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1620389 
Journal Article 
In vitro and in vivo study of the substantivity of p-aminobenzoic acid and two of its esters 
Morasso, MI; Thielemann, AM; Pinto, C; Figueroa, M; Arancibia, A 
1985 
0 
Journal of the Society of Cosmetic Chemists
ISSN: 0037-9832 
IPA/86/676078 
Soc 
REF 14 
355-362 
eng 
IPA COPYRIGHT: ASHP The substantivity of p-aminobenzoic acid (PABA; aminobenzoic acid; I) and its esters, octyl dimethyl p-aminobenzoate (Escalol 507; padimates O; II) and ethyl dihydroxypropyl p-aminobenzoate (roxadimate; Amerscreen P; III), in an alcoholic vehicle was studied in vitro and in 8 healthy volunteers (aged 20-30 yr) in order to establish the possible correlation between the 2 methods. In the in vivo study, the subjects' hands were placed in isopropanol (isopropyl alcohol; IV) solutions of I (5%), II (2%) or III (2%), then rinsed with water and extracted with IV at 50DGC to quantitate the amount of sunscreen retained by the skin. A crossover design was used using each of the sunscreens at one wk intervals. In the in vitro experiment, powdered human keratin (obtained from calluses of the feet) was kept in an ethanol (ethyl alcohol) solution of the sunscreen for 72 h, then treated with water for 48 h, and finally extracted with alcohol at 50DGC for 24 h to determine the amount of sunscreen retained. Spectrometric determinations showed that the in vivo percent substantivities were: I, 0.30 +- 0.05; II, 57.96 +- 0.63; III, 0.46 +- 0.08. The values for the in vitro method were: I, 0.30 +- 0.02; II, 50.84 +- 0.66; III, 0.47 +- 0.03. The differences are statistically significant (p|LT/0.01), with II showing the highest substantivity. Results obtained by both methods were linearly correlated. 
Aminobenzoic acid; substantivity; skin; Padimate O; skin; Roxadimate; Keratin; adsorption; sunscreen agents; Alcohols; vehicles; sunscreen agents; Alcohols; substantivity; aminobenzoic acid(Sunscreen agents; padimate O(Sunscreen agents; roxadimate(Sunscreen agents; Skin; substantivity; skin; Methodology; sunscreen agents; Escalol 507; p-Aminobenzoic acid; PABA; Octyl dimethyl p-aminobenzoate; Amerscreen P; Ethanol; Isopropanol; Ethyl dihydroxypropyl p-aminobenzoate; HUMAN