Molecular weight rule of skin penetration
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Tue Sep 11, 2012 6:22 pm

What is the molecular weight of Magnesium Ascorbyl Phosphate(MAP)? I can't seem to find out anywhere. Why do I ask?

Read the following:

Human skin has unique properties of which functioning as a physicochemical barrier is one of the most apparent. The human integument is able to resist the penetration of many molecules. However, especially smaller molecules can surpass transcutaneously. They are able to go by the corneal layer, which is thought to form the main deterrent. We argue that the molecular weight (MW) of a compound must be under 500 Dalton to allow skin absorption. Larger molecules cannot pass the corneal layer. Arguments for this "500 Dalton rule" are;

1) virtually all common contact allergens are under 500 Dalton, larger molecules are not known as contact sensitizers. They cannot penetrate and thus cannot act as allergens in man;

2) the most commonly used pharmacological agents applied in topical dermatotherapy are all under 500 Dalton;

3) all known topical drugs used in transdermal drug-delivery systems are under 500 Dalton. In addition, clinical experience with topical agents such as cyclosporine, tacrolimus and ascomycins gives further arguments for the reality of the 500 Dalton rule. For pharmaceutical development purposes, it seems logical to restrict the development of new innovative compounds to a MW of under 500 Dalton, when topical dermatological therapy or percutaneous systemic therapy or vaccination is the objective.

free skin care · Sat Sep 15, 2012 8:33 am

I tried looking up the chemical formula for MAP. The most consistent answer I got was
C6H8O9PM1.5 (C_6 H_8 O_9 P M_1.5), but I found other results, too. If the molecular formula above is correct, then I estimate the molecular weight as about 292 daltons. A good rule of thumb for estimating is the taking the atomic weights of each of the atoms and adding them up or totaling the number of protons and neutrons in the molecule. That should be about right, unless the chemical formula is otherwise. I hope this helps.

Also, check out this new article:

http://www.ncbi.nlm.nih.gov/pubmed/22664777

Mol Med Report. 2012 Aug;6(2):375-8. doi: 10.3892/mmr.2012.933. Epub 2012 May 30.
Magnesium ascorbyl phosphate and coenzyme Q10 protect keratinocytes against UVA irradiation by suppressing glutathione depletion.
Hwang TL, Tsai CJ, Chen JL, Changchien TT, Wang CC, Wu CM.
Source
Department of Surgery, Chang Gung Memorial Hospital, Tao-Yuan, Taiwan, ROC.
Abstract
The aim of this study was to investigate whether magnesium ascorbyl phosphate (MAP) and coenzyme Q10 (CoQ10) can protect keratinocytes against ultraviolet (UV)A irradiation by increasing the levels of glutathione (GSH). The cell survival fraction was 89.9% when the keratinocytes were irradiated with UVA at a dose of 4 J/cm2. The cell survival fractions were 48.4, 9.1 and 4.8%, at doses of 8, 16 and 32 J/cm2, respectively. MAP was added to the cells prior to UVA irradiation at a dose of 8 J/cm2 and then the cell viability was assayed. The cell survival fractions were 51.6, 55.5, 64.8 and 76.7%, when MAP was added at concentrations of 125, 250, 500 µM and 1 mM, respectively. The results showed that MAP is capable of protecting keratinocytes against UVA irradiation. The cell survival fractions were 77.2, 89.4 and 90.1%, when CoQ10 was added at concentrations of 2.5, 5 and 10 µM, respectively. The results revealed that CoQ10 is capable of protecting keratinocytes against UVA irradiation. At the same time, the levels of GSH within cells were detected. The level of GSH within cells was 0.3 mmol/g protein when the keratinocytes were irradiated with UVA at a dose of 8 J/cm2. We measured the levels of GSH within the cells after MAP or CoQ10 was added prior to UVA irradiation at a dose of 8 J/cm2. The levels of GSH within the cells were 0.344, 0.388, 0.456 and 0.5 mmol/g protein, when MAP was added at concentrations of 125, 250, 500 µM and 1 mM, respectively. The levels of GSH within the cells were 0.328, 0.35 and 0.394 mmol/g protein, when CoQ10 was added at concentrations of 2.5, 5 and 10 µM, respectively. These results imply that MAP and CoQ10 can protect the keratinocytes against UVA irradiation, possibly via increasing the levels of GSH.

HTH Smile

Sun Sep 16, 2012 1:39 pm

Awesome thank you!

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