Anyone interested in cancer-fighting foods must have heard of L-EGCG. Research on EGCG has expanded from antioxidant studies to the prevention of major diseases. Particularly when developed countries like the United States and Germany started producing and selling powdered and tablet supplements with EGCG as the main ingredient, China officially included L-EGCG in its “New Food Ingredients Catalog” (previously known as “New Resource Foods”).

The difference is that in China, the use of EGCG is still limited to antioxidant applications, while countries in Europe and America have taken larger steps by directly incorporating it into cancer adjuvant therapies. Many foreign EGCG product instructions not only recommend it for healthy individuals as a preventive measure against cancer but also suggest its use by cancer patients after chemotherapy.

So, what exactly is L-EGCG, and where does it come from?

L-EGCG is not mysterious; it comes from tea leaves and is one type of catechin, known in full Chinese as “epigallocatechin gallate,” with the English abbreviation EGCG (Epigallocatechin gallate).

Since EGCG belongs to the left-handed form of catechins (all of which are L-forms, while right-handed catechins are D-forms), to make a clear distinction, the notation “L-” is used, indicating both its left-handed nature and L-form. Therefore, this article discusses L-EGCG.

This raises the question: what is a left-handed form, and what is its biological significance?

We know that life is composed of carbon elements. When carbon atoms form organic molecules, four atoms or groups can bond through four covalent bonds to create a three-dimensional spatial structure. Due to the differences in the connected atoms or groups, two molecular structures can form. Although these two molecules have identical physical and chemical properties, they are still distinct. This is similar to an object and its mirror image being mirror images of each other.

Because it is a three-dimensional structure, no matter how they are rotated, they will not overlap, just like our left and right hands. Based on this method, people discovered a shocking fact: aside from a small amount of right-handed amino acids found in specific organs of some animals or insects, almost all amino acids that make up life on Earth are left-handed, with no right-handed amino acids present.

Right-handed molecules are the bane of human life because humans are composed of left-handed amino acids and cannot metabolize right-handed molecules well. Thus, consuming drugs containing right-handed molecules becomes a burden and can even harm living organisms. There is a typical case: In the 1960s, there was a Japanese girl named Noriko who was born without arms.

Yet, Noriko's parents were healthy and normal. Why was Noriko born without arms? Tens of thousands of disabled infants like Noriko were born worldwide. Later, it was discovered that the tragedy occurred because her mother took a drug called thalidomide (Note: also known as thalidomide, chemically named phthalimido-piperidine ketone, with R-phthalimido-piperidine ketone and S-phthalimido-piperidine ketone as two enantiomers. The R-enantiomer has sedative effects and can relieve morning sickness in pregnant women, while the S-enantiomer is the cause of fetal malformations.) One molecule in thalidomide had therapeutic effects, reducing early pregnancy symptoms, but its enantiomer (right-handed form) caused mothers taking the drug to give birth to disabled children.

It was precisely due to this lesson that modern drugs underwent more stringent screening and testing. For pharmaceutical companies, when producing a drug, it is best to separate out the other half. Examples include the antihypertensive drug “L-amlodipine,” the treatment for hypothyroidism “L-thyroxine,” and the antibacterial drug “L-ofloxacin.”

After understanding that L-EGCG is a left-handed form of catechin, we need to acknowledge another fact:

Can we simply consume L-EGCG by Drinking Tea?

Answer: Yes, but not entirely!

Firstly, regarding tea leaves, almost all fresh tea leaves contain L-EGCG, but the highest content is found in large-leaf Yunnan tea (72.83 mg/g dry weight). The content of L-EGCG in large-leaf Yunnan tea also varies by season, reaching its peak during summer (99.93 mg/g dry weight). This phenomenon also occurs in small- and medium-leaf varieties, with the lowest content in spring, the highest in summer, and the second-highest in autumn. This viewpoint is not the opinion of the author alone but is widely accepted in the tea academic community; for detailed information, please refer to the author's article “The Value of Pu'er Tea Geography” published in Pu'er Magazine.

Secondly, in individual tea plants, the first and second leaves from the top have the highest L-EGCG content. During this period, L-EGCG works together with other polyphenols to perform a “hydrogen transfer function,” which benefits photosynthesis and respiration in tea leaves. In contrast, the catechin content decreases gradually in smaller buds, older leaves, stems, and roots, with the lowest content found in the roots, which contain only non-lipid-type catechins L-EC and DL-C. We generally prefer Spring Tea for its fragrant aroma and dislike summer tea for its bitter taste, which is largely due to lipid-type catechins.

Thirdly, there is a special “hydrolysis effect” in traditional Tea processing, converting lipid-type catechins into simple catechins. The original bitterness of lipid-type catechins transforms into a mellow flavor. This biochemical phenomenon occurs in all types of tea.

Taking ripe Pu'er tea and black tea as examples, the formation of theaflavins, thearubigins, and theabrownins in finished tea originates from the oxidation and polymerization of polyphenols, primarily catechins, which are derivatives of polyphenols. During this process, L-EGCG gradually diminishes until it is completely depleted. Freshly made raw Pu'er tea (green tea) can detect L-EGCG, but its content is significantly reduced compared to freshly picked leaves due to the “rolling” and “sun-drying” processes. As for green tea, although it does not produce thearubigins and theabrownins, it naturally contains very little L-EGCG. Additionally, the “hydrolysis effect” during processing results in minimal L-EGCG remaining, even when producing a small amount of theaflavins. Therefore, supplementing L-EGCG through traditional tea consumption may not be effective or feasible.

Here, it is important to clarify that our discussion above is not intended to negate traditional teas and traditional tea-making methods. Traditional teas are consumed as beverages, evaluated based on sensory appraisal, and focus more on “taste, aroma, color, and shape.” They rely on the combined effects of various substances in tea for Health benefits.

In contrast, the discussion about L-EGCG leans more towards pharmacological mechanisms, using experimental scientific methods to study a single substance. It has two prerequisites: the chemical structure of the single substance (qualitative analysis) and the single substance's content (quantitative analysis). This is similar to Vitamin C, which many leafy green vegetables contain. However, our cooking methods may cause this substance to “disappear,” or its content is too low to meet intake requirements, leading to vitamin C deficiency. Many people's oral ulcers result from this. Therefore, vitamin C tablets or powders become frequently consumed health supplements for such individuals.

Regarding L-EGCG, it presents a different scenario, starting with antioxidant effects, then lowering blood lipids, and in recent decades, numerous research papers on its anticancer properties have been published. Scientists seem to have stumbled upon a “gold mine.” This substance derived from tea has become recognized in the pharmaceutical field as the “gold of tea.”