Pentameric procyanidin from Theobroma cacao selectively inhibits growth of human breast cancer cells

Use of conventional and -omics based methods for health claims of dietary antioxidants: a critical overview

This article describes the principles and limitations of methods used to investigate reactive oxygen species (ROS) protective properties of dietary constituents and is aimed at providing a better understanding of the requirements for science based health claims of antioxidant (AO) effects of foods. A number of currently used biochemical measurements aimed of determining the total antioxidant capacity and oxidised lipids and proteins are carried out under unphysiological conditions and are prone to artefact formation. Probably the most reliable approaches are measurements of isoprostanes as a parameter of lipid peroxidation and determination of oxidative DNA damage. Also the design of the experimental models has a strong impact on the reliability of AO studies: the common strategy is the identification of AO by in vitro screening with cell lines. This approach is based on the assumption that protection towards ROS is due to scavenging, but recent findings indicate that activation of transcription factors which regulate genes involved in antioxidant defence plays a key role in the mode of action of AO. These processes are not adequately represented in cell lines. Another shortcoming of in vitro experiments is that AO are metabolised in vivo and that most cell lines are lacking enzymes which catalyse these reactions. Compounds with large molecular configurations (chlorophylls, anthocyans and polyphenolics) are potent AO in vitro, but weak or no effects were observed in animal/human studies with realistic doses as they are poorly absorbed. The development of -omics approaches will improve the scientific basis for health claims. The evaluation of results from microarray and proteomics studies shows that it is not possible to establish a general signature of alterations of transcription and protein patterns by AO. However, it was shown that alterations of gene expression and protein levels caused by experimentally induced oxidative stress and ROS related diseases can be normalised by dietary AO.

Polyphenols in cocoa and cocoa products: is there a link between antioxidant properties and health?

Cocoa and cocoa products have received much attention due to their significant polyphenol contents. Cocoa and cocoa products, namely cocoa liquor, cocoa powder and chocolates (milk and dark chocolates) may present varied polyphenol contents and possess different levels of antioxidant potentials. For the past ten years, at least 28 human studies have been conducted utilizing one of these cocoa products. However, questions arise on which of these products would deliver the best polyphenol contents and antioxidant effects. Moreover, the presence of methylxanthines, peptides, and minerals could synergistically enhance or reduce antioxidant properties of cocoa and cocoa products. To a greater extent, cocoa beans from different countries of origins and the methods of preparation (primary and secondary) could also partially influence the antioxidant polyphenols of cocoa products. Hence, comprehensive studies on the aforementioned factors could provide the understanding of health-promoting activities of cocoa or cocoa products components.

Cytotoxic effects of digalloyl dimer procyanidins in human cancer cell lines

Flavanols, a class of polyphenols present in certain plant-based foods, have received increasing attention for their putative anticancer activity. In vitro and in vivo studies, which have compared the effectiveness of various monomer flavanols, indicate that the presence of a galloyl residue on the 3 position on the C-ring enhances the cytotoxicity of these compounds. Procyanidins, oligomerized flavanols, have been reported to be more cytotoxic than monomer flavanols in a variety of human cancer cell lines. Given the above, we evaluated the potential anticancer properties of dimer procyanidins that contain galloyl groups. Specifically, the cytotoxicity of synthetic digalloyl dimer B1 and B2 esters {[3-O-galloyl]-(-)-epicatechin-(4beta,8)-(+)-catechin-3-O-gallate (DGB1) and [3-O-galloyl]-(-)-epicatechin-(4beta,8)-(+)-epicatechin-3-O-gallate (DGB2), respectively} were tested in a number of in vitro models. DGB1 produced significant cytotoxicity in a number of human cancer cell lines evaluated by three independent methods: ATP content, MTT and MTS assays. For the three most sensitive cell lines, exposure to DGB1 and DGB2 for 24, 48 or 72 h was associated with a reduction in cell number and an inhibition of cell proliferation. Digalloyl dimers exerted significantly higher cytotoxic effects than the structurally related flavanols, (-)-epicatechin, (+)-catechin, (-)-epicatechin gallate, (-)-epigallocatechin gallate, (-)-catechin gallate and dimer B1 and B2. These results support the concept that the incorporation of galloyl groups and the oligomerization of flavanols enhances the cytotoxic effects of typical monomer flavanols. The therapeutic value of these compounds and their derivative forms as anticancer agents merits further investigation in whole animal models.

Flavan-3-ols: nature, occurrence and biological activity

Representing the most common flavonoid consumed in the American diet, the flavan-3-ols and their polymeric condensation products, the proanthocyanidins, are regarded as functional ingredients in various beverages, whole and processed foods, herbal remedies and supplements. Their presence in food affects food quality parameters such as astringency, bitterness, sourness, sweetness, salivary viscosity, aroma, and color formation. The ability of flavan-3-ols to aid food functionality has also been established in terms of microbial stability, foamability, oxidative stability, and heat stability. While some foods only contain monomeric flavan-3-ols [(-)-epicatechin predominates] and dimeric proanthocyanidins, most foods contain oligomers of degree of polymerization values ranging from 1-10 or greater than 10. Flavan-3-ols have been reported to exhibit several health beneficial effects by acting as antioxidant, anticarcinogen, cardiopreventive, antimicrobial, anti-viral, and neuro-protective agents. This review summarizes the distribution and health effects of these compounds.

Procyanidin oligomers from Japanese quince (Chaenomeles japonica) fruit inhibit activity of MMP-2 and MMP-9 metalloproteinases

The influence of procyanidin extract from Japanese quince fruit on the activities of matrix metalloproteinases MMP-2 and MMP-9 secreted to culture medium by human peripheral blood mononuclear cells (PBMC) and by human leukemia HL-60 cells was investigated by gelatin zymography. The extract proved to be an effective inhibitor of the enzymes activities (for MMP-2 and MMP-9 secreted by PBMC IC50 = 16-19 microg extract/mL and 22-25 microg extract/mL, respectively). To identify the most effective components of the extract it was fractionated by means of column chromatography on TSKgel Toyopearl HW-40 (S) bed. The obtained fractions were analyzed by TLC, HPLC, and MALDI-TOF MS. Their antioxidant activity was measured as cation radicals ABTS(.+) scavenging efficiency. The fractions VIII-XIV containing oligomers from trimer to hexamer (and probably higher oligomers) appeared to be the most effective inhibitors of MMP-2 and MMP-9 activity (IC50 value close to 4.6 microg total polyphenols/mL). To the best of our knowledge, it is the first report on gelatinase-inhibitory activity of Japanese quince fruit polyphenol extract. We conclude that polyphenols from Japanese quince can be used in cancer chemoprevention, although further studies are needed to elucidate the mechanisms underlying their biological activities.

Cocoa and health: a decade of research

It has been over 10 years since the first mention in a medical journal about cocoa and chocolate as potential sources of antioxidants for health. During this time, cocoa has been found to improve antioxidant status, reduce inflammation and correlate with reduced heart disease risk; with these results, and its popularity, it has received wide coverage in the press. However, after 10 years of research, what is known about the potential health benefits of cocoa and what are the important next steps in understanding this decadent source of antioxidants?

Sorghum bran in the diet dose dependently increased the excretion of catechins and microbial-derived phenolic acids in female rats

Sorghum bran is concentrated with procyanidins (predominately polymers), which may be beneficial for health in humans; however, the bioavailability of procyanidins is not well-understood. Female Sprague-Dawley rats were fed an AIN93G diet containing 0, 5, 10, 20, or 40% Hi-tannin sorghum bran (n = 5-7 for each group) for 50 days. Sorghum bran contained 23.3 mg/g of procyanidins. The urinary excretions of catechin, epicatechin, methylated catechins, and phenolic acids were analyzed using liquid chromatography-tandem mass spectrometry. Sorghum bran dose dependently increased the urinary excretion of catechin (0-2.2 nmol/day) and 3'-O-methylcatechin (0-9.5 nmol/day). Their serum concentrations also increased with dose (range of 0-14 nM for 3'-O-methylcatechin). Among the 14 phenolic acids analyzed, 3,4-dihydroxybenzoic acid, 3-methoxy-4-hydroxybenzoic acid, and 4-hydroxyphenylacetic acid dominated in the serum (1.8-8 micromol/L). In the urine, 3-methoxy-4-hydroxyphenylacetic acid, 3-hydroxyphenylacetic acid, and 3-hydroxyphenylpropionic acid dominated and their excretion increased significantly with the level of sorghum bran in the diet. The summed phenolic acid excretion was 0.8 micromol/day in the control group and increased to 23 micromol/day for 40% sorghum bran group. The hippuric acid excretion ranged from 2.2 to 16.2 micromol/day and peaked in the 10% sorghum bran group. On the basis of chromic oxide, a nonabsorbable marker, total procyanidins and polymers disappeared progressively, and significant degradation occurred in the cecum and colon. Catechins and procyanidins in sorghum were bioavailable; however, bacteria-derived phenolic acids were the predominant metabolites of procyanidins. Procyanidins degraded in the gastrointestinal tract. Depolymerization was not observed.

WTH3 is a direct target of the p53 protein

Previous results showed that overexpression of the WTH3 gene in multidrug resistance (MDR) cells reduced MDR1 gene expression and converted their resistance to sensitivity to various anticancer drugs. The WTH3 gene promoter was found to be differentially regulated in paired MDR vs non-MDR MCF7 cells owing to epigenetic modifications and transcription factor modulations. To understand further the mechanisms that govern WTH3's differential expression, we uncovered a p53-binding site in its promoter, which indicated that WTH3 could be regulated by the p53 gene. This hypothesis was then tested by different strategies. The resulting data revealed that (1) the WTH3 promoter was upregulated by the p53 transgene in diverse host cells; (2) there was a correlation between WTH3 expression levels and p53 gene status in a cell line panel; (3) a WTH3 promoter region was directly targeted by the p53 protein in vitro and in vivo. In addition, overexpression of the WTH3 gene promoted the apoptotic phenotype in host cells. On the basis of these findings, we believe that the negative role played by the WTH3 gene in MDR development is through its proapoptotic potential that is regulated by multiple mechanisms at the transcription level, and one of these mechanisms is linked to the p53 gene.

Procyanidin and catechin contents and antioxidant capacity of cocoa and chocolate products

Cocoa and chocolate products from major brands were analyzed blind for total antioxidant capacity (AOC) (lipophilic and hydrophilic ORAC(FL)), catechins, and procyanidins (monomer through polymers). Accuracy of analyses was ascertained by comparing analyses on a NIST standard reference chocolate with NIST certified values. Procyanidin (PC) content was related to the nonfat cocoa solid (NFCS) content. The natural cocoa powders (average 87% of NFCS) contained the highest levels of AOC (826 +/- 103 micromol of TE/g) and PCs (40.8 +/- 8.3 mg/g). Alkalized cocoa (Dutched powders, average 80% NFCS) contained lower AOC (402 +/- 6 micromol of TE /g) and PCs (8.9 +/- 2.7 mg/g). Unsweetened chocolates or chocolate liquor (50% NFCS) contained 496 +/- 40 micromol of TE /g of AOC and 22.3 +/- 2.9 mg/g of PCs. Milk chocolates, which contain the least amount of NFCS (7.1%), had the lowest concentrations of AOC (80 +/- 10 micromol of TE /g) and PCs (2.7 +/- 0.5 mg/g). One serving of cocoa (5 g) or chocolate (15 or 40 g, depending upon the type of chocolate) provides 2000-9100 micromol of TE of AOC and 45-517 mg of PCs, amounts that exceed the amount in a serving of the majority of foods consumed in America. The monomers through trimers, which are thought to be directly bioavailable, contributed 30% of the total PCs in chocolates. Hydrophilic antioxidant capacity contributed >90% of AOC in all products. The correlation coefficient between AOC and PCs in chocolates was 0.92, suggesting that PCs are the dominant antioxidants in cocoa and chocolates. These results indicate that NFCS is correlated with AOC and PC in cocoa and chocolate products. Alkalizing dramatically decreased both the procyanidin content and antioxidant capacity, although not to the same extent.