Studies of Acetal Phospholipides of Brain

Feulgen and Bersin (1) obtained from the hydrolysis products of the acet>al phospholipide present in muscle a mixture of thiosemicarbazones. They suggested that these thiosemicarbazones are derivatives of pahnitic and stearic aldehydes, although t,hey gave no analytical data supporting this view. Anchel and Waelsch (2) obtained from hydrolysates of lipide mixtures from different tissues, including brain, p-carboxyl phenylhydrazones as well as carboxymethoximes of fatty aldehydes. The analysis of a mixture of these derivatives suggested the presence of Cl6 and C18 fatty aldehydes. Separation of the two different aldehyde derivatives was not carried out because of the small amounts of material. Klenk (3) reported the hydrolysis of an acetal-containing substance which was apparently a mixture of acetal phosphatidic acid and acetal phospholipide. The hydrolysis yielded an aldehyde which he converted into the corresponding fatty acid. The titration of this fatty acid gave the equivalent weight of st>earic acid. Leupold (4) prepared in Klenk’s laboratory a mixture of methyl acetals by boiling the total phospholipide mixture of brain with methanolic hydrochloric acid. After conversion of the methyl acet,al mixture to the corresponding fatty acids, palmitic, stearic, and oleic acids were isolated. Evidence concerning the nature of the aldehyde groups of our crystalline acetal phospholipide from brain (5) will be reported in this paper. Two different procedures were applied for the separation and identification of the aldehydes: (1) separation of the free aldehydes by microdistillat’ion in a high vacuum, and (2) conversion of the aldehyde mixture to the corresponding fatty acids and separation of the methyl esters of the fatty acids by microdistillation in a high vacuum.