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New purification method for vitamin A derived aging pigments
A2E, vitamin A-derived aging pigment, implicated in the pathogenesis of age-related macular disease (AMD), is one of the major compounds that accumulate as lipofuscin pigments in retinal pigment epithelial (RPE) cells with age and in some retinal disorders. Here we report a new purification method for A2E and iso-A2E, a double bond isomer of A2E, from a reaction mixture of two all-trans-retinal molecules and one ethanolamine molecule by using cation exchange resin. When the mixture complexed with the resin, it was serially eluted with 80% methanol containing sodium hydroxide (pH12), 100% methanol and 100% methanol with 0.1% trifluoroacetic acid (TFA), most of A2E and iso-A2E were eluted with 100% methanol solution containing 0.1% TFA. All-trans-retinal was mostly eluted with 80% methanol containing sodium hydroxide (NaOH). Identities and recoveries of the isolated compounds were determined by HPLC analysis. This single method for the purification for vitamin A-derived aging pigments will provide an efficient scale up protocol for the preparation of A2E and iso-A2E.