Tea with a Film: Drink or Survive…

Tea (or, in other words, the extract of tea leaves) is a complex mixture in terms of chemical composition, consisting of catechins, their dimers (theaflavins) and polymers (thearubigins); proanthocyanidins; oxidized low-molecular-weight condensed tannins; purine derivatives: alkaloids caffeine, theophylline, theobromine, purine base guanine; terpenoid and aromatic alcohols (cinnamyl alcohol, benzyl alcohol, phenethyl alcohol, geraniol, citronellol, linalool, etc.); mineral salts; proteins; amino acids aspartic acid, glutamic acid, theanine, serine, alanine, lysine, arginine, valine, leucine, and phenylalanine; aldehydes (acetaldehyde, acetone, isobutyric, isovaleric, and caproic aldehydes), free acids (acetic, butyric, valeric, caproic, caprylic, etc.), vitamins.
Many of them have the property of osmolation, that is, forming a mixture of polycondensates and oxidation products under the action of oxidizers, particularly, atmospheric oxygen.

On the surface of many liquids (except for acids, alkalis, and chemically pure water), a thin oxide film forms as a result of contact with atmospheric oxygen. The more mineral and organic compounds, especially proteins, are present in the solution, the thicker this film becomes.
Thus, in tea: the aforementioned organic compounds, abundantly present in the brew (especially low-molecular-weight polyphenols based on catechins, proteins, and purine bases), upon contact with oxygen oxidize, polymerize, form complex compounds, partially precipitating and partially forming a film on the surface.
Studies have shown that caffeine in brewed tea is present not only in free form but also in combination with tannin as caffeine tannate. This compound is primarily responsible for the formation of the “film” on the surface of the tea extract, forming more complex complexes with proteins and mineral salts.
It has been established that the time for maximum transfer of caffeine from the tea leaf into the extract is 5 minutes for black tea and 6 minutes for green tea.

The composition of the film formed as a result of oxidative-enzymatic processes on the surface of the tea extract is very complex. It includes oxidized low-molecular-weight condensed tannins – derivatives of catechins – as well as protein molecules, nitrogenous bases (caffeine, theophylline, guanine), iron, calcium, magnesium.

When entering the human body, the layer of this insoluble film – the protein-tannin-purine-iron-calcium-magnesium complex – covers the mucous membrane of the stomach and intestines, hinders the absorption of nutrients, and irritates the gastrointestinal tract. This slows down intestinal peristalsis, food masses accumulate in the cavity of the gastrointestinal tract, under this insoluble film, bacterial activity significantly increases, fermentation and putrefaction processes begin, and the mucosa absorbs the resulting toxic substances, leading to erosive-ulcerative processes.
Of course, with a single intake of “stale” tea, significant problems with the gastrointestinal tract are not expected; however, with regular, repeated use several times a day, gastritis, duodenitis, erosions, and ulcerative diseases may occur, and in the most advanced cases – even malignant neoplasms.

But the danger of consuming non-fresh brewed tea lies not only in the effect on the gastrointestinal tract of the complex compound based on catechins, purines, and proteins – the insoluble film.
Even more serious consequences, particularly for the nervous and cardiovascular systems, may be caused by one of the purine derivatives that transfers into the tea extract after standing for more than 10 minutes – guanine.

The nitrogenous base guanine transfers into the tea extract 8–15 minutes after brewing or as a result of boiling.
Guanine is a purine base found alongside other purines (caffeine, theophylline) in tea leaves. This compound is not dangerous in itself; it is part of nucleic acids. The danger lies in its oxidation product – toxic guanidine.

Guanidine is an n-cholinomimetic, a toxic substance whose concentrated solutions cause alkaline burns upon contact with skin and have a stunning effect on the nervous system. Its action on the body is mainly similar to that of histamine.
The pharmacological action of guanidine consists of stimulating the respiratory center (analeptic effect) and increasing blood pressure as a result of interaction with n-cholinergic receptors of the chromaffin tissue of the adrenal glands (enhancing adrenaline release) and sympathetic ganglia (enhancing sympathetic impulses to the heart and blood vessels, increasing heart rate).
At high concentrations of guanidine, manifestations may include anxiety, irritability, tremors of the limbs, convulsions, psychomotor agitation, disorganized flow of thoughts and speech, dizziness, paresthesia in the mouth and limbs, hypertension, tachycardia, arrhythmia, suppression of bone marrow function, toxic liver damage, hypoglycemia, and decreased calcium concentration in the blood.
A case of mass poisoning in 2006 involving guanidine salts affected 162 people (three cases resulted in fatalities) in the municipal formation of Verkhnyaya Salda in the Sverdlovsk region, leading to the development of toxic hepatitis in survivors.

Furthermore, it is worth reminding that the purine bases contained in tea are directly related to metabolic processes, the disruption of which manifests as retention of uric acid in the body and deposition of its salts in tissues. In particular, the consequence of purine metabolism disturbance is almost always a very unpleasant and painful disease – gout.

Therefore, let us remember the possible negative consequences of consuming tea that has stood for more than 10 minutes after brewing.
A universal indicator for you will be the formation of a film on it. Such tea is harmful to the body, and it should be poured out (not drunk!) if, as M. Zhvanetsky said in his miniature, “You are interested in the result…”.

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