Terpenes have been found to have a range of medicinal benefits in their own right. For example, limonene has been shown to have anticarcinogenic properties (Elson et al. 1997); myrcene, limonene and citral have demonstrated sedative and motor relaxant effects (Vale et al. 2002); and myrcene has been shown to have analgesic effects on peripheral pain (Lorenzetti et al. 1991).
A number of studies also observed potential medical properties in the essential oil of various plant species. Essential oils, which are derived from plants via steam distillation or solvent extraction, typically contain terpenes in higher concentrations than any other constituent. For example, a 2008 study (Gilani et al) investigated the essential oil of Nepeta cataria (catnip), which contains the terpenes pinene and α-humulene, and found it to have bronchodilatory and antispasmodic effects. Another study (Farag et al. 1989) demonstrated that the essential oils of six herbs and spices (sage, rosemary, caraway, cumin, clove and thyme) known to be high in various terpenes including pinene, camphene and limonene demonstrated antimicrobial activity against various gram-positive bacteria. Sage and cumin oils exhibited particularly strong antimicrobial activity.