The mysterious, two leaf and a bud

Introduction

Botanically tea is known as Camellia sinensis belongs to Camelliaceae/Theaceae family with diploid chromosome number 2n=30. It is originated from South East Asia. Economic part is two leaf and a bud (Kumar, 2020) [12] . It has mainly two species i.e., Camellia sinensis (China tea) and Camellia assamica (Assam tea). China tea is a small shrub with short leaves, produces good quality tea after processing and resistant to cold, mainly cultivated in India. Assam tea is a tree with broad leaves, produces poor quality tea and resistant to drought, mainly cultivated in China. Another type of tea Camellia assamica ssp. Lasiocalyx is said to be cross between China and Assam tea. It is also known as Cambod tea, the characteristics are intermediate to both of its parents. Two leaf and a bud is considered as a golden tip, plucking of two leaf and a bud is known as fine plucking which is a symbol of perfection. It is concentrated with nutrients and natural antioxidants and rich in flavanols like catechins and amino acids like theanine. It has soft stem has no fibre which gives finer quality whereas lower leaves has harder stem with high fibre content produces poor quality tea after processing. The first consumption of tea has been started from 5000-6000 years ago during Shen Nong era of China. Cha was the first term coined, meaning tea in Cantonese language. Chinese were the first to use tea as a medicinal herb to cure various ailments. During Zhou dynasty, tea became popular as a drink and Tang dynasty started its production and processing and first monograph 'the classic era of tea' has been written during this period. Song dynasty has started first tea house and Ming dynasty has created the first tea manual (Chen, 2012) [3] . In India during 1837, British East India company has brought the tea plants and planted in English tea garden in Assam. Tea cultivation has been started during 1840 and commercial tea plantation has been started in Darjeeling where they followed estate model. Red label was the first tea brand established in India by Brooke bond company. Presently India is the largest consumer of black tea (1168 M kg/year) accounts for 18 percent of total world's consumption (Tea Board of India, 2024). India is the second largest producer of tea (1344.40 M Kg) and forth major tea exporting country in the world (PIB, 2023). In south India during 1878, James Finlay and Co. transformed the Kanan Devan Hills exclusively for tea crop. Due to widespread of coffee leaf rust led to an extensive planting of tea in south India. During 2022, Tamil Nadu (159.02 M kg) is the major producer followed by Kerala (67.70 M kg) and Karnataka (5.10 M kg) in south India (TRF, UPASI, 2024). Processing of tea • Harvesting: First and fore most thing is harvesting for processing, which means plucking in tea. Based on the method of processing, two leaf and a bud, three leaf and a bud and four leaf and a bud is harvested. • Withering: After harvesting leaves are kept under withering chamber, is almost similar to drying, initial moisture content is reduced upto 65 percent. • After withering there are two methods of processing of tea i.e., CTC (Crush, Tear and Curl) and Orthodox. • CTC: In this method, green leaf sifting is done which means removal of stems, iron particles etc., then it is passed through CTC machine, which is a continuous process leaves are moving from one roller to another roller where leaves are crushed, torn and curled. • Orthodox: Withered leaves are rolled in rotor vane, leaves get macerated, mixing up of enzymes and substrates will takes place. After rolling leaves will be in the form of clumps so roll breaking has to be done to break the clumps.

• Fermentation:

In orthodox method, during fermentation, the leaf changes colour and turns into a dark coppery tone. Typical aroma develops at this stage. The ideal conditions for fermentation are temperature <30 o C, moisture ~55 percent, pH 4.5 to 5.0 and relative humidity >90 percent. In CTC method, it takes in about 60-90 minutes with conditioned air. There are different types of fermentation like drum method, tray method, floor fermentation and recently UV fermentation has also been developed. During this, rubbing of leaf against leaf takes place and the juices present in the micro cells of leaf are evenly coated on the exterior of the tea leaf.

• Drying: In conventional drying, fermented leaf is subjected to a blast of hot air in such a manner that the hottest air first comes in contact with the tea having the least moisture content. In these driers, the fermented leaf falls on a series of moving perforated trays on which it is passed and repassed through a moving stream of hot air. Mechanical driers are also employed. The moisture content is reduced upto 3 percent. • Grading, Sorting and Packing: After drying based different size of leaves, graded into loose leaf, broken leaf, fannings and dust. Again these grades are sub graded into pekoe, Flowery orange broken pekoe, broken pekoe etc. then packed into bags.

Types of tea

Tea has been classified based on the fermentation time like yellow tea, white tea, green tea, oolong tea, black tea and dark tea. In yellow tea, after withering panning (light roasting) is done followed by sweltering where roasting is done in closed condition, green leaves are turned to yellow colour and then rolling and drying is done. In white tea, after withering, directly drying is done. It is the least processed tea. In green tea, after withering, panning, rolling and drying is done. These three are the unfermented teas.

In oolong tea, after withering short fermentation is done followed by panning, rolling, drying and firing. In black tea, Full fermentation is done then rolling and drying. In dark tea after full fermentation, it is left for natural aging which is responsible for its unique flavour. These three are the fermented teas (Vinci et al., 2022) [17] .

Chemical composition of tea

Tea leaves consist of 20-35 percent of tea polyphenols. It contains flavanols like catechins, epicatechins, epigallocatechin, epigallocatechin 3-gallate and epicatechin 3-gallate. It has flavanols glycosides like kaempferol, quercetin and myricetin. Amino acids accounts for 4 percent, mainly include theanine which is responsible for antioxidant and neurotransmitter property of tea. Free sugars accounts for 3-5 percent including glucose, fructose, sucrose, raffinose and stachyose. In alkaloids, caffeine is the major one accounts for 2-5 percent, which is responsible for the stimulative property of tea. It also includes theobromine and theophylline which are colour and flavour compounds respectively. Tannin are the compounds responsible for the astringency of the tea. It includes ellagitannins like corilagin, strictinin and tellimagrandin I (Chen, 2012) [3] .

Table 1: Difference between green and black tea (Xu and Chen, 2012) [3] Tea Boiling of tea leaves will cause acceleration of oxidation where the free radicles are released in our body which makes our body susceptible to diseases. It also releases the tannins which loses the original flavour of tea and leads to more bitterness and causes digestive issues. The right way of preparing tea includes, get 2g of dried tea leaves or powder take it in a beaker and add 10 ml hot water leave it for 3 minutes and then filter it to get a beverage. Adding of sugar and milk is optional (Ehoche et al., 2021) [4] . If a person consumes the tea in this manner, he can experience the health benefits of tea. Tea possesses many therapeutic properties like antidiabetic activity, anti-obesity, anticancer, antimicrobial, antioxidant, stimulative etc.

Health complications and related case studies Antidiabetic

In the normal blood vessel, there will be proper proportion of red blood cells, white blood cells and glucose, whereas in diabetic/hyperglycaemic condition the glucose molecules are more in blood vessels which increases the unutilized sugar level in the body. In the normal functioning of the body, beta cells present in the pancreas will produce the insulin, which will bind to the insulin receptor, which opens the glucose channel of a cell then glucose is uptaken and utilized for the energy synthesis. In type 1 diabetes, due to loss of beta cells pancreas do not produce insulin, where the glucose channel will remain closed and the glucose cannot be utilized but remain in the blood vessels thus increasing the sugar level in blood. In type 2 diabetes, cell will develop a insulin resistance, where insulin cannot bind to the receptor, thus glucose channel is kept closed and increases the sugar level in the blood. When tea is consumed, the tea bioactive compounds act in three ways by inhibition of α-amylase, enhancing the glucose transport across the membrane and stimulates the insulin secretion. By αamylase inhibition will reduce the carbohydrates absorption in body where the starch is not digested and will directly enter the large intestine and then pass out through colon. By this the glucose is not absorbed by the blood and thus reducing the blood glucose level.

In second way bioactive compounds will act as insulin and it breaks the insulin resistance in the cell membrane and enters into the cell. Then it activates the p13k and AKT enzymes which activates the GLUT-4 protein to move to the cell membrane. Then GLUT-4 protein will absorb the glucose molecules from blood and thus reducing the type-2 diabetes. In third way these bioactive compounds will activates beta cells and increases the insulin secretion, thus reducing the type-1 diabetes (Zanzabil et al., 2023) [19] .

A study conducted by Tolmie et al. (2023) [15] reported the antidiabetic property of green and purple tea extract, ellagitannins (Corilagin, Strictinin and Tellimagrandin I) inhibited the α-amylase and α-glucosidase activity, thus

reducing the blood glucose level by strongly binding to antidiabetic protein targets than the acarbose.

Anti-obesity: Consumption of high fat food will lead to the accumulation of fat in adipose tissue where the accumulated fat is not used for energy production (low energy expenditure). Thus, the levels of adipokines, pro inflammatory cytokines and mitogenic factors will increase. This will lead to obesity and its related diseases. When the tea is consumed, it increases the adiponectin (gene contributes to the control of glucose uptake and lipid metabolism) levels by increasing the P-AMPK and Sirt-1 enzymes which regulates the cellular metabolism and lipid metabolism respectively. Through PPAR-γ-translation, increased expression of GLUT-4 protein will occur, it increases uptake and breakdown of lipid molecules which is known as lipolysis (Salem et al., 2023) [14] . In another way, it will reduce the adipokines leptin, TNF-α, vaspin, omentin which also increases the glucose uptake and lipolysis and thus reducing the obesity. Chen et al. (2015) [2] recorded anti-obesity property of high dose of green tea extract in women with central obesity by significant weight loss and consistent decreases in total cholesterol and Low Density Lipoprotein (LDL) and increase in adiponectin and alanine transaminase levels which can be used to overcome obesity.

Anticancer

Cancer causes in five different ways (Nimmakayala et al., 2018) [13] ,

• Fusion of cancer cell with normal stem cell will lead to the cancer stem cells. • Horizontal gene transfer: When the mutation occurs, and mutant cell undergo replication, the fragment DNA of mutated cell is taken by another cell by phagocytosis which will cause cancer cells. • Continuous systematic division of mutant cell will develop cancer cells • Metabolic reprogramming: Variation in metabolism like hypoxia in presence of hypoxia inducible factor 1 a (HIF 1a) will convert oxyolytic to glycolytic which will cause metabolic shift and will develop cancer stem cells • Dedifferentiation: By wounding or exposing of differentiated cancer cell to NO or ionizing radiations cancer cells will dedifferentiate into cancer stem cells EGCG will increase the caspases protein which arrest cell cycle at G1 (growth) phase, further dividing of cancer cell will stop by the death of cancer cell. Polyphenon E will down regulate the proteins like VEGF, MMP9, STAT-3, HMVEC which are produced by cancer cells that forms new blood vessels (angiogenesis). EGCG will reduce the migration of cancer cells by inhibiting the nuclear factor NF-kB and activator protein AP-1, further proliferation is reduced and activates the cyclinD2 proteins which will reduce the metastasis (movement of cancer cell). Catechins as antioxidant will reduce the reactive oxygen species and free radicals and increase the radical scavenging activity, which will reduce the formation of cancer cells. As prooxidant, increase the ROS in cancer cells, causes decreased cancer cell growth and cell death (Chaudhary et al., 2023) [1] . A study reported that Green tea extract at 800 µg/ml inhibited the growth of Caco-2 cells (Colorectal cancer cell lines) and showed little effect on L929 normal cells. Expression of aquaporin-5 (AQP 5) protein was also decreased (Esghaei et al., 2018) [5] .

Antibacterial

Bacterial infection is common for all age groups, so taking antibiotics can cause many side effects on human health. So, consuming tea can be the best option to overcome bacterial infections. Consumption of tea will break the growth and development of bacterial cells and cause its death. Secondly, it will increase the activity of enzymes like phenyl alanine aminase, peroxidase, catalase, polyphenol oxidase etc. which will develop defence mechanism against the bacteria. Thirdly, it will cause electrolytic leakage from bacterial cell which will damage the cell membrane and cause the cell death (Yan et al., 2021) [18] . In an experiment, green tea and black tea extracts inhibited the growth of Methicillin-resistant Staphylococcus aureus bacterial strains at 80 µg/mL epigallocatechin 3-gallate (EGCG) concentration (Feilcke et al., 2023) [7] . Similar study with respect to streptococci and lactobacilli in the oral cavity of children has been carried out by Vilela et al.

(2020) [16] which showed the microbial reduction and its application as mouthwash for children.

Antioxidant

Increase in free radicals in human body will make the body susceptible to diseases. Since is rich in natural antioxidants it will scavenge the free radicals. A study reported total phenolic content and antioxidants were higher at T = 100°C for 10 min, green tea (916.12-1169.81 mg GAE/g) and black tea (932.03-1126.62 mg GAE/g) in natural mineral water which sowed the antioxidant activity (Vinci et al., 2022) [17] . Rather than health benefits, tea polyphenols can be used to extend the shelf life of food products. A study confirms that chitosan oligosaccharides (0.1%) combined with tea polyphenols (0.08%) inhibited microbial growth with slight increase in pH, maintaining same level of amino acid nitrogen and overall likeness score even after 18 months of room-temperature storage. It can be used as practical method to inhibit the spoilage of soy sauce (Zhu et al., 2023) [20] .

Another study revealed the utilization of green tea waste as soil amendments. It resulted that application of green tea waste (2.5%) has increased CO2 accumulation and other leaf parameters (Zou et al., 2023) [21] .

Limitations (Excessive consumption)

• Tannins bind to iron and reduce iron absorption in body and cause Fe deficiency • It will cause irritative digestive issues like nausea and stomach ache

• Black tea has higher amount of caffeine, it will cause anxiety and restlessness • Due to reduced melatonin, it will lead to insomnia • Higher caffeine will cause heartburn • It may cause miscarriage or low infant birth weight during pregnancy

Conclusion

Ellagitannins present in green tea extract will act as antidiabetic. Consumption of green tea will help to overcome obesity and also cancer. Tea will also act as antioxidant and antibacterial. Other than use of tea in pharmaceutical industry, it also has application in food industry in extension of shelf life of soy sauce. Green tea waste can also be used as soil amendment. It can also be used to treat cardiovascular diseases, Alzheimer's, Parkinson's, immunomodulatory etc.

References

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