Seasonal age-specific measurements of the sesquiterpene lactones and chromenes of Encelia farinosa

Age-specific concentrations of farinosin, a sesquiterpene lactone, and encecalin and euparin, both chromenes, were measured in two semi-desert populations of Encelia farinosa in California over a three month period. All three natural products differed significantly in concentration. The average concentration of encecalin is 10 times that of euparin and eight times that of farinosin. Farinosin concentrations did not differ between the two populations, but both euparin and encecalin were in higher amounts in the UC Riverside population than in the Home Gardens population. Seasonal changes in natural products differed at the 0.05 level for all populations and compounds except euparin in the UC Riverside population. Percent nitrogen content of dried leaves was similar in both populations, but differed between collection dates. Water content did not vary significantly with leaf age on one collection date. The significance of these results is discussed in the light of herbivore history.     

Distribution of chromenes and benzofurans in Encelia californica

Two populations of Encelia californica (Asteraceae) were analysed for chromenes and benzofurans on an organ specific basis using HPLC. Both classes of compounds were present in all parts of the plant studied including roots, stems, leaves, capitula and achenes. The distribution patterns were less complex in roots and achenes when compared to stems, leaves and capitula which yielded three chromenes and two benzofurans. In addition to the chromenes and benzofurans the capitula afforded a sesquiterpene lactone of the eudesmanolide type which was absent in the other parts of the plant.     

Microsampling: an alternative approach using sesquiterpene lactones for systematics

The localization of sesquiterpene lactones in glandular trichomes of numerous Asteraceae makes it possible to use a microtechnique to investigate their occurrence. General aspects of the utility and value of the method in comparison with standard procedures are discussed with special focus on the advantage of a quick, inexpensive and reproducible analytical technique in systematic and biochemical studies. Using analytical HPLC, it was possible to establish the sesquiterpene lactone profiles of all 64 known taxa of the genus Helianthus. Intraspecific variation of sesquiterpene lactones was found to be low in comparison to morphological characters. Hybrids were shown to possess the additive sesquiterpene lactone patterns of their parents. This suggests that the chemistry of these compounds could be a useful tool in taxonomy.     

Deterrent and insecticidal chromenes and benzofurans from Encelia (asteraceae)

Four analogous chromenes and benzofurans that are among the major natural products of the genus Encelia were bioassayed for deterrency and toxicity against pest insects. The chromene encecalin has both antifeedant and insecticidal properties towards larvae of the noctuid pests Peridroma saucia and Plusia gamma. In addition to reducing larval growth and decreasing survivorship of neonate larvae fed artificial diets containing encecalin, this chromene was directly insecticidal to neonate larvae after 4 hr using a residue contact bioassay. Topical application of encecalin to third instar larvae of Peridroma led to a reduction in dietary utilization, indicative of a metabolic cost of handling the compound. The demethyl analogue of encecalin is considerably less active, and the benzofurans euparin and methyleuparin, all common constituents of Encelia, were essentially inactive or only weakly active in all bioassays against the insects.     

New sesquiterpene lactones from Artemisia herba alba

The structures of herbolides A, B and C, new sesquiterpene lactones isolated from Artermisia herba alba, were determined by chemical and spectroscopic methods.     

Seven sesquiterpene lactones from Ferreyanthus species

The investigation of two Ferreyanthus species afforded seven germacranolides which have not been isolated previously. Two derivatives of linalol were also present. The structures were elucidated by spectroscopic methods. Chemotaxonomic relationships are briefly discussed.     

Guaianolides and chromenes from Calea species

Chemical analysis of Calea berteriana yielded, besides the known flavonoid acacetin and the sesquiterpene lactone calbertolide C, three new guaianolides, desacyl-8-tiglylsubcordatolide A and 8-epi-8-tiglylrupicolins A and B. C. prunifolia provided acacetin, calbertolide C, desacyl-8-tiglylsubcordatolide A, and two new chromenes, prunichromenes A and B. From C. solidaginea acacetin, heliangine, calbertolide C, 8-epi-8-tiglylrupicolin A and desacyl-8-tiglylsubcordatolide A were isolated. The structures of the new compounds were established by chemical and spectral methods.     

Glaucolide-like sesquiterpene lactones from Cotula cinerea

The aerial parts of Cotula cinerea gave, in addition to widespread compounds, a characteristic diacetylenic spiroketal enolether and several sesquiterpene lactones, three of them being glaucolide-like lactones. The structures were elucidated by highfield ¹H NMR spectroscopy.     

Further sesquiterpene lactones from Calea and Viguiera species

The aerial parts of Calea clematidea gave three new germacranolides, those of Viguiera procumbens two orizabin derivatives and those of V. linearis dihydrobudlein A. In addition to these lactones, several known ones were isolated.     

Two sesquiterpene lactones of Calea ternifolia var. Calyculata

Chemical analysis of Calea ternifolia var. calyculata yielded the known sesquiterpene lactone calein A, as well as two new modified heliangolid     

Pseudoguaianolides and other sesquiterpene lactones from Gaillardia species

The aerial parts of two Gaillardia species afforded in addition to known sesquiterpene lactones 23 new pseudoguaianolides, two dugaldiolide derivatives and two seco-neopulchellin derivatives. The structures were elucidated by spectroscopic methods. Biogenetic relationships are discussed briefly.     

Pungent sesquiterpene lactones of the european liverworts Chiloscyphus polyanthus and Diplophyllum albicans

The characteristic pungency of the European liverwort, Chiloscyphus polyanthus, is due to a mixture of four sesquiterpene lactones, two new structures ent-5β-hydroxydiplophyllin and ent-3-oxodiplophyllin, and the previously known diplophyllin and diplophyllolide. A new dihydrodiplophyllin, together with the pungent diplophyllolide and diplophyllin, has been isolated from Diplophyllum albicans. Ent-dihydrodiplophyllolides derived from the above pungent diplophyllolides produce intense numbness of the tongue. All pungent sesquiterpene lactones showed inhibitory activity towards the germination and root elongation of rice husks.     

Evolution of sesquiterpene lactones in angiosperms

The paper attempts to discover an outline of the evolutionary trends of sesquiterpene lactones in angiosperms. The working method involves the quantification of skeletal specialization and oxidation state of the compounds and the assignment of evolutionary advancement indices, based on such data, to taxa. In the angiosperms as a whole, sesquiterpene lactone evolution proceeds by diversification of structural types and by amplification of the oxidation state of the molecules. The opposite trend appears to operate at lower hierarchical level, in the Asteraceae. In this family, which contains most of the known compounds of the class, sesquiterpene lactone evolution follows two parallel pathways in the tribes belonging to two groups of the subfamily Asteroideae.     

Sesquiterpene lactones of diploid and tetraploid Ambrosia camphorata

Diploid and tetraploid specimens of Ambrosia camphorata have distinct sesquiterpene lactone patterns; however, no direct correlation between chemistry and morphological patterns is detectable.     

Sesquiterpene and diterpene lactones from melampodium longipilum

the aerial parts of Melampodium longipilum afforded two new diterpene lactones, 17-hydroxy- and 17-acetoxyacanthoaustralide, and a new sesquiterpene lactone, repandin E, besides the known melampolides enhydrin and fluctuanin.     

Diterpenes and sesquiterpene lactones from Mikania congesta

The chloroform extract of the aerial parts of Mikania congesta, afforded four new geranylnerol derivatives, new analogs of deoxyelephantopin, a new melampolide and several known compounds. Structures were elucidated by spectroscopic methods and chemical transformations.     

Quantitative flavonoid variation in Lupinus sericeus

One hundred and eighty-one plants representing 32 individual populations of Lupinus sericeus were collected from throughout the range of the species. Quantitative analyses of flavonoid derivatives were performed using high performance liquid chromatography. Peak height data were subjected to multivariate analysis. Principal components analysis suggested the existence of a north-south cline based upon differences in orientin concentration. Canonical variates analysis suggested that southerly, central and northerly populations were distinguishable. Simple statistical tests on orientin concentration, the major flavonoid seen in the study, clearly distinguished southerly populations from all others. Seeds were collected from representative populations from the range of L. sericeus and the plants obtained therefrom were grown under uniform conditions. Analysis of orientin concentration in these plants showed no significant differences between populations. We conclude from these studies that all L. sericeus plants appear to have similar capacities to accumulate orientin, and that differences in concentration of this compound seen in naturally occurring plants are a reflection of environmental influences and cannot be used as support for any infrageneric taxonomic distinctions.     

Sesquiterpene lactones of Xanthium strumarium in a texas population and in experimental hybrids

Morphologically diverse plants in a wild population of Xanthium strumarium in eastern Texas produced widely variant combinations of sesquiterpene lactones. Some plants showed a preponderance of xanthinin and related compounds, xanthanol and xanthatin, while others a predominance of stereoisomers, xanthumin, xanthumanol and deacetoxylxanthumin. Some plants produced only one sesquiterpene lactone and other plants yielded various mixtures of xanthinin, xanthumin and related compounds, including xanthinosin and/or tomentosin. Experimental hybridization between plants containing primarily xanthinin and plants containing xanthumin, but originating in diverse parts of the world, yielded F₁ progenies with xanthanol and/or xanthumanol as the predominant sesquiterpenoid component. The F₂ generation showed segregation of the xanthinin, xanthumin and related compounds. The Texas population occurs in an area where the “italicum” (xanthinin-predominants) and “chinense” (xanthumin-predominant) morphological complexes are sympatric. The diverse patterns of sesquiterpene lactones in the Texas population probably resulted from the natural hybridization of morphological complexes that originally were spatially isolated.     

Sesquiterpene lactones of Helianthus gracilentus

A series of four 2α-hydroxy-8β-acyloxygermacrolides and the heliangolide niveusin A were isolated from a dichloromethane extract of Helianthus gracilentus. The germacrolides include a new compound, 2α-hydroxy-8β-isovaleroyloxycostunolide. The terpenoid constituents of H. gracilentus are very similar to those of H. pumilus, which on morphological grounds is considered to be closely related to H. gracilentus.