ABSTRACT
Volatile constituents obtained by water distillation from the aerial parts and root of Onosma dichroanthum Boiss (Boraginaceae) native to the north of Iran were investigated by GC and GC/MS for the first time. Palmitic acid (39.61%) and decane (31.39%) were the major components in the root while decane (26.26%) and phytol (25.52%) were the predominant constituents in the aerial parts. Ketones, aldehydes, alkanes, fatty acids, oxygenated diterpenes and sesquiterpenes were characterized as the most phytochemicals in the aerial parts. Alkanes and fatty acids were identified as the main groups in the root volatile substances. There were two ketone derivatives, belong to apocarotenoids, in the aerial parts; β-ionone and hexahydrofarnesyl acetone.