Chapter 12 - Nanotechnology-Based Approach for Enhanced Bioavailability and Stability of Tea Polyphenols—A Review
Introduction
Tea, the most consumed nonalcoholic drink, is produced from two leaves and a bud of the plant Camellia sinensis. The genus Camellia incorporates 325 species, belongs to the family Theaceae and is now cultivated in more than 30 nations around the world. Green tea (unfermented tea) is consumed in China, Japan, and the Middle East which constitute around 20–22% of the total tea consumption; people in the eastern part of China, China–Taiwan, and Japan prefer oolong tea (semifermented tea) comprising less than 2% while rest of the world drink black tea (fermented tea) that constitute 76–78% of the total tea consumption [1], [2].
The distinctive aroma and health benefits of green tea are mostly due to its polyphenolic compounds [3], along with other bioactive compounds such as caffeine, theanine, saponin. Catechins, the major constituent of green tea polyphenols (GTP) contribute to about 30–42% of the dry weight of tea leaves. Various forms of catechins which majorly constitute the polyphenols include (−)-epicatechin (EC), (−)-epigallocatechin (EGC), (−)-epicatechin-3-gallate (ECG), and (−)-epigallocatechin-3-gallate (EGCG) (Fig. 12.1). Among these forms EGCG contributes to about 50–80% of the total catechins [4]. GTP as a whole demonstrated several profound biochemical and pharmacological activities [5].
Section snippets
Biosynthesis of Catechins
Catechins possess two benzene rings (A and B rings) and a dihydropyran heterocycle (C ring) with a hydroxyl group on carbon 3. A ring is similar to resorcinol moiety, while the B ring is similar to catechol moiety. The C6 (A) catechin ring is produced by the acetic–malonic acid pathway and C3–C6 (B) ring is produced by the shikimic–cinnamic acid pathway starting from the glucose pool. This fact was discovered during research in the synthesis of quercitin. When 14C-acetic acid is supplied,
Health Benefits of Tea
Tea is known to have several health benefits [7]. Compounds present in tea have an impact on a myriad of illness, a few of which include its immune functions, aging process, detoxification, and chemoprevention of some diseases. Compounds like flavonoids, amino acids, vitamins, caffeine, and polysaccharides are most important among more than 500 compounds present in tea. Tea flavonoids are 20-fold more capable antioxidants than vitamin C [8]. Among all these compounds, polyphenols, caffeine, and
Limitations of Tea Polyphenols
In spite of several impressive data available on health benefits of GTP, its application as a therapeutic agent is unsuccessful due to some of its limitations such as bioavailability, stability, and metabolic transformation under physiological conditions [22], [23], [24]. Despite exciting results obtained on efficacy of tea polyphenols against a number of diseases under in vitro conditions, its bioavailability poses a major challenge in reproducing these in vitro results under in vivo
Strategy to Overcome the Limitations
To overcome these limitations, several approaches have been put forth, of which the nanoparticulate approach has been widely attempted. Particles having a diameter of less than 200 nm are widely used in the field of medicine due to its several advantages, especially the small size of the particles. Several advances are being made to implement nanoparticles as a tool for the delivery of several drugs to the target site, thereby adapting a more effective drug delivery system. Several researchers
Nanoencapsulation of Green Tea Polyphenols
EGCG is one of the major constituent of GTP and is responsible for major health benefits. It has been reported that EGCG has the capability to obstruct tumor cell growth and induce DNA damage and apoptosis leading to chemotherapeutic action for colon cancer [50]. Though EGCG is known for its antioxidant activity, it was reported that nanoparticles containing EGCG showed promising antioxidant activity compared to free EGCG [51]. In another study, EGCG-encapsulated biopolymers showed potent
Conclusion
Drug delivery is a process or method to deliver a drug in human or animal to achieve its therapeutic effect. Selection of a drug delivery method has significant effect on the efficacy of the drug. Many important pharmacological properties of the drug, when used as free molecule, can be improved by using an appropriate drug delivery system. In the last few decades, methods of drug delivery have been changed dramatically and even much greater changes are expected in the near future. Among the new
Acknowledgments
We thank the management of VIT University for providing the facilities. Financial support from NTRF, Tea Board, Kolkata is also gratefully acknowledged.
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