Don’t get your oil soluble Vitamin C mixed up!

It has recently come to my attention that there is at least one brand selling a product that advertises on the front the active Ascorbyl Tetraisopalmitate but on the ingredients listing has Tetrahexyldecyl Ascorbate.

These are not the same chemical.

It took me a while to un-pick these two molecules as they have the same molecular weight and seem to have been registered under the same CAS number making it look like these could be two different names for the same molecule.

They are not the same chemical.

To make it easier for you to see what I see I’ve put the structure of the two chemicals side-by-side above.  As you can see the Tetrahexyldecyl ascorbate has its four arms held out perfectly straight and long whereas the Ascorbyl Tetraisopalmitate has bent arms.  This may not seem like much but this can mean a potentially significant difference in solubility or ability for the skin to utilise these chemicals.

If you were in the business of engineering chemicals (a truly fascinating business to be in) you would appreciate that getting those four arms to bend like that is a bit tricky given the heart of the structure.  The fact that this is quite tricky to achieve is just one reason the Ascorbyl Tetraisopalmitate is so much more expensive to make. The other thing that makes it more expensive (or valuable) is its efficacy data – there is quite a bit.  There is very little efficacy data for the Tetrahexyldecyl Ascorbate – it might well be a good molecule with excellent dermal functionality but there is next to no proof of that.

I wanted to let you know as things like this case of mis-labelling or mistaken identity can become endemic and make it hard for the lay-person to discern what they are getting.  You’ve only got to have a few bloggers say something like ‘these are just two names for the same thing’ or whatever and BINGO, the science goes out of the window.

In terms of use of these two chemicals, here in Australia the Ascorbyl Tetraisopalmitate is allowed in cosmetics at concentrations up to 10% although efficacy data shows it works at concentrations of 1% or even less.  In Japan this ingredient is listed as a quasi-drug and can be used for lightening the skin at concentrations of 3% and in Korea it is listed as a functional ingredient for skin lightening at 2% concentration.  The Tetrahexyldecyl Ascorbate has way less safety data and is only currently allowed at concentrations of 1% or less until the safety data deficit is addressed.

As these are both Vitamin C derivatives they play in a world where 20% Vitamin C rules – at least in terms of marketing.  This 20% number relates to Ascorbic Acid which is very cheap and quite unstable. It has been found in numerous studies to improve the appearance of the skin but that its increase in efficacy stops and then starts to go backwards at 20%. Basically if you use more than 20% you get no extra benefits and actually start getting side-effects – irritation being one of them.   Other forms of vitamin C like those mentioned here act in different ways and take different pathways through the skin meaning the 20% number is far less relevant.  In fact one study carried out by the manufacturers of the Ascorbyl Tetraisopalmitate found it to be taken up by the cells at 10 times the concentration of Ascorbic Acid.  That, combined with its greater stability and oil solubility helps to explain why 20% is not at all needed.

The moral of this story is this,  a background in chemistry helps you to pick a good and effective cosmetic product.  For everyone else there is this blog piece 🙂

Happy buying, selling and making.
Amanda x

PS: After writing this I’ve found that even this Cosmetic Ingredient Review board have lumped these two chemicals in together when looking at their dermal penetration and have also stated that they are indeed two names for the same chemical. That is not correct and I will write to them and tell them.  I wonder how that got passed their eyes. Makes things very difficult indeed…..