Patent ID: 8183048

Claim:
A method of screening an antioxidant for potential toxicity in vitro, the method comprising: (a) providing a constant absolute amount of a fluorescent sterol probe having a detectable signal, a bilayer forming lipid and optionally a spacing lipid to form a model system comprising unilamellar vesicles having a sterol superlattice formation, wherein a mole fraction of a sterol, including the fluorescent sterol probe, is varied from 18 mol % to 52 mole % in increments of about 0.3 mol %; (b) providing an antioxidant; (c) providing a prooxidant; (d) combining the unilamellar vesicles, the antioxidant and the prooxidant; (e) measuring (1) a fluorescence intensity of the fluorescent sterol probe from a time of the addition of the prooxidant to at least 5 minutes after a time of an abrupt change in sterol oxidation rate, and thereby obtaining a lag phase length (τ), or (2) a sterol fluorescence intensity from a time of the addition of the prooxidant to a time when the sterol fluorescence intensity vs, time begins to deviate from linearity, and thereby obtaining an initial rate of sterol oxidation in the presence of the antioxidant (Ri) and an initial rate of sterol oxidation in the absence of the antioxidant (Rio); (f) plotting the τ, or the Ri as a function of the sterol mole fraction to detect a biphasic effect; and (g) repeating said measuring at increasing doses of the antioxidant to determine a threshold concentration (C th ) of the antioxidant at which the biphasic effect substantially disappears, wherein a lower C th indicates a higher potential toxicity of the antioxidant.