Chemical, physical and antimicrobial properties of essential oils of Leptospermum scoparium and Kunzea ericoides.

The major components of commercial New Zealand essential oils of Leptospermum scoparium (manuka) and Kunzea ericoides (kanuka) are identified. In the manuka oil, monoterpenes are present at low levels (< or = 3%). Sesquiterpene hydrocarbons are predominant (> or = 60%) and include groups possessing cubebene/copaene, elemene, gurjunene/aromadendrene, farnesene/ caryophyllene, selinene, calamenene and cadinene skeletons. Oxygenated sesquiterpenes and triketones are present (< or = 30%). The antimicrobial activity of the manuka oil was associated with a fraction containing three major and three trace triketones, two of the latter were previously unreported. Kanuka oil was characterized by high levels of alpha-pinene (> 50%) and lower levels (< 10%) of viridiflorol and viridiflorene. GC-MS and GC-FID detector responses to the same components were noticeably different for some major components, including the triketones. Non-commercial manuka oils from different sites differed widely in composition and could be separated into four groups by the presence and levels of distinctive components. The density and refractive index of manuka and kanuka oils were closely correlated with the total sesquiterpene levels. The density of the commercial manuka oil was closely correlated with the level of the triketones. Simple density measurements enabled discrimination between the commercial oil and oils from other sites, and prediction of antimicrobial activity.