Leaf lipids from Euphorbia lagascae Spreng. and Euphorbia lathyris L.

Abstract

The Euphorbiaceae family is comprised of plant species that synthesise unusual fatty acids in their seed oils, e.g., Ricinus communis (ricinoleic or hydroxyoleic acid), Aleurites fordii (eleostearic acid) or Euphorbia lagascae (vernolic or epoxyoleic acid). Accumulation of triacylglycerols (TAGs) in plant leaves of many species can occur, although in smaller quantities than in seeds. This is the first report on leaf lipids in Euphorbia. Total lipid (TL) content ranged from 2274 to 5757 μg/g of fresh weight in Euphorbia lathyris and from 1562 to 9813 μg/g of fresh weight in E. lagascae. The first, fifth, tenth or fifteenth true leaves (each case from 2- to 40-day-old leaves) were sampled from plants grown in the open field and in the glasshouse at Instituto Murciano de Investigación y Desarrollo Agrario y Alimentario (Murcia, Spain). TAGs were separated by thin-layer chromatography (TLC) and represented up to 44.3% of TL in E. lagascae. The amount of TAG peaked in the first leaf and subsequently decreased with aging in all leaves. Microscope preparations revealed the presence of oil bodies (3–10 μm), possibly acting as intermediate storage products, in Euphorbia leaf mesophyll cells. Vernolic acid was identified in E. lagascae leaf lipids (0–25.7% of total fatty acids), but it was not incorporated into TAGs. These results imply that the active enzyme, diacylglycerol acyltransferase (DGAT), in the leaf of E. lagascae does not exhibit any selectivity towards the native unusual fatty acid.