Submitted to: Plant Lipids International Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: July 11, 1996
Publication Date: N/A
Interpretive Summary: It has recently come to light that a previously disregarded class of plant lipids (fats) called cerebrosides (CBs) can compose a major part of the structure of two vitally important cell membranes which control the flow of water and nutrients into the plant cell and sequester waste products. Furthermore, there is evidence that CBs are involved in responses to environmental stress, such as low temperature and drought. Plant CBs are structurally complex, and new methods for their detection and identification must be devised. This study entailed a comparison of two recent methods for the analysis of plant CBs. The results revealed the relative advantages and disadvantages of the the two methods, and indicated modifications that would possibly improve each of them. This information will be useful to other plant scientists in their efforts to further elucidate the importance and function of CBs. The ultimate goal of this work is to extend the shelf life of horticultural commodities and increase their tolerance to environmental stress, both before and after harvest.
Technical Abstract: Plant cerebrosides (CBs) can compose a major fraction of plasma membrane and tonoplast lipids and may play roles in stress responses and apoptosis. This lipid class often includes many molecular species because of diversity among the sphingoid (SP) and 2-hydroxy fatty acid (2h-FA) moieties. HPLC HPLC methods using a C18 or a C6 column have been devised for analysis of plant CBs. These HPLC methods were compared with respect to their sensitivity as well as their adequacy for separation based on 2h-FA chain length and SP hydroxylation, unsaturation, and cis vs. trans isomerization. Results with CBs from apple and melon fruits were as follows: 1) Because the absorbance maximum of CBs is at 204nm, the C6 method, which uses a gradient of MeCN in water with UV monitoring at 205nm, was 3-fold more sensitive than the C18 method (isocratic MeCN:MeOH, with UV detection at 210nm); 2) C6 was comparable to C18 for separation according to FA chain length and SP hydroxylation and unsaturation; 3) C18 gave near baseline resolution of CBs with 8-cis and 8-trans SP isomers, whereas C6 gave no or partial separation; 4) Total run times were 60 min on C18 vs. 40 min on C6 and CB retention times differed substantially. Overall, the C6 method is suitable for routine quantification and characterization of plant CBs, particularly when the amount of sample is limiting. However, for separation and identification of CB molecular species, the C18 method is clearly superior.