ROS was generated by HRF using $H_2O_2$-sensitive fluorescence of fluorescent 2', 7'-dichlorofluorescein ($H_2DCFDA$). These effects were blocked by anti-oxidant N-acetylcysteine (NAC). These results suggest that ROS generation could play a role as an intracellular messenger in histamine release by HRF.

• Journal of Microbiology and Biotechnology
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• v.18 no.11
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• pp.1862-1867
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• 2008

Streptochlorin is a small molecule isolated from marine Streptomyces sp. that is known to have antiangiogenic and anticancer properties. In this study, we examined the effects of this compound on reactive oxygen species (ROS) production and the association of these effects with apoptotic tumor cell death, using a human hepatocarcinoma Hep3B cell line. The results of this study demonstrated that streptochlorin mediates ROS production, and that this mediation is followed by a decrease in the mitochondrial membrane potential (MMP, ${\Delta}{\Psi}_m$), activation of caspase-3, and downregulation of antiapoptotic Bcl-2 protein. The quenching of ROS generation by N-acetyl-L-cysteine administration, a scavenger of ROS, reversed the streptochlorin-induced apoptosis effects via inhibition of ROS production, MMP collapse, and the subsequent activation of caspase-3. These observations clearly indicate that ROS are involved in the early molecular events in the streptochlorin-induced apoptotic pathway. Taken together, our data imply that streptochlorin-induced ROS is a key mediator of MMP collapse, which leads to the caspase-3 activation, culminating in apoptosis.

• Food Science and Preservation
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• v.15 no.1
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• pp.105-110
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• 2008

The antioxidant properties of bamboos sap isolated from Phyllostachys pubescens were investigated. This product scavenged intracellular reactive oxygen species (ROS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, and prevented lipid peroxidation. The radical scavenging activity of bamboo sap protected the viability of peritoneal macrophage cells exposed to hydrogen peroxide $(H_2O_2)$, Furthermore, bamboo sap reduced apoptotic cell formation induced by $H_2O_2$ as demonstrated by decreases in the number of hypo-diploid cells am apoptotic cell body formation. These results indicate that bamboo sap has radical scavenging activity and ameliorates $H_2O_2$ induced cytotoxicity.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3653-3659
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• 2015

This paper describes the reactive compatibilization of blends of a wholly aromatic thermotropic copolyester liquid crystalline polymer (TLCP) with random copolymers of ethylene and acrylic acid (EAA) and their salts. Blends were prepared by melt mixing in an intensive batch mixer, and the formation of a graft copolymer due to acidolysis between the TLCP and the acrylic acid group of the ionomer was evaluated. Chemical reaction was assessed by torque measurement during melt mixing and by thermal analysis and morphological observation. The Na-salt of the EAA ionomers was especially effective at promoting a grafting reaction. The extent of reaction depended not only on the cation, but also composition of the ionomer and reaction time. The product of the grafting reaction between the TLCP and a sodium-neutralized ionomer proved to be an effective compatibilizer for TLCP and EAA ionomers.

• Bulletin of the Korean Chemical Society
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• v.12 no.2
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• pp.163-169
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• 1991

The photochemical and photophysical properties of N-(2-haloarylmethyl)pyridinium, N-(arylmethyl)-2-halopyridinium, N-(2-haloarylmethyl)-2-halopyridinium salts and N-(2-halobenzyl)-isoquinolinium salt are studied. The pyridinium salts photocyclize to afford isoindolium salts, while the isoquinolium salts do not. In the photocyclization of N-(2-chlorobenzyl)-2-chloropyridinium salts, pyrido[2,1-a]-4-chloroisoindolium salt is formed by the cleavage of chlorine of pyridinium ring. This indicates that the excited moiety is not the phenyl ring, but the pyridinium ring. The triplet states of the pyridinium salts are believed to be largely involved in the photocyclization, since oxygen retards most of the reaction. Some assistance of a ${\pi}$-complex between the excited chlorine moiety of the salt and phenyl plane of the same molecule is required to explain the reactivity of the salts. N-(Benzyl)-2-chloropyridinium salt is two times more reactive than N-(2-chlorobenzyl)pyridinium salt. N-(Benzyl)-2-chloropyridinium salt can form ${\pi}-complex$ effectively because of the electron-rich phenyl group. The ${\pi}$-complex affords an intermediate, phenyl radical by cleaving the chlorine atom. The photocyclized product, isoindolium salt is obtained by losing the hydrogen atom from the phenyl radical. The reactive pyridinium salts 1a, 2a and 3a have a low fluorescence quantum yield (${\Phi}F$ < 0.01) and a higher triplet energy (ET > 68 kcal/mole) than the unreactive quinolinium salt. The unreactivity of isoquinolinium salt can be understood in relation to its high fluorescence quantum yield and its low triplet energy $(E_T = 61 kcal/mole).$.

• Journal of Pharmacopuncture
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• v.24 no.1
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• pp.24-31
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• 2021

Objectives: Accumulation of cellular reactive oxygen species (ROS) leads to oxidative stress. Increased production of ROS, such as superoxide anion, or a deficiency in their clearance by antioxidant defences, mediates cellular pathology. Grewia Spp fruits are a source of bioactive compounds and have notable antioxidant activity. Although the antioxidant capacity of Grewia Spp has been studied, there is very limited evidence that links the antioxidant activities of Grewia bicolor and Grewia flava to the inhibition of free radical formation associated with damage in biological systems. Methods: This study evaluated the protective effects of Grewia bicolor and Grewia flava extracts against free radical-induced oxidative stress and the resulting cytotoxicity effect using HeLa cells. Antioxidant properties determined using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and total phenolic content (TPC) assays showed significantly higher (p < 0.05) antioxidant activity in Grewia flava (ethanol extract) than Grewia flava (water extract) and Grewia bicolor (ethanol and water extracts). Results: Using 3-(4,5-dimethylthiazol-2-yl)-2,5diphenyltetrazolium bromide or MTT assay, cytotoxicity results showed that extracts of Grewia bicolor and Grewia flava were less toxic to HeLa cells at tested concentrations compared to the untreated control. This confirmed the low toxicity of these edible fruits at the tested concentrations in HeLa cells. Furthermore, hydrogen peroxide (H2O2)-induced cell loss was effectively reduced by pre-incubating HeLa cells with Grewia bicolor and Grewia flava extracts, with Grewia flava (ethanol extract) revealing better protection. Conclusion: The effect was speculated to be associated with the higher antioxidant activity of Grewia flava (ethanol extract). Additional studies will warrant confirmation of the mechanism of action of such effects.