To evaluate the interpopulation variability of volatile compounds in Melicope obscura, four samples representing four populations were collected all over the distribution area of the species in Reunion Island (Indian Ocean). The samples were extracted by hydrodistillation, and analyzed using GC/FID and GC/MS techniques. The study revealed that, in the four essential oils obtained, oxygenated sesquiterpenes were one of the major chemical classes (9.2 –35.2%), mainly consisting of a new compound, (þ)-6-ethenyl-2-hydroxy-6,10-dimethylundeca-2,9-dien-4-one (1), called melicopenol (8.6 – 30.1%). The compound was isolated by column chromatography and identified by spectral analyses including 1D- and 2D-NMR.