A Comparison of Volatile Components Across Native Australian Mentha (Lamiaceae)

<i>Mentha</i> are historically important regarding their volatile oils. Since limited accounts exist for Australian species, we document the variation in volatiles across all Australian <i>Mentha</i> species, using the GC/MS of pentane extractions from leaf samples of replicate populations for all known species. Oil yields were consistently poor (<0.2% <i>w</i>/<i>w</i>) for freshly dried and herbarium specimens. Many species uniformly had high percentages of volatiles characteristically attributed to <i>Mentha</i> (<i>viz.</i> Menthone, Pulegone); yet, others-consistently or variably-lacked them. <i>Mentha australis</i> had the highest concentrations of menthone (25%), isomenthone, (9%) and pulegone (24%), and <i>M. diemenica</i> had menthone (32.5%) and pulegone (29.8%). Extracts from <i>M. grandiflora</i> from herbarium specimens produced weak traces, high in menthone and pulegone. <i>Mentha satureioides</i> had the highest menthone (20-30%) and pulegone (22-28%) in populations across the extent of its range; yet, an entirely different chemotype was identified from eastern New South Wales that contained limonene (17%), 1,8-cineole (19%), and α-terpineol (8%). <i>Mentha laxiflora</i> consistently exhibited limonene (27%); yet, the levels of the other main components (e.g., menthone, β-pinene, germacrene-D, and bicyclogermacrene) varied across populations. <i>Mentha atrolilacina</i> exhibited the most unique oil profile, with main components consisting of linalool (21%), β-caryophyllene (14%), germacrene-D (14%), and bicyclogermacrene (23.7%). Commercial samples of <i>M. satureioides</i> were found only to be the chemotype high in limonene (17%) and 1,8-cineole, which warrants further taxonomic research and caution for the industry seeking mint flavours from Australian sources.