Black tea magic: Overview of global research on human health and therapeutic potentialities

Journal of Tea Science Research 2014, Vol.4, No.1, 1-16 http://jtsr.sophiapublisher.com

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Preferred citation for this article: Sharangi et al., 2014, Black Tea Magic: Overview of Global Research on Human Health and Therapeutic Potentialities, Journal of Tea Science Research, Vol.4, No. 1 1-16 (doi: 10.5376/jtsr.2014.04.0001) Received: 19 Nov., 2013 Accepted: 25 Nov., 2013 Published: 29 Nov., 2013

Research Article Open Access

Black Tea Magic: Overview of Global Research on Human Health and Therapeutic Potentialities A.B. Sharangi1 , M.D. Wasim Siddiqui2 , J. E. Dávila Aviña 3 1. Department of Spices and Plantation Crops Faculty of Horticulture, Bidhan Chandra Krishi Viswavidyalaya [Agricultural University], PO: KVV-741252, Mohanpur, Nadia, West Bengal, India 2. Department of Food Science and Technology Bihar Agricultural University, BAC, Sabour, Bhagalpur, Bihar , 813210, India 3. Laboratorio de Bioquímica y Genética de Microorganismos Facultad de Ciencias Biológicas, Uanl, Mexico

Corresponding author email: [email protected]; Author Journal of Tea Science Research, 2014, Vol.4, No.1 DOI: 10.5376/jtsr.2014.04.0001

Copyright ©2014 Sharangi et al. This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract Tea is the second most frequently consumed cheapest non-alcoholic beverage worldwide, black tea is the most produced

type, followed by green and Oolong tea. The venture of this paper is to focus on the latest research efforts regarding the health effects

related to consumption of black tea and derive some future research directions towards its therapeutic potentialities. With a view of

the above, comprehensive information on the fermentation process, composition, and quality of black tea has been provided. Several

major beneficial roles of black tea are antioxidant activity, antiulcer effect, anti-inflammatory effect, antimicrobial properties,

anticancer properties, antimutagenic activity along with the attenuating or reducing effects on blood pressure, CHD and

cardiovascular disease, atherosclerosis, oxidative damage are important. Moreover, black tea has been found to enhance insulin

activity, help in treating asthma, retard cataract, maintain fluid balance, bone health and dental health, improve mean body mass

index and body weight, prevent cellular DNA damage, inhibits HIV, lower stress hormone levels, etc. The potential effect on human

biosynthetic pathways related to oxidative processes as well as that on cognitive performance has also been discussed with citation

from various research findings.

Keywords Camellia sp; Black tea; Polyphenols; Human health; Therapy

1 Practical Applications Tea stands as the second most consumed non-alcoholic beverage around the world, and it is also the less expensive one (Sharangi, 2009). It is grown mainly in tropical and temperate areas, and made through the harvest of young leaflets (Hampton, 1999). Although the leaves from other plant portions have commercial use, tea basically consists of very few leaves, as many as three, including the terminal young apical buds of the species Camellia assamica, Camellia sinensis. Native from South-East Asia, has been grown since ancient times, Chinese mythology records that tea was discovered by emperor Shen Nung in 2737 BC (Harbowy and Balentine, 1997). The installment of tea as a profitable crop has been proved successful worldwide (Dutta et al., 2010). Tea production has increased considerable in the last years, going from 850 million kg between the years of 2000 and 2003, up to 980 million kg between the years 2004 and 2007. China and India are the main tea producing countries; other countries like Indonesia,

Sri Lanka and Kenya contribute to tea production in smaller scale. Currently, it is cultivated in over 30 countries (Eroğlu, 2011).

Tea can be classified into three major forms based on its processing. These forms are black tea, which is fermented or fully aerated, green tea, which is not fermented and, oolong tea, which is partially fermented (Ratnasooriva and Fernando, 2008).The tea consumption globally is divided in black tea, green tea, and Oolong tea, 78%, 20%, and 2% respectively. The majority of black tea is consumed in the western hemisphere, whereas green tea is most common in Asia, in the case of Oolong tea, it is almost restricted to Southern China (Ju et al., 2007; Khan and Mukhtar, 2007). The consumption of tea fits naturally in a healthy life style, which has made tea a popular commodity in the global market.

All the types of tea black, green, and Oolong are made from the leaves of the species Camellia sinensis. The flavor of black tea is usually stronger compared to

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other less oxidized forms, two varieties account for most of black tea. Orthodox and CTC (Cut– Tear–Curl) operations are performed during production (Hicks, 2009). CTC processed tea posses a strong liquor when brewed, in the other hand , orthodox processed tea delivers a very unique flavor, very appreciated by consumers willing to pay a expensive price.

After black tea is harvest (plucking of tender new leaves), a series of processes take place in order to have the final product, and these include withering, pre-conditioning, CTC, fermentation, and lastly drying (Robertson, 1992). The fermentation process is one of the key components for production of black tea. The fermentation process starts with the cut of green leaves, then they are partially dried, later subject of enzymatic action at high temperatures. The characteristic color we observed in black tea is caused by partial polymerization and oxidation of polyphenols and their esters ( catechins or flavan 3-ol and their gallates) to theaflavin and thearubigin. The known flavor of black tea is most likely due to the release of volatile aromatic aglycones by several glycosidases (Higdon and Frei, 2003; Halder and Bhaduri, 1998). The UK National Diet and Nutrition Survey [NDNS] indicated in a study conducted on 7000 adults that people between ages of 50–64 consume more black tea than younger population (ages 19-24) [mean consumption 644 vs 298 ml] Henderson et al (2002).

The paper encompasses various research initiatives related to black tea effects on human health. The main endeavour is to focus on the latest research efforts on some of the important questions regarding the health benefits related to consumption of black tea and derive some future research directions towards its therapeutic potentialities.

2 Black tea fermentation process Fermentation is basically an oxidation process where the leaves are subject to several treatments which include the removal of moisture by airflow (called withering), pre-conditioning, and CTC which refers to the cutting and maceration of leaves.The fermentation process can be performed in open air conditions, on the floor, or moving conveyor under controlled temperature, humidity, and airflow. Once the intracellular compartments are degraded, the oxidization

of polyphenols present in the cell vacuole triggered by enzymes, promotes the formation of theaflavin and thearubigin pigments which characterize black tea, (Robertson, 1992). During this process, the tea leaves gradually change in color going from green to coppery brown, releasing a floral smell. Considering the colour and smell attributes, smell is essential since a strong, unique fragrance emanates from the leaves after optimal fermentation. Monitoring tea aroma during fermentation has been proposed to be achieved through the use of a novel electronic nose-based approach (Bhattacharyya, 2007).

The fermented tea is more beneficial than black tea regarding both, nutrition and therapeutic advantages (Pasha and Reddy, 2005). Teas are available in various fermentation levels from green to black; however, the difference in biochemical composition in relation to fermentation has not been fully investigated. Fermentation of leaves diminishes the antioxidant potential and can result in lowering potential health benefits of flavonoids (Chan et al., 2011).

3 Composition of black tea Tea is a known rich source of antioxidants compounds, flavonoids, carotenoids, tocopherols, and ascorbic acid, among others (Wu and Wei, 2002). The major phenolic compounds observed to be present in teas include the flavan-3-ols and flavonols. Among the main flavan-3-ols present in green tea are [-]-epicatechin and its gallate derivatives. In contrast, in black tea, these compounds are observed to be present in small amounts which is supposed to be the result of the formation of theaflavins and thearubigins (Finger and Engelhardt, 1991; Balentine et al., 1997). The main flavonols contain lower levels of myricetin and are mainly conjugates of quercetin and kaempferol (Finger et al., 1991; Price et al., 1998; Wang and Sporns, 2000; Finger and Engelhardt, 1991). Other related compounds observed to be present in tea are gallic acid, quinic esters of gallic, coumaric, and caffeic acids, purine alkaloids such as theobromine and caffeine (Keihne and Engelhardt, 1996; Ashihara and Crozier, 1999), proanthocyanidins (Kiehne et al., 1997; Lakenbrink et al., 1999) and traces of flavones (Kiehne and Engelhardt, 1993).

Theaflavins (theaflavin, theaflavin-3-gallate, theaflavin-3′- gallate, and theaflavin-3, 3′-digallate) account for

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2~6% of the solids in brewed black tea, these compounds are responsible for the typical color and flavor of black tea. Twenty per cent of the solids present in brewed black tea are polyphenols, thearubigens (characterized by large molecular weights and obscure chemical composition) being the most abundant (Yang and Landau, 2000). Black tea contains low levels of catechins with the highest levels of theaflavins and thearubinins. According to Chan et al (2011) theaflavins and thearubinins have been observed to be as effective as the catechins in the control of cholesterol and prevention of heart diseases and cancer.

The flavonols found in tea have been proved to act as powerful antioxidants and are present in 2~3% of the water-soluble solids from tea leaves. On a dry weight basis, the contents of flavonol such as myricetin, quercetin, and kaempherol in green tea leaves has been observed to range from 0.83-1.59 g/kg, 1.79-4.05 g/kg and 1.56-3.31 g/kg, respectively. In contrast the values in black tea leaves, range from 0.24~0.52 g/kg, 1.04~3.03 g/kg and 1.7~2.31 g/kg, respectively. The particle size of ground leaves has been observed to have a important impact on the concentration of flavonols (Wang and Helliwell, 2001). Tea cream and haze [characterized by lack of clarity] in black tea infusions incremented with the increase of the temperature during the tea extraction process. High-performance liquid chromatography results confirmed that compounds with pyrogallol groups are involved in tea creaming (Liang and Xu, 2002). Taste dilution analyses performed on freshly prepared black tea infusions showed that a series of 14 flavon-3-ol glycosides are the main contributors to the astringent taste perceived when black tea is consumed. Among these glycosides, the apigenin-8-C-[α-L-rhamnopyranosyl- [1→2]-O-β-D-glucopyranoside] was identified for the first time in tea preparations (Scharbert et al., 2004).

During the production of black tea, most catechins are polymerized into more complex molecules called thearubigins. Information about the microbial degradation of these complex polyphenols is minimal; however, hippuric acid has been identified as a major urinary excretion product associated with black tea consumption (Mulder et al., 2005). Quantitative measurements have shown that geraniol along with eight odourants were significantly increased in the

infusion as compared to their concentration in the leaves (Schuh and Schieberle, 2006). Only a small quantity was leached into the brew, the majority being retained in the infused leaf/tea residue. Greater carotenoid degradation was observed in the CTC process compared to the orthodox process which is also greater in withered than unwithered, and in the order beta-carotene>zeaxanthin>lutein. Vitamin A value was greater in orthodox tea than CTC tea and varied depending on clones. Carotenoids in tea show a good stability as a result of the presence of antioxidants, such as polyphenols and catechins (Ravichandran, 2002).

4 Quality of black tea The quality of tea involves parameters such as color, appearance, flavors, and taste. Caffeine is an important factor for quality evaluation (Yao et al., 2006) in the way it indicates briskness and other taste properties (Dev Choudhury et al., 1991). It has been observed the liquor brightness has a negative effect in lower levels of caffeine contents in combination with high levels of epigallo catechin gallate (EGCG) and epicatechin (EC). Higher levels of EGCG and ECG, results in increase caffeine content in green leaf, whereas, the liquor brightness is affected by theaflavins and caffeine contents (Dutta et al., 2011).

Obanda et al. (2001) reported that degradation of individual theaflavins is variable during the fermentation process. Both duration and temperature levels had important effects on decreasing levels of individual theaflavins along with brightness and briskness. ECG and EGCG were found to be the main residual catechins in black tea.

Turkmen et al. (2006) evaluated the effect of water and different organic solvents viz., acetone, N, N-dimethylformamide (DMF), ethanol or methanol at several concentrations on the total polyphenol content and antioxidant activity of black and mate tea. The authors indicated that solvents with different polarity had a significant effect on polyphenol content and antioxidant activity. Polyphenol content was observed to be highly correlated with the antioxidant activity of tea extracts. Enzymatic extraction has been studied to improve the quality of black tea extracts with pretreatment of pectinase and tannase independently, successively and simultaneously. The results observed

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suggested that the use of a single enzyme, tannase, is preferable for the pre-treatment of black tea (Chandini et al., 2011). Tea tasters have assessed its chemical composition, parameter such as color differences of black tea infusions, and their relationships with sensory quality have been evaluated. Significant correlations between the individual quality attributes had been observed. Among the main factors, content of caffeine, nitrogen, amino acids, polyphenols, gallocatechin (GC), epigallocatechin (EGC), catechin (C), epicatechin (EC), epicatechin gallate (ECG), catechin gallate (CG), total catechins, theaflavin (TF) and theaflavin-30-gallate (TF30G) and infusion colour indicators of ΔL, Δa, Δb and ΔE were observed to be significantly correlated to total quality score (TQS) (Liang et al., 2003).

The metabolic pathways involved in biotransformation of flavonoids present in tea are little known. 1H nuclear magnetic resonance spectroscopy was utilized to obtain nonselective profiles of urine samples collected from three volunteers before and after a single dose of black tea. The major urinary black tea metabolite was confirmed to be Hippuric acid (Daykin et al., 2005). Additional sensory studies affirmed that the flavanol-3-glycosides gives a velvety astringent taste sensation to the oral cavity, contributing as well to the known bitter taste of tea infusions by amplifying the bitterness of caffeine (Scharbert and Hofmann, 2005). Effects of temperature and soaking duration on total phenolic and antioxidant activity of black tea and black and bush tea combined in 50:50 ratio was studied by Shonisani et al. (2011). They recommended brewing tea at 90°C for 3 min for optimum polyphenols and antioxidant activity in the brewed liquor. Normal effects of tea in protecting against cardiovascular disease get blocked by the addition of milk because casein from the milk binds to the molecules in the tea that cause the arteries to get relaxed, particularly EGCG (Lorenz et al., 2007). Other studies have found no significant effect of milk on the observed increase in total plasma antioxidant activity (Reddy et al., 2005). Previous studies have observed a beneficial effect of black tea, which was not attributable to the catechin content (Widlansky et al., 2005).

Warden et al (2001) conducted a research to evaluate the bioavailability of catechins from black tea in humans drinking tea throughout the day. Results

indicated that approximately 1.68% of ingested catechins were present in the plasma, urine, and feces, and the apparent bioavailability of the gallated catechins was lower than the nongallated forms, confirming thus the bioavalability of catechins.

5 Health Benefits and Therapeutic Potentialities of Black Tea 5.1 Antioxidant activity Highly reactive free radicals and oxygen species are found in nature from many sources, reactive free radicals oxidize nucleic acids, proteins, lipids, or DNA and can promote and initiate degenerative diseases. Antioxidant compounds like phenolic acids, polyphenols and flavonoids scavengefree radicals including peroxide, hydroperoxide or lipid peroxyl , inhibiting the oxidative mechanisms that could lead to degenerative diseases (Henning et al., 2004). Green and black tea polyphenols have been extensively studied as anti-cancer compounds. In vitro experiments have supported their significant antioxidant activity. The effect of black tea consumption, with and without milk, on the plasma antioxidant activity in humans produces a significant increase in plasma antioxidant activity reaching maximal levels at about 60 min (Henning et al., 2004). Adding milk to black tea did not have a differential effect on the increases in plasma antioxidant activity (Leenen et al., 2000).

Experimental studies have determined that the presence of polyphenols in black tea have a strong antioxidant potential in vitro and in vivo. Ryan and Sutherland (2011) analyzed and compare the total antioxidant capacity (TAC) of five brands of tea, they found that each of the teas was a significant source of antioxidants (7796–10,434 μmol/l FRAP). In this case the addition of milk lowered the TAC of each of the teas. When compared to tea with semi-skimmed bovine milk, each of the five teas presented either significantly higher antioxidant values or no change was observed after the addition of soya milk. The addition of soya milk to black tea may be a useful alternative to semi-skimmed bovine milk if the purpose is to maintain the overall antioxidant potential of the tea.

Luczaj and Skrzydlewska (2004) investigated the effect of black tea on antioxidant effects on the liver,

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blood serum, and brain of 12-months old rats which were subject to sub-chronical intoxication with ethanol during 28 days. Administration of black tea alone caused an increase in the activity and concentration of antioxidant factors, which was more extensively observed in the liver and serum compared to the brain. Black tea prevented considerably antioxidant parameters against changes caused by ethanol. These results indicate beneficial antioxidant effect of black tea regarding all examined organs, especially the liver.

Antioxidative activities of volatile extracts from six teas (one green tea, one Oolong tea, one roasted green tea, and three black teas) were studied by using an aldehyde/carboxylic acid assay and a conjugated diene assay. All extracts except roasted green tea exhibited dose-dependent inhibitory activity in the aldehyde/ carboxylic acid assay (Yanagimoto et al., 2003).

Dietary phenols are antioxidants, and their consumption could be an important factor in the prevention of cardiovascular diseases. Coffee and tea are some of the major sources of phenols in human diets. Olthop et al. (2003) identified and quantified a several potential phenolic acid metabolites in the urine of humans after the ingestion of ichlorogenic acid, tea phenols and quercetin-3-rutinoside. The in vivo antioxidant activity of dietary phenols might thus be lower than is expected because of their observed in vitro antioxidant activity.

the possible benefits of L-theanine in teas has raised some recent interest , thus bringing the issue that there are few data available on amounts of L-theanine contained in cups of commercially available teas. Brewing time was found to be a playing a mayor roll in the amount of L-theanine extracted, the addition of small amounts of milk and sugar was observed to have no significant effect. High levels of milk resulted in a decrease of the level of detectable L-theanine. A standard (200 ml) cup of black tea was found to contain the most L-theanine (24.2±5.7 mg) compared to a cup of green tea containing the least amounts (7.9±3.8 mg) (Keenan et al., 2011), this results contradicted previous studies . A study conducted by Ravichandran (2004) determined that the quality of black tea improves with time from pruning, and pruning itself leads to adverse effects on tea quality

because polyphenols were found to increase in first year and thereafter declined in content with time for pruning. Cherubini et al (1999) suggested that despite the antioxidant efficacy in vitro, black tea does not protect plasma from lipid peroxidation in vivo. The strong contradiction between the in vitro and ex vivo data could be most likely explained by the insufficient bioavailability of tea polyphenols in humans.

Princen et al. (1998) reports no effect of consumption of green and black tea on plasma lipid and antioxidant levels and on LDL oxidation in smokers. Healthy male and female smokers consumed 6 cups (900 mL) of black or green tea or water per day during a 4-week period, or they received as a supplement 3.6 grams of green tea polyphenols per day (which is the equivalent to consume 18 cups of green tea per day). Consumption of black or green tea showed no effect on plasma cholesterol and triglycerides, HDL and LDL cholesterol, plasma vitamins C and E, β-carotene, and uric acid. The antiradical activity of plant extracts is dependent on mechanisms of oxidative activity of free radicals used and the chemical structure of contained antioxidants (Gramza et al., 2005). Antioxidative properties of black tea are expressed by its ability to inhibit free radical generation, scavenge free radicals, and chelate transition metal ions. Black tea, as well as individual theaflavins, can have an effect on the activation of transcription factors such as NFκB or AP-1 (Luczaj and Skrzydlewska 2005). Green tea and black tea scavenge NO• and peroxynitrite, they inhibit the excessive production of NO• by the inducible form of nitric oxide synthase (iNOS), and suppress the LPS-mediated induction of iNOS. The high activity found in the polyphenol fraction of black tea (BTP) could not be explained however by the mixed theaflavin fraction (MTF) or catechins [epicatechin, epigallocatechin, epicatechin gallate, epigallocatechin gallate (EGCG)), which were tested separately (Paquay et al., 2000).

5.2 Reduces oxidative damage: Damage caused by free radicals to a cell through the oxidative process is called oxidative stress. The components present in natural extracts such as of black tea can be very effective in possible reduction of damage and in overcoming oxidant injury caused by exposure to agents like pesticides. Treatment with a black tea extract protects the liver tissue significantly

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from the oxidative damage and shifts the trend towards replenishment of the antioxidant status (Khan et al., 2005). Regular daily black tea consumption for one month has been shown to improve platelet function and to decrease thromboxane and 8-epi- PGF2α to a varying extent indicating a reduced in vivo oxidation injury. Black tea is a beverage widely accepted in different cultures around the globe, affordable price, with no toxicity or side effects ever been reported, not even with high intake (Wolfram et al., 2002).

Black tea extract has reported to be an efficient scavenger against several reactive oxygen compounds and can protect effectively against oxidative damage to human red blood cells caused by lipid peroxidation, cytoskeletal protein degradation, and general disruption of membrane structure. Other unidentified constituents of black tea might play an important role in his beneficial attributes (Halder and Bhaduri, 1998).

5.3 Anticancer properties: Uncontrollable cell division and growth are key characteristics of cancer, this leading to the formation tumors, and posterior invasion of nearby body parts. There are various forms of cancers viz. skin, lung, esophagus, stomach, liver, small intestine, pancreas, colon, bladder, prostate and mammary glands (Kiehne and Engelhardt, 1993; Yang and Wang, 1993; Katiyar and Mukhtar, 1996; Yang et al., 2000). Plant antioxidants, especially those found in tea, red wine and cocoa, have been reported to prevent and control cancer development. In types of cancer different than colorectal, the number of studies including data on black tea are very limited, and often, conflicting, making difficult to draw conclusions until further human studies are conducted (Lin and Liang 2000). It has been suggested that black tea is not as effective in its chemopreventive properties as green tea. Other studies have shown that black tea polyphenols–– theaflavins––exhibit stronger anticarcinogenic activity than EGCG. It is little known about the molecular mechanisms of cancer chemopreventive effects of tea polyphenols. Shukla and Taneja (2002) evaluated the anticarcinogenic activity of black tea using lung tumorigenesis model in Swiss albino mice. Diethylnitrosoamine (DEN), a known inducer of pulmonary tumours was given at the multiple [total eight] doses of 20 mg/kg body weight through oral

intubation in Swiss albino mice. Simultaneously, three different groups of animals received 1, 2 and 4% aqueous black tea extracts (ATE) as a unique source of drinking solution. The positive control group received DEN treatment only. In the positive DEN treated group, higher incidences of pulmonary tumours were observed, while in ATE treated groups, a lower incidence of DEN induced lung tumorigenicity was recorded. The histological examination revealed a significant decrease in pulmonary adenomas at all doses of ATE.

Epidemiological studies and experiments in carcinogen-induced rodent models of mammary cancer have suggested that tea consumption is correlated with a reduced risk of mammary cancer. Kaur et al (2007) evaluated the hypothesis that green tea catechins (GTC) or theaflavins from black tea (BTT) interfere with mammary carcinogenesis in C3(1) SV40 Tt antigen transgenic multiple mammary adenocarcinoma (TAg) mice, as well as GTC/BTT effect on tumour survival or oxidation status. TAg mice received GTC/BTT (0.05%) in drinking water for their lifetime and survived longer with smaller tumours as compared to control mice. The results observed, make the exploration of the breast cancer chemopreventive properties of tea preparations in humans worthwhile. The results of a meta-analysis by Sun et al (2006) indicated a lower risk for breast cancer associated with green tea consumption. Lambert and Yang (2003) discussed the cancer chemopreventive activity of tea and the tea polyphenols and the possible mechanisms for anticancer activity.

The theaflavin compound observed in blak tea has been reported as an excellent chemopreventor against reactive oxygen and nitrogen species (Sarkar and Bhaduri, 2001). Luceri et al (2002) reported that in red wine and black tea, polyphenols modulate COX-2, iNOS and glutathione-related gene expression in tumours, suggesting a potential hemotherapeutic effect. According to Eroğlu (2011) tea polyphenols protect cells from genotoxic or carcinogenic agents, which indicated the therapeutic and antioxidative role of catechins, flavonoids or other tea compounds. Caderni et al (2000) reported that black tea and wine extracts, could protect against AOM-induced colon carcinogenesis this most likely through an increased

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apoptosis in tumours.

Black tea consumption has been correlated with a linear decline in ovarian cancer risk, with individuals consuming two or more cups daily experiencing a 30% decline in risk (Baker et al., 2007). Some studies suggestd that tea polyphenols inhibited AP-1 activity and the mitogen-activated protein kinase pathway, which contributed to the growth inhibition, however, different mechanisms, may be involved in the inhibition by catechins and theaflavins (Chung et al., 1999). Nomura et al. (2000) studied the effects of theaflavins on ultraviolet (UV) B radiation–induced activator protein-1 [AP-1] –dependent transcriptional activation and compared them with EGCG, this late known as a major green tea polyphenol with chemopreventive effects. Theaflavins and EGCG inhibited UVB-induced AP-1 activation in a concentration-dependent process. The inhibitory effects of theaflavins were observed to be stronger when compared to EGCG. Oral administration of green tea or black tea (dose 6 mg tea solids/ml) to UVB-pretreated high-risk SKH-1 mice for 23 weeks after stopping UVB treatment, caused a decrease in the number of tumours/mouse, also decreasing the size of the parametrial fat pads, decreased in the thickness of the dermal fat layer away from tumours and directly under tumours was also reported (Lu et al., 2001).

Combined chemoprevention using tea polyphenols has received recent consideration. Mohan et al (2006) evaluated the antiproliferative and apoptosis inducing effects of bovine lactoferrin (BLF) and black tea polyphenols (Polyphenon-B: P-B) combination of 7,12-dimethylbenz [a] anthracene (DMBA) -induced hamster buccal pouch (HBP) carcinogenesis. The findings suggested that a “designer item” approach would be useful for human oral cancer prevention strategies. Unlike many other anti-cancer agents, black tea is observed to have not only a immunosuppressive effect, but also acts as an immune-restorer in tumour-bearing host. These results, thus, raise the possibility of inclusion of black tea in successful therapeutic regimen against cancer (Bhattacharyya et al., 2004). Tea consumption can reduce the incidence of skin cancer in hairless mice, also black tea may provide more protection against simulated solar irradiation compared to green tea, these findings in

agreement with earlier reports (Record as and Dreosti, 1998). Research has suggest that not only the green tea polyphenol, EGCG, but also the black tea polyphenol, TF-3, have an negative effect on the growth of tumour cells, and the mechanisms of antiproliferation could block the growth factor binding to its receptor thus suppressing the mitogenic signal transduction (Liang et al., 1999). Previous research has reported the Antimutagenic and anticancer effects of black tea polyphenols theaflavins (TF) and thearubigins (TR). In one study, Bhattacharyya et al. (2011) fractioned TR to three fractions namely TR-1, TR-2, and TR-3, by chromatography processes and studied antimutagenic and anticancer activities on 4 Salmonella strains by Ames assay and on human leukemic cells U937 respectively. They suggested that TR-2 is the most active component of TR.

5.4 Prevents cellular DNA damage: Tea polyphenols have been demonstrated as chemopreventive agents in a number of experimental models. However, lesser has been documented about the mechanism of chemoprevention by black tea compared with that of green tea. Feng et al. (2002) investigated some beneficial properties of theaflavins, the black tea polyphenols. They reported that theaflavins exhibited suppression of cytochrome P450 1A1 induced by omeprazole in the human hepatoma HepG2 cell line. Also when HepG2 cells were pretreated with omeprazole to induce CYP1A1, and then exposed to benzo (a) pyrene (B (a) P), DNA damage was observed using the comet assay, however, theaflavins could inhibit the damage to DNA, this indicating that theaflavins could prevent cellular DNA damage by inhibiting oxidative stress and suppressing cytochrome P450 1A1 in cell cultures.

6 Miscellaneous Health Benefits Coronary heart disease (CHD) and cardiovascular disease (CVD): It refers to any disease that affects the cardiovascular system and those related to atherosclerosis and/or hypertension. Black tea consumption has been correlated with a lower incidence of heart disease and cardiac death, and a reduction in risk factors. It has been hypothesized that manganese in black tea could impact positively on heart disease risk, via the role of manganese superoxide dismutase in supporting cardiac muscle function and diminishing lipid

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peroxidation. One study was conducted to determine the relationship between dietary Mn intake, circulating Mn levels and leucocyte expression of two Mn-dependent enzymes in tea drinkers and non-tea drinkers (Hope et al., 2006). However, Dietary Mn intake has slight influence on markers of Mn status or expression of Mn-dependent enzymes. The Boston Area Health Study reported in a study that subjects who drank one (200~250 mL) or more cups of black tea per day had approximately half the risk of a heart attack compared with those who did not drink tea at all (Sesso et al., 1999). The antioxidant properties of tea polyphenols may have a beneficial effect on endothelial function thus reducing the risk of coronary events (Hodgson et al., 2002). It has been suggested that one mechanism for the protective properties of tea polyphenols in vascular diseases, is the one involving the inhibition of the oxidation of LDL, known to be related with the development of atherosclerosis One of the proposed mechanisms for the possible protective effect of tea (Wiseman et al., 1997). The effect of black tea on soluble P-selectin might provide a potential mechanism for the cardiovascular benefits of regular ingestion of tea as reported by Hodgson et al. (2001). The chronic dietary flavonoid status appears to relate to endothelial function, possibly suggesting that other flavonoids or polyphenolic components of tea favourably influence vascular health and risk for cardiovascular disease (Widlansky et al., 2005). Several studies have reported black tea consumption cause a significant reduction of oxidative stress in vivo. Inclusion of tea in a diet moderately low in fat can lower LDL cholesterol significantly, reducing the risk of coronary heart disease (Davies et al., 2003). Short- and long-term black tea consumption caused a reversion on endothelial vasomotor dysfunction in patients diagnosed with coronary artery disease. The results explained the association between tea intakes and decreased cardiovascular disease events (Duffy et al., 2001). Ruxton and Mason (2012) suggested an association between regular black tea consumption and a reduced risk of coronary heart disease at around three or more cups per day.

Antiulcer effect: An ulcer is a breakdown in a bodily membrane that cause the organ of which that membrane is a part of continuing its functions in a normal fashion Tea has

provided new hope in the treatment of peptic ulcer and gastric malign conditions (Chatterjee et al 2012). A study in albino rats conducted by Maity et al. (1995) indicated that the hot water extract of Indian black tea possess anti-ulcer activity. The polyphenols present in black tea might be responsible for this activity. The extracts also altered favorably the changes in acid and peptic activity of gastric secretion induced by various ulcerogens, aspirin, indomethacin, ethanol, reserpine and CRS (cold restraint stress). The observation also suggested that this anti-ulcer activity is possibly mediated through prostaglandins.

Antimutagenic activity: Antimutagen is applied to refers to any compound that reduces the rate of spontaneous mutations, counteracts, or reverses the action of a mutagen. Studies have proved the availability for absorption of potential antimutagenic compounds present in tea and on the influence of a food matrix on this activity. Between 60 and 180 minute after the tea was introduced into the model, antimutagenic activity was recovered from the jejune compartment by means of dialysis (Krul et al., 2001). Gupta et al. (2002) tested and updated the comparative antimutagenic and anticlastogenic effects of green tea, black tea and their polyphenols in different test systems. Previous studies have suggested that the protective effect of black tea is comparable to green tea, however, more studies need to e conducted to draw any conclusion. Steele et al (2000) reported a strong evidence of antimutagenic properties of black tea. Pan et al (2000) stated that TF-3 might exert its anti-inflammatory and cancer chemopreventive actions by suppressing the activation of NFκB through inhibition of IKK activity.

Antiinflammatory effect: Anti-inflammatory refers to the property of a substance or treatment that reduces inflammation. Inflammation is defined as the response by the body to remove the injurious stimuli and to initiate the healing process. Without inflammation, wounds and infections would never heal. Black tea has anti-inflammatory effects, which has been advocated to protect against CVD (Steptoe et al., 2007). In a study by Nag Chaudhuri et al. (2005) the anti-inflammatory and other related pharmacological properties of the hot water extract of black tea (Camellia sinensis, Sikkim variety) were tested along with some standard drugs

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such as nimesulide and aspirin. Black tea extract showed significant inhibition against glucose oxidase-mediated inflammation. These findings suggest the efficacy of this particular variety of black tea, both in the exudative and proliferative forms and as well in the chronic phase of inflammation.

Enhances insulin activity: Insulin is a hormone, produced by pancreas, playing vital role in regulating carbohydrate and fat metabolism in the body. Insulin causes cells in the liver, muscle, and fat tissue to take glucose from the blood, storing it as glycogen in the liver and muscle. Tea has been shown to increase insulin activity>15-fold in vitro in an epididymal fat cell assay. Black, green, and Oolong teas, but not herbal teas, were all observed to cause an increased insulin activity. For black tea, the insulin-potentiating property was observed in several regions of the chromatogram corresponding to, in addition to epigallocatechin gallate, tannins, theaflavins, and other undefined compounds (Anderson and Polansky, 2002). MacKenzie et al (2007) evaluated the efficacy of an extract of green and black tea to improve glucose control over a 3-month period. A double blind, placebo-controlled, randomized multiple-dose [0, 375, or 750 mg per day for 3 months] study in adults with type 2 diabetes mellitus not taking insulin was performed. The primary end point was change in glycosylated haemoglobin at 3 months. The 49 subjects who completed this study were predominantly white with an average age of 65 years and a mean duration of diabetes of 6 years, and 80% of them reported using hypoglycemic medication. After 3 months, the mean changes in glycosylated haemoglobin were +0.4 (95% confidence interval, 0.2-0.6), +0.3 (0.1-0.5), and +0.5 (0.1-0.9) in the placebo, 375-mg, and 750-mg arms, respectively. Gomes et al. (1995) reported that, like green tea, black tea also possesses antidiabetic activity.

Body mass index and body weight alterations: Obesity is one of the most important risk factors accounting for overall mortality in many countries, particularly, Japan. The likelihood of developing conditions, such as type 2 diabetes (Field et al., 2001), heart disease (Kenchaiah et al., 2002; National Task Force on the Prevention and Treatment of Obesity 2000), cancer (Key et al., 2002), and osteoarthritis (Gary et al., 2006) of the weight-bearing joints,

increases with body weight gain and has resulted in substantial health care costs (WHO 1998) and economic losses. A randomized, double-blind, placebo-controlled study suggests the reducing effects of BTE on mean BMI and body weight values in pre-obese or overweight Japanese subjects from 8 to 12 weeks after intake and 4 weeks after termination. Not only that, but, BTE reduced BMI and body weight after 12-week ingestion without any secondary effects (Kubota et al., 2011).

Cognitive performance: Black tea ingestion has been observed to cause an increase in the alertness and improvements in mood (Quinlan et al., 2000). The capacity to process information was also increased, while adverse effects of sleep duration or quality were not evident. A study in rats found that theanine modulated serotonin and dopamine levels and appeared to improve memory and learning ability (Unno et al., 1999). Work on humans is needed to confirm this finding. Bruin et al (2011) conducted a research on whether black tea causes an improvement in attention and self-reported alertness in two double blind, randomised, placebo-controlled, crossover studies. Participants received commercially available black tea in one condition and placebo tea (hot water with food colours and flavours) similar in taste and appearance to real tea in the other condition. Attention was measured objectively by attention tests (the switch task and the intercessory-attention test) and subjectively with a self-report questionnaire (Bond–Lader visual analogue scales). Black tea significantly improved accuracy on the switch task (study 1 p<.002, study 2 p=.007) and self-reported alertness on the Bond–Lader questionnaire (study 1 p<.001, study 2 p=.021). The first study also proved d better auditory (p<.001) and visual (p=.030) intersensory attention after black tea compared to placebo. Trivedi et al (2012) found positive effects of black tea extract on several neuropathological changes caused by NaF in different parts of the brain of male mice. Song et al (2012) stated that tea drinking has been observed to have beneficial effect on cognitive function in elderly persons.

Antimicrobial properties: An antimicrobial is a substance or compound with properties that kill or inhibit the growth of

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microorganisms such as bacteria, fungi, or protozoans. Tea leaves produce organic compounds that may be actively involved in the defense of the plants against invasion of pathogens including insects, bacteria, fungi, and viruses. Funmilayo et al (2012) reported on antimicrobial properties of black tea (Lipton brand) on Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Bacillus subtilis

Attenuates blood pressure: Blood pressure is the force of blood pushing against the artery walls as the heart pumps blood. If this pressure rises and stays high over time, it can damage the body in many ways causing coronary heart disease, heart failure, stroke, kidney failure, and other health problems. Epidemiological studies have shown that tea consumption slightly reduces blood pressure. Negishi et al (2004) conducted two studies to test whether black and green tea can lower blood pressure in stroke-prone spontaneously hypertensive rats. The results shown that both black and green tea polyphenols attenuate blood pressure increases through their antioxidant properties in stroke-prone spontaneously hypertensive rats because of decreased MLC phosphorylation related to NO bioavailability and an increase in catalase, a scavenger of H2O2 in rat aorta. But according to Hodgson et al (1999) tea ingestion caused larger acute increases in blood pressure than caffeine alone. However, any acute effects of tea on blood pressure did not translate into significant alterations in ambulatory blood pressure during regular tea consumption.

Reduces atherosclerosis: Atherosclerosis (also known as arteriosclerotic vascular disease) is a condition in which an artery wall thickens due to the accumulation of fatty compounds such as cholesterol. Most scientists as well as tea consumers believe that green tea is healthier than black tea because of the low incidence of heart disease and cancer in Asia. Vinson et al. (2004) reported on a first dose response comparison of a green and black tea on normal hamsters after long-term supplementation and on a hamster model of atherosclerosis. The teas were equally effective in inhibiting atherosclerosis with the lower dose decreasing it 26−46 percentage and the high dose decreasing it 48−63 percentage. Atherosclerosis was apparently inhibited by three mechanisms:  hypolipemic, antioxidant, and antifibrinolytic.

Black tea inhibited the proliferation of smooth muscle cells involved in the development and progression of atherosclerosis, and suppressed the production of oxidized low-density lipoprotein. This strongly suggesting that black tea has an antiatherosclerotic action (Yokozawa et al., 1999).

Treats asthma: Asthma is a condition that causes the airways of the lungs to swell and narrow, leading to wheezing, shortness of breath, chest tightness, and coughing. Little information is available on the use of alternative therapies in adult asthma and their impact on human health, Blanc et al (1997) conducted an experiment to evaluate the prevalence and mortality of asthma self-treatment with herbs, coffee or black tea with encouraging results. They reported that even among adults with access to special care for asthma, self-treatment with nonprescription products was common and was associated with increased risk of reported hospitalization.

Retards cataract: As we age, proteins in the eye lens begin to break down and the lens becomes cloudy, and blurry. This condition is known as a cataract. Aqueous extracts of green and black tea are shown to quench reactive oxygen species such as singlet oxygen, superoxide and hydroxyl radicals, preventing the oxidative cross-linking of test proteins and inhibit single strand breakage of DNA in whole cells. They are also seen to be able to counteract the oxidative insult mounted by cigarette smoke. In rats in which cataract was induced by subcutaneous injection of selenite, administration of green or black tea extracts slowed down the progression of lens opacity, suggesting the potential cataracto-static ability of tea (Thiagarajan et al., 2001).

Maintains fluid balance: Fluid balance is critical for physical and mental performance (Gardner et al., 2006). In human homeostasis, the amount of fluid lost from the body is equal to the amount of fluid taken in. The National Drinks Survey (2003) suggests that tea contributes significantly to fluid intakes, particularly in those aged 65 years and over where the tea consumption represents 85% of all beverages taken.

Maintains bone health: studies have shown that black tea consumption had a

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moderately positive effect on bone mineral density (BMD), this been particular observed in older women. BMD increased significantly with higher levels of tea consumption (four or more cups per day) (Chen et al., 2003). Black tea was also suggested to be independent protective factor in the risk of hip fractures in men in the Mediterranean Osteoporosis Study (Johnell et al., 1995; Kanis et al., 1999; Hegarty et al., 2001).

Maintains dental health: Dental caries involves the fermentation of carbohydrates by plaque bacteria. This process causing demineralization of tooth enamel over time (Kandelman, 1997). Fluoride–both systemic and topical–attenuates the risk of demineralisation. A systematic review has suggested that fluoride from tea may benefit dental health (NHS CRD, 2000). Zhang and Kashket (1998) suggested that brews of black tea suppress salivary amylase activity, which could reduce the cariogenic potential of starch that acts as a slow-release source of fermentable carbohydrate. Other studies have been reported that black tea caused a decrease in tooth surface pH, and suppressed the growth and virulence of periodontal pathogens in vitro (Simpson et al., 2001; Wei and Wu, 2001).

Inhibits HIV: Human immunodeficiency virus [HIV] is a member of the retrovirus family that causes acquired immunodeficiency syndrome (AIDS)in humans , a condition in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive. Research results indicated that tea, especially black tea, may be used as a source of anti-HIV agents and theaflavin derivatives may be applied as lead compounds for developing HIV-1 entry inhibitors targeting gp41 (Liu et al., 2005) and through the disruption of gp41 6-HB core structure (Yang et al., 2012).

Lowers stress hormone levels: Drinking black tea might cause a decrease of the hormone cortisol after a stressful episode occurs (Steptoe et al., 2007; http://www.ucl.ac.uk/media/ library/tea). A research study reports that individuals who had been drinking 4 cups of black tea daily for 6 weeks had a 20% greater decrease in cortisol compared to the placebo group, after being subjected to fifty minutes of challenging tasks. Blood platelet activation,

a process linked to blood clotting and the risk of heart attacks were also lower in tea drinkers.

Anti-venom effects: Antivenin activity of melanin extracted from black tea (MEBT) was reported for the first time in 2004 (Hung et al., 2004). The antivenin activity of MEBT is due to chelating of Ca++ and non-specific binding of phospholipase A2. The inhibitory effect of MEBT on phospholipase A2 determined for different venoms was similar to that obtained with pure enzyme. The low toxicity of MEBT combined with its antagonistic activity against different venom toxins could provide with a effective life-saving treatment against snake-bites. Such application of MEBT is important when identification of the snake is difficult or if specific treatment is not available

Effects on human oxidative energy metabolism and/or biosynthetic pathways: Dorsten et al (2006) compared the effects of black and green tea consumption on human metabolism. Their results show that NMR-based metabonomics analysis can differentiate between the metabolic effects of green tea, black tea, and a caffeine control. Furthermore, metabonomics analysis data reveal that tea intake might have an effect on human oxidative energy metabolism and biosynthetic pathways.

7 Conclusions The rapid progress of physiological and biochemical research coupled with the emerging health consciousness acts as a driving force towards designing newer drugs, exploring the potential of plant based bioactives and gaining lesser reliance to the chemicals by the researchers as well as the end users at their own levels. An insight on the history of tea usage is sufficient to help us believe that the use of black tea is older than that of its green counterpart. Alongside the sudden increasing trend and focus in green tea and other herbals, black tea research has also found its own steady course in gaining recognition of its users needing only to be time tested and revisited in areas of its enormous potential. The impacts of black tea on several biosynthetic pathways in human beings and different other animals along with its possible effects on their cognitive performance are encouraged. Still, it is too early to conclude straightway by mere analysing several research

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findings. As human body and mind too, is enormously complex, finding and perceiving all possible impacts are far more complicated. It is to be tested, verified, and critically reviewed for reaffirmation. Sometimes the evidences are insufficient, sometimes they are complicated with associated negative impacts, and sometimes it is too early to make any hasty comment. However, an organized effort to collect, collate, analyse, scan and derive a meaningful conclusion is necessary as a logical step towards reaching a positive direction. It is believed that more concerted and proactive research in this novel direction will create an insight to pave the way for revealing several vistas of black tea magic.

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Black tea magic: Overview of global research on human health and therapeutic potentialities

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