Chemotaxonomy of commercial Buchu species (Agathosma betulina and A. crenulata)
1996
Collins, N.G. | Graven, E.H. | Beek, T.A. van | Lelyveld, G.P.
The essential oils of Agathosma betulina, A. crenulata and their hybrids were analyzed to determine whether the taxa could be distinguished by their monoterpene chemistry. Pulegone was found to be the key component for identification of the oils. A. betulina is identified by a pulegone content of 2.4% to 4.5%, the hybrids have 7.6% to 27.8% and A. crenulata has 31.6% to 73.2% pulegone. A. betulina and the hybrids have a higher content of 8-mercapto-p-menthan-3-one than 8-acetylthio-p-menthan-3-one while, the reverse is true for A. crenulata. The cis-8-mercapto-p-menthan-3-one content is higher than that of the trans-isomer for A. betulina and the hybrids, but the reverse is true for A. crenulata. Two A. betulina chemotypes were identified. The Diosphenol chemotype is characterized by high psi-diosphenol (> 10%) and diosphenol (> 12%), and low isomenthone (< 29%) concentrations. The Isomenthone chemotype is characterized by high isomenthone (> 31%) and low psi-isomenthone (< 0.16%) and diosphenol (< 0.14%) concentrations. No chemotypes were found for A. crenulata, and those found for the hybrids were not significant due to the small sample size. No significant correlation was found between oil composition and geographic origin for any taxon. The Isomenthone chemotypes of A. betulina are restricted to the Piketberg mountain range.
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