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

Chlorogenic acids – coffee polyphenols

Coffee contains many polyphenols, especially CGAs, which have purported antioxidant abilities. Chlorogenic acid (CGA), also known as 5-O-caffeoylquinic acid, is a polyphenol commonly found in human dietary products, especially in coffee beans.

Chlorogenic acids are phenolic acids with vicinal hydroxyl groups on aromatic residues that are derived from esterification of cinnamic acids, including caffeic, ferulic and p-coumaric acids with quinic acid.

Chlorogenic acids are naturally occurring phenolic compounds found in all higher plants. They have substantial biological activities and may be responsible for the beneficial effects of coffee on glucose regulation and the development of type 2 diabetes.

Due to their various biological properties, such as antispasmodic, antioxidant, inhibition of the HIV-1 integrase and inhibition of the mutagenicity of carcinogenic compounds, they are very important plant secondary metabolites. There is also evidence to show that chlorogenic acids exhibit anti-inflammatory activities by modulating a number of important metabolic pathways.

Chlorogenic acid activates endogenous antioxidant systems to defense and scavenge against free radicals. It enhances Nrf2 translocation from cytosol to the nucleus; thereby activating antioxidant gene sets to cytoprotection against cellular toxicity.

Chlorogenic acid significantly improved the impairment of short-term or working memory induced by scopolamine and significantly reversed cognitive impairments and decreased escape latencies in mice.

Chlorogenic acids exists in raw coffee and is also widespread in many kinds of seeds and fruits such as sunflower seeds and blueberries. It has also been found in the seeds and leaves of many dicotyledonous plants. It is thermally unstable and is readily decomposed to quinic acid and caffeic acid. Lower content of chlorogenic acids has also been detected in potatoes, tomatoes, apples, pears and eggplants, but consumption of these sources accounted for nearly 5–10% of that from coffee beverage source.

Chlorogenic acid strongly influences the taste of coffee, such as astringent, sweet, and sour tastes, which change with the concentration.
Chlorogenic acids – coffee polyphenols

Chemical compound of antioxidants in green tea

Tea also refers to the aromatic beverage prepared from the cured leaves by combination with hot or boiling water. At the moment tea is the second most popular beverage in the world. Green tea is available for sale in three variants: In the form of leaves, in tea bags or as powder.

Tea extracts are source of polyphenols, which are antioxidant components. Green tea phenolic compounds are predominately composed of catechin derivatives, although other compounds such as flavanols and phenolic acids are also present in lower proportion.

The content of polyphenols in green tea is higher than those of black tea. Over the past few years, numerous studies have indicated that catechins and other polyphenols in tea exhibit powerful antioxidant activities.

Flavonoids (and their fraction – catechins) are the basic phenolic compounds in green tea responsible for antioxidant activities such as neutralization of free radicals that are formed in the process of metabolism. Free radicals are formed from molecules via breakage of a chemical bond such that each fragment keeps one electron, by cleavage of a radical to give another radical and, also via redox reactions. Free radicals are the main factors responsible for the initiation of formation of cancer cells.

Antioxidants terminate these chain reactions by removing free radical intermediates, and inhibit other oxidation reactions.

The main catechin compounds found in green tea are (-) Epigallocatechin Gallate (EGCG), that represents approximately 59% of the total content of catechins; (-) Epigallocatechin (EGC), 19%; (-)Epicatechin Gallate (ECG), 13.6%; and (-)Epicatechin (EC), 6.4% and also other compounds.
Chemical compound of antioxidants in green tea

Beetroot juice: Uses and health benefits

Beetroot (Beta vulgaris L.) is crop belonging to the Chenopodiaceae family having, bright crimson color. Beetroot is grown for food uses (pickles, salad, juice) rather than for sugar production. In contrast to other fruits, the main sugar in beetroot is sucrose with only small amounts of glucose and fructose.

Beet juice is a popular health food betanins, obtained from the roots, are used industrially as red food colorants e.g. to improve the color of tomato paste, sauces, desserts, jams and jellies, ice cream, sweets and cereals. Red beet also makes a rich, red, Burgundy style wine.

Many researches have provided compelling evidence that beetroot ingestion offers beneficial physiological effects that may translate to improved clinical outcomes for several pathologies, such as; hypertension, atherosclerosis, type 2 diabetes and dementia. Hypertension in particular has been the target of many therapeutic interventions and there are numerous studies that show beetroot, delivered acutely as a juice supplement or in bread significantly reduce systolic and diastolic blood pressure.

The intense red color of beetroots derives from high concentrations of betalains, a group of phenolic secondary plant metabolites. Betalains are used as natural colorants by the food industry, but have also received increasing attention due to possible health benefits in humans, especially their antioxidant and anti-inflammatory activities.

The total betalain content was found to range between 0.8 and 1.3 g/L fresh juice (about 60% betacyanins and 40% betaxanthins) that accounted for 70–100% of the total phenolics content. Other phenolics were hydroxycinnamic acids, which accounted for up to 2.6% of total phenolics.

A number of studies report that beetroot, in the form of a juice supplement, protects against oxidative damage to DNA, lipid and protein structures in vitro. In 2011 study suggests that a key mechanism by which beetroot juice exerts its antioxidant effects is by scavenging radical species.

Effects of a commercially available beetroot juice on inflammation is strongly involved in the development and progression of several clinical conditions including coronary heart disease and cancer, beneficial effect of beetroot extract may relate to this anti-inflammatory capacity.
Beetroot juice: Uses and health benefits