Dermalogica Age Smart Map-15 Regenerator has a strong whiff of faux, futuristic science about it. The blurb claims it is a "revolutionary powder-to-emulsion treatment that delivers the highest
concentration of Magnesium Ascorbyl Phosphate (MAP) directly into the
skin". Magnesium Ascorbyl Phosphate is Vitamin C, hardly revolutionary. However, it turns out all vitamin Cs are not alike and so is there is something about this MAP thing that makes Dermlogica stand out from some of the other vitamin C anti-aging creams?
First, get to know your vitamin Cs. Once you do, you'll be much more discerning about which product to buy.
The most basic is ascorbic acid and as a skin cream ingredient this is next to useless. Vitamin C in its ascorbic acid form is unstable. It starts to disappear the moment you unscrew the cap. After three months you may as well forget about getting anything from it. Cellex-C, which I once tried and found completely ineffective, contains ascorbic acid. I also found Cellex-C made my skin very dry - this was probably due to the dominant ingredient, an astringent.
Dermalogica's MAP is superior to ascorbic acid. It is water soluble and stable and is taken into the cells more easily than the ascorbic. MAP is also better for people with sensitive skin, since ascorbic acid is also an exfolliant. It can last up to
200 days before there is loss of activity. I did read somewhere that
the 200 day countdown starts when the cream is produced. If that is
true, it is impossible to know reliably how long you've got unless
(unlikely) it comes with a sell-by date.
However, MAP is not the best.
Next up is ascorbyl palmitate. This tends to be marketed as vitamin C
ester and is used by good, old Dr Perricone. This has the advantage of
being fat soluble and is long lasting, but it is difficult to include in cosmetic
formulations in high doses without adding in some form of alcohol.
The standard-bearer for cosmetic vitamin C is ascorbyl tetraisopalmitate. It can be used in high doses, is welcomed by sensitive skin and lasts up to 18 months. It seems quite rare, however. Perhaps it is expensive. I did find it in a product called Blanc Nouveau C50, which has it concentrations of 50%.
UPDATE 3/30/2008: I've just come across a new super vitamin C called Aminopropyl Ascorbyl Phosphate. It is in (amongst other things) DDF's new age spot cream.