Recent advances on tea polyphenols
Jyoti Kanwar1, Mujtaba Taskeen 1, Imthiyaz Mohammad1, Congde Huo2, Tak Hang Chan2, Qing Ping Dou1
1
The Developmental Therapeutics Program, Barbara Ann Karmanos Cancer Institute, and Departments of Oncology, Pharmacology and Pathology, School of Medicine, Wayne State University, Detroit, Michigan, USA, 2 Department of Chemistry, McGill University, Montreal, Quebec, H3a 2k6, Canada
TABLE OF CONTENTS
- 1. Abstract
- 2. Introduction
- 3. Tea Polyphenols
- 3.1. History and tea ingredients
- 3.2. Pharmacokinetics and bioavailability of green tea
- 3.3. Chemical properties of tea constituents
- 3.3.1. Antioxidant nature of green tea polyphenols (GTPs)
- 3.3.2. EGCG structure and activity
- 3.3.3. Stability
- 3.3.4. Effect of substitutions on different rings
- 4. Epidemiological Studies
- 4.1. Gastrointestinal cancer
- 4.2. Breast cancer
- 4.3. Pancreatic cancer and ovarian cancer
- 4.4. Prostate cancer
- 4.5. Lung cancer
- 5. Mechanism of action
- 5.1. Cell cycle arrest & induction of apoptosis
- 5.2. EGCG affects Ras/MAPK pathway
- 5.3. Phosphoinositide 3 kinase (PI3kinase)/Akt pathway
- 5.4. Inhibition of insulin like growth factor (IGF) -1 pathway
- 5.5. Inhibition of metastasis
- 5.6. EGCG affects transcription factors
- 5.6.1. Nuclear factor kappa B (NF-kappa B)
- 5.6.2. Activator protein 1 (AP-1)
- 6. Molecular targets of EGCG
- 6.1. Cyclooxygenase
- 6.2. Telomerase
- 6.3. Tumor suppressor p53
- 6.4. Vascular endothelial growth factor (VEGF)
- 6.5. Proteasome
- 7. Clinical trials of green tea
- 7.1. Chemoprevention trials
- 7.1.1. Breast cancer
- 7.1.2. Prostate cancer
- 7.1.3. Lung cancer
- 7.1.4.Chronic lymphocytic leukemia (CLL)
- 7.2. Combinational treatments
- 7.3. Issues related to cancer therapy with green tea
- 8. Conclusion and future direction
- 9. Acknowledgements
- 10. References
1. ABSTRACT
Over the past decade many scientific and medical studies have focused on green tea for its long-purported health benefits. There is convincing evidence that tea is a cup of life. It has multiple preventive and therapeutic effects. This review thus focuses on the recent advances of tea polyphenols and their applications in the prevention and treatment of human cancers. Of the various polyphenols in tea, (-)-Epigallocatechin-3-gallate (EGCG) is the most abundant, and active compound studied in tea research. EGCG inhibits several molecular targets to inhibit cancer initiation and modulates several essential survival pathways to block cancer progression. Herein, we describe the various mechanisms of action of EGCG and also discuss previous and current ongoing clinical trials of EGCG and green tea polyphenols in different cancer types.
