Differential accumulation of isoprenoids in glanded and glandless Artemisia annua L

The relative abundance of steam-distillable isoprenoids and other volatile compounds in leaves of glanded and glandless Artemisia annua L. was investigated. Steam distillation of leaves bearing glandular trichomes yielded 0.24% essential oil on a fresh weight basis. Monoterpenes were predominant in this essential oil, of which α -pinene (26.7%), pinocarvone (15.8%), and artemisia ketone (11.0%) were the major constituents. The essential oil distilled from glandless leaves amounted to 0.06% of fresh weight, and consisted mostly of sesquiterpenes, of which germacrene- D (49.8%) and β -caryophyllene (25.1%) were the major components. Only one monoterpene, β -ocimene, present in trace amounts, was detected in the oil distilled from the glandless tissue. The sesquiterpene artemisinin, found only in the glanded biotype, is heat-labile and cannot be extracted by steam distillation, during which it decomposes into non-distillable products.