Sesquiterpene lactones identification

P h y t o c h e m i c a l investigations of plant species of Parthenium, Encelia and Pi coria (Asteraceae) from semi-arid and arid zones of the United States and Mexico has resulted in the isolation and identification of numerous sesquiterpene lactones and benzopyrans that are active insect feeding deterrents. The chemistry, biological effects and possible mode of action of bioactive pseudoguaianolides and chromenes are reviewed. 

Over the years, numerous plants have been used in folk medicine against gastroduodenal disorders. The development of phytochemical techniques has allowed the identification and isolation of numerous principles from some of them, such as alkaloids [70], sesquiterpen lactones [71, 72], or polyphenolic compounds [66-69]. 

Two major breakthroughs of the past few decades have renewed the assault of scientists to this infective disease. The first is the complete sequencing of the genome of Plasmodium falciparum [4] that is expected to provide useful information for the identification of new drug targets. The second is the discovery by Chinese researchers of artemisinin (qinghaosu), an endoperoxide sesquiterpene lactone, as the active principle of the sweet wormwood, Artemisia annua, an herbal remedy used in folk Chinese medicine for 2000 years [5]. This molecule and its... 

An example of the power of this method in structural elucidation is shown for the sesquiterpene lactone acetyhsomontanohde (Fig. 5.77). The complete carbon skeleton of the molecule can be traced directly in the spectrum, with breakdown occurring only when heteroatom linkages arise. Unfortunately, it is rare indeed to have sufficient sample quantities at hand to consider employing this technique, and still it remains of limited application in its original form. Nevertheless, in very proton-sparse systems, it may present the only option as in the identification of the nitration product of 5.11a. The product was to... 

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