HPLC-MS : Chapter Nine

Chapter nine

Analysis of Molecular Species of Plant Glycolipids

by HPLC/APCI-MS

Ryo Yamauchi

Department of Applied Life Science, Faculty of Applied Biological Sciences, Gifu University,

Gifu 501-1193, Japan

Introduction

Edible plant glycolipids are thought to be nutrients in the human diet. Glycolipids in higher plants consist mainly of steryl glycosides, glyceroglycolipids, and sphingoglycolipids. These glycolipids are widely distributed, if not universal, in edible plants (1,2). Plant glycolipid classes have been separated directly and quantified by normal-phase high-performance liquid chromatography (HPLC) in previous studies (3,4). However, the molecular species of each glycolipid class were not fully characterized. Ripe fruit of the red bell pepper (Capsicum annuum L.) are used widely as vegetables and food additives, such as ground pepper (paprika) and oleoresin, which are good sources of carotenoid pigments. Red bell peppers also contain all three of the above-mentioned glycolipid classes (5,6), and some micronutrients such as vitamins A, C, and E (7–9), but limited information is available on the content and composition of such nutrients in fresh or processed products. Atmospheric pressure chemical ionization mass spectrometry (APCI-MS) has proven to be a very valuable technique for analysis of lipids from a variety of classes (10). This paper describes direct analyses of glycolipids from red bell pepper using HPLC coupled with on-line APCI-MS. The glycolipid classes were first separated by silica-gel column chromatography to obtain acylated steryl glucoside (ASG, 1), steryl glucoside (SG, 2), monogalactosyldiacylglycerol (MGDG, 3), digalactosyldiacylglycerol (DGDG, 4), and ceramide monoglucoside (glucocerebroside, CMG, 5) (Fig. 9.1), and then the molecular species of each glycolipid were separated and characterized by reversed-phase HPLC/APCI-MS.

Materials and Methods

Materials

Fruit of the red bell pepper (C. annuum L. var. Capia) was supplied by a local distributor. The fruits were processed into pastes within the same day after harvest and stored at –30°C until analysis.