Simultaneous solubilization of steroid hormones I: estrogens and C21 steroids.

The simultaneous solubilization of some estrogens and C21 steroids in aqueous polysorbate 40, tetradecyltrimethylammonium bromide, and sodium lauryl sulfate was studied. The less soluble estrogen estradiol was solubilized independently of the C21 steroids. The micellar solubilities of ethinyl estradiol and both corticosterone and hydrocortisone were independnet of the presence of each other while the solubility of 11alpha-hydroxyprogesterone was enhanced by ethinyl estradiol. The solubilizations of ethinyl estradiol and the two C21 steroids, progesterone and 21-hydroxyprogesterone, were dependent on each other so that a varying amount of the steroid solubilized first was precipitated by an excess of the second steroid. If saturated solutions of the two steroids were mixed, no precipitation occurred. A possible mechanism for the simultaneous solubilization of steroids and its relation to structure are discussed.