**3. Nutritional value of green tea**

**2. Sources and compositions of green tea**

364 Pharmacology and Nutritional Intervention in the Treatment of Disease

oven (800 watt, 3 minutes) at a working temperature of 115 º

oven (800 watt, 3 minutes) at a working temperature of 115

attributed to the biological activities of the catechin species.

**Figure 1.** Chemical structures of catechins in green tea (Redrawn from [4])

hot water in a 3-minute brew (an approximate temperature of 80

**2. Sources and compositions of green tea** 

a 3-minute brew (an approximate temperature of 80 º

of the catechin species.

and disorders.

Tea has traditionally been cultivated across four continents in the manufacturing of a refresh‐ ing drink. The tea products that are available are directly related to the process used at the origin, and can be classified as black tea, green tea, yellow tea, red tea, green pressed tea, as well as instant tea and tea dyes [1]. Green tea is manufactured by using conventional and modified methods. One of these methods involves a 2-3-day process of to drying fresh tea leaves and then rolling the dry leaves with a commercial machine. Alternatively, another method involves the very rapid process of baking the tea leaves in a house-hold microwave

Tea has traditionally been cultivated across four continents in the manufacturing of a refreshing drink. The tea products that are available are directly related to the process used at the origin, and can be classified as black tea, green tea, yellow tea, red tea, green pressed tea, as well as instant tea and tea dyes [1]. Green tea is manufactured by using conventional and modified methods. One of these methods involves a 2 - 3-day process of to drying fresh tea leaves and then rolling the dry leaves with a commercial machine. Alternatively, another method involves the very rapid process of baking the tea leaves in a house-hold microwave

 **Pharmacology and Nutritional Intervention in the Treatment of Disease** 

pharmacological properties depending on several specific active phytochemical constituents; particularly catechins. Nowadays, crude extracts, purified catechin fractions and synthetic catechin derivatives of green tea are applicable in alternative and complementary medicines for the prevention, treatment and co-treatment of many diseases

persisting PPO enzyme and result in higher catechins content [2]. A typical green tea beverage is normally prepared at a proportion of 1 g dry weight of tea leaves in 100 ml of hot water in

mg tea solids, 30 – 42% catechins (74 mg) and 3–6% caffeine [3]. HPLC analysis shows the green tea extract (GTE) is comprised of at least six major catechins, including (-)-epicatechin (EC), (-)-epicatechin 3-gallate (ECG), (-)-epigallocatechin (EGC), (-)-epigallocatechin 3-gallate (EGCG), (+)-catechin (C) and (-)-gallocatechin (GC), of which EGCG is the major isomer followed by ECG, EGC and EC (Figure 1) [4]. Gallic acid (GA) is derivatized to one of the hydroxyl groups of the catechins, which has been directly attributed to the biological activities

persisting PPO enzyme and result in higher catechins content [2]. A typical green tea beverage is normally prepared at a proportion of 1 g dry weight of tea leaves in 100 ml of

contains 250 – 350 mg tea solids, 30 – 42% catechins (74 mg) and 3–6% caffeine [3]. HPLC analysis shows the green tea extract (GTE) is comprised of at least six major catechins, including (-)-epicatechin (EC), (-)-epicatechin 3-gallate (ECG), (-)-epigallocatechin (EGC), (-) epigallocatechin 3-gallate (EGCG), (+)-catechin (C) and (-)-gallocatechin (GC), of which EGCG is the major isomer followed by ECG, EGC and EC (**Figure 1**) [4]. Gallic acid (GA) is derivatized to one of the hydroxyl groups of the catechins, which has been directly

2

Moreover, tea products have different amounts and compositions of catechins, which is possibly due to biodiversity, different processing methods, different planting areas and different varieties of tea strains. For instance, Khokhar and colleagues reported that 1 g dry weight of tea product contained 48.4 mg total catechins (9.1 mg EGC, 7.9 mg EC, 22.9 mg EGCG, and 8.5 mg ECG) for Ceylon (NL) black tea; 5.6 mg total catechins (<0.5 mg EGC, 3.1 mg EC,

(-) EC (MW = 290) (-) ECG (MW = 442) (-) EGC (MW = 306)

(-) EGCG (MW = 458) (+) C (MW = 290) (-) GC (MW = 306)

C. This process will shock the

C). This brew usually

C. This process will shock the

C). This brew usually contains 250 – 350

In general, an antioxidant refers to any substance capable of preventing the oxidation catalyzed by reactive oxygen species (ROS)/reactive nitrogen species (RNS). Thus, an antioxidant that protects against iron toxicity is a substance that can: i) chelate iron and prevent the reaction with oxygen or peroxides; ii) chelate iron and maintain it in a redox state that makes iron unable to reduce molecular oxygen; iii) trap already formed radicals, which is a putative action of any substance that can scavenge free radicals in biological systems, regardless of whether they have originated from iron-dependent reactions or not. Not only can natural products chelate iron, but also synthetic compounds are capable of chelating iron *in vivo*, thereby limiting its participation in free radical reactions. Thus, iron chelators also serve as antioxidants by suppressing iron-mediated oxidation in biological systems. Surprisingly, thiol compounds (e.g. glutathione) that are synthesised by mammals can afford significant antioxidant protec‐ tion. This protection is related to the ability of glutathione to trap radicals, reduce peroxides, as well asits ability to work to maintain the redox state of the cells [12].

loaded mice (approximately 50% in WT, 30% in BKO and 40% in DH mice), whereas EGCG treatment caused significantly lower plasma MDA levels (approximately 30% in all the mice), suggesting that GTE and EGCG are strong antioxidants and exert potent anti-plasma lipid peroxidation. Consistently, the GTE and EGCG increased levels of reduced glutathione (GSH) in the plasma of all the mice despite under iron overload. Thus, it can be said that green tea catechins, particularly EGCG, chelate the redox irons and consequently inhibit the ironcatalyzed lipid peroxidation reactions in plasma lipids, as well as membrane phospholipids, resulting in an improvement of a powerful antioxidants as reduced glutathione is reduced in

**N diet Fe diet (0.2% ferrocene, w/w)**

WT (n = 24) -0.27±0.23 11.17±0.26\* 6.83±1.49† 6.80±1.75† 6.81±2.23† BKO (n = 16) 0.34±0.26 19.78±1.36\* 10.20±1.92† 10.66±1.60† 11.75±1.21† DH (n = 10) -0.07±0.11 13.41±1.84\* 7.74±1.38† 7.81±0.71† 7.83±1.41†

WT (n = 24) -2.49±1.00 1.19±0.42\* -2.26±1.98† -2.47±1.25† -2.01±2.76† BKO (n = 16) 0.87±0.22 2.30±1.08\* 0.30±2.57† -0.21±1.37† 0.35±1.05† DH (n = 10) -0.15±0.52 0.81±0.26\* 0.26±0.61† 0.47±0.63 0.34±0.70

WT (n = 24) 13.39±5.10 39.97±8.67\* 23.26±8.30† 28.39±6.66† 32.58±8.73† BKO (n = 16) 26.80±3.59 54.34±9.88\* 37.62±9.23† 41.85±11.8† 52.29±7.51† DH (n = 10) 18.79±2.31 46.89±4.56\* 26.62±5.14† 32.72±2.46† 38.13±5.09†

WT (n = 24) 11.53±2.50 7.73±4.70\* 15.15±7.72† 16.04±6.61† 15.89±8.43† BKO (n = 16) 7.73±4.25 6.24±3.89 15.12±9.76\*,† 15.63±7.74\*,† 16.50±8.75\*,† DH (n = 10) 10.97±5.00 5.81±1.44\* 14.78±5.16† 17.03±7.27† 14.19±4.89†

**Table 2.** NTBI, LPI, MDA and GSH concentrations (mean+SD) in the WT, BKO and DH mice fed with a normal (N) diet (iron content 180 mg/kg) and an iron (Fe) diet (iron content 780 mg/kg) and treated with deionized water (DW), 90

Among these polyphenolic compounds, the hierarchy of antioxidant activity is ECG > EGCG > EGC > GA > EC ≈ C [24]. With the chelating activity of such prooxidant metals as iron (Fe2+),

+GTE (90 mg/kg/day)

**Plasma NTBI concentrations (**μ**M)**

**LPI concentrations (**μ**M)**

**Plasma MDA concentrations (**μ**M)**

**Plasma GSH concentrations (**μ**M)**

+EGCG (50 mg/kg/day)

+DFP (50 mg/kg/day)

Green Tea: Just a Drink or Nutraceutical http://dx.doi.org/10.5772/57519 367

+DW +DW

\**p* <0.05 compared to N diet; †*p* <0.05 compared to DW.

mg/kg/day GTE, 50 mg/kg EGCG and 50 mg/kg DFP for 6 months.

**5. Fate of green tea catechins in the body**

**5.1. Gastrointestinal absorption**

the plasma compartment.

**Mice**

The potential of green tea to prevent or ameliorate chronic diseases is currently the subject of considerable scientific investigations. Although a number of mechanisms have been proposed for their beneficial effects, the radical scavenging and antioxidant properties of green tea catechins are frequently cited as important contributors. Emerging evidence has also shown that catechins and their metabolites possessmany additional mechanisms of action [13] by affecting numerous sites, potentiating endogenous antioxidants and elicit‐ ing dual actions during oxidative stress. Much of the evidence supporting an antioxidant function for green tea catechins is derived from assays of their antioxidant activity *in vitro*. However, the evidence that green tea catechins are acting either directly or indirectly as antioxidants *in vivo* is limited [14]
