52 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS EoQ D -65 ///• ô ......... • a C• AS i C. •AOS •/-'•m • C•nAS j ClazAOS c C' •AS k C ' =AOS 12 16 d C14AS m C18AOS e C. LAS zf c•s ñu c I2•s 12 hg C.. LAS C16LAS ...................... 0.5 l•0 1.5 ( l•3mole/g ) Adsorption by Callus ( 1,0%, 40C, 2 hr ) Figure 9. Relationship of adsorbing ability onto skin measured by adsorbed amounts of surfactants onto isolated callus after incubation of 1% concentration for 2 hr at 40øC., and specific rotation of BSA in the presence of the 1.5% surfactant. Note that there is a positive correlation (r=0.93) with a significant difference of 95%. AS: alkyl sulfate, LAS: linear alkyl benzene sulfonate, AOS: alfo-olefin sulfonate. -651 - 60 -55 o CI0 AS ß C•18F D t10 MAP monona nC8 %_,/. 0 5 1.0 1.5 Snrfactant Concentration( g /100ml) Figure 10. Changes in specific rotation of BSA plotted against the concentrations of monoalkyl phosphates. AS: alkyl sulfate, MAP: monoalkyl phosphate.

SKIN IRRITATION BY ANIONIC SURFACTANTS 53 ø+$.0 • -$.0 C8 C10 CISF1 MAP MAP MAP C12 C12 C!2 C!2 C123 C!28 C!2 AS AOS LAS SAS ES ES B CI2 C1214 AGS S B EO CSII Figure 11. Changes in specific rotation of BSA measured at 1.5% concentration of various surfactants. MAP: monoalkyl phosphate, AS: alkyl sulfate, LAS: linear alkyl benzene sulfonate, SAS: paraffin sulfonate, AOS: alfa-olefin sulfonate, ES: alkyl ether sulfate, B: alkyl betain, SB: alkyl sulfobetain, EO: alkyl polyoxyethlene, AGS: alkyl acylglutamate. IN VITRO ADSORBING PROPERTIES It is well known (12) that when certain amounts of surfactants are adsorbed on protein, protein denaturation, namely unfolding of the secondary or tertiary structure, is induced. Thus, the interaction between bovine serum albumin (BSA) and surfactants as evaluated by using the optical rotation technique (13) was investigated as a more sensitive and convenient model for estimating the adsorptive effect of surfactants on Surfact ant no adsorption} Indigo strong staining T reatmen t weak adsorption Camine l Treatment strong adsorption weak staining no staining Na0$5 E=E $0aNa ß indigo. carmine H H a adsorption site Indigo Carmine Figure 12. Theory for in vivo evaluation of adsorbing ability of anionic surfactants by using acidic dye such as indigo carmine.