THE STEROL COMPOSITION OF 5 PLANT-SPECIES GROWN AS CELL-SUSPENSION CULTURES

The free sterols, steryl esters, steryl glycosides and acylated steryl glycosides were examined from five plant species grown as cell suspension cultures, i.e. Apium graveolens, Morinda citrifolia, Nicotiana tabacum, Solanum tuberosum and Tabernaemontana divaricata. The amount and composition of the various steryl lipid classes varied between plant species, but some features previously reported in suspension cultures of A. graveolens were common to other species. Firstly, stigmasterol, which represented between 3 and 44% of the free sterols of the cultures, was either undetected or contributed very little to the steryl ester fraction. Secondly, the precursor sterols (cycloartenol, obtusifoliol) were esterified in greater proportion to palmitic acid than to the C-18 fatty acids. There did not appear to be a simple relationship between the amount of free sterol and the extent of esterification in the various cultures, as the free sterol:esterified sterol ratio varied from 0.39 to 79.25. The composition of the steryl lipids of S. tuberosum differed markedly from that of the other cultures. The steryl glycosides of this species contained both pyranosides and furanosides, which were separable under the GC conditions employed. The steryl lipids of N. tabacum and S. tuberosum were also at variance with reported lipid analyses of the whole plant tissue of these species.