PURPLE TEA: A SYSTEMATIC REVIEW

PURPLE TEA: A SYSTEMATIC REVIEW

Vishakha G. Thakur *, Niki Jain, Nikita Khule, Nimisha Raut and Talha Siddiqui

Department of Pharmaceutical Chemistry, Viva Institute of Pharmacy, Veer Savarkar Road, Virar East, Maharashtra, India.

ABSTRACT: Camellia sinensis has been used since several decades owing to its numerous health benefits. The purpose of this study is to investigate the developments in new varieties of Camellia sinensis. This new variety of tea possesses striking, purple-colored leaves, and hence, it is more commonly referred to as purple tea. This study analyzes the detailed mechanism of color change. An over-expression of genes in C. sinensis leads to an increase in the proportion of its anthocyanin content which is responsible for its color change. The genes accountable are CsAN1 (R2R3-MYB transcription factor), CsGL3 and CsEGL3 (bHLH transcription factor) and CsTTG1 (WD repeat protein). This feature stimulated us to review purple tea. The review article discusses its history, taxonomy, geography, process of cultivation and collection with the appropriate harvesting seasons, macroscopic and microscopic characteristics, and its extraction processes. The constituents obtained from Camellia sinensis and the chemical structures of its phytoconstituents were also discussed. The therapeutic properties like anti-diabetic, anti-allergic, anti-pyretic, anti-inflammatory, anti-oxidant anti-aging and anti-parasitic associated with C. sinensis are also described. C. sinensis can also be used for the treatment of osteoarthritis, obesity and cardiovascular diseases (atherosclerosis, hypertension). Furthermore, it provides protection to gastro-intestinal tract from excess secretion of gastric acid and bones from abnormal hormonal levels. It also possesses other properties for treatment of chronic diseases like Cancer and Alzheimer’s.

Keywords: Purple Tea, Anthocyanins, Catechins, Flavonoids, Antioxidants

INTRODUCTION: Tea, scientifically known as Camellia sinensis, is a popular beverage consumed worldwide for its numerous health benefits. Recently, there has been considerate development regarding a new variety of tea, known as Purple Tea, which gets its name due to its unique purple color. This color is believed to be prominent due to the accumulation of anthocyanin - a purple color pigment belonging to the family of flavonoid compounds.

This tea is mainly cultivated and developed in countries like India, China, Japan and Kenya ¹. It is primarily grown at high elevations in areas with a cool climate. Just like the traditional black tea, it has a mild earthy, sweet taste ².

Along with the presence of eight anthocyanin fractions, purple tea also contains gallic acid, caffeine, free amino acids and polyphenols such as epigallocatechin (EGC), catechin, epicatechin (EC), epigallocatechin gallate (EGCG), and epicatechin gallate (ECG) – all of which are of great importance in improving health ³. Studies have shown that regular consumption of the polyphenols, such as in purple tea, is beneficial in assisting anti-diabetic, anti-aging, anti-inflammatory, anti-pyretic, anti-allergic and anti-parasitic activity. Additionally, catechins present in the tea are also effective in treating other serious illnesses like Osteo-Arthritis, Cancer, Alzheimer’s, and certain cardiovascular diseases ^{4, 5}. This paper presents an overview of various aspects of purple tea such as its cultivation, extraction, phytoconstituents, microscopy, mechanisms of color change and its various health benefits.

History: Originally discovered in the gardens of Assam, India, Purple tea captured its interest by standing apart from the traditional green colored leaves because of its rich purple color ⁶.

Twenty-five years later, after the bush was given to The Tea Research Foundation of Kenya, its genetic clone TRFK 31/8 was breathed into existence. TFRK 31/8 is now used as the standard yield control clone to determine the performance of the new variety, TRFK 306/1, produced for commercial use. This cultivar was developed by cross-breeding of traditional tea with its anthocyanin-rich cousin Camellia irrawadiensis. First introduced as seedlings to small-scale Kenyan farmers in 2011, it has quickly gained renown after its five-year investment plan.⁷ Since then, four additional producers have entered the market. Estimates suggest that purple tea will account for approximately $60 million i.e., 5 percent of Kenya’s tea exports ⁸.

Taxonomical Classification:

Kingdom: Plantae

Subkingdom: Viridiplantae

Division: Tracheophyta

Class: Magnoliopsida

Family: Theaceae

Genus: Camellia L

Species: Camellia sinensis

Biological Source: It contains prepared purple leaves and leaf buds of Camellia sinensis (Linne) kuntz., belonging to family Theaceae.

Geographical Source: It is mainly grown in India (Assam), Sri Lanka, China, Japan and Kenya.

Cultivation and Collection: Camellia sinensis is an evergreen shrub cultivated across the world but primarily in countries like India (Assam), China, South and Southeast Asia, Sri Lanka, East Africa, Japan and Mauritius ^{9, 10}. The plant requires well drained, sandy, moist, thoroughly aired, loamy, deep and nutritious with a healthy layer of hummus ¹¹. It prefers acidic soil i.e., low, or neutral pH soil ranging between 5 to 7. Tea is well-cultivated in cool temperatures of 14-27^o C; Purple Tea is grown in cooler conditions ^13, it prefers a wet summer and a cool but not very frosty dry winter with an annual rainfall in the range 70-310 cm ⁹. However, the crop yields best quality plants between rainfall of 250-300 cm and temperatures of 18-20 °C ¹¹.  The plant requires at least 5 hours of direct or 11 hours indirect sunlight daily, but can grow favorably in semi-shade ^{9, 11}. It is cultivated at extremely high elevations of between 4500-7500 feet resulting in strong antioxidant properties ¹³ and is sometimes grown at altitudes as high as 3000 m from sea level ¹¹.

Tea plants are propagated sexually by seeds and asexually by vegetative propagation ¹¹. Stored seeds are soaked for 24 hours in warm water and the hard covering around the micropyle should then be filed down to leave a thin covering. It takes about one to three months for germination to occur, and once seedlings are large enough to handle, they are potted into individual pots and grown in light shade in a greenhouse for their first winter. Once they cross the 15cm mark, they are replanted into their permanent position for 1-3 years outdoors. A seedling takes about 4-12 years before they start to produce seeds ⁹. Bushes take 3 to 6 years to mature ¹³. The harvest time may differ based on environmental conditions ¹². The harvesting depends upon the availability of young terminal buds and adjacent leaves of tea plants. Once the tea plants are fully grown, they are trimmed to produce shoots in a regular manner ¹⁰.

The level of elevation is an essential factor in determining the amount of catechin in tea. Higher altitudes cause an increase in amino acid content increases and decrease in the quantity of polyphenols. Although higher altitudes cause a decrease in the yield of tea, there is a considerate increase in the quality of crops produced.

Vice-versa, increased irrigation causes growth in height and the number of new leaves, however there is an ultimate fall in quality due to lower level of catechins ¹². Additionally, extreme conditions like drought, excessive heat, water logging and frost are also responsible for decreases in the yield and quality of tea plant. Excess rainfall, in areas such as Sri Lanka, also limits the growth and sunlight absorbed ¹¹. There are several types of tea, such as white, oolong, black and purple tea, prepared from Camellia sinensis (L.) O. Kuntze (Theaceae), which vary considerably depending on their differences in fermentation processing, leading to variations in taste and aroma ¹¹. For harvesting purple tea, the leaves are hand-plucked for purple leaves only (two leaves and a bud) and allowed to slightly wither. They are lightly pan-fried to arrest further oxidation, and dried, after which they are packed for shipment for commercial use.

TABLE 1: HARVEST SEASONS ¹¹

Macroscopy and Microscopy: The purple tea plant mostly possesses characteristics that resemble green tea plant – an evergreen shrub that can reach heights up to 9 meters, possessing dark green elliptical, serrated-edged, pointy leaves. They are hairy in nature. White-yellow flowers may grow solitarily or in clusters of 2-4. However, the predominant differentiating factor that stands the two varieties apart is the flush of purple color due to the presence of anthocyanins ¹⁴.

Transverse section of the leaf shows the upper epidermis with presence of polygonal cells with slight wavy walls and a thick cuticle and the lower epidermis with smaller cells containing stomata. The mesophyll is asymmetric in nature with two layers of parenchyma cells, characterized with a number of sclerenchymatous idioblasts varying in shape. Calcium oxalate crystals are also present in the spongy parenchyma. Vascular bundle, consisting of xylem and phloem, is covered by a band of pericyclic fibers ¹⁴.

Morphological observation through Standard Electron Microscopy determined the change in characteristics during the three developmental stages of tea leaf i.e., Juvenile Green (JG), Light Purple (LP), and Dark Purple (DP). Differences were observed in terms of morphological characters like cell size, shape, and structure. While cell size and stomatal number decreased as leaves developed from JG to DP, dark purple leaves were more likely to acquire flocculent structure. Analysis of pigments (chlorophyll, xanthophyll, anthocyanin) recorded a decrease in chlorophyll and xanthophyll content, and an increase in anthocyanin content which is a remarkable property of purple tea, as leaves progressed to DP stage. Moreover, DP tea leaves were also found to possess an increased rate of photosynthesis as compared to LP and JG due to increased activity of chlorophyl ATP synthase subunit ³.

A study comparing the level of photosynthetic pigments, proanthocyanidins, anthocyanin and lignin was carried out, which found that the concentration of photosynthetic pigments was low in purple tea leaves compared to green tea leaves. The level of proanthocyanidin was 7.05% higher compared to green leaves. The anthocyanin concentration was 6.2-fold higher in purple tea leaves whereas the lignin concentration was lower in purple tea leaves.¹⁵

Mechanism of Color Change: The uniqueness of this tea is mainly due to its distinctive purple color, which occurs as a result of hyper-accumulation of anthocyanin in the plant. Anthocyanins are biosynthesized from the flavonoid biosynthetic pathway in the cytosol of the cell, and then the glycosylated end products are deposited in the vacuole ¹⁶.  Plant anthocyanins show different transition in colors like red, purple, or reddish violet, in the form of cyanine glycosides after methylation, acetylation and glycosylation from an anthocyanin monomer. The concentration of anthocyanin in purple leaves was found to be 707 µg·g −1 Dry Weight in Zijuan tea (Camellia sinensis), which is 10-fold higher than the concentration usually found in normal tea varieties ¹⁷. In case of purple tea leaves, a gradual color change is seen. Firstly the juvenile leaves are green in color, which later show transition to light purple color, and finally dark purple color as they pass through various stages of growth and development ³. With the use of various biotechnologies, researchers have stated that anthocyanin is due to upregulation of genes such as CsAN1 (R2R3–MYB transcription factor), CsGL3 and CsEGL3 (bHLH transcription factor), and CsTTG1 (WD-repeat protein). Studies have also shown that the direct or indirect interaction of proteins, photosynthesis processes, transcription factors and anthocyanin biosynthesis involved in metabolism leads to the color change of purple tea leaves ¹⁸.

FIG. 1: MECHANISM OF COLOR CHANGE

The various structural enzymes involved in synthesis of anthocyanin in purple tea leaves include: phenylalanine ammonialyase (PAL), cinnamic acid-4-hydroxylase (C4L), 4-coumarate: CoA ligase (4CL), chalconesynthase (CHS), chalconeisomerase (CHI), flavanone 3-hydroxylase (F3H), flavonoids 30 -hydroxylase (F30H), dihydrofavonol4-reductase (DFR), and anthocyanin synthase (ANS). Studies have found that the activity of PAL was 2-fold higher in purple leaves than in green ones. In addition, it was found that CHI activity in the purple leaves was significantly greater compared to that in green ones, which explains the increase in anthocyanin level in purple tea leaves ^{17, 19}. In anthocyanin synthesis, gene expression levels are regulated by transcription factors such as R2R3-MYB, bHLH, WD40, and HY5.¹⁷ Studies have revealed that activation of the R2R3-MYB transcription factor (TF), anthocyanin1 (CsAN1) specifically upregulated the bHLH TF CsGL3 and anthocyanin late biosynthetic genes (LBGs) to accumulate in purple tea. It was also found that CsAN1 interacts with bHLH TFs (CsGL3 and CsEGL3) and WD-repeat protein CsTTG1 to form the MYB-bHLH-WDR (MBW) complex ¹⁶. In leaves of purple tea, this MYB–bHLH–WDR complex regulates anthocyanin accumulation by activating mRNA expression of F3H, DFR and ANS.  The abundance levels of bHLH 66-like and bHLH 135 in purple leaves were significantly higher than those in green leaves tea, and the mRNA expression level of bHLH was also higher in purple leaves.¹⁷ Another protein, long hypocotyl5 (HY5) also found in abundance as compared to green tea was observed andreported that HY5 also regulates anthocyanin biosynthesis by inducing the transcriptional activation of the MYB75/PAP1. Thus, higher abundance of bHLH and HY5 may increase the transcription of anthocyanin biosynthetic genes ¹⁷.

Phytoconstituents:

FIG. 2: PIE CHART SHOWING COMPARISON OF PHYTOCONSTITUENTS

Purple tea consists of various phytoconstituents such as alkaloids, flavonoids, polyphenols, tannins, saponins, steroids, terpenoids and anthocyanins ¹⁸. Among them, anthocyanin is the most important and is also responsible for the purple color which distinguishes this tea from other types of teas. Anthocyanin is a water-soluble pigment and belongs to the family of compounds known as flavonoids ²⁰. Anthocyanins are classified as glycosides of polyhydroxy or poly-methoxy derivatives of 2-phenylbenzopyrylium and consist of two benzoyl rings in between a heterocyclic ring, which in turn form the flavylium cation. Anthocyanins are most commonly present as tri-, di- or mono-saccharide units and when hydrolyzed, anthocyanins yield anthocyanidins and sugars ²¹. Purple tea shows presence of 8 anthocyanin fractions which are pelargonidin-3,5-diglucoside, cyanidin-3-O-galactoside, cyanidin-3-O-glucoside, delphinidin, cyanidin, pelargonidin, peonidin, and malvidin, among which malvidin is the most predominantly detected anthocyanin for some plants cyanidin-3-O-galactoside for other plants. This difference is observed mainly due to difference in the genotype and the environment of plant growth ²². Polyphenols found in purple tea consist of catechins such as epigallocatechin (EGC), catechin, epicatechin (EC), epigallo-catechin gallate (EGCG) and epicatechin gallate (ECG).  These catechins are responsible for the antioxidant property of tea ²². Catechin synthesis is done using malonic acid-and shikimic acid metabolic pathways ²³. Since high amount of gallic acid is also present in the tea, it is derived as an intermediary product during shikimic acid pathway ^{20, 23}. The amount of catechin found in purple tea is less when compared with other varieties of tea ²⁰. Regarding free amino acids, tyrosine and cysteine, lysine, alanine, aspartic acid, methionine, valine and isoleucine are found in trace amounts. Alkaloids such as caffeine and theobromine are also found. Caffeine is mainly a trimethyl derivative of purine 2, 6-diol ²³. The amount of caffeine found in purple tea is lower than other varieties of tea such as green and black tea. This difference may be attributed to the genotypic factors ^{18, 20}.

Purple Tea extract contains total polyphenol (50.4%), caffeine (4.5%), theobromine (1.6%), GHG (7.4%), EGCG (9.8%), ECG (5.8%), chlorogenic acids (0.9%), total anthocyanin (1.5%) ¹⁸.

Extraction of Phytoconstituents: Several isolation techniques such as Soxhlet extraction, heated reflux extraction (HRE), organic solvent extraction (OSE), and maceration are commonly used for extraction of bioactive compounds ²⁴. Some recent developments in modernization of extraction techniques have proved to be more advantageous as compared to conventional degrees due to higher degrees of sophistication and improved performance. These methods generated higher yields of extractions at much lower temperatures and utilized low extraction time, thus producing high quality extracts. Some of these are: Ultrasound-Assisted Extraction (UAE), Microwave-Assisted Extraction (MAE), Microwave Assisted High Pressure Extraction, Ultrasound/Microwave Assisted Extraction (UMAE), Supercritical Fluid Extraction (SFE), Subcritical Water Extraction (SCWE), High Hydrostatic Pressure Extraction (HHPE), Pulsed Electric Field (PEF) processing, Accelerated Solvent Extraction (ASE), Sequential Alkaline Extraction method (SAE) and others ^{24, 25}.

Ultrasonic Assisted Extraction showed better efficiency in the extraction of tea polyphenols, amino acids and caffeine as compared to conventional extraction strategies. UAE effectively increased the extraction efficiency of catechin and decreased the extraction time and solvent consumption ²⁴.

A new molecularly imprinted polymer (MIP) prepared using catechin as a template enabled selected extraction of catechin from tea samples with high selectivity.

Efficient extraction of phytoconstituents largely depends on the type of solvents used. A range of highly polar solvents like water, ethanol, and methanol, and non-polar solvents such as n-hexane, are often used for successful extraction of a wide variety of compounds with varying polarity. Other factors that affect the extract yield are extraction temperature, extraction time, pH of the extract as well as the nature of compound to be extracted ²⁵.

The combination of solvents generally used for extraction of phytochemicals from tea are as follows ²⁴:

• Flavonoids - ethanol, methanol, water, and combinations of these solvents
• Catechins – ethanol, ethyl acetate, n-butanol, n-hexane, deep eutectic solvents

In case of extraction of bioactive molecules of tea, it has been proved that higher temperatures and increased extraction time leads to degradation of such compounds. For example, UAE extraction of polyphenols gives better yield at 65^oC as compared to 85^oC. Often, combinations of higher temperature and decreased extraction time, or a lower temperature and increased extraction time are modified to provide optimum results ^{25, 26}.

Therapeutic Properties

Osteoarthritis ^{27, 28, 29, 39}: The phytoconstituents present in C. sinensis are useful for patients with Osteoarthritis. Polyphenols, principally catechins, have anti-arthritic property. The catechins present in major concentration are epicatechin, epicatechin-3-gallate, epigallocatechin and epigallocatechin-3-gallate (EGCG). A study on mouse as an experimental model suggests that EGCG has ability to regulate PGE2, chemokines, and cytokines expression.

The suppression of prostaglandin E2 (PGE2) is done by inhibiting Cyclooxygenase-2 (COX-2) enzyme (similar to NSAIDS). These chemicals have a prominent role in inducing and maintaining inflammation in joints. In patients with Osteoarthritis, the level of these inflammatory mediators is significantly high. Additionally, the study suggests that EGCG can be used for prophylactic purposes. Moreover, the expression of Interlukin-6 (IL-6) is also down regulated by EGCG. IL-6 is another molecule which induces Arthritis in cartilages of synovial joints and is also involved in Gout.

Obesity ^{31, 32}: Obesity is a common problem observed in several countries across the world, which has potential to cause other metabolic disorders which could sometimes prove fatal. Research conducted by Hiroshi et.al studied the efficacy of purple tea phytoconstituents in controlling obesity. Results have suggested that extracts of C. sinensis can reduce the gain in bodyweight. BMI and body fat mass also show marked reduction in body fat ratio. As fat content decreases, muscle mass ratio increases. By inhibition of lipid absorption in intestines, serum triglycerides have also been shown to reduce. This was observed by olive oil ingestion which contains esters of oleic, linoleic and palmitic acid. In another study conducted on animal model, lower amount of fat was deposited in the adipocytes of mice. Thereby, hyperlipidemia can be prevented.

Other metabolic disorders such as fatty liver disease can also be prevented by consumption of purple tea. As C. sinensis extracts increase hepatic elimination of cholesterol, there is evident lowering of blood cholesterol levels. Furthermore, enzymes like alpha-ketoglutarate, pyruvate dehydrogenase – both of which are required for biosynthesis of Cholesterol – and squalene epoxidase, the rate limiting enzyme in cholesterol biosynthesis are also inhibited.

Anti-Cancer ^{33, 34, 35, 36}: Catechins, one of the most prominent phytoconstituent of C. sinensis, possesses anti-cancer effects. Many researchers have reported that catechins have the potential to inhibit matrix metalloproteinases. Matrix metalloproteinases are enzymes that degrade components of extracellular matrix (ECM) and aid in tumor invasion.  A study by Ahmad et. al also reported that EGCG found in purple tea disrupts the cell cycle progression in tumor cells. EGCG induces cyclin kinase inhibitors which, by downregulation of cyclin, impedes the cycle progression at G0-G1 phase. Another strategy by which cancer cells metastasize is angiogenesis. C. sinensis extracts can suppress angiogenesis in cancer patients by inhibiting Vascular Endothelial Growth Factor (VEGF). Some cancers are induced as a result of harmful effects of ultra-violet light. These types of cancers can also be suppressed by oral administration of purple tea.

Anti-Alzheimer’s/Dementia ^{37, 38}: Alzheimer’s is a disease characterized by deposition of beta amyloid plaques and neurofibrillary tangles in brain. This leads to degeneration of neurons, which are responsible for memory retention, thereby inducing dementia. In research done on animal models by Kavon et. al, it was reported that EGCG extracted from purple tea has anti-amyloidogenic effect. A 50mg/kg dose of EGCG markedly reduced deposition of beta amyloid plaques in hippocampus region, cingulate cortex region and entorhinal cortex region of brain. This study also suggested that memory performance was improved by EGCG treatment. Moreover, as EGCG also possesses anti-ageing property by down regulation of the pro-apoptotic genes responsible for cell apoptosis, it can also be employed in the geriatric population as they are more prone to Alzheimer’s and Dementia. EGCG also exhibits antioxidant activity and has greater potency than Ascorbic Acid (Vitamin C) and Tocopherols (Vitamin E).

Cardiovascular Diseases ^{39, 40}: Several studies have suggested that drinking purple tea is beneficial in the treatment of cardiovascular diseases. Hartley et. al reported that drinks, capsules and tablets made of extracts of C. sinensis can be used as prophylaxis in cardiovascular diseases. Trials conducted on human subjects have reported that subjects consuming C. sinensis extracts showed significantly lower levels of low-density lipoproteins (LDL), biomolecules that are deposited in the arteries of the heart. This deposition of lipids thickens the blood vessels and interferes with physiological blood flow. Since the heart does not receive sufficient oxygen, hypoxia occurs. This condition is termed Atherosclerosis and the deposits are called as Atherosclerotic plaque. Hartley et. al also confirmed that the systolic and diastolic pressure were also lowered in test subjects. In another study by Antonello et. al, systolic and diastolic pressure induced by doses of Angiotensin II was reduced by C. sinensis extracts especially EGCG.  These observations indicate the efficacy of C. sinensis extracts in treating hypertension.

Anti-diabetic ^{41, 42, 43}: Purple tea has been known to possess a number of phytochemicals such as alkaloids, flavonoids, phenols, tannins, saponins, steroids and terpenoids.  However, only polyphenols like catechins, flavanols, theaflavins and thearubigins, have the potential to decrease the risk of diabetes mellitus.

The presence of epigallocatechin gallate (EGCG), the most abundant and powerful antioxidant present in tea, has been proven to assist in Type 1 Diabetes Mellitus. It acts by inhibiting the inflammatory factors and reducing the reactive oxygen species, thereby reducing the production of nitric oxide synthase (iNOS). This protects the function of pancreatic Islet β-cells. Clinically, it has demonstrated promise by lowering blood glucose 4th and 6th hour after administration. Another water-soluble compound, gallic acid, reduces blood glucose level by promoting the transport of glucose into skeletal muscles. Additionally, lowering of blood glucose levels also occurs due to presence of catechins which inhibit the carbohydrate digestive enzymes. Thus, glucose production decreases in the GT, which results in overall lower levels of glucose, which in turn reduces serum glucose level, and finally decreases liver glycogen.

Lastly, Purple tea has also been reported to increase insulin sensitivity. This occurs due to an increase in RBP-4 signaling from mature adipocytes, which increase insulin-stimulated glucose uptake in adipocytes, thereby decreasing cellular glucose uptake. This mechanism has also been determined to occur due to presence of EGCG.

Anti-ageing/Antioxidant ^{44, 45, 46, 47, 48}: Biological aging is particularly characterized by certain oxidative stress parameters, namely erythrocyte malondialdehyde (MDA), glutathione peroxidase (GPx) or glutathione reductase and catalase (CAT). Accumulation of lipid peroxidation (LPO) and reactive oxygen species (ROS) takes place, thereby deteriorating cellular enzymes. This leads to progressive loss of structural organization, diminishing functional capacity and other neurological disorders.

Catechins, normally found in purple tea, have been known to prevent oxidative damage in the brain by activation of antioxidative enzymes. Intake of catechins causes an age-dependent increase in erythrocyte MDA level and a decrease in GSH and membrane–SH group concentration, thereby providing protection to erythrocytes against oxidative stress.

Decreased membrane GSH, and thus, increased brain glutathione levels account for an increase in brain anti-oxidant capacity. This increase in brain GSH imply the neuroprotective potential of purple tea in neurodegenerative conditions.

The presence of fine dust particles in the air has led to severe signs of skin aging in most population. The most prominent tea-catechin, epigallocatechin gallate (EGCG), stimulated skin aging in human dermal fibroblasts (HDFs) by scavenging ROS. Collagen synthesis was recovered, and intracellular elastase and collagenase activities were inhibited, thereby making EGCG a potential molecule for FDP-induced skin aging. In SAMP10 mice with accelerated senescence, catechin intake was proven to suppress cerebral atrophy. Additionally, in the Caenorhabditis elegans organism model, catechins improved the tolerance of worms to oxidative stress by germline signaling pathways, thus proving its anti-oxidant and anti-aging potential.

Anti-Inflammatory ^{49, 50}: Anthocyanins have been considered as key modulators of inflammations, however, other phytochemicals like alkaloids, flavonoids, steroids, and tannins may also exert some anti-inflammatory effects.

It is also suggested that Purple Leaf Tea may ameliorate inflammation by increasing the population of beneficial gut species such as Ruminococcaceae. These bacterial species possess the ability to degrade cellulose and hemicellulose, which are then converted into short chain fatty acids (SCFAs) by the process of fermentation. These SCFAs have been shown to protect against inflammation

In a study involving reproducible mouse models with Post-Treatment Reactive Encephalopathy (PTRE), mice that did not receive any antioxidant treatment with Kenyan Purple Tea anthocyanins of coenzyme-Q10 showed a more marked presence of inflammatory cells.

Anti-Pyretic: Little is known about the anti-pyretic activity of purple tea, only that it helps reduce fever in some cases, however there is no particular scientific evidence to support the same.

Anti-Allergic ^{51, 52}: Purple tea has been known to possess some significant immunomodulatory properties, owing to the presence of saponins, polysaccharides, and polyphenols like catechins. Although the exact inhibitory mechanism remains undefined, some hypotheses have been put into place, of which EGCG plays an important role. EGCG causes inhibition of NADPH oxidase translocation in mast cells, which are believed to play a central role in the initiation of allergic immune response. The phytochemicals act by inhibiting allergen–IgE complex formation and reducing FcεRI expression or allergen–IgE complex binding to FcεRI, thus helping to alleviate symptoms of allergy.

Additionally, the presence of tealeaf saponins (TLF) was proven to strongly inhibit histamine release, a chemical mediator involved in allergic reaction.

IR and UV–Visible spectroscopy analysis of purple tea extract revealed the presence of bio-active compounds, which could exert its clinical effects in conditions such as asthma, allergic rhinitis, other food and respiratory allergies, atopic dermatitis, and anaphylaxis.

ACE Inhibition / Blood Pressure Regulation ^{53, 54}: GC-MS based isolations of tea infusions and decoctions identified a total of fifty-one metabolites, which included the presence of organic and inorganic acids, amino acids, sugars, alcohols, phenols, flavonoids, and fatty acids.

These metabolites, including catechins, were found to significantly reduce the activity of membrane-bound Angiotensin-converting enzyme, an important chemical mediator found in blood pressure regulation. The exact mechanism of this inhibition was determined to be the conversion of hippuryl-l–histidyl-l-leucine to hippuric acid.

Gastrointestinal Protection ^{55, 56}: The gastro-protective effects of purple tea may be attributed to the following mechanisms: increasing the content, thickness, pH, and blood flow to the gastric mucus, and reducing the gastric acid output.

In albino rats with ethanol-induced gastric ulcers, Camilla sinensis offered protection by inhibiting the 5- lipoxygenase pathway.

Anti-parasitic ^{57, 58}: Purple tea demonstrated some anti-parasitic effects owing to the presence of catechins. Catechin gallate inhibited the recombinant T. cruzi arginine kinase, a key enzyme in the energy metabolism of the parasite by about 50%. Camilla sinensis Purple Tea also demonstrated the potential to inhibit the Acanthamoeba parasite by exerting lethal effects on Acanthamoeba cysts.

Prevention of Bone Degradation ^{59, 60}: Certain findings in bilaterally ovariectomized rat model have suggested that aqueous tea extracts may be effective in preventing bone loss due to ovarian hormone deficiency. However, the exact underlying mechanism for the same remains unknown. Other observed actions are increase in serum estrogen level, prevention of bone loss, increase in bone density), and preservation of microarchitecture of bone.

CONCLUSION: Nature has bestowed mankind with innumerable resources which can truly be utilized for various ailments. Purple tea is one such example which has a high anthocyanin profile. In this review article, we have discussed the pharmacognostic aspects of C. sinensis, some mechanistic insights on color change and its numerous therapeutic properties which is exhibited majorly by a class of phytochemicals i.e., polyphenols. Polyphenols especially Epigallocatechin gallate (EGCG) have great potential to treat fatal diseases like cancer which synthetic anti-cancer drugs and Radiotherapy didn’t cure satisfactorily. Also, it could treat those neurodegenerative diseases which are, till date, still declared as ‘Only Manageable’. However, there are some questions that pose unanswered like its efficacy in human studies, side effects and other adverse effects associated with use of polyphenols as drug. If thorough research is conducted in future, it will surely prove to be a boon for humans.

ACKNOWLEDGEMENT: The authors would like to express their gratitude to the researchers and scholars in the field whose work laid the foundation for this review. They also would like to thank the editorial team and reviewers for their constructive feedback and suggestions during the review process. Their input has significantly enhanced the clarity and coherence of this article

CONFLICTS OF INTEREST: Ms. Vishaka G. Thakur, Ms. Niki Jain, Ms. Nikita Khule, Ms. Nimisha Raut, and Mr. Talha Siddiqui have no competing interests to declare.

REFERENCES:

1. Li XX, Li ZY, Zhu W, Wang YQ, Liang YR, Wang KR & Zheng XQ: Anthocyanin metabolism and its differential regulation in purple tea (Camellia sinensis). Plant Physiology and Biochemistry 2023; 107875.
2. Jarvis C: Purple Tea Guide: Health and Flavor — Rosie loves tea. Rosie Loves Tea. https://rosielovestea.com/blog/what-is-purple-tea Accessed date: 15th October, 2023.
3. Kumari, M., Thakur, S., Kumar, A., Joshi, R., Kumar, P., Shankar, R., & Kumar, R. (2020). Regulation of color transition in purple tea (Camellia sinensis). Planta, 251, 1-18.
4. Lin C, Lin H, Chang H, Chuang L, Hsieh C, Lu S, Hung C & Chang J: Prophylactic effects of purple shoot green tea on cytokine immunomodulation through scavenging free radicals and no IN LPS-stimulated macrophages. Current Issues in Molecular Biology 2022; 44(9): 3980–4000.
5. LI, MR, ZHOU YZ, DU GH & QIN XM: Research progress about the anti-aging effect and mechanism of flavonoids from traditional Chinese medicine. Acta Pharmaceutica Sinica 2019; 1382-1391.
6. Atlas Tea Club: What is Purple Tea? History, Benefits & More. https://atlasteaclub.com/blogs/tea-blog/what-is-purple-tea Accessed date: 15th October, 2023 2022.
7. Tea Research Foundation of Kenya. (2009). The tea research foundation of Kenya pre-releases purple tea variety for processing health tea product. http://repository.seku.ac.ke/handle/123456789/3075 Accessed date: 15th October, 2023
8. World Bank Group. (2017). Creating Kenya’s Purple Tea Market – Markets and Competition Policy in Action. World Bank. https://www.worldbank.org/en/news/feature/2017/08/29/creating-kenyas-purple-tea-market---markets-and-competition-policy-in-action Accessed date: 15thOctober, 2023
9. Biren Shah and Avinash Seth: Textbook of Pharmacognosy and Phytochemistry. Elsevier India 2017.
10. Agarwal U, Pathak DP, Bhutani R, Kapoor G & Kant R: Review on Camellia sinensis: Nature’s gift. International Journal of Pharmacognosy and Phytochemical Research 2017; 9(8): 1119-1126.
11. Ahmed S & Stepp JR: Green tea. In Elsevier eBooks 2013; 19–31.
12. Daly D: Growth and Culture of Camellia sinensis under in-vitro conditions. Research Gate 2018.
13. Choubey M, Paul B, Ray A, Mohanto K, Mazumdar A, Chhetri P & Kujar R: Purple Tea: Prospects of Darjeeling Tea Plantation. International Journal of Agriculture Innovations and Research [online] 2020; 9(3): 169-174.
14. Tea - Pharmacognosy. (2019). pharmacy180.com. https://www.pharmacy180.com/article/tea-156/ Accessed date: 15th October, 2023
15. Kumari M, Thakur S, Kumar A, Joshi R, Kumar P, Shankar R & Kumar R: Regulation of color transition in purple tea (Camellia sinensis). Planta 2020; 251: 1-18.
16. Lu R, Song M, Wang Z, Zhai Y, Hu C, Perl A & Ma H: Independent flavonoid and anthocyanin biosynthesis in the flesh of a red-fleshed table grape revealed by metabolome and transcriptome co-analysis. BMC Plant Biology 2023; 23(1): 361.
17. Shui L, Li W, Yan M, Li H & Guo F: Characterization of the R2R3-MYB transcription factor CsMYB113 regulates anthocyanin biosynthesis in tea plants (Camellia sinensis). Plant Molecular Biology Reporter 2023; 41(1): 46-58.
18. Li Y, Yuan P, Wang C & Wu Z: The research progress of main chemical constituents and functional activity in purple tea. International Journal of Nutrition and Food Sciences 2021; 10(1): 24.
19. Song S, Tao Y, Gao L, Liang H, Tang D, Lin J & Li C: An integrated metabolome and transcriptome analysis reveal the regulation mechanisms of flavonoid biosynthesis in a purple tea plant cultivar. Frontiers in Plant Science 2022; 13: 880227.
20. Mattioli R, Francioso A, Mosca L & Silva P: Anthocyanins: A comprehensive review of their chemical properties and health effects on cardiovascular and neurodegenerative diseases. Molecules 2020; 25(17): 3809.
21. de Sousa Moraes LF, Sun X, Peluzio MDCG & Zhu MJ: Anthocyanins/anthocyanidins and colorectal cancer: What is behind the scenes?. Critical reviews in food science and nutrition 2019; 59(1): 59-71.
22. Abdel‐Aal EM, Rabalski I, Mats L & Rai I: Identification and quantification of anthocyanin and catechin compounds in purple tea leaves and flakes. Molecules 2022; 27(19): 6676.
23. Kar S, Saloni S & Sindhu: Green tea - its chemical constituents and health benefits. International Journal of Engineering Research and Technology 2016; 5(02).
24. Raghunath S, Budaraju S, Gharibzahedi SMT, Koubàa M, Roohinejad S & Mallikarjunan K: Processing Technologies for the Extraction of Value-Added Bioactive Compounds from Tea. Food Engineering Reviews 2023; 15(2): 276–308.
25. Kumar A, Nirmal P, Kumar MN, Jose A, Tomer V, Öz E, Proestos C, Zeng M, Elobeid T, Sneha K & Öz F: Major Phytochemicals: recent advances in health benefits and extraction method. Molecules 2023; 28(2): 887.
26. Jahanbakhsh A, Hosseini M, Jahanshahi M & Amiri A: Extraction of catechin as a flavonoid compound via molecularly imprinted polymers. International Journal of Engineering 2022; 35(5): 988-995.
27. Karima A, Indriaswati L, Fatmariyanti S & Kurniasari N: Effect of epigallocatechin gallate (EGCG) on neutrophils count and interleukin-6 (IL-6) expression in Pseudomonas aeruginosa keratitis: an experimental study on Rattus norvegicus rat. Bali Medical Journal 2023; 12(3): 2646-2655.
28. Fechtner S, Singh A, Chourasia M & Ahmed S: Molecular insights into the differences in anti-inflammatory activities of green tea catechins on IL-1β signaling in rheumatoid arthritis synovial fibroblasts. Toxicology and Applied Pharmacology 2017; 329: 112–120.
29. Misra S, Ikbal AMA, Bhattacharjee D, Hore M, Mishra S, Karmakar S & Palit P: Validation of antioxidant, antiproliferative, and in-vitro anti‐rheumatoid arthritis activities of epigallo‐catechin‐rich bioactive fraction from Camellia sinensis var. assamica, Assam variety white tea, and its comparative evaluation with green tea fraction. Journal of Food Biochemistry 2022; 46(12): 14487.
30. Lee F, Bae KH, Ng S, Yamashita A & Kurisawa M: Hyaluronic acid–green tea catechin conjugates as a potential therapeutic agent for rheumatoid arthritis. RSC Advances 2021; 11(24): 14285–14294.
31. Shimoda H: Purple tea and its extract suppress diet-induced fat accumulation in mice and human subjects by inhibiting fat absorption and enhancing hepatic carnitine palmitoyltransferase expression. Int J Biomed Sci 2015; 11(2): 67–75.
32. Suzuki T, Pervin M, Goto S, Isemura M & Nakamura Y: Beneficial effects of tea and the green tea catechin epigallocatechin-3-gallate on obesity. Molecules 2016; 21(10): 1305.
33. Quintero-Fabián S, Arreola R, Becerril-Villanueva E, Torres-Romero JC, Arana-Argáez V, Lara-Riegos J & Alvarez-Sánchez ME: Role of matrix metalloproteinases in angiogenesis and cancer. Frontiers in oncology 2019; 9: 1370.
34. Joshi R, Rana A, Kumar V, Kumar D, Padwad Y, Yadav SK & Gulati A: Anthocyanins enriched purple tea exhibits antioxidant, immunostimulatory and anticancer activities. Journal of Food Science and Technology 2017; 54(7): 1953–1963.
35. Stojanović S, Sprinz H & Brede O: Efficiency and mechanism of the antioxidant action of trans-resveratrol and its analogues in the radical liposome oxidation. Archives of Biochemistry and Biophysics 2001; 391(1): 79-89.
36. Koskei LC: In-vitro studies of the effects of purple tea (camellia sinensis) extracts on selected human cancer cell lines and Multi-drug Resistant Bacteria (Doctoral dissertation, University of Nairobi) 2019.
37. Rezai‐Zadeh K, Arendash GW, Hou H, Fernandez F, Jensen M, Runfeldt M, Shytle RD & Tan J: Green tea epigallocatechin-3-gallate (EGCG) reduces β-amyloid mediated cognitive impairment and modulates tau pathology in Alzheimer transgenic mice. Brain Research 2008; 1214: 177–187.
38. Research progress of EGCG in the treatment of Alzheimer’s disease. (2022). International Journal of Frontiers in Medicine, 4(6).
39. Hartley L, Flowers N, Holmes J, Clarke A, Stranges S, Hooper L & Rees K: Green and black tea for the primary prevention of cardiovascular disease. The Cochrane Library 2013; (6).
40. Antonello M, Montemurro D, Bolognesi M, Di Pascoli M, Piva A, Grego F, Sticchi D, Giuliani L, Garbisa S & Rossi GP: Prevention of Hypertension, Cardiovascular Damage and Endothelial Dysfunction with Green Tea Extracts. American J of Hypertension 2007; 20(12): 1321–1328.
41. Wen L, Wu D, Tan X, Zhong M, Xing J, Li W, Li D & Cao F: The Role of Catechins in Regulating Diabetes: An update review. Nutrients 2022; 14(21): 4681.
42. Rahimifard M, Baeeri M, Bahadar H, Moini-Nodeh S, Khalid, M, Haghi‐Aminjan H, Mohammadian H & Abdollahi M: Therapeutic Effects of Gallic Acid in Regulating Senescence and Diabetes; an In-vitro Study. Molecules 2020; 25(24): 5875.
43. Wu X, Yang M, He Y, Wang F, Kong Y, Ling T & Zhang, J: EGCG-derived polymeric oxidation products enhance insulin sensitivity in db/db mice. Redox Biology 2022; 51: 102259.
44. Andrade JP: Protective action of green tea catechins in neuronal mitochondria during aging. Frontiers in Bioscience 2015; 20(2): 247–262.
45. Haque A, Hashimoto M, Katakura M, Tanabe Y, Hara Y & Shido O: Long-Term administration of green tea catechins improves spatial cognition learning ability in rats. Journal of Nutrition 2006; 136(4): 1043–1047.
46. Wang L, Lee W, Cui YR, Ahn G & Jeon Y: Protective effect of green tea catechin against urban fine dust particle-induced skin aging by regulation of NF-κB, AP-1, and MAPKs signaling pathways. Environmental Pollution 2019; 252: 1318–1324.
47. Unno K, Takabayashi F, Kishido T & Oku N: Suppressive effect of green tea catechins on morphologic and functional regression of the brain in aged mice with accelerated senescence (SAMP10). Experimental Gerontology 2004; 39(7): 1027–1034.
48. Fei T, Fei J, Huang F, Xie T, Xu J, Zhou Y & Yang P: The anti-aging and anti-oxidation effects of tea water extract in Caenorhabditis elegans. Experimental Gerontology 2017; 97: 89–96.
49. Geoffrey KK, Kagira J, Maina N & Karanja S: Qualitative Phytochemical Screening of Camellia sinensis and Psidium guajava Leave Extracts from Kericho and Baringo Counties. International Journal of Advanced Biotechnology and Research (IJBR) 2020; 5(3): 506-512.
50. Rashid K, Wachira FN, Nyariki JN & Isaac A: Kenyan purple tea anthocyanins and coenzyme-Q10 ameliorate post treatment reactive encephalopathy associated with cerebral human African trypanosomiasis in murine model. Parasitology International 2014; 63(2): 417–426.
51. Li Q, Wang Y, Liang Y & Lu J: The anti-allergic potential of tea: a review of its components, mechanisms and risks. Food & Function 2021; 12(1): 57–69.
52. Balaji G, Chalamaiah M, Hanumanna P, Vamsikrishna B, Kumar DJ & Babu VV: Mast cell stabilizing and anti-anaphylactic activity of aqueous extract of green tea (Camellia sinensis). International Journal of Veterinary Science and Medicine 2014; 2(1): 89–94.
53. Ray S, Dutta M, Chaudhury K & De BK: GC–MS based metabolite profiling and angiotensin I-converting enzyme inhibitory property of black tea extracts. Revista brasileira De Farmacognosia 2017; 27(5), 580–586.
54. Moore RJ, Jackson KG & Minihane A: Green tea (Camellia sinensis) catechins and vascular function. British Journal of Nutrition 2009; 102(12): 1790–1802.
55. Ratnasooriya W & Fernando TSP: Gastroprotective activity of Camellia sinensis black tea brew in rats. Pharmaceutical Biology 2009; 47(8): 675–682.
56. Ngobidi KC, Igbokwe GE, Ajayi AA, Otuchristian G, Obasi SE, Osigwe AO & Adindu SC: Anti-Ulcerative effect of ethanol leaf extract of camellia sinensis on albino rats induced ulcer with ethanol. Int J Res Pharm Biosci 2016; 3(7): 28-33.
57. Hajihossein R, Eslamirad Z, Rafiei F, Naderi G & Assadi M: Anti-Acanthamoeba effect of Camellia sinensis extract (black and green tea) in-vitro. J Med Plants 2020; 19: 163-169.
58. Sosa AM, Moya Alvarez A, Bracamonte E, Korenaga M, Marco JD & Barroso PA: Efficacy of topical treatment with (−)-epigallocatechin gallate, a green tea catechin, in mice with cutaneous leishmaniasis. Molecules 2020; 25(7): 1741.
59. Das AS, Mukherjee M & Mitra C: Evidence for a prospective anti-osteoporosis effect of black tea (Camellia Sinensis) extract in a bilaterally ovariectomized rat model. Asia Pacific Journal of Clinical Nutrition 2004; 13(2): 210-216.
60. Mitra C, Das D, Das AS & Preedy VR: Black Tea (Camellia sinensis) and Bone Loss Protection. Tea in Health and Disease Prevention 2013; 603-612.
    

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    Thakur VG, Jain N, Khule N, Raut N and Siddiqui T: Purple tea: a systematic review. Int J Pharm Sci & Res 2024; 15(3): 614-25. doi: 10.13040/IJPSR.0975-8232.15(3).614-25.

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