Volatile oil comparison of cotyledon leaves of chemotypes of Melaleuca alternifolia.

Oil quantity and quality were measured for the cotyledon leaves of the commercial terpinen-4-ol chemical variety of Melaleuca alternifolia. Oil yield obtained by ethanolic extraction was 3.8 micrograms per leaf or 2.6% (dry weight basis). The major components of the oil were alpha-pinene (7.4%), beta-pinene (12.0%) and terpinolene (27.3%). The non-commercial terpinolene chemical variety was found to be rich in 1,8-cineole (12.5%) and terpinolene (25.4%). The non-commercial 1,8-cineole chemical variety was rich in 1,8-cineole (37%) with significant quantities of alpha-pinene (15.5%), beta-pinene (23.3%) and terpinolene (10.9%). The cotyledon leaf composition, when compared with that of mature leaf from the same chemical variety, was found to be biased toward pinene and terpinolene biogenetic pathway constituents and hence not a good indicator of mature tree quality especially for the commercial terpinen-4-ol chemical variety. The implications of these analyses for the determination of M. alternifolia plantation quality and the understanding of oil formation, are discussed.