**4. Analysis of polyphenols in tea**

The high level of interest in green tea composition has been linked to antioxidant activity and, as a result, elevated phenolic content. Recently, a wide range of compounds

**Figure 4.**

*Chemical structures of the green tea polyphenols (*−*) -epicatechin (EC), (+) catechin (CT), (*−*) -epigallocatechin (EGC), (*−*) -epicatechin gallate (ECG), and (*−*) epigallocatechin gallate (EGCG) [51].*

have been identified, and several methods for identifying and quantifying these compounds have been developed. Some phenolic compound properties have been considered for identifying each class of phenolic compounds in several matrices. Because degradation of important phenolic compounds in green tea can reach 70% at temperatures lower than those used in gas chromatography, thermal sensitivity necessitates the use of liquid chromatography rather than gas chromatography [43]. The double bonds in the aromatic ring of phenolic allow for UV–visible spectrophotometric measurements. The maximum absorption evaluation indicates, at the very least, the subclass (e.g., flavanol, flavonol, and flavones) or supports the identification with a standard.

The distinct fragmentation pattern of each phenolic compound enables identification in mass analyzers or provisional identification for compounds lacking a standard, even for complex and high molecular weight compounds (**Figures 1**, **3** and **4** depicts the phenolic structures present in different teas) [31, 44]. Given the aforementioned characteristics, liquid chromatography separation followed by spectrophotometry and/or mass spectrometry analysis can provide valuable information for the investigation of the phenolic profile in tea extracts. Other analyses were also carried out using nuclear magnetic resonance (NMR) to provide solid information on the phenolic profile of tea [44].

### **5. Health beneficial effects of tea**

Epidemiological studies on the benefits of green tea consumption against major diseases, supported by *in vitro* and *in vivo* experiments have revealed promising protective effects. Catechins, the major phenolic constituents of green tea, are also the compounds linked to health benefits through modulation of relevant mechanisms altered by important diseases, as discussed in this section. Tea is high in antioxidants.

*Phenolic Compounds in Tea: Phytochemical, Biological, and Therapeutic Applications DOI: http://dx.doi.org/10.5772/intechopen.98715*

Caffeine content of tea is lower than that of coffee. Tea may lower your chances of having a heart attack or having a stroke. It may aid in weight loss and beneficial to your bones. Tea may help you keep your grin bright. It helps to enhance the immune system and aid in the fight against cancer. Herbal tea may be beneficial to the digestive system. The benefits of tea are depicted in **Figure 5** and explained in detail below.

#### **5.1 Antioxidant properties of tea polyphenols**

Antioxidant activity is defined as a molecule's or ion's ability to avoid oxidative reactions with other molecules. Phenolic compounds found in green tea leaves have antioxidant potential through a variety of mechanisms, providing additional protection against oxidants as well as additional protection against oxidative reactions and reactive species [44]. The oxidative series of events proposed by Miguel et al. [39] provides an overview of the major antioxidant effects (preventive and primary antioxidants), which may also be presented by polyphenol-rich green tea extracts. Preventive antioxidants can protect against oxidative reactions by lowering local oxygen concentrations, preventing the initiation of chain reactions by scavenging radicals (e.g., HO•, O2•-), preventing radical generation, and breaking down lipid peroxides to peroxyl and alkoxyl radicals.

Primary antioxidants play a role in subsequent events by causing peroxides to decompose into nonradical products and inhibiting hydrogen removal from oxidable by intermediate radicals such as peroxyl and alkoxyl radicals. These radicals are reactive oxygen species that cause oxidative damage to biological and food systems. The major effects are related to lipid and protein oxidation, membrane damage, mutagenesis, and carcinogenesis, and it is critical to assess how natural extracts impact and mitigate these effects.

Many studies have found a strong and positive correlation (*p*> 0.05) between the phenolic compounds and their antioxidant potential in several plant species [52, 53]. This

**Figure 5.** *Health benefits of tea.*

antioxidant mechanism found in plants plays an important role in reducing lipid oxidation in (plant and animal) tissues, because when it is included in the human diet, it not only preserves the food's quality, but it also lowers the risk of developing certain diseases.

The correlation between phenolic content and antioxidant activity as measured by multiple methods is an important finding in studies on phenolic compounds in green tea extracts. Green tea's structural differences among phenolic compounds also play an important role in antioxidant activity. Individual flavanol content of green tea was found to be inversely related to radical content of green tea leaves in a study conducted by Socha et al. [54]. The correlation coefficient for epigallocatechin gallate was higher than that of the other tested flavanols. This result was linked to the presence of hydroxyl groups in the aromatic rings of gallyl and galloyl substituents, because flavanols lacking this substituent had lower antioxidant activity.

Induction of antioxidant enzymes by EGCG with detailed molecular mechanism have been studied [9]. EGCG has been studied for antiradical activity which was proved to have stronger activity than the antioxidants such as vitamin E and vitamin C [55]. By binding to different molecules, catechins in particular EGCG modulate the compounds' activity and inturn regulates the cell-signalling pathway [56].

#### **5.2 Cardiovascular disease**

Cardiovascular diseases are one of the leading causes of death, accounting for nearly one-third of all deaths globally. Sano et al. [57] investigated the relationship between green tea consumption and the incidence of cardiovascular disease and discovered that patients without cardiovascular disease consumed more green tea than those with cardiovascular disease (5.9 and 3.5 cups, respectively). Green tea consumption was linked to a lower risk of coronary artery disease in Chinese patients, according to Wang et al. [58]. In this study, the risk was found to be inversely related to green tea consumption, with a dose-dependent effect as the frequency, period, and amount of green tea consumed increased. Fung et al. [59] reported that chronic green tea consumption results in a different pattern of behaviour. Plasma levels of selected catechin derivatives were measured after 1 and 2 hours of green tea consumption, as well as after 7 days of daily consumption. After 1 hour of tea consumption, the plasma level of epigallocatechin gallate was the highest among the catechin derivatives tested, followed by epigallocatechin and epicatechin gallate, which remained elevated even after 2 hours of green tea consumption. An unexpected result was observed in the chronic consumption evaluation because only epicatechin gallate had a higher level in plasma.

The effectiveness of tea polyphenols against CVD by regulating lipid metabolism, cell proliferation, platelet aggregation and antithrombotic activity has been studied by reduction of total cholesterol, LDL and triglycerides which are helpful in development of atherosclerosis [60]. The study on EGCG has been shown effective in reduction of lipid metabolising enzyme activities in the serum and cardiac tissue thereby resulting into less lipidemic pathologies [61]. In an in vivo study on mice, 40 mg/kg/ day of EGCG was administered which resulted in decrease of LDL and the size of atherosclerotic plaques in the aortas, and increase in HDL [62].

#### **5.3 Anti-cancer properties**

Increased levels of reactive oxygen species (ROS) and oxidative stress modulation have an important role in the activation of carcinogenesis, and polyphenols act against these mechanisms by preventing or controlling the tumorigenesis [63]. Tea polyphenols

#### *Phenolic Compounds in Tea: Phytochemical, Biological, and Therapeutic Applications DOI: http://dx.doi.org/10.5772/intechopen.98715*

have been effective in inhibiting enzymes related to cell proliferation and tumour progression [34]. Theaflavins in tea can act as anti-cancerous compounds by controlling the DNA damage which is the main cause of induction of cancer. They act by scavenging the free radicals which inhibits the mutagenicity and cleavage of single strand DNA [41].

Suppression of elevated cytochrome P450 1A1 (CYP1A1) in cells is inhibited by theaflavins which inturn prevents the cellular DNA damage, carcinogen related DNA damage and oxidative stress induced cytotoxicity [59]. EGCG has been investigated for proliferation of epidermal cell line A431 in humans. *In vitro* inhibition of protein tyrosine kinase activities of EGF-R, PDGF-R and FGF-R are strongly inhibited the DNA synthesis of A431 cells [64]. Tea polyphenols have been shown inhibition for PKC, MAPK, and AP-1 activities in NIH 3 T3 cells [65]. In mouse epidermal JB6 C1 41 cells inhibition of UVB-induced phosphatidylinositol-3-kinase (PI3K) activation was studied for tea polyphenols [66]. Some tea catechins of green and black tea have been potent inhibitor of Bcl-2 antiapoptotic family proteins, which shows a strong link of tea polyphenols and their anticancerous properties [34].

Given the growing interest in the relationship between dietary flavonoids and cancer initiation and progression, this important field is likely to see increased effort and attract and stimulate additional vigorous research [67]. In liver carcinoma cells, effect of tea catechins have studied and showed that due to the activity of EGCG, H2P2 mediated cytotoxicity was supressed with increase in cellular glutathione levels [63]. The effect of catechin, epicatechin, ECG, EGC and EGCG in A549 cells have been studied for apoptosis and cell profileration [68]. Tea polyphenols have been shown for inhibition activity for the enzymes involved in oestrogen biosynthesis, which might play role in the development of breast cancer [69].

#### **5.4 Obesity and lipogenesis**

Tea catechins have been proved to be very effective for obesity by the acting on the adipose tissue. These tea catechins have been effective for suppression of enzymes involved in fatty acid, triacylglycerols and cholesterol metabolism [70]. Rocha et al. [71] showed in rat model study that daily consumption of green tea extract decreased adipose tissue, adiposity index, cholesterol, triacylglycerols and reduction in hypertrophy of adipocytes. Green tea catechins were showed for inhibition of enzymes metabolising noradrenaline, this mechanism have been effective in lipid metabolism [72]. A study conducted in the United States on men and women for consumption of black, oolong and green tea was showed inverse association for body mass index and metabolic syndrome markers [73].

#### **5.5 Other health beneficial effects**

Significant in vitro and animal model research support the beneficial effects of polyphenols in a variety of gastrointestinal diseases [74]. Recent human studies suggest that green tea may help to promote oral health as well as other physiological functions like anti-hypertensive effect, body weight control, anti-inflammatory, anti-antibacterial, and antiviral activity, solar ultraviolet protection, bone mineral density increase, anti-fibrotic properties, and neuroprotective power [20, 75]. Tea catechins have been studied for beneficial activity on bone, wherein the cell lines and animal model studies revealed that they are effective for osteoporosis [76]. Green tea catechins have been investigated as dietary polyphenols for their neurodegenerative diseases due to their anti-amyloidogenic properties [77]. Also EGCG has been studied for neuroprotective properties by evaluation of its brain accessibility [78]. Tea catechins also have been shown effective against hyperglycemia and its related type 2 diabetes mellitus complications [79]. Green tea consumption has increased bone formation and improved bone strength; however, it decreased the process for deterioration of bone microstructure which was studied in postmenopausal women [80].

Manach et al. [81] estimated the daily intake of catechin and proanthocyanidin dimers and trimers to be 18–50 mg/d. In Caco-2 cells, efflux transport was greatest in the following order: EC > EGC > ECG = EGCG [82]. Pgp, MRP1 and MRP2 efflux transporters have also been found to play roles in the absorption and excretion of green tea catechins [83]. Recent research has shown that green tea catechins undergo methylation, glucuronidation, and sulfation in in vitro, animal, and human systems [81, 83, 84].

### **6. Effect of tea phenolic on iron absorption**

Iron is stored in the body as ferritin and hemosiderin, which are found throughout the body, with a largest amount typically found in the liver, spleen, and bone marrow. Tea flavonoids are responsible for tea's inhibitory action on non-heme iron absorption [85]. Tea flavonoids are polyphenols with two aromatic rings and two or more hydroxyl groups as a functional group [86]. The development of a complex compound of tea flavonoids with iron is the process through which tea inhibits iron absorption. Iron is selectively bound by the galloyl group primarily present in these phenolic compounds [87]. Merhav et al. [88] revealed the iron status of Israeli infants in their investigation. They discovered an overall frequency of anaemia of 48.4% and a tenfold greater incidence of microcytic anaemia in tea-drinking neonates compared to the non-tea-drinking control group. Razagui et al. [89] investigated the iron status of 15 mentally challenged menstruation women, a population with limited food intake. They examined the link between tea drinking and iron status. It was discovered that participants with depleted iron levels consumed much more tea during meals (563 ml/meal/d) than ladies with adequate iron reserves (184 ml/meal/d). According to Zijp et al. [90], simultaneous consumption of tea reduces iron absorption from a test meal by 60 to 70 percent.

### **7. Application of tea phenolics in textile and allied sectors**

Polyphenols can be grafted onto fibres and fabrics using both enzyme-mediated and non-enzyme-mediated techniques, and their bioactivities vary depending on the type of phenolic compound used. In the development of environmentally friendly coloration and functionalization of textiles, polyphenol grafting onto textile fibres is a promising alternative to conventional synthetic dyestuffs [91]. Cheng et al. [92] reported in the literature on the use of tea as a natural dye and flame retardant finish on silk. They discovered that the oxidative polymerisation of polyphenols during alkaline extraction resulted in the formation of macromolecular polyphenols, which could give silk flame retardancy. Postmordanting with metal salts clearly improved the poor fastness characteristics. Because sufficient tea stem extract was used, dyed silk demonstrated good flame retardant, antibacterial, and antioxidant properties. According to Bonet-Aracil et al. [93], tea extracts behave differently depending on the type of tea used (green, red, or black). Green tea has the highest total antioxidant content when it comes to antioxidant effect. While dyeing, red tea had the highest colour strength value, whereas green tea had the lowest UPF value and red and black had higher values.

*Phenolic Compounds in Tea: Phytochemical, Biological, and Therapeutic Applications DOI: http://dx.doi.org/10.5772/intechopen.98715*
