Abstract
Abstract: :
Purpose: Lipofuscin (LF) and melanolipofuscin (MLF) have been implicated in the cause of age–related macular degeneration (AMD), yet LF has only partially been characterized and no components from MLF have been characterized to date. Evidence for known LF components, A2E and especially A2E photo–oxidation products', involvement in AMD is strong; however, their involvement does not rule out the possibility of AMD's etiology being multifactorial. It is important to characterize all of the components in LF and MLF, before any one component's involvement in AMD can be completely understood. The purpose of this study is to begin to characterize new components in LF and MLF, as well as to quantify known components in LF. Methods:Synthetic standards of amino–retinoid compounds were made by reacting all–trans retinal with a series of biogenic amines. LF and MLF were isolated, and extractions of organic materials out of a homogenized solution LF/ MLF in phosphate buffered solution and methanol were performed using chloroform and dichloromethane. New amino–retinoid peaks were identified using high performance liquid chromatography (HPLC) and ultraviolet (UV) spectroscopy. Lipids were observed in LF and MLF by fast atom bombardment mass spectrometry (FAB+ MS). A2E was quantified using synthetic standards, HPLC analysis and FAB+ MS. Results: New HPLC peaks of novel amino–retinoid compounds similar structure to A2E have been identified in LF and MLF. Synthetic standards, as well as UV spectroscopy were used to identify peaks as representing amino–retinoid compounds. Known LF lipid components were observed by FAB+ MS. These compounds were also observed in MLF. A2E was extracted from isolated LF in greater yields than has previously been reported. A2E was extracted from MLF for the first time. Conclusions:Novel amino–retinoid compounds observed in LF and MLF may also play a role in AMD. Isolation and full characterization of these compounds will enable biological assays to confirm their role in AMD. A2E may play a larger role in AMD than previously thought, because of the larger quantities that have been isolated from LF than had been previously reported and because of the quantities that have been isolated from MLF.
Keywords: age–related macular degeneration • macular pigment • retinal pigment epithelium