Surface tension of aqueous solutions of prostaglandins and related unsaturated fatty acids.

Abstract

The surface properties of prostaglandins F2a, E2, D2, A2 and B2 at the air-water interface were studied under conditions where these compounds are stable. Our values of critical micelle concentrations (cmc) of prostaglandins F2a, E2, A2 and B2 at pH 7.80 were 2.7×10-2, 1.3×10-2, 8.8×10-3 and 6.2 ×10-3 mol·dm-3, respectively, whereas the formation of micelles at pH 4.96 was not detected for any of the prostaglandins tested. The cmc for prostaglandin D2 could not be determined due to the instability of the compound at pH 7.80. However, the surface behavior of prostaglandin D2 at pH 4.96 was very similar to that of prostaglandin E2, indicating that prostaglandin D2 may have a value of cmc at pH 7.80 close to that of prostaglandin E2. These values of prostaglandins are comparable to those of sodium decyl sulfate, dodecanoic acid and tetradecyl phosphate. Possible structures of prostaglandins at the air-water interface and probable mechanisms of membrane penetration and permeation are discussed.