Here is some additional information on hops chemistry if you are interested.
Recently, white tea tincture (extract) was listed as a “must have” ingredients in the anti aging and anti acne products on the market along with rooibos tea extract. The use of such a wide range of teas in cosmetics has caused some confusion for the consumer and quite a bit of excitement for the cosmetic formulators and chemists.
White tea is rare and expensive. Green, black and white tea are all processed from the same bush called Camellia Sinensis. White tea only uses the finest leaves from each bush and is picked early. The tea leaves and white colored buds are slightly steamed and then mostly sun dried using a minimal amount of processing. Because the tea has been hardly processed it contains high levels of antioxidants.
New studies have found that white tea is 10% more effective than green tea. “We found the application of white tea extract protects critical elements of the skin’s immune system,” says Elma Baron, MD, Director of the Skin Study Center at University Hospitals of Cleveland and Case Western Reserve University. Dr. Baron says. “Similar to the way oxidation causes a car to rust, oxidative stress of the skin causes a breakdown in cellular strength and function. The white tea extract protects against this stress. This study further demonstrates the importance of researching how plant products can actually protect the skin.”
Oregon State University researcher Roderick H. Dashwood, Ph.D. said recently, “Our theory was that white tea might have equivalent or higher levels of these polyphenols than green tea, and thus be more beneficial.” Chemical analysis confirmed their theory when they found that white tea contains the same types of polyphenols as green tea, but in different proportions. “Those present in greater amounts may be responsible for white teas enhanced cancer-fighting potential” said Dashwood.
Scientists at the University Hospitals of Cleveland (UHC) and Case Western Reserve University (CWRU) recently proved that topical application of white tea is effective in boosting the immune function of skin cells and protecting them against the damaging effects of sun exposure. White tea was found to protect the skin from oxidative stress and immune cell damage.
Researchers believe that the antioxidant property of white tea is what makes it effective as an anti-aging ingredient in cosmetics. Kevin Cooper, MD, chairman of the department of dermatology at UHC and CWRU said, “We know that younger skin tends to be able to resist the oxidative stress associated with exposure to the destructive rays of sunlight. The white tea extract also appears to build the skin’s resistance against stresses that cause the skin to age.”
I have been told that Gallic Acid is water soluble only in the presence of other compounds – in the case of tea, notably thearubigin. Can you confirm/refute this? I wonder if you can also explain the mechanism if you believe it to be soluble? Lastly, what do you beleive are the implications for bio-availability?
Gallic acid has very low water solubility, and for it to dissolve in water, one of two situations are required:
1) The presence of another substance which acts as a solvent for gallic acid (eg propylene glycol)
2) The addition of an alkaline substance such as sodium hydroxide which, in this example, produces one of the sodium salts of gallic acid (several are possible) which will be more soluble in water.
Thearubigins are a class of compounds known as polymeric polyphenols, some of which are actually based on gallic acid, and I doubt that they contribute to solubilising gallic acid. I would guess that the very low concentrations of gallic acid present in tea are sufficiently soluble in water to have a measurable presence when the hot water is added to the tea leaves.
I am not quite sure what the questioner requires when asking about the mechanism of solubility and I have no idea of the bioavailability of gallic acid.
I agree that the question is about tea – maybe they are looking to put a tea extract in their formulation which isn’t unusual! Ok so this is what I understand of the tea process as background to answering this question:
Tea is rich in polyphenols which have antioxidant properties. Polyphenols can be further classified into different chemical families including tannins and flavonoids – Gallic Acid fits into the tannin family and thearubigin is a flavoniod.
Thearubigin is formed during the fermentation process that is required to make black tea where it makes up between 10-20% of the dry weight. To confuse matters further thearubigin degrades to form (among other things) gallic acid if the fermentation is allowed to progress too far. This has an adverse affect on the taste.
OK so as for the question, gallic acid is soluble up to 1.1g per 100g water and has a better solubility in alcohol. It’s solubilityalso increases with temperature. This info can be found here, meaning that the answer to the first part of the question is NO.
As for the implications for bioavailability this isn’t something that can be answered as the question is stated as one would need to know the dose being ‘taken’ or applied, the other properties of the formulation and the experimental conditions. As far as skincare actives go, being water soluble doesn’t give them a skin-penetration advantage as the skin barrier is lipidic.
The reader may have been getting confused between green, white and black teas.
It’s good to remind people that cosmetics aren’t supposed to interact with the body’s metabolism so the bio availability of the material should really be negligible if it’s going into a cosmetic. If it actually has a metabolic effect, then you’re creating a drug (at least in the US).
Gallic acid is a plant chemical found in most plants but especially abundant in tea, grapes and oak. It is in a group of chemicals called phenolics. Phenolics are chemicals based on the structure of phenol which is a molecule with a ring structure containing 6 carbons with a –OH (hydroxyl group) attached to one of the carbons. A molecule with more than one phenol ring is called a polyphenol. These phenols and polyphenols are known as powerful antioxidants and found in many plants.
Interestingly, this 6 member ring structure also referred to as an aromatic nucleus is only synthesized by plants and microorganisms, not animals or humans. Generally speaking phenolics are acidic meaning their pH is low (from 1-7).
Gallic acid has 3 –OH groups and one –COOH (carboxylic acid) group attached to the ring. Note that in these abbreviated structures shown that each of the 6 corners represents a carbon atom, so there are 6 carbon atoms in phenol.
Gallic acid can be found either alone or as part of plant tannins. Tannins are a family of high molecular weight, water soluble plant molecules. Another definition of tannin is a natural product containing phenolic structures that can precipitate proteins. They have an astringent taste (think tea) and have the ability to tan leather. When gallic acid becomes linked to a sugar such as glucose it can form a polygalloyl ester which is a simple type of tannin.