**Abstract**

This book chapter describes about the phytochemicals in tea which are significantly useful in preparing nutraceutical products. The polyphenols along with other bioactive compounds present in tea have many pharmacological properties which attribute to the development of various food products where tea constitutes as an active ingredient. This chapter also discusses the potential uses of tea and their bioactive constituents in treatment and prevention of diseases in human which infer the potentiality of developing and popularizing nutraceuticals of tea.

**Keywords:** nutraceuticals, phytochemicals, catechins, polyphenols, antioxidant, therapeutic properties

## **1. Introduction**

Nutraceuticals are promising class of natural products that encompasses the combined terms "nutrition" and pharmaceuticals" which incorporates the characteristics of both nutritional and pharmaceutical and thus exhibit several health benefits. The food or food products having nutraceuticals properties can be used as medicine in addition to nutritional values and have been used to support proper functioning of the body, treat and prevention of diseases, and increase the life expectancy of human beings [1–4]. Currently nutraceuticals have been explored in several diseases in prevention and cure such cancer, diabetics, cardiovascular, diseases etc.

Tea (*Camellia sinensis* L.) is one of the most popular and widely consumed beverage world-wide. Commercially tea is mostly available in three varieties viz. black (red tea), green and oolong (yellow tea) tea which differ in their physical and chemical characteristics arised from their different manufacturing process. Black tea consumption is highest in western countries which accounts for around 78% of worldwide consumption. The green tea is mostly consumed in Japan and china and accounts for 20% whereas oolong tea is consumed 2% only. Black tea is widely consumed in India and India is one of the largest tea producers in the world and it occupies about 70% of domestic consumption of the total tea production in the country.

The black tea is fully fermented and known for its characteristics brown liquor whereas green tea is unfermented and known for its light greenish yellow liquor. The oolong is semi-fermented and liquor characteristic lies in between the black and green tea. All the three types differ in their taste and flavor and accordingly their chemical profiling also varies.

Tea contains a variety of bioactive compounds such as polyphenols, polysaccharides, vitamins, amino acids etc. having medicinal properties which can be used as food additives in preparation of nutraceuticals [5–8]. Tea is mainly chemically

characterized by their polyphenolic compounds and their polymeriszed products along other bioactive compounds in minor quantities.

The polyphenols which are produced by the plant as secondary metabolites are the major constituents in tea. Other secondary metabolites present in tea are phenolic acids, purine alkaloids, tannins, flavonols and their glycosides. The polyphenols in tea are catechins (C) and their conjugated products viz. epigallocatechingallate (EGCG), epigallocatechins (EGC), epicatechingallate (ECG) and epicatechins (EC) and present in higher quantities in green tea. The other two class of polyphenols found in black tea are theaflavins (TFs) and thearubigins (TRs) which are present in significant quantities in black tea and less quantity in oolong tea. The catechin polyphenols in tea are health-promising due to their antioxidant properties and are very useful in preparation of nutraceuticals from tea [9–14].

In addition, tea contains other beneficiary substances to our health such as fluoride, caffeine, minerals, trace elements e.g. manganese, chromium etc. which also added nutraceutical value of tea and its food additive which also add nutraceutical value of tea or its food additives [15]. Looking to the therapeutic properties of these phytochemicals in tea, different food products have been prepared with tea or its extract which are rich in these active ingredients. These products include ready to drink beverages, instant tea, confections, cereal bars, pet foods, candy etc. So, there is a huge possibility of using bioactive constituents in tea as food additive which provide medical or health benefit in prevention and treatment of disease and thus tea can be potentially used for the development of nutraceuticals.

In this chapter, various bioactive compounds in tea (green, black, oolong and white teas) and their properties which can be employed as nutraceuticals in the form of food or part of food products has been discussed. Further, we have addressed the role of these tea nutraceuticals and their application in prevention and treatment of various diseases.

#### **2. Phytochemicals in tea**

There are a variety of chemicals in tea which are therapeutically important and they also vary in different types of commercially available teas viz. green, black and oolong tea. The chemical characteristics of tea are also varying with variation of plant species, geographic locations, climatic condition, horticultural practices as well as plucking parameters of the tea leaves [16, 17]. Polyphenols comprises of a large group of phytochemicals, the major polyphenolic constituents in tea which account for maximum 30% total dry weight of tea leaves are the flavanols, also known as catechins. Of these polyphenolic catechins, eight catechins are appeared in significant quantities which include (+)-catechin, (-)- epicatechin, (-) gallocatechin, (-)-epigallocatechin, (-)-catechin gallate, (-)-epicatechin gallate, (-)-gallocatechin gallate, (-)-epigallocatechin gallate.

Tea beverage is chemically characterized mainly by polyphenolic constituents (mostly flavonoids) and their polymerized compounds. Four polyphenolic catechins which are in large quantities in green tea are (–)–epigallocatechin- 3-gallate (EGCG), (–)–epigallocatechin (EGC), (–)–epicatechin-3- gallate (ECG), and (–)– epicatechin (EC) (**Table 1**). These catechins are highest in green tea (30-40% in dry weight) and least in black tea (10% in dry weight) in which catechins undergo condensation and polymerization into other phenolic compounds theaflavins and thearubigins during enzymatic oxidation of catechins during fermentation process of black tea manufacturing [18, 19]. The oolong tea has substantial amount of catechins with other oligomeric polyphenols [20].

*Nutraceuticals of Tea* (Camellia sinensis) *for Human Health DOI: http://dx.doi.org/10.5772/intechopen.96506*

Apart from polyphenols, there are a number of phytochemicals which are significantly important in medicinal use. These phytochemicals are oxyaromatic acids (gallic, caffeic, quinine, chlorogenic and n-coumaric acids, flavonols (Quercetin, kaempferol, myricetin), pigments (carotenoids, chlorophyll), alkaloids (caffeine, theophylline, theobromine), amino acids, lipids, polysaccharides, vitamins, lignans and saponins which also attribute to the widely explored medicinal value of tea [21–23].

The major polyphenolic compounds in different types of tea which differ due to their manufacturing processes are highlighted in **Table 2**. The white tea is least processed of all the tea types and thus it intakes maximum polyphenols whereas the black tea is fully fermented through enzyme mediated oxidation of polyphenols into oligomeric and polymeric flavanols (theaflavins, thearubigins and other oligomers) with characteristics flavor and color. In black tea processing, tea leaves (standard plucking two and a bud) are crushed to undergo enzymatic oxidation (polyphenol oxidase) and subsequent condensation of tea catechins in to the formation of theaflavins (TFs) (oligomeric) and thearubigins (TRs) (polymeric) products. This fermentation process is being limited in case of oolong tea. In green tea this enzymatic oxidation is prevented by steaming (or pan-frying) of fresh tea leaves. Therefore, the green tea infusion contains major quantities of polyphenol catechins (30-40% dry weight of four major catechins viz. (–)-Epigallocatechin-3-gallate (EGCG), (–)-epigallocatechin (EGC), (–)-epicatechin-3-gallate (ECG), and (–) epicatechin (EC)). Since all major polyphenols are oxidized in black tea, it contains less amount of catechins (3-10%) along with theaflavins (2-6%), thearubigins (>20%) and gallic acids in significant quantities. The oolong contains green tea catechins and less amount of black tea theaflavins and thearubigins due to its partial fermentation process.

In water extract, all types of tea also contain caffeine in quantity of 2-5%.

#### **3. Nutraceutical properties of tea phytochemicals**

The therapeutic properties of tea extract are associated with the polyphenolic contents which have the highest antioxidant capacity amongst other bio-active compounds. The green tea extract has higher antioxidant capacity than that of black tea or oolong tea due the higher quantities of catechin polyphenols viz. EGCG, EGC, ECG, EC [24]. The EGCG has the highest anti-oxidant activity followed by ECG and EC whereas EGC has the lowest activity [25]. The EGCG can inhibit the production of hydrogen peroxide and superoxide radicals by tumor promoter-activated neutrophils in our body. Among the three major types of tea (green, black, oolong), green tea has the highest antioxidant activity and black tea has the lowest one. The antioxidant activity of green tea and its polyphenols have been studied in a number of *in vitro* and *in vivo* experiments and in most of these researches EGCG (major constituent in green tea) is well documented and significantly important. These nonnutritive phytochemicals are potential nutraceuticals and their easy bioavailability makes their useful consumption in prevention of diseases. The higher antioxidant properties of black tea are associated with minor quantities of catechins and other oligomeric polyphenols. In addition to different types of tea which differ in chemical contents, the health-promising factors of tea also varies with cultivars to cultivars and their geographic locations. Therefore, it is very important to determine the bioactivity of tea of different varieties in obtaining nutraceutical values.

Recent researches have gained attention in therapeutic use of tea polyphenols of green and black tea in diseases associated to metabolic syndromes. Green tea

**Table**

**1.**


**Table 2.**

*Major polyphenols and processing conditions of different varieties of tea.*

catechins have been explored to antioxidant, anticarcinogenic, anti-inflammatory, probiotic, anti-inflammatory, thermogenic, and antimicrobial activities. These have been found to inhibit carcinogenesis of the skin, lung, esophagus, stomach, liver, small intestine, colon, bladder, prostate, and mammary gland in animal studies [26]. Black and green tea can protect oxidative damage of red blood cells [27].

Looking in to the various health benefits of tea phytochemicals, tea extracts in liquid or powder form can be effectively used in food products such as sweets, biscuits, bread, cake, candies, ready-to-drink beverages as well as other polyphenol rich food supplements. The tea nutraceuticals are also available in various form of tablets, capsules and health drinks. In addition, tea also contains other nutritional substances such as dietary fiber and proteins after polyphenols extraction in tea for use in nutraceuticals which also give health benefits [28]. Consumption of tea with lemon juice (ascorbic acid) has manifold benefits in making more accessible of tea antioxidants (catechins) to get absorbed as well as enhance the iron absorption in our body [15]. Further, compounds in tea can inhibit iron absorption from foods; drinking green tea with lemon reduces that effect. The combination of honey with green tea has been used since very past as they are very effective in healing wounds. The health-promoting activities of tea also vary cultivar to cultivar and thus it is important to identify the cultivars having specific bioactivity so as to use the nutraceutical properties properly. The phytochemicals in tea and their nutraceutical properties are depicted in **Figure 1**.

#### **Figure 1.** *Role and mechanism of nutraceutical properties of tea phytochemicals.*
