Camellia sinensis (L.) Kuntze

Last updated: 17 Nov 2016

Scientific Name

Camellia sinensis (L.) Kuntze

Synonyms

Camellia arborescens Hung T. Chang & F.L. Yu, Camellia bohea (L.) Sweet, Camellia chinensis (Sims) Kuntze, Camellia thea Link [Illegitimate], Camellia viridis Sweet, Thea bohea L., Thea cantoniensis Lour., Thea chinensis Sims, Thea cochinchinensis Lour., Thea grandifolia Salisb., Thea olearia Lour. ex Gomes, Thea oleosa Lour., Thea parvifolia Salisb., Thea sinensis L., Thea viridis L., Theaphylla cantonensis (Lour.) Raf. [1]

Vernacular Name

Malaysia Teh [2]
English Chinese tea, tea, tea plant [3]; green tea [4]
China Cha, cha ye, ming, yeh ch’a [3]
India Caha, cay, cha, cha soppu, chaha, chaha soppu, chai, chai siyah, chaipati, chay, chha, chiya, karupputteyilai, nallateyaku, pachaitteyilai, saatong, singo, syamaparni, teyaaku, teyila, teyilai, teyla, thayilai, thesoppu, theyaku, theyale, theyilai, thingpui, tiyaku [3]
Indonesia Teh [2]
Thailand Cha [2]
Laos S’a, hmièngx [2]
Myanmar Lappet [2]
Philippines Tsa [2]
Cambodia Taè [2]
Vietnam Ch[ef], tr[af] [2]
Japan Cha, cha-no-ki, Shina-cha, Taiwan-cha [3]
Nepal Chad, chah, chay, chhapa, chhyo, chiya, hoshad-awaku, mukuwa [3]
France Théier, thé [2].

Geographical Distributions

The natural habitat of Camellia sinensis is the lower montane forest on mainland Asia from south-western China (Sichuan) to north-eastern India (Assam). The primary centre of origin is presumed to be near the source of the Irrawadi (Ayeyawadi) river in northern Burma (Myanmar), but early human interest in the stimulating properties of tea may have been instrumental in its wider dispersal in Asia. The C. sinensis was already known to the Chinese people more than 4000 years ago. Written records dating from the 5th Century AD confirm its widespread cultivation and general use as a refreshing beverage in several Chinese provinces. C. sinensis cultivation in Japan was started in the 9th Century with seed introduced from China. Tea became an important export commodity for China, first through the Mongols by old overland trading routes in central Asia to Turkey and Russia (mainly as brick tea), and then from the early years of the 17th Century also to Europe by sea, through the Dutch and English East India Companies (green, and later black tea). For more than 300 years all the tea drunk in the Western world came from China (100 000 t in 1850), but this monopoly on the international tea market gradually came to an end with the development of tea plantations in India (1840), Sri Lanka (1870) and Indonesia (1880). By 1925 very little of the 300 000 of tea imported into Europe came from China. Tea exports from China were resumed in quantity in the 1960s. [2]

The tea grown in China and Japan is all C. sinensis var. sinensis ('China tea'), which has smaller leaves and more cold tolerance but grows less vigorously than C. sinensis var. assamica (Mast.) Kitamura ('Assam tea') discovered in the forests of north-eastern India in 1823. Assam tea and subsequently hybrids between the two varieties ('Indian hybrid tea') became the basis for the tea industries of South, Southeast and West Asia, as well as for those established in Africa and South America. In Southeast Asia, tea cultivation is most important in Indonesia, Vietnam, Papua New Guinea, Malaysia and Thailand. [2]

Botanical Description

Camellia sinensis is an evergreen, multi-stemmed shrub which can grow measuring up to 3 m tall (var. sinensis), or tree up to measure 10-15 m tall with one main stem (var. assamica). In cultivation it is pruned to measure about 1-1.5 m and trained as a low profusely branching and spreading bush. The strong taproot and many lateral roots rise to a dense mat of feeding roots in the top 50-75 cm of the soil. Some lateral roots grow 3-4 m deep. The feeding roots are in association with endotrophic mycorrhiza while the root hairs lack. The branchlets are finely pubescent at the apex. [2]

The leaves are arranged alternate and with short petiole. The blade is obovate-lance-shaped, measuring 4-30 cm x 1.5-10 cm, serrate, obtuse with broad cusp to acuminate, slightly pubescent on the lower surface when young, stomata on the lower surface only, characteristic sclereids (stone cells) in mesophyll and calcium oxalate crystals in phloem of petiole. In var. sinensis the blade is leathery and usually stiff-erect, narrow and usually less than 10 cm long. It is dark green with dull, flat surface and indistinct marginal veins while in var. assamica it is thinly leathery and horizontal or pendant, wider and longer (15-20 cm long), lighter green with glossy, blistered upper surface and distinct marginal veins. [2]

The flowers are axillary, single or in clusters measure of 2-4, 2.5-4 cm in diameter and very fragrant. The pedicel is short. The sepals are 5-7 and persistent. The petals are 5-7, obovate, concave in shape, white or light pink in colour and slightly coherent at the base. The stamens are 100-300 and with 2-celled yellow anthers. The outer filaments are fused at the base and coherent with petals while the inner ones are free. The pistil is with 3—5-loculed superior ovary, 4-6 ovules per carpel, and 3-5 free (var. sinensis) or partly fused (var. assamica) styles with stigmatic lobes. [2]

The fruit is a nearly spherical capsule, measuring 1.5-2 cm in diameter, thick-walled and woody. It is brownish-green, usually 3-lobed and 3-loculed and with 1-2 seeds per locule. [2]

The seed is spherical or flattened on one side, measuring 1-1.5 cm in diameter, light brown testa (shell) and hard and integument thin papery. The endosperm is absent. The cotyledons are thick and rich in oil while embryo is straight. The seedling is with epigeal germination. [2]

Cultivation

C. sinensis originated from an area of monsoon climates (warm, wet summers and cool, dry winters) but is presently grown in a range varying from Mediterranean to tropical climates, between 42°N (Georgia) and 27°S (Argentina) latitudes, as well as from sea-level to 2300 m altitude.; Mean annual rainfall varies from 1500 mm (Uganda) to 3500 mm (West Java). About 1700 mm annual rainfall is the minimum requirement for economic tea production. Additional irrigation is only effective under sufficiently high air humidity. On the other hand, rainfall of 5000 mm has no adverse effect on tea growth. Rainfall should not fall below 50 mm per month for any prolonged period. Hail can be a serious hazard to tea, causing yield losses of 10-30% in some areas (e.g. in Kenya above 2000 m altitude). Generally, optimum temperatures for shoot growth are between 18-30°C. The base temperature (Tb), below which shoot growth stops, is about 12.5°C, but this can vary between genotypes from 8-15°C. The thermal time - i.e. the product of number of days and effective temperatures (T - Tb) - for the SRC in tea is on average 475 day, in the absence of water stress. It has been shown to be a very useful parameter to estimate seasonal and geographical effects of temperature on the length of the SRC and consequent yield patterns. At average daily temperatures of 22.5°C the SRC would thus be 48 days against 79 days at 18.5°C. The thermal time parameter is not applicable at temperatures above 30°C, as the co-occurring high vapour pressure deficits of the air (> 23 mbar) depress shoot growth. Tea is not killed by the night frost that occurs in important tea-growing areas at higher latitudes. China-type teas are more tolerant of colder climates. Day length does not have a large influence on seasonal variation in growth (yield) or flowering. [2]

At high altitudes in tropical areas the photosynthesis of whole canopies of the tea crop becomes saturated at 75% of full sunlight. Tea is generally more productive without shade, but shade trees may be necessary to reduce air temperatures during hot periods, e.g. in Assam and Bangladesh. Shelter belts of trees planted between fields are beneficial in protecting tea against prevailing strong winds. [2]

Tea is grown successfully in a wide range of soil types developed from diverse parent rock material under high rainfall conditions. Soils suitable for tea cultivation should be free-draining, have a depth of 2 m, a pH between 4.5 and 5.6, a texture of sandy loam to clay and good water-holding capacity. [2]

Climatic conditions have a great influence on the quality of the tea, especially on the flavour. Fast shoot growth — for instance at low altitudes, during the best part of the growing season or shortly after the bushes have been pruned back — is detrimental to the quality of tea, particularly the flavour, but induces high production. Hence, both in respect of plucking method and inputs to encourage growth (e.g. heavy manuring) the grower has to choose between high yield and good quality. Nevertheless, high yields and excellent quality tea can be obtained in tropical countries on fertile soils, especially at elevations of 1200—1800 m above sea-level. At still higher elevations, the tea will have a well-developed flavour but it will lack strength and yields will be lower. Likewise, the retarded shoot growth during a dry period and the proliferation of growing points with an attendant reduction in shoot vigour shortly before the next pruning round result in better flavour but low yields. [2]

Chemical Constituent

C. sinensis has been reported to contain caffeine, proanthocyanidins, myicetin, caempherol, quercetin, epicatechin, epicatechin gallate, epigallocatechin gallate, gallocatechin, gallocatechin gallate [4]. It was also documented to contain polyphenols, methyl xanthines, theasinensins, carotenoids and lignin [5]

The chemical constituent of green tea that has documented also includes, 5-N-ethylglutamine, glutamic acid, tryptophan, glycine, serine, aspartic acid, tyrosine, aline, leucine, threonine, arginine, lysine, cellulose, pectins, glucose, fructose, sucrose, calcium, magnesium, chromium, manganese, iron, copper, zinc, molybdenum, selenium, sodium, phosphorus, cobalt, strontium, nickel, potassium, fluorine, aluminium, linoleic, stigmasterol, caffeine, theophylline, and xanthic bases. [6]

Plant Part Used

Leaf [2]

Traditional Use

In recent years, the health benefits of consuming green tea, including the prevention of cancer and cardiovascular disease, the anti-inflammatory, antiarthritic, antibacterial, antiangiogenic, antioxidative, antiviral, neuroprotective, and cholesterol lowering effect. [6]

Green tea is commonly used as a beverage, by infusing the leaves into hot water, the beverage provides a stimulating and refreshing feeling. [2]

Preclinical Data

Pharmacology

Antioxidant activity

The effect of green tea on the lipid peroxidation products formation and parameters of antioxidative system of the liver, blood serum and central nervous tissue of healthy young rats drinking green tea for five weeks was tested. Bioactive ingredients of green tea extract caused in the liver an increase in the activity of glutathione peroxidase and glutathione reductase and in the content of reduced glutathione as well as marked decrease in lipid hydroperoxides (LOOH) , 4-hydroksynonenal(4-HNE) and malondialdehyde (MDA). The use of green tea extract appeared to be beneficial to rats in reducing lipid peroxidation products. [7]

Green tea’s antioxidant effects seem to be dependent upon the polyphenol (catechin) fraction [8][9]. The antioxidative action of the green tea polyphenols includes inhibiting lipid peroxidation, iNOS and the production of inflammatory cytokines along with reducing the α-tocopheroxyl radical to regenerate alpha-tocopherol [10][11]. (-)-epigallocatechin gallate (EGCG), isolated from green tea, displays antioxidant properties in vitro and is thought to act as an antioxidant in humans and be responsible for much of green tea’s therapeutic effects [12][13].

Insulin resistance

3 groups of Sprague-Dawley were fed with standard chow and water (control group), high fructose diet and water (fructose group), high fructose diet with green tea (fructose/green tea group) for 12 weeks. Compared to the control group, the fructose group developed fasting hyperglycemia, hyperinsulinemia, and elevated blood pressure. Insulin-stimulated glucose uptake and insulin binding of adipocytes were significantly reduced, and the glucose transporter IV content of adipocytes also decreased. The fructose/green tea group showed improvement in all of these metabolic defects and insulin resistance and blood pressure which suggest that the amelioration of insulin resistance by green tea is associated with the increased expression of GLUT IV. [14]

Anticarcinogenic activity

The inhibitory effects of green tea on Carcinogenesis have been investigated in laboratory studies using (-)epigallocatechin gallate (EGCG) or crude green tea extract [15]. Further, EGCG has been reported to inhibit the growth of cancer cells, lung metastasis in an animal model and urokinase activity [16][17]. Investigators have reported that increased consumption of green tea was associated with decreased numbers of axillary lymph node metastases among pre-menopausal women with stage I and II breast cancer and with increased expression of progesterone and estrogen receptors among postmenopausal women [18][19]. Claims have been made that increased consumption of green tea prior to clinical cancer onset may be associated with improved prognosis of stage I and II breast cancer. This association may be related to a modifying effect of green tea on the clinical characteristics of the cancer [20].

As stated, green tea and its major polyphenolics have been studied to determine if they prevent chemically induced tumors in a variety of experimental animal models [21][22]. The exact mechanism(s) of the anticarcinogenic activity remains to be found, but green tea polyphenolics are reported to enhance antioxidant (glutathione peroxidase, catalase and quinone reductase) and phase II (glutathione-S-transferase) enzyme activities, inhibit chemically induced lipid peroxidation, inhibit irradiation- and TPA-induced epidermal ornithine decarboxylase (ODC) and cyclo-oxygenase activities, inhibit protein kinase C and cellular proliferation, as anti-inflammatory activity and enhance gap junction intercellular communication. [23]

A review of studies from 1996-2008 found that consuming 2 cups/day of green tea was associated with an 18% decrease risk of developing lung cancer [24]. A 2006 meta-analysis of epidemiological studies found green tea consumption was correlated with a decreased risk for breast cancer [25]. A 2009 meta-analysis found that green tea consumption (2 cups/day) decreases the risk of endometrial cancer [26]. A Cochrane Database System Review in 2009 found that evidence of green tea consumption and decreased cancer risks is limited and more studies need to be performed, especially using standardized extracts [27].

Literature suggests that carcinogenic substances, termed heterocyclic amines, can be found in cooked foods such as meats (especially when broiled or grilled), greatly increasing the risks of colon cancer [28]. In vitro and laboratory animal experiments have reported that the polyphenols in green tea may inhibit the formation and destructive capabilities of these heterocyclic amines. [29][30]

Anti-inflammatory activity

An antioxidant-rich polyphenolic fraction isolated from green tea has been reported to possess anti-inflammatory properties in laboratory animals. One laboratory animal study reported positive benefits on collagen-induced arthritis in mice. The mice exhibited a significant reduction in the incidence of arthritis (33% to 50%) as compared with mice not given green tea polyphenols. Analysis showed a marked reduction in the expression of inflammatory mediators such as cyclooxygenase 2, IFN-gamma, and TNF-α in arthritic joints of green tea polyphenol fed mice. Additionally, total IgG and type II collagen-specific IgG levels were lower in serum and arthritic joints of the treated mice. The authors concluded that a polyphenolic fraction from green tea may be useful in the prevention of onset and severity of arthritis. [31]

Toxicity

No documentation

Clinical Data

Clinical findings

Antioxidant activity

A clinical study on the antioxidant capacity of green tea catechins was conducted. Eighteen healthy male volunteers were administered an oral green tea extract (254 mg of total catechins per individual). One hour after administration, plasma was drawn and tested for its antioxidant capacity. The individuals that ingested the green tea had significantly lower phosphatidylcholine hydroperoxide levels correlating inversely with an increase in plasma green tea constituent (ECGC) levels - indicating a rise in the antioxidant capacity of these treated subjects. [32]

Another clinical study investigated the antioxidant effect of green tea ingestion in 10 healthy individuals (5 women, 5 men, ages 23-25). The results were that 150 mL of green tea did not significantly increase the antioxidant capacity of plasma, but after ingesting 300 mL, the total antioxidant capacity of plasma had increased significantly, having an antioxidant capacity of 7.0% after 60 min and 6.2% after 120 min. Also, after ingesting the 450 mL of tea, the antioxidant capacity of the plasma increased 12.0% after 60 min and 12.7% after 120 min over the baseline value. [33]

Cigarette smoking is one of the major causes of death in the United States [34]. A study compared the chemopreventive effects of green tea and coffee in cigarette smokers [35]. Results showed that the frequencies of sister-chromatid exchange (SCE) in mitogen-stimulated peripheral lymphocytes from smokers was elevated (9.46 +/- 0.46) vs. non-smokers (7.03 +/- 0.33); however, the frequency of SCE in smokers who consumed green tea (7.94 +/- 0.31) was comparable to that of non-smokers, with the authors concluding that green tea can block the cigarette-induced increase in SCE frequency. Coffee did not exhibit a significant inhibitory effect on smoking-induced SCE. Another human study confirms the decrease in oxidative DNA damage caused by cigarette smoking when green tea is consumed [36]. Green tea topically in sunscreens have also been reported to have potential photoprotective effects on UVR-induced photoaging and photoimmunosuppression based on the antioxidant properties [37]. Another 2 year, double-blind, randomized placebo-controlled trial found that use of green tea polyphenols topically did not improve histological photoaging parameters in human subjects [38].

Cardiovascular protection

Positive benefits on the cardiovascular system, particularly blood lipid levels, have been reported with the use of green tea in human subjects [39][40]. Green tea was reported to lower cholesterol levels by blocking the lipid peroxidation of LDL [41][42]. Consumption of green tea has been associated with decreased serum concentrations of total lipids and triglycerides, an increase in HDL cholesterol, together with a decreased proportion of LDL and VLDL [43]. Also, an increased resistance of LDL to in vivo oxidation has been reported [44]. In two studies, consumption of green tea as a beverage did not show any benefit in reducing serum cholesterol, but the positive effects are reported from other studies [45][46]. Mechanisms of green tea’s lipid lowering activity also include fatty acid synthase gene suppression by tea polyphenols (EGCG, theaflavins) which leads to down-regulation of EGFR/PI3K/Akt/Sp-1 signal transduction pathways [47].

Use of a standardized green tea product may significantly increase the benefits of decreasing LDL oxidation. One in vitro study reported the addition of catechins from green tea had a gradual regenerative effect on alpha-tocopherol in human LDL [48]. Green tea has also been reported to be an inhibitor of thromboxane formation and platelet aggregation, of importance in the prevention of atherosclerosis [49][50].

A randomized, double-blind, placebo-controlled, parallel study using green tea in 111 healthy adult volunteers 21-70 y old was performed. After 3 weeks, the green tea was effective for decreasing systolic and diastolic blood pressure, blood pressure, LDL cholesterol, oxidative stress, and markers of chronic inflammation, all independent cardiovascular risk factors. [51]

Chemotherapy enhancement and radiation protection

The oral administration of green tea reportedly enhanced the inhibitory effects of doxorubicin on tumor growth [52][53]. The doxorubicin concentration in the tumor was increased by the combination of green tea with doxorubicin. In contrast, the increase in doxorubicin concentration was not observed in normal tissues after green tea combination [54]. Green tea has also been reported to increase the tumor inhibiting effects of Adriamycin (doxorubicin). [55][56]

A recent human study reported that a topical application of EGCG from green tea prior to exposure to UV radiation had preventative effects on damage to the skin. A single UV exposure of 4x MED to human skin was found to increase catalase activity (109-145%) and decrease glutathione peroxidase (GPx) activity (36-54%) and total glutathione (GSH) level (13-36%) at different time points studied. Pretreatment of the skin with EGCG from green tea was found to restore the UV-induced decrease in GSH level and protection of the skin to the antioxidant enzyme GPx. Further studies are warranted to elucidate the preventive effects of EGCG against multiple exposures to UV light on human skin. [57]

Metabolic health

A double-blind controlled study found that using green tea extract in patients with type 2 diabetes who were not on insulin resulted in a more significant decrease in waist circumference along with increasing adiponectin levels [58]. The authors concluded that green tea in the prevention of obesity aids in the recovery of Ins-secretory ability and helps maintain low hemoglobin A(1c) levels in type 2 diabetic patients who do not yet require insulin therapy. A small counter-balanced crossover study in healthy male subjects found that acute green tea extract ingestion can increase fat oxidation during moderate-intensity exercise and can improve insulin sensitivity and glucose tolerance [59]. Another small clinical study found that green tea consumption lowered hemoglobin A1c levels in individuals with borderline type 2 diabetes [60]. Another clinical study found no change in glycemic control after 3 months of supplementation with green tea extract in adults with type 2 diabetes. [61]

Weight control/ Thermogenic activity

A randomized, placebo-controlled study of 10 individuals was conducted to investigate whether a green tea extract could increase the 24-h energy expenditure and fat oxidation in humans [62]. Compared to the placebo, the green tea extract resulted in a significant increase in 24-h energy expenditure (4%; p < 0.01) and a significant decrease in 24-h respiratory quotient without a change in urinary nitrogen. Twenty-four-hour urinary excretion of norepinephrine was higher during treatment with the green tea extract than with the placebo. Treatment with caffeine alone in amounts equivalent to those found in the green tea extract had no effect on energy expenditure and respiratory quotient nor on urinary nitrogen or catecholamine excretion. The authors concluded that green tea has thermogenic properties and promotes fat oxidation beyond that explained by its caffeine content, with the green tea extract having a role in the control of body composition via sympathetic activation of thermogenesis, fat oxidation, or both. Another clinical study reported similar results, that green tea extract may stimulate brown adipose tissue thermogenesis to an extent which is much greater than can be attributed to its caffeine content, with thermogenic properties residing primarily in an interaction between its high content in catechin-polyphenols and caffeine with sympathetically released noradrenaline (NA). [63]

A randomized, placebo-controlled, double-blind parallel trial was conducted in 80 overweight and moderately obese subjects to compare weight loss using green tea + caffeine or placebo, both in addition to an adequate protein (AP) diet (50-60 g protein/d) or an HP diet (100-120 g protein/d) [64]. The green tea-caffeine mixture, as well as the HP diet, improved weight loss independently through thermogenesis, fat oxidation, sparing FFM, and, for the HP diet, satiety; a possible synergistic effect failed to appear. Another double-blind parallel multicenter study found that green tea polyphenols given to 240 patients led to a reduction in body fat, systolic blood pressure, and LDL cholesterol [65].

Precautions

Use green tea extracts with caution in individuals with impaired liver function. Hepatotoxicity has been reported in 7 case reports where green tea was a probable cause [66][67]. However, a placebo-controlled study using high polyphenol green tea extract showed no impairment of liver function [68].

Side effects

No documentation

Dosage

No documentation

Poisonous Management

No documentation

Line drawing

 

104

Figure 1: The line drawing of C. sinensis [2]

References

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