Ascorbic acid esters - lipophilicity and penetration
Jacek Arct 1/, Ewa Starzyk 2/
1/ Fundacja dr Seidla w Warszawie
2/ Polski Związek Przemysłu Kosmetycznego
Introduction. Ascorbic acid (vitamin C), its phosphates and salts are used in cosmetology as antioxidants., Sustaining collagen and lightening. The use of free vitamin C is limited. This is due to the low bioavailability of this compound when used externally and with its limited durability.
Aim. The possibility of improving the permeation of ascorbic acid by stratum corneum in model conditions by its lipophilization was investigated. This procedure has been reported by examining the esters of ascorbic acid with fatty acids of different lipophilicity.
Materials and methods. The commercially available ascorbic acid and its acyl esters synthesized in laboratory conditions were used. The lipophilicity of acyl derivatives was determined experimentally with the shake-flask method and on the basis of available computer data. The permeation rate was investigated experimentally on stratum corneum models using the method described earlier. The mathematical equations were prepared on the basis of the experimental results.
Results. The relationship between the experimentally determined lipophilicity and the available computer data was determined. It was found that lipophilization increases the permeation rate of ascorbic acid derivatives over the stratum corneum model. It was found that the dependence of the penetration rate on the lipophilicity has the inflexion point (parabolic or bilinear caretaker). Based on the experimental data, mathematical equations were determined.
Conclusions. The obtained results indicate the desirability of lipophilization and thus increasing the dermal bioavailability of ascorbic acid. At the same time, to some extent, they question the freeze-drying models used so far. It seems that the advisability of using specific lipophilic derivatives of ascorbic acid should be re-analyzed.
Key words: ascorbic acid, acyl derivatives, lipophilicity, penetration