Abstract The essential oils from leaves of Ceratophyllum demersum L. and Vallisneria spiralis L. from China were isolated by steam distillation in yields of 0.15% and 0.10%, respectively, and their chemical composition was examined by GC and GCâMS. More than 50 constituents were identified, representing 87% of the total oils. The main components were basically the same in the two plants' essential oils. 2âMethylpropanoic acid 3âhydroxyâ2,4,4âtrimethylpentyl ester (&gt;15%), 2âmethylpropanoic acid 2,2âdimethylâ1â(2âhydroxyâ1âmethylethyl)propyl ester (&gt;3%), Î² âiononeâ5,6âepoxide (&gt;7%), toluene (&gt;6%), hexanal (&gt;5%) and 1,2âbenzenedicarboxylic acid di(2âmethylpropyl) ester (&gt;5%) were the major components. Copyright Â© 2006 John Wiley &amp; Sons, Ltd.