Anticancer Effects of Extracts from Three Different Chokeberry Species.

Colon cancer risk appears to be lowered by consumption of a diet rich in fruits and vegetables. Chokeberries are rich in phytochemicals that may act as potent anticancer agents. Phytochemicals that are particularly abundant in chokeberries include anthocyanins and phenolic acids. In this study, we compared the growth inhibitory activity of three chokeberry extracts in HT-29 human colon cancer cells. The three extracts tested were derived from Aronia arbutifolia (red), Aronia prunifolia (purple), and Aronia melanocarpa (black). Cells were incubated with either red, purple, or black chokeberry extracts and cell viability was quantified using the thiazolyl blue tetrazolium bromide (MTT) assay. The black chokeberry extract had the greatest effect in reducing cell proliferation. The extracts were also characterized for total phenols (Folin-Ciocalteu assay), total antioxidant activity (oxygen radical absorbance capacity assay), and levels of bioactive phenolic acids (high-performance liquid chromatography). The growth inhibitory activities of the extracts correlated well with total phenolic content, antioxidant activity, and levels of caffeic and chlorogenic acids. The black chokeberry extract had the greatest level of total phenols, antioxidant activity, and individual phenolic acids. This research suggests that the phenolic profile of foods such as chokeberries can help determine their cancer cell growth inhibitory activity.

Enhancing the Cancer Cell Growth Inhibitory Effects of Table Grape Anthocyanins.

The risk for breast and colon cancer may be lowered in part by high intake of fruits and vegetables. Fruits such as grapes are abundant in bioactive compounds such as anthocyanins. The potential anticancer activity of anthocyanins may be limited by their metabolism in the gut and liver. One metabolic transformation is due to the enzyme catechol-O-methyltransferase (COMT), which methylates polyphenols such as anthocyanins. Entacapone is a clinically used inhibitor of COMT, and has been shown to modulate the methylation of food-derived polyphenols. In this study, we compared the effect of entacapone on the cell viability of colon (Caco-2 and HT-29) and breast (MDA-MB-231) cancer cell lines treated with anthocyanins. Cells were treated with either cyanidin-3-glucoside, delphinidin-3-glucoside, or an anthocyanin-rich grape extract, in the absence or presence of entacapone. Cell viability was assessed using the thiazolyl blue tetrazolium bromide (MTT) assay. Entacapone in combination with the anthocyanins had a greater than additive effect on growth inhibition of the Caco-2 cells. In the MDA-MB-231 cell line, entacapone similarly enhanced the growth inhibitory activity of the anthocyanin extract. Entacapone also had antiproliferative effects when used as a single treatment. Total hydroperoxides was quantified in the cell culture media. Greater concentrations of the treatments resulted in higher levels of total hydroperoxides, indicating that oxidative stress may be an important mechanism for growth inhibition. In conclusion, the antiproliferative activity of fruit-derived anthocyanins was improved in human cancer cell lines by the clinically used drug entacapone. The efficacy and mechanisms of entacapone/anthocyanin combinations should be carefully studied in vivo. PRACTICAL APPLICATION: Chemical components of grapes are good for our health and have been shown to lower risk for certain cancers. Their beneficial health effects could also be enhanced by consuming other molecules that improve their bioavailability.

The Impact of the Roast Levels of Coffee Extracts on their Potential Anticancer Activities.

Coffee is one of the most widely consumed beverages in the world and contains numerous phytochemicals that are beneficial to consumer health. The phytochemical profile of coffee, however, can be affected by the roast level. In this study, we compared the effect of roasting level on the growth inhibitory activity of HT-29 (colon) and SCC-25 (oral) cancer cell lines. The different roasting stages selected for this study were green, cinnamon/blonde, city/medium, full city/medium-dark, and full city plus/dark. Cancer cells were treated with various concentrations of coffee extracts for 72 hr. Cell viability was quantified using the thiazolyl blue tetrazolium bromide assay. It was found that the lighter roast extracts, Cinnamon in particular, reduced cell growth more than darker roast extracts. The Cinnamon extract had the greatest amount of total phenolic content and antioxidant activity. Relative levels of gallic, caffeic, and chlorogenic acid in the extracts were also compared. The Cinnamon coffee extract had the highest levels of gallic and caffeic acids, which have both been widely-regarded as bioactive phytochemicals. In conclusion, the consumption of lighter roasted coffee, may contribute to the prevention of certain types of cancer such as oral and colon. PRACTICAL APPLICATION: Chemical compounds in coffee may reduce the risk for certain types of cancers. These compounds may be particularly abundant in lighter roasted coffee. Therefore, lighter roasted coffee could contribute to the prevention of cancer through a healthy diet.

Prevention of hepatitis C virus infection using a broad cross-neutralizing monoclonal antibody (AR4A) and epigallocatechin gallate.

The anti-hepatitis C virus (HCV) activity of a novel monoclonal antibody (mAb; AR4A) and epigallocatechin gallate (EGCG) were studied in vitro using a HCV cell culture system and in vivo using a humanized liver mouse model capable of supporting HCV replication. Alone, both exhibit reliable cross-genotype HCV inhibition in vitro, and combination therapy completely prevented HCV infection. In vitro AR4A mAb (alone and combined with EGCG) robustly protects against the establishment of HCV genotype 1a infection. EGCG alone fails to reliably protect against an HCV challenge. In conclusion, AR4A mAb represents a safe and efficacious broadly neutralizing antibody against HCV applicable to strategies to safely prevent HCV reinfection following liver transplantation, and it lends further support to the concept of HCV vaccine development. The poor bioavailability of EGCG limits HCV antiviral activity in vitro.

The catechol-O-methyltransferase inhibitor, tolcapone, increases the bioavailability of unmethylated (-)-epigallocatechin-3-gallate in mice.

(-)-Epigallocatechin-3-gallate (EGCG), has been shown to inhibit cancer in vivo. EGCG, however, is rapidly methylated by catechol-O-methyl transferase (COMT), which reduces its cancer preventive efficacy. Tolcapone (TOL), is a clinically-used COMT inhibitor. Here, we examined the effect of TOL on the bioavailability of EGCG in male CF-1 mice. Plasma and tissue levels of EGCG and its methyl metabolites were determined following intragastric administration of EGCG (100 mg/kg), TOL (30 mg/kg), or the combination. In mice treated with EGCG, unmethylated plasma EGCG accounted for 63.4 % of the total. Co-administration of TOL increased this fraction to 87.9 %. In the urine, unmethylated EGCG accounted for 29.2 % of the total, whereas treatment with EGCG plus TOL increased this to 81.8 %. Similar effects were observed in the major organs examined. TOL effectively inhibited the methylation of EGCG in vivo. Future studies should examine the cancer preventive effects of the combination.

Dietary pretreatment with green tea polyphenol, (-)-epigallocatechin-3-gallate reduces the bioavailability and hepatotoxicity of subsequent oral bolus doses of (-)-epigallocatechin-3-gallate.

Human case-studies have reported an association between green tea-based dietary supplements and hepatotoxicity. Studies have demonstrated the hepatotoxicity of high-dose oral bolus dosing with the tea polyphenol (-)-epigallocatechin-3-gallate (EGCG) in mice and dogs. We examined the effect of pretreatment with dietary EGCG on the hepatotoxicity and bioavailability of acute oral bolus dosing with EGCG in CF-1 mice. EGCG (750 mg/kg, i.g., once daily for 3 days) increased plasma alanine aminotransferase by 80-fold, decreased both reduced (by 59%) and total (by 33%) hepatic glutathione, and increased hepatic levels of phosphorylated histone 2AX. Pretreatment with dietary EGCG (3.2 mg/g diet) for 2 weeks mitigated hepatotoxicity. Acute oral EGCG also decreased mRNA expression of glutathione reductase. Dietary pretreatment prevented these decreased and increased glutathione peroxidase (Gpx)2, Gpx3, Gpx5, and Gpx7 expression. We found that dietary EGCG reduced the plasma (57% reduction) and hepatic (71% reduction) EGCG exposure following oral bolus dosing compared to mice that were not pre-treated. Overall, it appears that EGCG can modulate its own bioavailability and that dietary treatment may reduce the toxic potential of acute high oral bolus doses of EGCG. These data may partly explain the observed variation in hepatotoxic response to green tea-containing dietary supplements.

The role of the mitochondrial oxidative stress in the cytotoxic effects of the green tea catechin, (-)-epigallocatechin-3-gallate, in oral cells.

SCOPE: The tea catechin, (-)-epigallocatechin-3-gallate (EGCG), has potential cancer preventive effects. The prooxidant activity of EGCG may play a role in these effects. METHODS AND RESULTS: Here, we report that EGCG exerted cytotoxic effects against oral cancer cell lines (IC50 = 83-95 µM). EGCG treatment resulted in formation of extracellular reactive oxygen species (ROS), however, these ROS were rapidly cleared (half-life = 1.7 h). EGCG treatment increased the production of mitochondrial H2 O2 in SCC-25 cells (0-6 h) before the induction of apoptosis. Subsequently, an opening of the mitochondrial transition pore and a decrease in mitochondrial membrane potential were observed. The mitochondria-specific antioxidant, MitoTEMPO, reduced these effects. HGF-1 human gingival fibrobasts were resistant to EGCG (IC50 > 200 µM) and EGCG-induced ROS. EGCG induced differential expression of genes related to antioxidant defense in oral cancer cells and gingival fibroblasts: metallothionein 3, superoxide dismutase 2/3, and thioredoxin reductase 2 were downregulated in SCC-25 cells, but upregulated in HGF-1 cells. CONCLUSION: We conclude that induction of mitochondrial ROS and mitochondrial dysfunction by EGCG play a role in the inhibition of oral cancer, and that gingival fibroblasts are spared from these effects in part because of a selective induction of antioxidant responsive genes.

The anthocyanin metabolites gallic acid, 3-O-methylgallic acid, and 2,4,6-trihydroxybenzaldehyde decrease human colon cancer cell viability by regulating pro-oncogenic signals.

Anthocyanins are a class of polyphenols abundant in the skins of red grapes, and have been shown to have anti-cancer effects in models of colon cancer [Cooke et al. Int J Cancer 2006;119:2213-2220; Jing et al. J Agric Food Chem 2008;56:9391-9398]. Gut microflora metabolize anthocyanins to phenolic acids and aldehydes. These metabolites may explain the relationship between anthocyanin consumption and reduced incidence of colorectal cancer (CRC). Previously, gallic acid (Gal), 3-O-methylgallic acid (Megal), and 2,4,6-trihydroxybenzaldehyde (THBA) were found to decrease Caco-2 cell viability to a larger extent than other anthocyanin metabolites. To better understand the potential anti-CRC action of these compounds, this paper investigated their capacity to modulate the cell cycle, and induce apoptotic cell death. Dividing Caco-2 cells were incubated for 24-72 h in the presence of 10-100 µM Gal, Megal, THBA, and malvidin-3-glucoside (M3g). THBA reduced cell viability only at 100 µM, while Gal and Megal (10-100 µM) caused a time- and dose-dependent decrease in cell viability. After 72 h incubation, the metabolites caused cell cycle arrest at G0 /G1 . The activation of the apoptotic pathway by Megal, Gal, and THBA was evidenced by the activation of caspase-3. However, only Megal and Gal caused DNA fragmentation and nuclear condensation. Megal, Gal, and THBA inhibited transcription factors NF-κB, AP-1, STAT-1, and OCT-1 which are known to be activated in CRC. In conclusion, the anti-cancer effects of Megal and Gal occurs as a consequence of both the inhibition of cell proliferation and induction of apoptosis. The inhibition of transcription factors that promote cell proliferation and survival can in part underlie the observed effects.

Synergistic inhibition of lung cancer cell lines by (-)-epigallocatechin-3-gallate in combination with clinically used nitrocatechol inhibitors of catechol-O-methyltransferase.

(-)-Epigallocatechin-3-gallate (EGCG) has exhibited been studied for lung cancer inhibitory activity in vitro and in animal models, but it is rapidly methylated and inactivated by catechol-O-methyltransferase (COMT). Entacapone and tolcapone, COMT inhibitors, are used to mitigate the symptoms of Parkinson's disease. We investigated the synergistic effects of entacapone/tolcapone and EGCG against lung cancer cell lines in culture. EGCG, entacapone and tolcapone inhibited the growth of H1299 human lung cancer cells (IC50 = 174.9, 76.8 and 29.3 µM, respectively) and CL-13 murine lung cancer cells (IC50 = 181.5, 50.7 and 19.7 µM, respectively) as single agents following treatment for 72h. Treatment with 1:10, 1:5, 1:2.5 and 1:1 combinations of EGCG and tolcapone or entacapone resulted in synergistically enhanced growth inhibition. The growth inhibitory effect of the combinations was mediated by induction of intracellular oxidative stress, cell cycle arrest and decreased nuclear translocation of nuclear factor-κΒ. Methylation of EGCG was dose dependently inhibited by entacapone and tolcapone (IC50 = 10 and 20 µM, respectively) in a cell-free system, and both compounds increased the intracellular levels of unmethylated EGCG. Treatment of mice with EGCG in combination with tolcapone increased the bioavailability of EGCG and decreased the methylation of plasma norepinephrine: no apparent liver or behavioral toxicity was observed. In conclusion, the combination of EGCG and entacapone/tolcapone synergistically inhibited the growth of lung cancer cells in culture, and the mechanistic basis for this synergy is likely due in part to inhibition of COMT with resultant increase in the levels of unmetabolized EGCG.

Inhibition of starch digestion by the green tea polyphenol, (-)-epigallocatechin-3-gallate.

SCOPE: Green tea has been shown to ameliorate symptoms of metabolic syndrome in vivo. The effects could be due, in part, to modulation of postprandial blood glucose levels. METHODS AND RESULTS: We examined the effect of coadministration of (-)-epigallocatechin-3-gallate (EGCG, 100 mg/kg, i.g.) on blood glucose levels following oral administration of common corn starch (CCS), maltose, sucrose, or glucose to fasted CF-1 mice. We found that cotreatment with EGCG significantly reduced postprandial blood glucose levels after administration of CCS compared to control mice (50 and 20% reduction in peak blood glucose levels and blood glucose area under the curve, respectively). EGCG had no effect on postprandial blood glucose following administration of maltose or glucose, suggesting that EGCG may modulate amylase-mediated starch digestion. In vitro, EGCG noncompetitively inhibited pancreatic amylase activity by 34% at 20 µM. No significant change was induced in the expression of two small intestinal glucose transporters (GLUT2 and SGLT1). CONCLUSIONS: Our results suggest that EGCG acutely reduces postprandial blood glucose levels in mice when coadministered with CCS and this may be due in part to inhibition of α-amylase. The relatively low effective dose of EGCG makes a compelling case for studies in human subjects.

The role of antioxidant versus pro-oxidant effects of green tea polyphenols in cancer prevention.

Consumption of green tea (Camellia sinensis) may provide protection against chronic diseases, including cancer. Green tea polyphenols are believed to be responsible for this cancer preventive effect, and the antioxidant activity of the green tea polyphenols has been implicated as a potential mechanism. This hypothesis has been difficult to study in vivo due to metabolism of these compounds and poor understanding of the redox environment in vivo. Green tea polyphenols can be direct antioxidants by scavenging reactive oxygen species or chelating transition metals as has been demonstrated in vitro. Alternatively, they may act indirectly by upregulating phase II antioxidant enzymes. Evidence of this latter effect has been observed in vivo, yet more work is required to determine under which conditions these mechanisms occur. Green tea polyphenols can also be potent pro-oxidants, both in vitro and in vivo, leading to the formation of hydrogen peroxide, the hydroxyl radical, and superoxide anion. The potential role of these pro-oxidant effects in the cancer preventive activity of green tea is not well understood. The evidence for not only the antioxidant, but also pro-oxidant, properties of green tea is discussed in the present review.

Gut metabolites of anthocyanins, gallic acid, 3-O-methylgallic acid, and 2,4,6-trihydroxybenzaldehyde, inhibit cell proliferation of Caco-2 cells.

Gut microflora metabolize anthocyanins to phenolic acids and aldehydes. These metabolites may explain the relationship between anthocyanin consumption and reduced incidence of colon cancer. Here, all six major metabolites, along with a Cabernet Sauvignon anthocyanin extract, were incubated with Caco-2 cells at concentrations of 0-1000 microM over 72 h to determine effects on cell proliferation and for 24 h to assess cytotoxicity effects and at 140 microM for 24 h to measure induction of apoptosis. These measurements were based on colorimetric methods. Gallic acid and 3-O-methylgallic acid inhibited cell proliferation and lacked cytotoxicity at low concentrations. The aldehyde metabolite and anthocyanin extract also inhibited cell proliferation at low concentrations and had low cytotoxicity at a wide range of concentrations. Of the four substances that effectively reduced cell proliferation, the aldehyde was the best inducer of apoptosis. In addition, these same four treatments degraded quickly in growth media, suggesting the involvement of subsequent oxidation products in the reduction of cell viability. These results indicate that the anthocyanin microfloral metabolites gallic acid, 3-O-methylgallic acid, and 2,4,6-trihydroxybenzaldehyde reduce cell proliferation in Caco-2 cells more effectively than anthocyanins and may offer protection against colon cancer after their formation in the gut.

Metabolites are key to understanding health effects of wine polyphenolics.

Phenolic compounds in grapes and wine are grouped within the following major classes: stilbenes, phenolic acids, ellagitannins, flavan-3-ols, anthocyanins, flavonols, and proanthocyanidins. Consumption of foods containing phenolic substances has been linked to beneficial effects toward chronic diseases such as coronary heart disease and colorectal cancer. However, such correlations need to be supported by in vivo testing and bioavailability studies are the first step in establishing cause and effect. Class members from all phenolic groups can be glucuronidated, sulfated, and/or methylated and detected at low concentrations in the bloodstream and in urine. But the majority of phenolic compounds from grapes and wine are metabolized in the gastrointestinal tract, where they are broken down by gut microflora. This typically involves deglycosylation, followed by breakdown of ring structures to produce phenolic acids and aldehydes. These metabolites can be detected in bloodstream, urine, and fecal samples by using sophisticated instrumentation methods for quantitation and identification at low concentrations. The health effects related to grape and wine consumption may well be due to these poorly understood phenolic acid metabolites. This review discusses the known metabolism of each major class of wine and grape phenolics, the means to measure them, and ideas for future investigations.

Identification of Cabernet Sauvignon anthocyanin gut microflora metabolites.

Anthocyanins are polyphenol antioxidants that have been shown to prevent many chronic diseases, including colon cancer. The compounds are largely metabolized by various enzymes and bacteria in the large intestine, and the health benefits of consuming foods rich in anthocyanins could be due mostly to the effects of these metabolites. In this study, the contents of the large intestine of pigs were used to model anthocyanin metabolism because pig and human intestinal microflora are similar. An anthocyanin extract from Cabernet Sauvignon grapes that contained delphinidin-3-glucoside, petunidin-3-glucoside, peonidin-3-glucoside, and malvidin-3-glucoside was employed. The extract was incubated anaerobically in the contents of the large intestine of freshly slaughtered pigs for 0, 0.5, and 6 h (final concentrations of 20.9, 28.2, 61.4, and 298.0 microM of the above anthocyanin compounds, respectively, at t = 0 h). Anthocyanins and their metabolites were measured by LC-ESI-MS. After 6 h, anthocyanins were no longer detected, and three metabolites were identified as 3-O-methylgallic acid, syringic acid, and 2,4,6-trihydroxybenzaldehyde. Results from this study suggest that consumption of Cabernet Sauvignon grape anthocyanins could lead to the formation of specific metabolites in the human gut, and it is possible that these metabolites offer the protective effect against colon cancer attributed to anthocyanin consumption.