Hydrolyzable tannins: potent inhibitors of hydroperoxide production and tumor promotion in mouse skin treated with 12-O-tetradecanoylphorbol-13-acetate in vivo

Tannic acid ameliorates the hazards effect of beryllium induced neuro-alterations and oxidative stress in adult male rats

Background

Tannic acid (TA) is one of the most consumed and famous polyphenols with a widespread attention in the medical field according to its unique structural, pharmaceutical, physicochemical, antioxidant and other biological features. A rare study was conducted on the hazard effect of beryllium (Be) on the central nervous system.

Aims

This study aims to show the ability of beryllium to cross the blood brain barrier. Demonstrate the effect of beryllium and tannic acid separately or with each other on brain ions (Na+, K+, Ca++) and on norepinephrine, dopamine, serotonin, finally on the glutathione and malondialdehyde.

Animals grouping

Seventy-two rats were divided into four groups as control, Be, TA, and Be+TA where Be was injected intraperitoneally as 1 mg/Kg b. wt, TA was orally administrated as 5% in aquas solution.

Results

The administration of beryllium showed its ability to cross the blood brain barrier and accumulated in cortex > cerebellum>hypothalamus also, a significant increase in Na+, Ca++ cooperated with a significant decrease in K+ ions content was observed. Norepinephrine, dopamine, and serotonin showed a general significant decrease in their content joined with a significant decrease in glutathione (GSH) and elevation in malondialdehydes (MDA) because of Be intoxication. On the other hands the daily oral administration of tannic acid showed a general significant decrease in Na+, Ca++ ions content parallel with a significant increase K+ also, a non-significant change in the three measured neurotransmitters was noticed.

Conclusion

Tannic acid showed a mitigation effect against Be intoxication which may regarded to the tannic acid antioxidant, chelating effect.

Curcumin and Its Derivatives Induce Apoptosis in Human Cancer Cells by Mobilizing and Redox Cycling Genomic Copper Ions

Turmeric spice contains curcuminoids, which are polyphenolic compounds found in the Curcuma longa plant’s rhizome. This class of molecules includes curcumin, demethoxycurcumin, and bisdemethoxycurcumin. Using prostate cancer cell lines PC3, LNCaP, DU145, and C42B, we show that curcuminoids inhibit cell proliferation (measured by MTT assay) and induce apoptosis-like cell death (measured by DNA/histone ELISA). A copper chelator (neocuproine) and reactive oxygen species scavengers (thiourea for hydroxyl radical, superoxide dismutase for superoxide anion, and catalase for hydrogen peroxide) significantly inhibit this reaction, thus demonstrating that intracellular copper reacts with curcuminoids in cancer cells to cause DNA damage via ROS generation. We further show that copper-supplemented media sensitize normal breast epithelial cells (MCF-10A) to curcumin-mediated growth inhibition, as determined by decreased cell proliferation. Copper supplementation results in increased expression of copper transporters CTR1 and ATP7A in MCF-10A cells, which is attenuated by the addition of curcumin in the medium. We propose that the copper-mediated, ROS-induced mechanism of selective cell death of cancer cells may in part explain the anticancer effects of curcuminoids.

Pomegranate juice anthocyanidins induce cell death in human cancer cells by mobilizing intracellular copper ions and producing reactive oxygen species

Anthocyanidins are the most abundant polyphenols in pomegranate juice. This class of molecules includes Delphinidin (Del), Cyanidin (Cya), and Pelargonidin (Pel). Using prostate, breast and pancreatic cancer cell lines PC3, MDA-MB-231, BxPC-3 and MiaPaCa-2, we show that anthocyanidins inhibit cell proliferation (measured by MTT assay) and induce apoptosis like cell death (measured by DNA/Histone ELISA). Copper chelator neocuproine and reactive oxygen species scavengers (thiourea for hydroxyl radical and superoxide dismutase for superoxide anion) significantly inhibit this reaction thus demonstrating that intracellular copper reacts with anthocyanidins in cancer cells to cause DNA damage via ROS generation. We further show that copper-supplemented media sensitizes normal breast epithelial cells (MCF-10A) to Del-mediated growth inhibition as determined by decreased cell proliferation. Copper supplementation results in increased expression of copper transporters Ctr1 and ATP7A in MCF-10A cells, which is attenuated by the addition of Del in the medium. We propose that the copper mediated, ROS-induced mechanism of selective cell death of cancer cells may in part explain the anticancer effects of anthocyanidins.

Antidiarrheal, Antimicrobial, and Antioxidant Properties of the Aqueous Extract of Tunisian Persimmon (Diospyros kaki Thunb.) Fruits

Medicinal plants were used to prevent and treat numerous gastrointestinal disorders owing, in part, to their antioxidant capacity. The protective effects of Diospyros kaki fruit aqueous extract (DKFAE) against castor oil (CO)-induced diarrhea was studied. The in vitro antioxidant and antibacterial properties were investigated using colorimetric and biochemical analyses. In vivo, 60 male rats were divided into 6 groups of 10 animals each (n = 10): control (C), CO, CO+various doses of DKFAE (100, 200, and 400 mg/kg, b.w., p.o.), and CO+loperamide (LOP, 10 mg/kg, b.w., p.o.).The DKFAE was rich in tannins and showed interesting antioxidant and antibacterial activities. The liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) analysis resulted in the identification of 16 phenolic compounds, among which quinic acid was the main one. The in vivo study showed that diarrhea was accompanied by an oxidative stress status as measured by an increase of lipid peroxidation, a decrease of glutathione and thiol group levels, as well as antioxidant enzyme activity depletion, such as glutathione peroxidase, superoxide dismutase, and catalase. The DKFAE administration significantly decreased the gastrointestinal transit in a dose-dependent manner. Besides, DKFAE protected against CO-induced diarrhea and intestinal fluid accumulation. Interestingly, DKFAE pretreatment counteracted all the oxidative stress status deregulation induced by CO intoxication. D. kaki fruit could be suggested for its strong protective effect against CO-induced acute diarrhea, which could be explained, in part, to its antimicrobial and antioxidant properties.

The Mechanism Underlying the Protective Effects of Tannic Acid Against Isoproterenol-Induced Myocardial Fibrosis in Mice

Tannic acid (TA) belongs to a class of complex water-soluble polyphenolic derivatives that show anticarcinogenic, antiinflammatory, antioxidant, and scavenging activities. Here, we investigate the protective effects of TA against isoproterenol (ISO)-induced myocardial fibrosis (MF) in mice. Mice received TA and ISO dosing and were sacrificed 48 h later. The activities of creatine kinase (CK), creatine kinase-MB (CK-MB), lactate dehydrogenase (LDH), and mitochondria enzymes were measured. Cardiac histopathology was done using H&E, Sirius red, and Masson’s Trichrome staining. Immunohistochemical staining was applied to indicate changes in B-cell lymphoma-2 (Bcl-2), Bcl-2-associated X protein (Bax), and basic fibroblast growth factor (bFGF) protein expressions in cardiac tissue. RT-PCR was used to measure the expression of atrial and brain natriuretic peptides (ANP and BNP, respectively), c-fos, and c-jun. Western blotting was used to measure the expression of nuclear factor-κB (NF-κB) p65, phosphorylated NF-κB p65), toll-like receptor 4 (TLR4), p38, phosphorylated p38, Bax, Bcl-2, and caspase-3. Compared to the ISO group, the TA group had reduced levels of TLR4, p38, p-p38, NF-κB (p65), p-NF-κB (p-p65), caspase-3, Bax, and Bcl-2, as well as CK, CK-MB, and LDH. These results indicate that TA protects against ISO-induced MF, possibly through its ability to suppress the TLR4-mediated NF-κB signaling pathway.

Medicinal importance of gallic acid and its ester derivatives: a patent review

Gallic acid and its derivatives have a large number of applications in various fields of science. In nature, these compounds are widely distributed in plants and fruits, and thus they are being used as food stuffs, preservatives, etc. directly or indirectly by human community. They have also been implicated as anticarcinogenic, antimicrobial, antimutagenic, antiangiogenic and anti-inflammatory agents besides their use in treating critical diseases like depression, cancer, microbial infections, lipid-related diseases, etc. Herein, an attempt has been made to summarize the important uses of gallic acid derivatives which have extensively been disclosed particularly in various patents. This review would certainly create a great interest of the scientific community toward the developments and uses of gallic acid based compounds in the future.

Cancer Therapy by Catechins Involves Redox Cycling of Copper Ions and Generation of Reactive Oxygen species

Catechins, the dietary phytochemicals present in green tea and other beverages, are considered to be potent inducers of apoptosis and cytotoxicity to cancer cells. While it is believed that the antioxidant properties of catechins and related dietary agents may contribute to lowering the risk of cancer induction by impeding oxidative injury to DNA, these properties cannot account for apoptosis induction and chemotherapeutic observations. Catechin (C), epicatechin (EC), epigallocatechin (EGC) and epigallocatechin-3-gallate (EGCG) are the four major constituents of green tea. In this article, using human peripheral lymphocytes and comet assay, we show that C, EC, EGC and EGCG cause cellular DNA breakage and can alternatively switch to a prooxidant action in the presence of transition metals such as copper. The cellular DNA breakage was found to be significantly enhanced in the presence of copper ions. Catechins were found to be effective in providing protection against oxidative stress induced by tertbutylhydroperoxide, as measured by oxidative DNA breakage in lymphocytes. The prooxidant action of catechins involved production of hydroxyl radicals through redox recycling of copper ions. We also determined that catechins, particularly EGCG, inhibit proliferation of breast cancer cell line MDA-MB-231 leading to a prooxidant cell death. Since it is well established that tissue, cellular and serum copper levels are considerably elevated in various malignancies, cancer cells would be more subject to redox cycling between copper ions and catechins to generate reactive oxygen species (ROS) responsible for DNA breakage. Such a copper dependent prooxidant cytotoxic mechanism better explains the anticancer activity and preferential cytotoxicity of dietary phytochemicals against cancer cells.

The gnotobiotic brine shrimp (Artemia franciscana) model system reveals that the phenolic compound pyrogallol protects against infection through its prooxidant activity

The phenolic compound pyrogallol is the functional unit of many polyphenols and currently there has been a growing interest in using this compound in human and animal health owing to its health-promoting effects. The biological actions of pyrogallol moiety (and polyphenols) in inducing health benefitting effects have been studied; however, the mechanisms of action remain unclear yet. Here, we aimed at unravelling the underlying mechanism of action behind the protective effects of pyrogallol against bacterial infection by using the gnotobiotically-cultured brine shrimp Artemia franciscana and pathogenic bacteria Vibrio harveyi as host-pathogen model system. The gnotobiotic test system represents an exceptional system for carrying out such studies because it eliminates any possible interference of microbial communities (naturally present in the experimental system) in mechanistic studies and furthermore facilitates the interpretation of the results in terms of a cause effect relationship. We provided clear evidences suggesting that pyrogallol pretreament, at an optimum concentration, induced protective effects in the brine shrimp against V. harveyi infection. By pretreating brine shrimp with pyrogallol in the presence or absence of an antioxidant enzyme mixture (catalase and superoxide dismutase), we showed that the Vibrio-protective effect of the compound was caused by its prooxidant action (e.g. generation of hydrogen peroxide, H2O2). We showed further that generation of prooxidant is linked to the induction of heat shock protein Hsp70, which is involved in eliciting the prophenoloxidase and transglutaminase immune responses. The ability of pyrogallol to induce protective immunity makes it a potential natural protective agent that might be a potential preventive modality for different host-pathogen systems.

Redox cycling of endogenous copper by ferulic acid leads to cellular DNA breakage and consequent cell death: A putative cancer chemotherapy mechanism

Ferulic acid (FA) is a plant polyphenol showing diverse therapeutic effects against cancer, diabetes, cardiovascular and neurodegenerative diseases. FA is a known antioxidant at lower concentrations, however at higher concentrations or in the presence of metal ions such as copper, it may act as a pro-oxidant. It has been reported that copper levels are significantly raised in different malignancies. Cancer cells are under increased oxidative stress as compared to normal cells. Certain therapeutic substances like polyphenols can further increase this oxidative stress and kill cancer cells without affecting the proliferation of normal cells. Through various in vitro experiments we have shown that the pro-oxidant properties of FA are enhanced in the presence of copper. Comet assay demonstrated the ability of FA to cause oxidative DNA breakage in human peripheral lymphocytes which was ameliorated by specific copper-chelating agent such as neocuproine and scavengers of ROS. This suggested the mobilization of endogenous copper in ROS generation and consequent DNA damage. These results were further validated through cytotoxicity experiments involving different cell lines. Thus, we conclude that such a pro-oxidant mechanism involving endogenous copper better explains the anticancer activities of FA. This would be an alternate non-enzymatic, and copper-mediated pathway for the cytotoxic activities of FA where it can selectively target cancer cells with elevated levels of copper and ROS.

Cardioprotective Effects of Tannic Acid on Isoproterenol-Induced Myocardial Injury in Rats: Further Insight into 'French Paradox'

Tannic acid (TA) is a polyphenolic compound, which has shown diverse pharmacological effects with antimutagenic, anticarcinogenic and antibactericidal properties. However, cardioprotective effects of TA have not been reported. To investigate the protective effects of TA, rats were administered TA for 7 days and then intoxicated with isoproterenol (ISO). Myocardial ischemia injury was indicated by changes in electrocardiographic (ECG) patterns, morphology and cardiac marker enzymes. Furthermore, protein expression levels of c-fos, c-jun, tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), cleaved-caspase-3 and -9 were analyzed by immunohistochemistry, and activities of apoptosis-related proteins Bax, Bcl-2, caspase-3 and nuclear factor kappa B (NF-κB) were detected by Western blot. Pretreatment with TA ameliorated changes in morphology and ECG, reduced activities of marker enzymes, suppressed overexpression of apoptosis-related proteins, upregulated expression of antioxidants. Moreover, TA pretreatment contributed to the decrease in ratio of Bax/Bcl-2, as well as reduced expression of TNF-α, IL-1β, caspase-3, cleaved-caspase-3 and -9. TA displayed cardioprotective effects, which may be attributed to lowering of Bax/Bcl-2 ratio, c-fos and c-jun expression and inhibition of NF-κB activation, as well as oxidative stress, inflammation and apoptosis. These findings provide further insight into the 'French paradox' and the mechanisms underlying the beneficial effects of TA. Copyright © 2015 John Wiley & Sons, Ltd.

Persimmon (Diospyros kaki) fruit: hidden phytochemicals and health claims

Currently, nutrition and health linkages focused on emerging strategy of diet based regimen to combat various physiological threats including cardiovascular disorders, oxidative stress, diabetes mellitus, etc. In this context, consumption of fruits and vegetables is gaining considerable importance as safeguard to maintain human health. Likewise, their phytochemicals and bioactive molecules are also becoming popular as promising demulcent against various ailments. The current review is an effort to sum up information regarding persimmon fruit with special reference to its phytochemistry and associated health claims. Accordingly, the role of its certain bioactive molecules like proanthocyanidin, carotenoids, tannins, flavonoids, anthocyanidin, catechin, etc. is highlighted. Owing to rich phytochemistry, persimmon and its products are considered effective in mitigating oxidative damage induced by reactive oxygen species (ROS). The antioxidant potential is too responsible for anti-malignant and anti-melanogenic perspectives of persimmon functional ingredients. Additionally, they are effectual in soothing lifestyle related disparities e.g. cardiovascular disorders and diabetes mellitus. There are proven facts that pharmacological application of persimmon or its functional ingredients like proanthocyanidin may helps against hyperlipidemia and hyperglycemia. Nevertheless, astringent taste and diospyrobezoars formation are creating lacuna to prop up its vitality. In toto, persimmon and its components hold potential as one of effective modules in diet based therapy; however, integrated research and meta-analysis are still required to enhance meticulousness.

The prooxidant action of dietary antioxidants leading to cellular DNA breakage and anticancer effects: implications for chemotherapeutic action against cancer

Plant-derived dietary antioxidants have attracted considerable interest in recent past for their ability to induce apoptosis and regression of tumors in animal models. While it is believed that the antioxidant properties of these agents may contribute to lowering the risk of cancer induction by impeding oxidative injury to DNA, it could not account for apoptosis induction and chemotherapeutic observations. In this article, we show that dietary antioxidants can alternatively switch to a prooxidant action in the presence of transition metals such as copper. Such a prooxidant action leads to strand breaks in cellular DNA and growth inhibition in cancer cells. Further, the cellular DNA breakage and anticancer effects were found to be significantly enhanced in the presence of copper ions. Moreover, inhibition of antioxidant-induced DNA strand breaks and oxidative stress by Cu(I)-specific chelators bathocuproine and neocuproine demonstrated the role of endogenous copper in the induction of the prooxidant mechanism. Since it is well established that tissue, cellular, and serum copper levels are considerably elevated in various malignancies, such a prooxidant cytotoxic mechanism better explains the anticancer activity of dietary antioxidants against cancer cells.

Preventive effect of tannic acid on 2-acetylaminofluorene induced antioxidant level, tumor promotion and hepatotoxicity: a chemopreventive study

Tannic acid, present in almost every food derived from plants, has been widely investigated as a chemopreventive agent because, apart from its use as a food additive, pharmacological studies have demonstrated its many health-promoting properties. In this study, we show the modulatory effect of tannic acid on 2-acetylaminofluorene (2-AAF)-mediated hepatic oxidative stress and cell proliferation in rats. 2-AAF (50 mg/kg body weight) caused reduction in hepatic glutathione content and the activities of hepatic anti-oxidant enzymes and phase-II metabolizing enzymes with an enhancement of xanthine oxidase activity, lipid peroxidation and hydrogen peroxide content. 2-AAF treatment also induced serum oxaloacetate and pyruvate transaminase, lactate dehydrogenase and gamma-glutamyl transpeptidase. Treatment of rats orally with tannic acid (125 and 250 mg/kg body weight) resulted in significant recovery of hepatic glutathione content, antioxidant and phase-II metabolizing enzymes. Also, significant decreases in lipid peroxidation, xanthine oxidase, hydrogen peroxide generation and liver damage marker enzymes were observed. The antiproliferative efficacy of the tannic acid was also evaluated. The promotion parameters induced (ornithine decarboxylase activity and DNA synthesis) by 2-AAF administration in the diet with partial hepatectomy (PH) were also significantly suppressed, dose dependently, by tannic acid. Hence, we propose that tannic acid might suppress the promotion stage via inhibition of oxidative stress and polyamine biosynthetic pathway.

Redox cycling of endogenous copper by thymoquinone leads to ROS-mediated DNA breakage and consequent cell death: putative anticancer mechanism of antioxidants

Plant-derived dietary antioxidants have attracted considerable interest in recent past for their chemopreventive and cancer therapeutic abilities in animal models. Thymoquinone (TQ) is the major bioactive constituent of volatile oil of Nigella sativa and has been shown to exert various pharmacological properties, such as anti-inflammatory, cardiovascular, analgesic, anti-neoplastic, anticancer and chemopreventive. Although several mechanisms have been suggested for the chemopreventive and anticancer activity of TQ, a clear mechanism of action of TQ has not been elucidated. TQ is a known antioxidant at lower concentrations and most of the studies elucidating the mechanism have centered on the antioxidant property. However, recent publications have shown that TQ may act as a prooxidant at higher concentrations. It is well known that plant-derived antioxidants can switch to prooxidants even at low concentrations in the presence of transition metal ions such as copper. It is well established that tissue, cellular and serum copper levels are considerably elevated in various malignancies. Copper is an important metal ion present in the chromatin and is closely associated with DNA bases, particularly guanine. Using human peripheral lymphocytes and comet assay, we first show that TQ is able to cause oxidative cellular DNA breakage. Such a DNA breakage can be inhibited by copper-chelating agents, neocuproine and bathocuproine, and scavengers of reactive oxygen species. Further, it is seen that TQ targets cellular copper in prostate cancer cell lines leading to a prooxidant cell death. We believe that such a prooxidant cytotoxic mechanism better explains the anticancer activity of plant-derived antioxidants.

Tannic acid is a natural β-secretase inhibitor that prevents cognitive impairment and mitigates Alzheimer-like pathology in transgenic mice

Amyloid precursor protein (APP) proteolysis is essential for production of amyloid-β (Aβ) peptides that form β-amyloid plaques in brains of Alzheimer disease (AD) patients. Recent focus has been directed toward a group of naturally occurring anti-amyloidogenic polyphenols known as flavonoids. We orally administered the flavonoid tannic acid (TA) to the transgenic PSAPP mouse model of cerebral amyloidosis (bearing mutant human APP and presenilin-1 transgenes) and evaluated cognitive function and AD-like pathology. Consumption of TA for 6 months prevented transgene-associated behavioral impairment including hyperactivity, decreased object recognition, and defective spatial reference memory, but did not alter nontransgenic mouse behavior. Accordingly, brain parenchymal and cerebral vascular β-amyloid deposits and abundance of various Aβ species including oligomers were mitigated in TA-treated PSAPP mice. These effects occurred with decreased cleavage of the β-carboxyl-terminal APP fragment, lowered soluble APP-β production, reduced β-site APP cleaving enzyme 1 protein stability and activity, and attenuated neuroinflammation. As in vitro validation, we treated well characterized mutant human APP-overexpressing murine neuron-like cells with TA and found significantly reduced Aβ production associated with less amyloidogenic APP proteolysis. Taken together, these results raise the possibility that dietary supplementation with TA may be prophylactic for AD by inhibiting β-secretase activity and neuroinflammation and thereby mitigating AD pathology.

Extract from Terminalia chebula seeds protect against experimental ischemic neuronal damage via maintaining SODs and BDNF levels

The fruit of Terminalia chebula Retz has been used as a traditional medicine in Asia and contains tannic acid, chebulagic acid, chebulinic acid and corilagin. Extract from T. chebula seeds (TCE) has various biological functions. We observed the neuroprotective effects of TCE against ischemic damage in the hippocampal C1 region (CA1) of the gerbil that had received oral administrations of TCE (100 mg/kg) once a day for 7 days before the induction of transient cerebral ischemia. In the TCE-treated ischemia group, neuronal neuclei (a marker for neurons)-positive neurons were distinctively abundant (62% of the sham group) in the CA1 4 days after ischemia-reperfusion (I-R) compared to those (12.2% of the sham group) in the vehicle-treated ischemia group. Four days after I-R TCE treatment markedly decreased the activation of astrocytes and microglia in the ischemic CA1 compared with the vehicle-treated ischemia group. In addition, immunoreactivities of Cu, Zn-superoxide dismutase (SOD1), Mn-superoxide dismutase (SOD2) and brain-derived neurotrophic factor (BDNF) in the CA1 of the TCE-treated ischemia group were much higher than those in the vehicle-ischemia group 4 days after I-R. Protein levels of SOD1, SOD2 and BDNF in the TCE-treated ischemia group were also much higher than those in the vehicle-ischemia group 4 days after I-R. These results indicate that the repeated supplement of TCE protected neurons from ischemic damage induced by transient cerebral ischemia by maintaining SODs and BDNF levels as well as decreasing glial activation.

Protective effect of gallic acid against lindane induced toxicity in experimental rats

Lindane is an organochlorine pesticide that persists in the environment, bioaccumulate through food chain and has a risk of causing adverse effects to human health and the environment. It induces cell damage by producing free radicals and reactive oxygen species. The aim of the present study is to investigate the protective effect of gallic acid (a plant derived polyphenol) against lindane induced hepatic and renal toxicity in rats. Liver damage was assessed by hepatic serum marker enzymes like SGOT, SGPT and ALP and histopathological observation. Renal damage was observed by histopathological examination and serum markers like creatinine and urea. Treatment with lindane increased the levels of lipid peroxidation, serum marker enzyme activity with a concomitant decrease in GSH, CAT, SOD, GPx and GST. Histological alterations were also observed in kidney and liver tissue with lindane treatment. Co-treatment of gallic acid significantly prevented the lindane induced alterations in kidney and liver tissues with a decrease in LPO, serum marker enzyme activity and a significant increase in antioxidant levels. These results suggest that gallic acid has protective effect over lindane induced oxidative damage in rat liver and kidney.

Oxidative stress-mediated bimodal regulation of polymorphonuclear leukocyte spreading by polyphenolic compounds

Pyrogallol-bearing polyphenolic compounds induce spreading of polymorphonuclear leukocytes (PMNL), although their optimal concentrations for induction of spreading are quite different (2000, 200, and 2 μM for pyrogallol, (-)-epigallocatechin gallate (EGCG), and tannic acid (TA), respectively), and TA tends to inhibit spreading at higher concentrations. In this study, we examined the involvement of oxidative stress in the regulation of PMNL spreading by these compounds. All three compounds in solution generated H(2)O(2) to a similar extent. Adsorption of the polyphenols to cell surfaces and their accumulation within cells were assessed by detection of the H(2)O(2) precursor O(2)(-) produced by the compounds through reduction of cytochrome c and p-nitro-blue tetrazolium, respectively. TA showed the highest degree of adsorption. EGCG adhered only to PMNL pre-fixed by paraformaldehyde, whereas pyrogallol did not adhere. None of the compounds caused intracellular O(2)(-) generation. A non-pyrogallic compound, 1,2,4-benzenetriol (BT), also produced H(2)O(2); it had no stimulatory effect on PMNL spreading, but inhibited spreading induced by other stimuli. BT did not adhere to PMNL but accumulated within them, and generated O(2)(-) in the presence of glycine. Thiol antioxidants abrogated all of the above spreading-regulatory effects of the polyphenolic compounds. We conclude that H(2)O(2)-generating polyphenols bimodally regulate the spreading of PMNL by subjecting them to oxidative stress. The ability of polyphenol to adhere to, or accumulate within, PMNL may govern the nature of the oxidative stress and determine the optimal concentration of each compound for induction of spreading, as well as whether spreading is promoted or inhibited.

A plant-derived hydrolysable tannin inhibits CFTR chloride channel: a potential treatment of diarrhea

PURPOSE

The present study examined the effects and mechanisms of actions of penta-m-digalloyl-glucose (PDG), a hydrolysable tannin extracted from Chinese gallnut, on cystic fibrosis transmembrane conductance regulator protein (CFTR).

MATERIALS AND METHODS

Fisher rat thyroid cells stably expressing human CFTR (FRT cells) and human intestinal T84 cells were used as cell models to investigate the effects of PDG on chloride secretion using short-circuit current analysis. The mechanisms by which PDG affected chloride secretion were also examined. Finally, in vivo antidiarrheal efficacy and effects of PDG on intestinal fluid absorption were evaluated in mouse closed-loop models.

RESULTS

In FRT cells, apical chloride current induced by forskolin, CPT-cAMP and apigenin were reversibly inhibited by PDG (IC50 approximately 10microM) without effects on intracellular cAMP content and cell viability. Similarly, in T84 cells, PDG effectively inhibited chloride secretion induced by forskolin and cholera toxin. However, it had no effect on calcium-induced chloride secretion. In mice, a single intraluminal injection of PDG (0.6 mg/kg) reduced cholera toxin-induced intestinal fluid secretion by 75% with no effect on intestinal fluid absorption.

CONCLUSIONS

PDG represents a new class of CFTR inhibitors. Further development of this class of compounds may provide a new therapeutic intervention for diarrhea.

The activity of medicinal plants and secondary metabolites on eosinophilic inflammation

Eosinophils are leukocytes that are present in several body compartments and in the blood at relatively low numbers under normal conditions. However, an increase in the number of eosinophils, in the blood or in the tissues, is observed in allergic or parasitic disorders. Although some progress has been made in understanding the development of eosinophil-mediated inflammation in allergic and parasitic diseases, the discovery of new compounds to control eosinophilia has lagged behind other advances. Plant-derived secondary metabolites are the basis for many drugs currently used to treat pathologic conditions, including eosinophilic diseases. Several studies, including our own, have demonstrated that plant extracts and secondary metabolites can reduce eosinophilia and eosinophil recruitment in different experimental animal models. In this review, we summarize these studies and describe the anti-eosinophilic activity of various plant extracts, such as Ginkgo biloba, Allium cepa, and Lafoensia pacari, as well as those of secondary metabolites (compounds isolated from plant extracts), such as quercetin and ellagic acid. In addition, we highlight the medical potential of these plant-derived compounds for treating eosinophil-mediated inflammation, such as asthma and allergy.

Persimmon cv. Hachiya (Diospyros kaki Thunb.) fruit: some physical, chemical and nutritional properties

The persimmon cv. Hachiya (Diospyros kaki) fruits were analysed for some physical properties (fruit dimensions, fruit mass, fruit volume, fruit density, aspect ratio, geometric mean diameter, sphericity, spread area, projected area, bulk density, skin and flesh firmness, skin and flesh colour as L, a and b values, coefficient of static friction on different surfaces and porosity), chemical properties (moisture, ash, pH, acidity, vitamin C, total soluble solids) and nutritional properties (phosphorus, potassium, calcium, magnesium, sodium, iron, manganese, copper and zinc). The fruit characteristics ranged from 169 g for average fruit mass, 65.97 mm for the geometric mean diameter, 1.03% for sphericity and 180 cm3 for volume of fruit. The bulk density, fruit density and porosity were determined as 5,817 N/m3, 9,300 N/m3 and 38.06%, respectively. The present study also revealed important nutritional values of persimmon fruits.

Origanum vulgare induces apoptosis in human colon cancer caco2 cells

Oregano spice is widely used in the Mediterranean diet, which is associated with a low risk for colon cancer. Although the medicinal benefits of oregano, such as the anti-inflammatory and antimicrobial activities, are well known; nonetheless, only few data are available on its effect in cancer prevention, especially concerning the mechanism of action. Here, we investigated the effect of Origanum vulgare ethanolic extracts on redox balance, cell proliferation, and cell death in colon adenocarcinoma Caco2 cells. Oregano extract leads to growth arrest and cell death in a dose- and time-dependent manner. Changes in glutathione content, as well as the increase in its oxidized form, may be involved in oregano-triggered death. Both extrinsic and intrinsic apoptotic pathways appear to be activated by spice extract. Our findings suggest that oregano amounts found in the Mediterranean diet can exert proapoptotic effects, which are selective for cancer cells. Moreover, whole extract, instead of a specific component, can be responsible for the observed cytotoxic effects.

Biphasic regulation of polymorphonuclear leukocyte spreading by polyphenolic compounds with pyrogallol moieties

Green tea polyphenols have been reported to have anti-inflammatory activities, although the molecular mechanisms responsible for this effect remain unclear. In the present study, we examined the effect of green tea extract and a variety of polyphenolic compounds on spreading of peripheral blood polymorphonuclear leukocytes (PMNs) over fibrinogen-coated surfaces. Green tea extract exerted a biphasic effect on PMN spreading; it induced or suppressed spreading at low and high concentrations, respectively. We also found that pyrogallol-bearing compounds have spreading induction activity. Among the compounds tested, tannic acid (TA) had the strongest activity; the concentrations required for induction of maximal spreading were 2 microM for TA, 200 microM for (-)-epigallocatechin gallate, and 2000 microM for the other active compounds. Furthermore, TA was the only compound showing a biphasic effect similar to that of green tea extract; TA at 20 or 200 microM suppressed spreading. The spreading-stimulatory signal was still latent during PMN exposure to TA at concentrations that inhibited spreading, because the pre-exposed PMNs underwent spreading when plated after removal of free TA by centrifugation. The spreading-inhibitory effect of TA at high concentrations overcame the induction of spreading by other stimuli, including phorbol 12-myristate 13-acetate, hydrogen peroxide, denatured fibrinogen surfaces, and naked plastic surfaces. These results suggest that TA as well as green tea extract is bi-functional, having pro-inflammatory and anti-inflammatory effects at low and high concentrations, respectively. Pharmacological use of TA may thus provide new strategies aimed at regulation of PMN spreading for control of inflammation.

Chemopreventive efficacy of gallic acid, an antioxidant and anticarcinogenic polyphenol, against 1,2-dimethyl hydrazine induced rat colon carcinogenesis

Colon cancer is a major cause of morbidity and mortality in developed and developing countries and its etiology is known to be a combination of hereditary, environmental, dietary factors and lack of physical activity. Chemoprevention offers a novel approach to control the incidence of colon cancer. Gallic acid (GA) is a polyphenol widely present in tea and other plants which is popularly used in the traditional medicine of China. The present study was to evaluate the efficacy of GA supplementation on tissue lipid peroxidation and antioxidant defense system in 1,2-dimethyhydrazine (DMH) induced colon carcinogenesis in male Wistar rats. The rats were assorted into six groups, viz., group1 control rats received modified pellet diet; group 2 rats received GA (50 mg/kg body weight) orally along with modified pellet diet; group 3 rats received DMH (20 mg/kg body weight) subcutaneously once a week for the first 15 weeks; groups 4, 5 and 6 rats received GA along with DMH during the initiation, post- initiation stages and the entire period of study respectively. All the rats were sacrificed at the end of 30 weeks and the tissues were evaluated biochemically. We observed decreased lipid peroxidation (LPO) products such as thiobarbituric acid reactive substances (TBARS), lipid hydroperoxides (LOOH) and conjugated dienes (CD) and diminished levels of antioxidants such as superoxide dismutase (SOD), catalase (CAT), reduced glutathione (GSH), glutathione reductase (GR) and glutathione peroxidase (GPx) in the tissues of DMH treated rats, which were elevated significantly on GA supplementation. Moreover, enhanced activity of ascorbic acid and alpha-tocopherol levels were also observed in DMH alone treated rats which were significantly reduced on GA supplementation. Our results suggest that GA could exert a significant chemopreventive effect on DMH induced colon carcinogenesis.

Tannic acid facilitates expression of the polypyrimidine tract binding protein and alleviates deleterious inclusion of CHRNA1 exon P3A due to an hnRNP H-disrupting mutation in congenital myasthenic syndrome

We recently reported that the intronic splice-site mutation IVS3-8G>A of CHRNA1 that encodes the muscle nicotinic acetylcholine receptor alpha subunit disrupts binding of a splicing repressor, hnRNP H. This, in turn, results in exclusive inclusion of the downstream exon P3A. The P3A(+) transcript encodes a non-functional alpha subunit that comprises 50% of the transcripts in normal human skeletal muscle, but its functional significance remains undetermined. In an effort to search for a potential therapy, we screened off-label effects of 960 bioactive chemical compounds and found that tannic acid ameliorates the aberrant splicing due to IVS3-8G>A but without altering the expression of hnRNP H. Therefore, we searched for another splicing trans-factor. We found that the polypyrimidine tract binding protein (PTB) binds close to the 3' end of CHRNA1 intron 3, that PTB induces skipping of exon P3A and that tannic acid increases the expression of PTB in a dose-dependent manner. Deletion assays of the PTB promoter region revealed that the tannic acid-responsive element is between positions -232 and -74 from the translation initiation site. These observations open the door to the discovery of novel therapies based on PTB overexpression and to detecting possible untoward effects of the overexpression.

Tannic acid-induced apoptosis and -enhanced sensitivity to arsenic trioxide in human leukemia HL-60 cells

Tannic acid (TA), a glucoside of gallic acid polymer, has been shown to possess anti-bacterial, anti-enzymatic, anti-tumor and astringent properties. However, the anti-cancer activity of TA in leukemia is still obscure. In this study, we showed TA-induced apoptotic death in acute myeloid leukemia (AML) HL-60 cells via dose- and time-dependent manner as well as increase of sub-G1 fraction, chromosome condensation, and DNA fragmentation. Further analysis demonstrated the involvement of activation of caspase cascade, cleavage of poly (ADP-ribose) polymerase (PARP), disruption of mitochondrial membrane potential, and release of Cytochrome C, in TA-induced apoptosis. These effects were probably associated with the increase of intracellular superoxide in mitochondrial signaling pathway which attributed to the down-regulation of superoxide dismutase (SOD). Notably, a low dose of TA is sufficient to aggravate arsenic trioxide (As(2)O(3))-induced cytotoxicity in HL-60 cells. Altogether, this study suggested the effects of TA to induce apoptosis in HL-60 and therapeutic potential in AML by being an adjunct to As(2)O(3).

Red wine polyphenols for cancer prevention

Conventional cancer therapies, the second leading cause of death worldwide, result in serious side effects and, at best, merely extend the patient's lifespan by a few years. Searching for effective prevention is of high priority in both basic and clinical sciences. In recent decades natural products have been considered to be an important source of cancer chemopreventive agents. Red wine polyphenols, which consisted of various powerful antioxidants such as flavonoids and stilbenes, have been implicated in cancer prevention and that promote human health without recognizable side effects. Since resveratrol, a major component of red wine polyphenols, has been studied and reviewed extensively for its chemopreventive activity to interfere with the multi-stage carcinogenesis, this review focuses on recent progress in studies on cancer chemopreventive activities of red wine polyphenol extracts and fractions as well as other red wine polyphenols, like procyanidin B5 analogues and myricetin.

Synthesis and biological activity of a 3,4,5-trimethoxybenzoyl ester analogue of epicatechin-3-gallate

Despite presenting bioavailability problems, tea catechins have emerged as promising chemopreventive agents because of their observed efficacy in various animal models. To improve the stability and cellular absorption of tea polyphenols, we developed a new catechin-derived compound, 3- O-(3,4,5-trimethoxybenzoyl)-(-)-epicatechin (TMECG), which has shown significant antiproliferative activity against several cancer cell lines, especially melanoma. The presence of methoxy groups in its ester-bound gallyl moiety drastically decreased its antioxidant and prooxidant properties without affecting its cell-antiproliferative effects, and the data indicated that the 3-gallyl moiety was essential for its biological activity. As regards its action mechanism, we demonstrated that TMECG binds efficiently to human dihydrofolate reductase and down-regulates folate cycle gene expression in melanoma cells. Disruption of the folate cycle by TMECG is a plausible explanation for its observed biological effects and suggests that, like other antifolate compounds, TMECG could be of clinical value in cancer therapy.

Antimutagenic, antioxidant and antimicrobial properties of Maytenus krukovii bark

The hydroalcoholic extract of Maytenus krukovii bark was investigated for its in vitro mutageno-protective activities by means of the Ames Salmonella/microsome assay. The extract showed an inhibitory effect in both T98 and T100 strains against the mutagenic activity of promutagen 2-aminoanthracene but was not protective against directly acting mutagens sodium azide and 2-nitrofluorene. When tested as a radical scavenger and antioxidant it produced a dose-dependent inhibition. The extract did not show significant antibacterial properties, and was weakly active against dermatophyte and phytopathogenic fungi, but inhibited the growth of phytopathogen Pithyum ultimum.

Tannic acid inhibits in vitro iron-dependent free radical formation

The antioxidant activity of tannic acid (TA), a plant polyphenol claimed to possess antimutagenic and anticarcinogenic activities, was studied by monitoring (i) 2-deoxyribose degradation (a technique for OH detection), (ii) ascorbate oxidation, (iii) ascorbate radical formation (determined by EPR analysis) and (iv) oxygen uptake induced by the system, which comprised Fe(III) complexes (EDTA, nitrilotriacetic acid (NTA) or citrate as co-chelators), ascorbate and oxygen. TA removes Fe(III) from the co-chelators (in the case of EDTA, this removal is slower than with NTA or citrate), forming an iron-TA complex less capable of oxidizing ascorbate into ascorbate radical or mediating 2-deoxyribose degradation. The effectiveness of TA against 2-deoxyribose degradation, ascorbate oxidation and ascorbate radical formation was substantially higher in the presence of iron-NTA (or iron-citrate) than with iron-EDTA, which is consistent with the known formation constants of the iron complexes with the co-chelators. Oxygen uptake and 2-deoxyribose degradation induced by Fe(II) autoxidation were also inhibited by TA. These results indicate that TA inhibits OH formation induced by Fe(III)/ascorbate/O(2) mainly by arresting Fe(III)-induced ascorbate oxidation and Fe(II) autoxidation (which generates Fe(II) and H(2)O(2), respectively), thus limiting the production of Fenton reagents and OH formation. We also hypothesize that the Fe(II) complex with TA exhibits an OH trapping activity, which explains the effect of TA on the Fenton reaction.

Protection of DNA and membrane from gamma radiation induced damage by gallic acid

Gallic acid (3,4,5-trihydroxybenzoic acid, GA) is a naturally occurring plant phenol. In vitro and in vivo studies have shown that this phytochemical protected DNA and membranes against ionizing radiation. Rat liver microsomes and plasmid pBR322 DNA were exposed to various doses of gamma radiation in presence and absence of GA. Exposure of the microsomes to gamma radiation resulted in the formation of peroxides of membrane lipids measured as thiobarbituric acid reactive substances and presence of GA during irradiation prevented the formation of lipid peroxidation. Gamma irradiation of plasmid DNA resulted in induction of strand breaks in DNA resulting in disappearance of the supercoiled (ccc) form. Presence of GA during irradiation protected the DNA from undergoing the strand breaks. In in vivo studies it was found that whole body exposure of mice to gamma radiation (4 Gy) increased the formation of lipid peroxides in various tissues and damage to cellular DNA (as measured by alkaline comet assay) in peripheral blood leucocytes. Administration of GA to mice prior to whole body radiation exposure reduced the peroxidation of lipids and the damage to the cellular DNA indicating in vivo radiation protection of membranes and DNA by GA.

Plant polyphenols mobilize endogenous copper in human peripheral lymphocytes leading to oxidative DNA breakage: A putative mechanism for anticancer properties

Plant polyphenols are important components of human diet and a number of them are considered to possess chemopreventive and therapeutic properties against cancer. They are recognized as naturally occurring antioxidants but also act as prooxidants catalyzing DNA degradation in the presence of transition metal ions such as copper. Using human peripheral lymphocytes and Comet assay we have previously confirmed that resveratrol-Cu(II) is indeed capable of causing DNA degradation in cells. In this paper we show that the polyphenols alone (in the absence of added copper) are also capable of causing DNA breakage in cells. Incubation of lymphocytes with neocuproine inhibited the DNA degradation confirming that Cu(I) is an intermediate in the DNA cleavage reaction. Further, we have also shown that polyphenols generate oxidative stress in lymphocytes which is inhibited by scavengers of reactive oxygen species and neocuproine. These results are in further support of our hypothesis that anticancer mechanism of plant polyphenols involves mobilization of endogenous copper, possibly chromatin bound copper, and the consequent prooxidant action.

Resveratrol-Cu(II) induced DNA breakage in human peripheral lymphocytes: implications for anticancer properties

Resveratrol (3,4',5-trihydroxy stilbene), a plant derived polyphenol found in mulberries, grapes and red wine is considered to possess chemopreventive properties against cancer. It is recognized as a naturally occurring antioxidant but also catalyzes oxidative DNA degradation in vitro in the presence of transition metal ions such as copper. Using a cellular system of lymphocytes isolated from human peripheral blood and Comet assay, we have confirmed that resveratrol-Cu(II) system is indeed capable of causing DNA degradation in cells such as lymphocytes. Also, trans-stilbene, which does not have any hydroxyl groups, is inactive in the lymphocyte system. Pre-incubation of lymphocytes with resveratrol indicates that it is capable of either traversing the cell membrane or binding to it. Our results are in partial support of our hypothesis that anticancer properties of various plant derived polyphenols may involve mobilization of endogenous copper and the consequent prooxidant action.