An active metabolite of cholesterol; formed when cholesterol is metabolized by CYP27A1; decreases Aβ42 (EC50 = 250 nM) and increases Aβ38 levels with no effect on total Aβ in CHO2B7 cells; decreases endogenous murine Aβ42 production (60% and 75% decrease at concentrations of 3 and 10 μM, respectively)