Pseudoguaianolide sesquiterpene

Ligulatin B (= Incanin) (pseudoguaianolide sesquiterpene lactone) Parthenium ligulatum, P. spp. (Asteraceae) Insect antifeedant... 

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. 

Herrmann, H.D., G. Willuhn, and B.M. Hausen. 1978. Helenalinmethacrylate, a new pseudoguaianolide from the flowers of Arnica rrumtana L. and the sensitizing capacity of their sesquiterpene lactones. Plant a Med. 34(3) 299-304. 

Although many details of the biosynthesis of sesquiterpene lactones are not established, guaianolides, eudesmanol-ides, and pseudoguaianolides in the Asteraceae appear to be derived from germacranolide precursors (Fischer, 1978, 1990 Fischer et al, 1979). Biomimetic reactions leading to the formation of these and other types of sesquiterpene lactones have been proposed (Fischer, 1990). 

Populations of Ambrosia confertifloray a ragweed disttib-uted widely through Texas and Mexico, reveal complex sesquiterpene lactone chemistry. Most populations from south-central Texas are characterized by a chromosome number n = 66 and the pseudoguaianolides confertiflorin (95) and desacetylconfertiflorin (99), whereas plants from northeastern Mexico yield germacranolides and a few eudesmanol-ides. All of those studied have chromosome number n = 54. A dilactone race (with both = 54 and n = 66) occurs further west in Texas and in Mexico along the western slopes of the Sierra Madre into the area where Ambrosia cumanensis occurs. A fourth race characterized by the presence of germacranolides occurs in northwestern Mexico (Mabry, 1972). 

The following outline of advances appearing in the literature over the three-month period August-November 1977 provides an illustration of current efforts to discover new higher and lower plant cancer chemotherapeutic drugs. In 1973, we reported the first pseudoguaianolide-type sesquiterpene to display in vivo antineoplastic activity. ° At that time, we found the sesquiterpene lactone helenalin to be quite active against the... 

Further sesquiterpene Bijvoet determinations, including guaianolides and pseudoguaianolides... 

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