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

## TL;DR

This study compares the volatile components of all native Australian mint species, revealing significant variation in their chemical profiles.

## Contribution

The paper provides the first comprehensive documentation of volatile oil variation across all Australian Mentha species.

## Key findings

- Mentha australis and M. diemenica had high concentrations of menthone and pulegone.
- Mentha satureioides showed a distinct chemotype in eastern New South Wales with limonene and 1,8-cineole.
- Mentha atrolilacina had a unique oil profile with linalool and β-caryophyllene as main components.

## Abstract

Mentha are historically important regarding their volatile oils. Since limited accounts exist for Australian species, we document the variation in volatiles across all Australian Mentha 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% w/w) for freshly dried and herbarium specimens. Many species uniformly had high percentages of volatiles characteristically attributed to Mentha (viz. Menthone, Pulegone); yet, others—consistently or variably—lacked them. Mentha australis had the highest concentrations of menthone (25%), isomenthone, (9%) and pulegone (24%), and M. diemenica had menthone (32.5%) and pulegone (29.8%). Extracts from M. grandiflora from herbarium specimens produced weak traces, high in menthone and pulegone. Mentha satureioides 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%). Mentha laxiflora consistently exhibited limonene (27%); yet, the levels of the other main components (e.g., menthone, β-pinene, germacrene-D, and bicyclogermacrene) varied across populations. Mentha atrolilacina 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 M. satureioides 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.