Unveiling the Complexities of Tannins in Tea

Tea, renowned for its numerous health benefits ranging from antioxidants to artificial coloring, owes much of its character to the presence of tannins. These active chemicals, naturally occurring in tea leaves, play pivotal roles in not only shaping the growth and health benefits of teas but also in determining their color and flavor profiles.

Tannins, scientifically known as tannic acid, represent a class of water-soluble polyphenols with a molecular weight ranging between 500 and 3,000. Beyond their phenolic properties, tannins exhibit the unique ability to precipitate alkaloids, gelatine, and other proteins. This diversity underscores their multifaceted effects on health.

The applications of tannins extend beyond tea brewing; they serve as potent antiseptics and astringents. Their antioxidant properties endow them with anti-carcinogenic and anti-mutagenic attributes. Furthermore, tannins showcase remarkable antimicrobial prowess, demonstrating efficacy against a broad spectrum of bacteria, fungi, and viruses.

Chemically, tannins manifest as polyphenol compounds with the formula C76H52O46, ranging in color from colorless to yellowish. Their presence significantly influences the taste, color, and aroma of tea. Tannins impart a characteristic astringency, hue, and flavor to the brew. Interestingly, the deepening of tea color attributed to tannins occurs independently of the aromatic compounds responsible for its diverse flavor profile.

In tea plants, tannins primarily reside within cell vacuoles or the cuticle. Intriguingly, these compounds remain dormant within the plant's cellular structures during its lifetime, only becoming metabolically active post-mortem during cell breakdown processes.

The intricate interplay between tannins and tea underscores the complexity underlying this beloved beverage. From enhancing flavor to providing health benefits, tannins stand as essential constituents of tea's allure. Understanding their roles sheds light on the nuanced chemistry driving tea's multifaceted nature, enriching our appreciation for this timeless beverage.
Unveiling the Complexities of Tannins in Tea

Ellagitannins in pomegranate juice

Since ancient times, pomegranate has been known for its medicinal properties. Most of those beneficial effects have been attributed to the pomegranate metabolites such as polyphenols, with a particular focus on hydrolysable tannins. The health benefits of pomegranate have been mainly related to its ellagitannins and ellagic acid content.

Ellagitannins belong to the chemical class of hydrolyzable tannins, which release ellagic acid on hydrolysis. In addition, pomegranate juice contains other polyphenols, such as anthocyanins that are present in the fruit arils and impart its brilliant red-purple color.

Ellagitannins are bioactive polyphenols present in pomegranate. Pomegranate juice obtained by squeezing the whole fruit has the highest concentration of ellagitannins than any commonly consumed juice and contains the unique ellagitannin, punicalagin.

In the commercial pomegranate juice industry, these ellagitannins are extracted from the husk in significant quantities into the juice due to their hydrophilic properties.

Ellagitannin is a hydrolyzable polymer contrary to the rest of the family of tannins and can be hydrolyzed to more simple monomers that can be eventually metabolized and that can become bioavailable with subsequent exposition of the body to these metabolites. More than 60 hydrolysable tannins have been found in the fruit peel, arils and membranous walls.

The main ellagitannins identified in foods (specially in fruits, nuts, and seeds) are punicalagin, sanguiin H6, lambertianin C, pedunculagin, vescalagin, castalagin, casuarictin and potentillin (seeds). In particular, punicalagin is the predominant form of the hydrolysable tannins present in pomegranate and is responsible for more than 90% of antioxidant bioactivity contained in pomegranate juice.
Ellagitannins in pomegranate juice