Monday, January 25, 2010

Green tea extract: Tannins and catechins

Yep, I'm still going on about the awesome power of green tea extract, but it really does deserve four posts! We've already looked at caffeine and proanthocyanins, and tomorrow we'll take a look at the other things found in green tea. Today - tannins and catechins!

Green tea extract is filled to the brim with polyphenolic goodness - up to 30% of the dry weight - so let's turn our attention to the flavonoids that make green tea so incredible!

Flavonoids behave as anti-oxidants on our skin and in our bodies by scavenging the free radicals produced at our cell membranes. It is thought (meaning there aren't enough studies or nothing conclusive) the flavonoids offer anti-inflammatory benefits by inhibiting pro-inflammation mediators in our bodies, such as prostaglandins.

Catechins are a type of flavonoid, also called condensed tannins, making up 10% to 18% of the polyphenols in green tea. (We also find hydrolyzable tannins like procyanidins, which we investigated yesterday.) They offer anti-oxidizing features - they have been shown to be more effective than BHT, which is incredibly effective - as well as anti-microbial and anti-fungal properties. There are 6 main catechins found in green tea, but the most exciting is epigallocatechin gallate (EGCg or EGCG), which is probably the most studied and the most active polyphenolic. (The others are catechin, gallocatechin, epicatechin, epigallcatechin, and epicatechingallate).

EGCg seems to be a wonder ingredient. It is an anti-inflammatory that provides protection from photo-damage. One study showed it could inhibit an essential bacterial enzyme by binding to it, thereby behaving as an anti-bacterial. Another, albeit small, study showed EGCg s effective against tooth decay! It is a very powerful anti-oxidant, up to 200 times more powerful than Vitamin E in in vitro studies.

As a note, tannins are very large molecules - if a catechin has 20 or more hydroxyl groups (-OH) groups, it's considered a tannin. Look at the size of that molecule!

Chlorogenic acid offers anti-oxidant, anti-viral, anti-fungal, and anti-bacterial benefits. Kaempferol is a very strong anti-oxidant and anti-inflammatory compound that can prevent oxidative damage on our skin. You might remember gallic acid from evening primrose, pomegranate, and mango posts - it is being studied as a burn and wound healer. Quercetin - also found in mango butter - is a powerful anti-oxidant. Rutin is both a powerful anti-oxidant and good anti-inflammatory ingredient. It is being studied for the treatment of varicose veins and other circulation issues, and it can prevent water retention.

Join me tomorrow to look at more awesomeness found in green tea before a few posts in using green tea extract in your creations!


Anonymous said...

Wow what a great article! I LOVE green tea and know it's very healthy to drink so I try to drink a cup, or two, or three a day! I want to learn more about green tea and what sort of things I can do with it's extracts/essential oils. Also, I'm a little confused of the difference between a catechin and a tannin? From what I read in this article, all tannins are catechins, but not all catechins are tannins? They have to be a molecule of twenty strands or more.

Thanks again!

Susan Barclay-Nichols said...

There are three classes of tannins: Hydrolyzable tannins, like gallic acid; Condensed tannins, which are non-hydrolyzable, like proanthocyanidins; and Phlorotannins (from algae).

Green tea contains hydrolyzable tannins and condensed tannins. Molecular weight does play a role - "Tannins have molecular weights ranging from 500 to over 3,000[2] (gallic acid esters) and up to 20,000 (proanthocyanidins)."

From Wikipedia: "The term catechins is also commonly used to refer to the related family of flavonoids and the subgroup flavan-3-ols (or simply flavanols)."

To relate tannins and catechins: "Catechin and epicatechin are the building blocks of the proanthocyanidins, a type of condensed tannin."

So catechin and epicatechin are the building blocks for proanthocyanidins, which are a type of condensed tannin, which is a non-hydrolyzable tannin. (I've written a post on the proanthocyanidins in green tea, if you're interested.)