# Effects of Epigallocatechin-3-O-Gallate on Bone Health
## 1 Introduction  
Whilst green tea (_Camelia sinensis_) contains various classes of chemical compounds, such as catechins, phenolic acids, polyphenolic acids, amino acids, proteins, and lipids,in this paper, we will focus on catechchins as represented by flavonoids. This is significant because the following catechchins are all found in green tea: epigallocatechin gallate (EGCG), epicatechin gallate (ECG), epigallocatechin (EGC), and epicatechin (EC). This fact makes green tea much richer in catechins than black tea (one cup of brewed green tea contains about 200-300 mg of EGCG, whereas black tea contains only about 18 mg per cup), and subsequently, its antioxidant capacity is directly proportional to the catechin content [1; 2; 3; 4; 5]. The number and proportion of active compounds depend on various factors related to the conditions of cultivation, including soil, climate, light, geography, microorganisms, and temperature. During black tea processing, fermentation takes place, and most catechins present in fresh green tea leaves undergo oxidation to theflavins. These substances are the origin of the characteristic features of black tea--its dark colour and astringent taste [6]. EGCG, the major catechin with a polyphenolic structure, which was first isolated from green tea, has become a popular subject of research due to its intriguing properties [7]. The number of studies on this compound has proportionally begun to increase since the early 2000s. EGCG can be found in other plants such as _Camellia gymnnogyna_ (Baiyacha), a wild tea plant species closely related to _C. sinensis_. Research has shown that Baiyacha contains high levels of methylated EGCG derivatives, such as 3\({}^{\prime\prime}\)-methyl-epigallocatechin gallate (EGCG3\({}^{\prime\prime}\)Me), which are rarely observed in regular tea plants [8]. While _Camellia sinensis_ is by far the richest and most studied source, trace amounts of EGCG or structurally related gallbladder catechchins have been detected in the leaves, skins, or seeds of some fruits (e.g., apples, plums, blackberries, cranberries), nuts (hazelnuts and pecans), and other plants (onions), but these levels are generally much lower [9]. EGCG has the ability to quench reactive radicals and chelate transition metal ions, avoiding the formation of reactive oxygen species (ROS) [7]. Its varied therapeutic properties have made it a popular bioactive ingredient and drug carrier in novel formulations. Due to its antioxidant, antivirus, and anti-inflammatory effects, it seems to be a promising compound for potential use in the treatment of many diseases [2; 3; 8; 9]. Interestingly, epigallocatechin-3-gallate has been found to influence neuroprotection, including relapsing-remitting multiple sclerosis [10; 11; 12; 13; 14]. However, EGCG exhibits several limitations, such as poor solubility in lipids, low bioavailability, rapid decomposition and a short half-life. In order to overcome these limitations, it would be necessary to either use its highly effective dose in vivo to get the expected pharmacological effect and/or modify the EGCG structure. As far as structural modification is concerned, [PERSON] et al., in their study, presented its impact on the properties of EGCG derivatives. Changes in the chemical structure contributed to improved stability, uptake by tumour cells, solubility in lipids, and the ability to penetrate cells [14]. EGCG can effectively neutralise ROS and, therefore, prevent oxidative damage in healthy cells. It reveals chemopre properties as it contributes to apoptosis and stops cancer cells from growing. These effects are mediated by the modulation of cell cycle regulatory proteins, the activation of killer caspases, and the suppression of oncogenic transcription and pluripotency maintenance factors. EGCG has demonstrated its ability to affect many signal transduction pathways and block telomerase activity, causing the stimulation of telomere fragmentation.