Timosaponin BII, a natural product isolated and purified from the rhizomes of Anemarrhena asphodeloides Bunge with antioxidant and anti-dementia activities, can inhibit the up-regulation of BACE1 and reduced the over-production of β-CTF and Aβ in rat retina, which was induced by FeCl3, and may be useful for the treatment of type 2 diabetes.