Submitted to: Phytochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 19, 1999
Publication Date: N/A
Interpretive Summary: The plant Artemisia annua produces a group of medicinally useful compounds. Foremost is artemisinin, which has anti-microbial and antimalarial activity. Interest in the production of artemisinin and related compounds for use as an alternative treatment of malaria continues to increase, as the resistance of the parasite to traditionally used drugs becomes more widespread. Production of artemisinin rarely exceeds 0.8% of dry plant weight. In addition to artemisinin and related sesquiterpenes, A. annua yields an aromatic essential oil with possible commercial applications. We have established the differences in the essential oil components of two different kinds of this plant species; one with a type of glands in the leaves called glandular trichomes, and one without these glands. Ninety-two components were identified between both types. Examination of the differences provided evidence for the sites of accumulation of these compounds as well as providing leads to making plants which might produce a higher content of the commercially important compound artemisinin.
Technical Abstract: 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 yiel 0.24% essential oil, on a fresh weight basis. Monoterpenes were predominant this essential oil, of which alpha-pinene (26.7%), pinocarvone (15.8%), and dartemisia ketone (11.0%) where 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 beta- caryophyllene (25.1%) were the major components. Only one monoterpene, beta ocimene, present in trace amounts, was detected in the oil distilled from t glandless tissue. The sesquiterpene artemisinin, found only in the glanded biotype, is heat-labile and can not be extracted by steam distillation, dur which it decomposes into non-distillable products.