Abstract
Solvent mixtures containing trimethyl borate virtually eliminated the pronounced interconversion of 1,2- and 1,3-dipalmitins during their resolution by thin-layer chromatography on Silica Gel G. With trimethyl borate, an average of 1-2% of 1,2-dipalmitin was converted to 1,3-dipalmitin. A four-directional-development TLC procedure incorporating trimethyl borate resolves cholesteryl glucoside, ceramides, monogalactosyl diglyceride, 1- and 2-monopalmitin, palmitic acid, cholesterol, 1,2- and 1,3-dipalmitin, tripalmitin, methyl palmitate, cholesteryl palmitate, beta-carotene and some of its degradation products, squalene, and tetracosane. Digalactosyl diglyceride, phosphatidic acid, phosphatidylglucose, cerebrosides, and other phospholipids remain near the origin. A mixture containing triolein, 1,2- and 1,3-diolein, 1- and 2- monoolein, oleic acid, and cholesterol was resolved in one dimension. A similar series of palmitic-containing neutral lipids was also resolvable in one dimension. These procedures were applied to the TLC of human sera lipids.
Highlights
A four-directional-development thin-layer chromatography (TLC) procedure or oncoated glass plates(UniplatesA, naltechI,nc., incorporatingtrimethylborate resolvescholesterylglucoside, ceramides, monogalactosyl diglyceride, 1- and 2-monopalmitin, palmitic acid, cholesterol, 1,2- and 1,3-dipalmitin, tripalmitin, methyl palmitate, cholesteryl palmitate, &carotene and some of its degradationproducts,squalene,andtetracosane.Digalactosyl diglyceride, phosphatidic acid, phosphatidylglucose, cerebrosides, and other phospholipids remain near the origin
Thaeppearance of two additional spots indicated that conversion took place during the 150-min drying period or during migration in the second dimension (Fig. 1). These unexpected spots were identified as 173-dipalmitinarising from 1,2dipalmitin and a lesser amount of 1,2-dipalmitin arising from 1,3-dipalmitin
As suggested by the dataof Mattson and Volpenhein [12], all free hydroxyls of monoglyc2rides and diglycerides may be susceptible to derivitizntion by Mattson and Volpenhein [12] used trimethyl and triethyl borate for the synthesis of monoglycerides
Summary
Thaeppearance of two additional spots indicated that conversion took place during the 150-min drying period or during migration in the second dimension (Fig. 1). These unexpected spots were identified as 173-dipalmitinarising from 1,2dipalmitin and a lesser amount of 1,2-dipalmitin arising from 1,3-dipalmitin. The percentage conversion of 1,2- to 1,3-dipalmitin was calculated by first adding the amount of glyceride found inthe two spots derived from the slower moving 1,2dipalmitin in the first direction. Glass TLC plates were used without drying, spotted with 250pg of 1,2-dipalmitin, and chromatographed in two dimensions with BEA containing various amounts of trimethyl borate. A slightly higher concentration of borate was required for maximal
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