Preparation of epigallocatechin gallate esters and evaluation of their antioxidant, antiviral, anti-inflammatory and anticancer effects

Zhong, Ying (2010) Preparation of epigallocatechin gallate esters and evaluation of their antioxidant, antiviral, anti-inflammatory and anticancer effects. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

Epigallocatechin gallate (EGCG), a major green tea polyphenol, has been widely studied and proposed as a functional food ingredient and nutraceutical for therapeutic use. However, EGCG is highly hydrophilic with poor solubility in lipophilic media which hinders its widespread application in foods and affects its absorption in vivo, resulting in limited uptake by the cells and bioavailability when ingested orally. Therefore, it is important to alter the hydrophilicity/lipophilicity balance (HLB) of EGCG in order to take better advantage of its multifunctional properties. This work investigated structural modification of EGCG, more specifically esterification with fatty acids of different chain length and degree of unsaturation, as an approach to improving the lipophilicity while maintaining the maximum efficacy or even introducing novel bioactivities not found in the original EGCG. Additional perspectives may exist using the health beneficial omega-3 polyunsaturated fatty acids (PUFA) as acyl donors. For this purpose, lipophilic ester derivatives of EGCG with butyric, stearic, eicosapentaenoic, docosapentaenoic, and docosahexaenoic acids were prepared, and their bioactivities evaluated, including antioxidant activities in different model systems, anti-inflammatory, antiviral and anticancer activities. The results indicated that lipophilization by esterification, especially with omega-3 PUFA, significantly improved the antioxidant and anti-inflammatory activity of EGCG. Moreover, the ester derivatives totally arrested colon cancer in mice, and exhibited an anti-HCV (hepatitis C virus) activity 1700-folds greater than that of the positive control embelin. These findings strongly suggest that the EGCG ester derivatives are of great potential as lipophilic alternatives of the water-soluble EGCG and may serve as novel functional ingredients for food, cosmetics, and nutraceutical/therapeutical applications and for use in medicine and natural health products.

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