Abstract: The fatty acid components of the seed oils of five species of Euphorbiaceae collected in Xishuanbanna district, Yunnan province—Aleurites montana (Lour.) Wis., Mallotus paniculatus (Lam.) Muell-Arg., Ostodes paniculata Bl., Mcaranga denticulata (Bl.) Muell-Arg., and Trewia nudiflora L.- have been analyzed. Long-chain fatty acids were first converted to corresponding 2-substituted 4,4-dimethyloxazoline derivatives (DMOX) by condensing with 2-amino- 2-methylpropanol (AMP) and subsequently analyzed by GC-MS. The position of unsaturation (double and triple bonds) and substituents (e.g., hydroxyl) in the aliphatic chain can easily be located by interpreting the mass spectra recorded in this way. The qualitative as well as quantitative results can be provided for all constituents in a single GC-MS run. This me thod proves simple and efficient, with good reliability, and is well suitable for the structure determination without reference specimens.

Key words: Aleurites montana, Mallotus paniculatus, Ostodes paniculata, Trewia nudiflora, Mcaranga denticulata, Identification of fatty acids