Tea, polyphenols, and you - PART II: POLYPHENOL PARTICULARS:

In part 1 I explained what antioxidants are and why we need them. Here, I'll elaborate on the particular antioxidants present in our beloved C. Sinensis bush, why roughly 30% of their dry weight are polyphenols, and how polyphenols (and any antioxidant for that matter) keep us alive and kickin'.

First, I know a lot of people get tripped up by the naming involved in all of this. Believe me, chemical nomenclature is nothing to shake a stick at. Nonetheless, here's a little disambiguation than may help. A lot of the chemical terms that get thrown around relating to tea really mean the same thing, but at different levels of specificity - think of the biological naming system (kingdom, phylum, etc.) and you get the right idea. Following the same model, here's a list of terms from broadest to most specific that may help clear things up:

Antioxidants -> Polyphenols -> flavanoids -> chatechins -> (most of the specific "good" molecules).

A flavanoid doesn't necessarily have to be a polyphenol, but if it is, it's most certainly an antioxidant. Here is a big scary image that may (or may not) help my point:
This image shows the relation of the 3 major antioxidants (AOX, hereafter) present in green tea. As you can see, all are based on a flavanoid backbone molecule (actually called flavone) and differ only slightly from one another. These three catechins account for roughly 25-30% of the dry weight of tea leaves (that's a lot!). These are all technically flavan-3-ols (one of 3 types of flavanoids), but no one really cares about that. The only thing interesting enough to note is that anthocyanidins (remember from the purple-leaf post?) are similar enough to be in the same 'group' of flavanoids.

So why do tea bushes need so much protection from oxidation? Well, as a partial answer, they are exposed to light for roughly 12 hours per day, spend much of their time at high altitudes where the atmosphere is thinner, and enjoy the company of many small insects who munch away at their leaves. In part 1 we learned that free radicals are formed by UV radiation. If you are a tea plant sitting atop a mountain basking in light that as been only ever so slightly obscured by the atmosphere, you better bet that there are some free radicals being formed. Thus, the tea plant will produce a significant amount of AOX to help combat this damage. This is exactly why high-altitude teas tend to be more bitter if overbrewed compared to their base-of-the-mountain counterparts (in my experience at least) - there are a higher percentage of polyphenols present, which also happen to be extremely bitter. A tea plant will also produce more AOX in response to environmental stress. - Oriental Beauty oolongs are a prime example. Whether it is only as a precaution or do directly combat whatever damage has been caused to the leaf, I do not know. I also don't know the reason why tea plants have a higher proportion of AOX in their leaves than say, a tree or shrub at the same altitude. Maybe they don't... I don't know. If anyone has any input I'd love to hear it.

So the tea plants produce polyphenols - particularily catechins (EC, EGC, EGCG) - to help prevent oxidative damage to their cells, but how does it work? This image shows how your body uses vitamin E to neutralize the radical of hydrogen peroxide. This is one of the most important reactions in your body and just about any radical can be substituted for H peroxide. Also, any polyphenol will follow the same pattern almost exactly.

The reaction begins when a free radical comes across a molecule of vitamin E. We learned that free radicals will react with just about anything, but it just so happens that they will preferentially react with an AOX (hence how they prevent the continued oxidation). The peroxide radical will yank off a hydrogen from the AOX, effectively 'donating' (this isn't really what happens, but it works for simplicity's sake) its single radical electron to the AOX (vitamin E). The peroxide radical then becomes hydrogen peroxide which is stable enough to behave on its own. The antioxidant is also stable enough to not react further - the radical just kind of hangs around until ANOTHER peroxide radical finds it. Then, the AOX radical will react with the other radical, tacking on a peroxide group to one of its rings. The AOX is then inert and in most cases will simply be expelled from the body or broken down in the liver.

In effect, one molecule of Vitamin E will remove two free radical molecules - some AOX can remove even more. Pretty cool huh? Keep out the radicals and you can... keep out the... cancer? I'll leave that up to those in advertising.

Again, this is certainly more information than you would ever need. I've tried to hit on the basics and keep it fairly tame, but if there's anything that just sounds too out there, please don't hesitate to let me know.

tb.