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EGCG – The Wonder of Nature

Author: Nina Devrnja, PhD in Biology

Despite the development of an advanced modern pharmaceutical industry in chemical synthesis, more recently, the use of natural medical plants has re-emerged as one of the main areas of scientific research. Natural products have been the centre of attention of the scientific community in the last decades, and the surrounding interest continues to grow incessantly. Even before the rise of modern chemical pharmacology, natural compounds has been used for centuries as components of traditional medicines. Nowadays, some of the traditional healing practices, such as Indian Ayurveda, traditional Chinese medicine or African herbal medicines, remain the primary treatment option for many people across the world, due to economic reasons, personal beliefs or the difficulty in accessing pharmaceutical products. In modern pharmacology, natural products have become one of the most important resources for developing new lead compounds. Drugs used in the treatment of various cancers, cardiovascular diseases, diabetes, and more are often NPs or their derivatives. For instance, between 1981 and 2014 over 50% of newly developed drugs were developed from natural products (9).

The consumption of green tea has been reported to confer many health benefits. The green tea plant (Camellia sinensis) is a species of evergreen shrubs or small trees with glossy green, pointed and fragrant leaves. Smaller young leaves and leaf buds are used for making green tea, the older larger leaves for oolong and black tea, and the buds for white tea. The differences in taste, colour, and aroma between these teas are achieved by varying the variety, climate, harvest, oxidation, and processing.

In general, green tea has been found to be superior to black tea in terms of health benefits.  Green tea leaves are not fermented and this is why it preserves green colour but this also enhances its antioxidant polyphenols content and antioxidant properties concerning black tea (1), which may explain why it’s so healthful.

Green tea polyphenols and their benefits

In recent years, the health benefits of polyphenols have been the focus of nutritionists, along with many preclinical and clinical studies supporting their beneficial effects on human health. As very potent antioxidants, polyphenols can prevent various oxidative stress-associated diseases. It is known that oxidative stress is related to the development and progress of various chronic degenerative diseases including heart disease, cancer and ageing. Polyphenols possess an ideal chemical structure for free radical scavenging activities and many studies suggest that polyphenols as powerful antioxidants in vitro which can reduce oxidative stress more potent than Vitamin C and E or carotenoids (5,6).

The strong antioxidant properties of neutralizing reactive oxygen and nitrogen species are attributed to tea flavonoids named catechins. Green tea contains more catechins than other teas because of the way it is processed after harvesting (halted oxidation).

What are the main catechins in green tea?

The four major catechins in green tea are the epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECG) and epigallocatechin-3-gallate (EGCG). Scientific research suggests that EGCG (and other catechins) is responsible for the majority of the potential health benefits attributed to green tea consumption. Recent scientific data indicates that the number of hydroxyl groups (-OH) and the presence of characteristic structural groups have a major impact on the antioxidant activity of catechins.

Extraction of EGCG from green tea preserves its biological activity and provides a source of high-quality polyphenol. The water extraction of green tea leaves provides a quite soft way for EGCG extraction without using aggressive solvents which agree with FDA Food Safety Regulations. However, native EGCG has poor bioavailability, which greatly limits its commercial application. Studies show that some factors affect the stability and pharmacokinetics of EGCG, like high pH or temperature promoting its degradation or that intake of EGCG along with Vitamin C or minerals such as selenium or chrome, enhances the antioxidant capacity of EGCG (2,3).

EGCG – and its potential health benefits

In the past decade, there were many studies focusing health benefits of EGCG (4). Many recently published clinical efficacy studies have been conducted with purified EGCG and various products that contain EGCG (i.e., various regular and decaffeinated green tea extracts). Some of these have been well-designed double-blinded and properly controlled studies.

The potential health benefits ascribed to green tea and EGCG include antioxidant effects, cancer chemo-prevention, improving cardiovascular health, enhancing weight loss, protecting the skin from damage caused by ionizing radiation, and others.

Nowadays, there are many drugs with anti-inflammation properties, but this therapeutics have limitations. Non-selective nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly prescribed for pain and inflammation, but they are also linked with gastrointestinal irritation. The clinical and pre-clinical testing of EGCG from green tea accentuates its potential therapeutic application for the treatment of disorders with inflammatory components, as well as its potential to regulate cardiovascular complications linked with rheumatoid arthritis (10). The anti-inflammatory properties of EGCG are very much due to its strong antioxidant activity. Less inflammation means less pain; for many people, less pain means more movement, which is a crucial action for wellbeing.

EGCG against UV-induced skin damage

EGCG has also been associated with the treatment of UV-induced skin damage.

Elmets with associates (7) applied extracts of green tea polyphenols (GTP) or purified catechins (EGCG, ECG, EGC or EC) onto the skin of healthy volunteers. The treated sites were then exposed to a dose of simulated solar radiation at two times the minimum level that was required to produce erythema in untreated skin. The UV-treated tissues were examined for erythema, UV- induced DNA damage, reduction in UV-sensitive Langerhans cells, and the presence of sunburn cells. Pretreatment of the skin with a 5% solution of GTP dramatically reduced the UV-induced erythema response (>80% reduction), reduced the number of sunburned cells (66% reduction), increased the survival of Langerhans cells (58% reconstitution of the population), and reduced the UV-induced DNA damage (45% reduction). The only purified green tea polyphenols that were able to exert a similar UV-protective effect were EGCG and EC. This study revealed the potential of GTP and EGCG in the treatment of UV injury and photoaging.

Spurred by previous results that indicated EGCG could inhibit cervical cancer cell growth in vitro, Ahn et al. (8) investigated the clinical efficacy of various EGCG and green tea preparations on human cervical lesions. Overall, 35 out of the 51 patients treated with either EGCG or green tea extract preparations showed a clinically significant positive response. While a small number of the patients in the untreated group had some degree of improvement, a significantly larger portion of these patients showed no improvement or progressed to more advanced stage disease.

The therapeutic properties of plants have been recognized since time immemorial, and many pathological conditions have been treated using plant-derived medicines. Modern medicine, however, requires the isolation and purification of one or two active compounds. Innovative drug discovery starts by deriving inspiration from natural products for the effective treatment of disease conditions.

EGCG is for sure a very powerful polyphenolic extracted from green tea with the potential to access a host of health and wellness benefits you just can get from nature.

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References:

1. Ki Won Lee, Hyong Joo Lee, Chang Yong Lee, Antioxidant Activity of Black Tea vs. Green Tea, The Journal of Nutrition, Volume 132, Issue 4, April 2002, Page 785
2. Peters CM, Green RJ, Janle EM, Ferruzzi MG (2010). Formulation with ascorbic acid and sucrose modulates catechin bioavailability from green tea. Food Res Int. 43: 95-102.
3. Giunta B, Hou H, Zhu Y, Salemi J, Ruscin A, Shytle RD, Tan J (2010). Fish oil enhances anti-amyloidogenic properties of green tea EGCG in Tg2576 mice. Neurosci Lett. 471: 134-8.
4. Singh B., Shankar S., Srivastava R. (2011) Green tea catechin, epigallocatechin-3-gallate (EGCG): Mechanisms, perspectives and clinical applications, Biochem. Pharmacol. 82: 1807-1821.
5. K. Mukai, S. Mitani, K. Ohara, and S.-I. Nagaoka, “Structure- activity relationship of the tocopherol-regeneration reaction by catechins,” Free Radical Biology and Medicine, vol. 38, no. 9, pp. 1243–1256, 2005.
6. C.A.Rice-Evans,N.J.Miller,P.G.Bolwell,P.M.Bramley,andJ. B. Pridham, “The relative antioxidant activities of plant-derived polyphenolic flavonoids,” Free Radical Research, vol. 22, no. 4, pp. 375–383, 1995.
7. Elmets, C.A., Singh, D., Tubesing, K., Matsui, M., Katiyar, S., Mukhtar, H., 2001. Cutaneous photoprotection from ultraviolet injury by green tea polyphenols. J. Am. Acad. Dermatol. 44, 425–432.
8. Ahn, W.-S., Yoo, J., Huh, S.W., Kim, C.-K., Lee, J.-M., Namkoong, S.- E., Bae, S.-M., Lee, I.P., 2003b. Protective effects of green tea extracts (polyphenon E and EGCG) on human cervical lesions. Eur. J. Cancer Prev. 12, 383–390.
9. Newman DJ, Cragg GM (2016) Natural products as sources of new drugs from 1981 to 2014. J Nat Prod 79:629–661.
10. Ohishi T, Goto S, Monira P, Isemura M, Nakamura Y. Anti-inflammatory Action of Green Tea. Antiinflamm Antiallergy Agents Med Chem. 2016;15(2):74-90.