cancer-prevention

Author: Chung S. Yang and Hong Wang and Guang Xun Li and Zhihong Yang and Fei Guan and Huanyu Jin

The cancer preventive activities of tea (Camellia sinensis Theaceae) have been studied extensively. Inhibition of tumorigenesis by green tea extracts and tea polyphenols has been demonstrated in different animal models, including those for cancers of the skin, lung, oral cavity, esophagus, stomach, small intestine, colon, bladder, liver, pancreas, prostate, and mammary glands. Many studies in cell lines have demonstrated the modulation of signal transduction and metabolic pathways by (−)-epigallocatechin-3-gallate (EGCG), the most abundant and active polyphenol in green tea. These molecular events can result in cellular changes, such as enhancement of apoptosis, suppression of cell proliferation, and inhibition of angiogenesis. Nevertheless, the molecular mechanisms of inhibition of carcinogenesis in animals and humans remain to be further investigated. Future research directions in this area are discussed.

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Author: Jian-Min Yuan and Canlan Sun and Lesley M. Butler

Experimental studies have consistently shown the inhibitory activities of tea extracts on tumorigenesis in multiple model systems. Epidemiological studies, however, have produced inconclusive results in humans. A comprehensive review was conducted to assess the current knowledge on tea consumption and risk of cancers in humans. In general, consumption of black tea was not associated with lower risk of cancer. High intake of green tea was consistently associated with reduced risk of upper gastrointestinal tract cancers after sufficient control for confounders. Limited data support a protective effect of green tea on lung and hepatocellular carcinogenesis. Although observational studies do not support a beneficial role of tea intake on prostate cancer risk, phase II clinical trials have demonstrated an inhibitory effect of green tea extract against the progression of prostate pre-malignant lesions. Green tea may exert beneficial effects against mammary carcinogenesis in premenopausal women and recurrence of breast cancer. There is no sufficient evidence that supports a protective role of tea intake on the development of cancers of the colorectum, pancreas, urinary tract, glioma, lymphoma, and leukemia. Future prospective observational studies with biomarkers of exposure and phase III clinical trials are required to provide definitive evidence for the hypothesized beneficial effect of tea consumption on cancer formation in humans.

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Author: H.-H. Sherry Chow and Iman A. Hakim

Green tea and its major polyphenols constituents, tea catechins, have been shown to have many health benefits including cancer prevention. Tea catechins and tea catechin metabolites/catabolites are bioavailable in the systemic circulation after oral intake of green tea or green tea catechins. The metabolites/catabolites identified in humans include glucuronide/sulfate conjugates, methylated tea catechin conjugates, and microflora-mediated ring fission products and phenolic acid catabolites. Plasma levels of unchanged tea catechins in humans are mostly in the sub-μM or nM concentration range, which is much lower than the effective concentrations determined in most in vitro studies. However, some of the catechin metabolites/catabolites are present in the systemic circulation at levels much higher than those of the parent catechins. The contribution of catechin derived metabolites/catabolites to the biological effects associated with green tea is yet to be defined. A limited number of chemoprevention trials of green tea or green tea catechins have been conducted to date and have observed potential preventive activity for oral, prostate, and colorectal cancer. Emerging data from multiple ongoing intervention trials will further contribute to defining the cancer preventive activity of green tea or green tea catechins.

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Author: S.M. Abdeen and T.C. Mathew and H.M. Dashti and S. Asfar

Author: David Banji and Otilia J.F. Banji and Saidulu Abbagoni and Md. Sikinder Hayath and Srilatha Kambam and Vijaya Lakshmi Chiluka

Exposure to toxicants prenatally and postnatally could have deleterious consequences on the offspring. Postnatal exposure to valproate in mice pups is capable of inducing experimental autism resulting in neurobehavioral aberrations. Consumption of green tea has been associated with neuronal protection against the impact of toxicants. We investigated the role of green tea extract in reversing cardinal behavioral changes and aberrations in oxidative stress induced by valproate exposure. Young mice of both genders received a single dose of valproate (400 mg/kg subcutaneously) on postnatal day 14 followed by a daily dose of green tea extract (75 and 300 mg/kg) orally up to postnatal day 40. Mice pups were subjected to behavioral testing to assess motor co-ordination, nociceptive response, locomotion, anxiety, exploratory activity and cognition on various postnatal days up to postnatal day 40. At the end of behavioral testing, blood was withdrawn from the retro orbital plexus for the estimation of lipid peroxides. Animals were sacrificed on postnatal day 41 and whole brain was subjected to histopathological examination. Our studies revealed a significant improvement in behavioral assessments particularly with 300 mg/kg of green tea extract. Formation of markers of oxidative stress was reduced at both dose levels. Histological findings confirm the neuroprotective effect of green tea at a dose of 300 mg/kg. In conclusion it can be stated that green tea exerts neuronal cytoprotective action possibly due to anti-oxidant action and could be efficacious in the management of autism.

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Author: Sudathip Sae-tan and Kimberly A. Grove and Joshua D. Lambert

Green tea (Camellia sinensis, Theaceace) is the second most popular beverage in the world and has been extensively studied for its putative disease preventive effects. Green tea is characterized by the presence of a high concentrations of polyphenolic compounds known as catechins, with (−)-epigallocatechin-3-gallate (EGCG) being the most abundant and most well-studied. Metabolic syndrome (MetS) is a complex condition that is defined by the presence of elevated waist circumference, dysglycemia, elevated blood pressure, decrease serum high-density lipoprotein-associated cholesterol, and increased serum triglycerides. Studies in both in vitro and laboratory animal models have examined the preventive effects of green tea and EGCG against the symptoms of MetS. Overall, the results of these studies have been promising and demonstrate that green tea and EGCG have preventive effects in both genetic and dietary models of obesity, insulin resistance, hypertension, and hypercholesterolemia. Various mechanisms have been proposed based on these studies and include: modulation of dietary fat absorption and metabolism, increased glucose utilization, decreased de novo lipogenesis, enhanced vascular responsiveness, and antioxidative effects. In the present review, we discuss the current state of the science with regard to laboratory studies on green tea and MetS. We attempt to critically evaluate the available data and point out areas for future research. Although there is a considerable amount of data available, questions remain in terms of the primary mechanism(s) of action, the dose–response relationships involved, and the best way to translate the results to human intervention studies.

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Author: Raul Dominguez-Perles and Diego A. Moreno and Micaela Carvajal and Cristina Garcia-Viguera

Organic green tea, one of the most-consumed beverages worldwide, is rich in bioactive compounds (flavonols and flavanols) with healthy properties. Broccoli byproducts, consisting of leaves and stalks, are rich in bioactive compounds, including nitrogen–sulphur compounds (glucosinolates and isothiocyanates) and phenolics (chlorogenic and sinapic acid derivatives, and flavonoids), as well as essential nutrients (minerals and vitamins). They are of high interest as a source of health-promoting compounds, useful as ingredients for the development of functional foods. This work analyses minimally-processed broccoli byproducts as a source of bioactive ingredients to design novel beverages, using organic green tea as a food matrix. Green tea enriched with broccoli concentrates showed improved physical quality, phytochemical composition and antioxidant capacity. The functional quality of these novel beverages depends on the proportion of broccoli extracts added to the green tea. The results obtained in the present work should encourage the use of broccoli byproducts as ingredients in novel functional foods. Industrial relevance The industrial use of broccoli byproducts as an ingredient in the development of novel, functional foods may help to add value to the large amount of plant wastes generated in every cropping season, thus reducing their environmental impact. The objectives and aims of the EU producers, industry and stakeholders on the relationships between foods, nutrition and health, and therefore, the use of suitable ingredients from the agriculture to have impact on human health and the environment, with a sustainable use of natural resources are in agreement with this work, adding value to broccoli byproducts and encouraging the production of novel products and applications for nutritional and/or health claims under the EU Regulations (EC) No. 1924/2006 and 834/2007.

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Author: Youngmok Kim and Kevin L. Goodner and Jong-Dae Park and Jeong Choi and Stephen T. Talcott

Monomeric flavonoids (flavan 3-ols or tea catechins) present in Camellia sinensis leaf are transformed to polymeric theaflavin and thearubigin by oxidation occurring during tea fermentation. The distinctive colour, decreased bitterness and astringency, and characteristic flavour are derived from the fermentation process giving fermented teas a marked distinction from non-fermented green tea. Even though teas are available in many different fermentation levels from green to black, the difference in phytochemicals and volatile compounds in teas with different degrees of fermentation has not been fully investigated yet within the same tea leaf. The objective of this study was to observe non-volatile phytochemicals including polyphenolic and volatile compounds changes by oxidation under strict processing control and to evaluate the degree of fermentation for the maximum antioxidant capacity with the same tea material. Harvested tea leaf was immediately processed to different degrees of oxidative fermentation (0%, 20%, 40%, 60%, and 80%). Tea infusions brewed with each processed tea leaf were analysed for polyphenolic profile, total soluble phenolics, antioxidant capacity, and volatile profile using LC–MS, HPLC, Folin–Ciocalteu assay, Oxygen Radical Absorbance Capacity (ORAC), and GC–MS analyses. The flavonoids in non-fermented green tea were significantly lessened during the oxidative fermentation process and the decreased monomeric flavonoids were transformed to polymeric theaflavin and thearubigin as the leaves were more processed. Total soluble phenolics and antioxidant capacity were significantly higher as tea leaves were less processed with a high correlation with individual polyphenolic changes. Volatile compounds present in tea leaf were analysed by GC–MS to observe changes due to processing and were utilised to create a model to differentiate fermentation based on volatile composition. Twenty-four compounds were used to build an initial model which was optimised to 16 compounds with complete separation of the groups using discriminant function analysis. The data suggested that fermentation diminished antioxidant capacity of tea and could result in lowering potential health benefits from flavonoids. This result should be considered for tea manufacturing and the development of functional foods desiring maximum potential health benefits from antioxidant flavonoids in tea.

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Author: Santosh K. Katiyar

Excessive exposure of the skin to solar ultraviolet (UV) radiation is one of the major factors for the development of skin cancers, including non-melanoma. For the last several centuries the consumption of dietary phytochemicals has been linked to numerous health benefits including the photoprotection of the skin. Green tea has been consumed as a popular beverage world-wide and skin photoprotection by green tea polyphenols (GTPs) has been widely investigated. In this article, we have discussed the recent investigations and mechanistic studies which define the potential efficacy of GTPs on the prevention of non-melanoma skin cancer. UV-induced DNA damage, particularly the formation of cyclobutane pyrimidine dimers, has been implicated in immunosuppression and initiation of skin cancer. Topical application or oral administration of green tea through drinking water of mice prevents UVB-induced skin tumor development, and this prevention is mediated, at least in part, through rapid repair of DNA. The DNA repair by GTPs is mediated through the induction of interleukin (IL)-12 which has been shown to have DNA repair ability. The new mechanistic investigations support and explain the anti-photocarcinogenic activity, in particular anti-non-melanoma skin cancer, of green tea and explain the benefits of green tea for human health.

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Author: A.V.S. Perumalla and Navam. S. Hettiarachchy

Using “natural green” plant extracts or their derived products in various food and beverage applications is an increasing trend in the food industry. Selection of these plant extracts and their application depends on their functional properties, availability, cost effectiveness, consumer awareness and their effect on the sensory attributes of the final product. Green tea extract (GTE) and grape seed extract (GSE) are two popular plant extracts that have been widely used in various food and beverage applications. Green tea is a widely consumed beverage that has attracted more attention in the recent years due to its health benefits like antioxidant, antimicrobial, anticarcinogenic and anti-inflammatory properties. Grape seed extract is derived from the grape seeds that is extracted, dried and purified to produce polyphenolic compounds-rich extract that also has well documented antioxidant, antimicrobial and anti-inflammatory properties. These two plant extracts (polyphenolic and proanthocyanidin rich compounds) have potential antioxidant properties by inhibiting the lipid oxidation and warmed over flavors and antimicrobial activities against major food borne pathogens like Listeria monocytogenes, Salmonella Typhimurium, Escherichia coli O157:H7, and Campylobacter jejuni in preventing pathogen contamination. Furthermore, they have demonstrated synergism in antimicrobial activity when used in combination with organic acids (malic, tartaric acid, benzoic acids etc.), bacteriocins like nisin or chelating agents like EDTA in various model systems including fresh produce (fruits and vegetables), raw and ready-to-eat meat and poultry products. Apart from beneficial effects of grape seed extract in food safety and quality, concerns regarding the side effects of GSE are also addressed. Nevertheless, persistent recalls of the food products involving foodborne pathogens despite various control measures calls for efficient bacteriostatic and bactericidal agents and technologies to deliver the active components for an effective inhibition of pathogens. Therefore, further research involving electrostatic spray and nanoscale delivery of the active components present in these natural, green, plant extracts and using them as a component in multiple hurdle approach would enhance the food safety and quality in addition to providing alternative “green” solutions to the food processors.

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