Virginia E. Sosa

10-epideoxycumambrin B and other constituents of Stevia yaconensis var. subeglandulosa

Abstract The aerial parts of Stevia yaconensis var. subeglandulosa afforded in addition to the known guaianolides ludartin and dehydroleucodin a new guaianolide 10-epi-8-deoxycumambrin B whose relative and absolute configurations were established by X-ray crystallography. Chemical transformations of ludartin established its relative and absolute stereochemistry.

Sesquiterpene lactone variability in Parthenium hysterophorus L.

A population of Parthenium hysterophorus collected in Salta Argentina afforded two ambrosanolides, 2beta-hydroxycoronopilin and 1alpha,2beta,4beta-trihydroxypseudoguaian-6beta,12-olide, as well as five known others. Plants of the fructification from those transplanted from the Puna Argentina at 1200 m over the sea level produced hymenin.

Phytogrowth-inhibitory activities of a clerodane from Viguiera tucumanensis

Abstract The phytotoxicity of clerod-14-ene-3α,4β,13ξ-triol, obtained from Viguiera tucumanensis (Hook. et Arn.) Griseb, was examined in Petri dish bioassays. This clerodane inhibited both germination and root growth of Sorghum halapense and Chenopodium album , and also slightly inhibited Ipomoea purpurea. Crop species also showed inhibitory activity: the growth and germination of Avena sativa was strongly inhibited. Germination of Brassica napus was unaffected. The strongest plant growth inhibitory activity of the clerodane was on C. album , and has been expressed as the p I 50.

Sesquiterpene lactones and other constituents of Arnica acaulis

Abstract Chemical investigation of the aerial parts of Arnica acaulis resulted in isolation of 12 known helenanolides, one new melampolide baileyin acetate and the transfused guaianolides florilenalin acetate and 11 α H , 13dihydroflorilenalin acetate as well as other relatively common plant constituents. The implications for the biogenesis of helenanolides and the chemotaxonomic situation in Arnica are discussed.

Longipinanes and a germacranolide carboxylic acid from Stevia potrerensis

Abstract The herb Stevia potrerensis afforded five longipinene derivatives, three of them new, and a new germacranolide carboxylic acid.

Ambrosanolides and secoambrosanolides from Ambrosia tenuifolia

Abstract Populations of Ambrosia tenuifolia from four regions of North Central Argentina differed substantially in sesquiterpene lactone content. Lactones and lactone derivatives isolated were peruvin, ambrosic acid, cumanin, psilostachyin, psilostachyins B and C, dihydropsilostachyin C, altamisin and altamisic acid.

Chemotaxonomy of Parthenium: P. Hysterophorus—P. Glomeratum

Abstract From aerial parts of five plants lots of Parthenium hysterophorus-P. glomeratum collected along 72 km in Salta Province, Argentina, seven known and four new pseudoguaianolides have been found. p -Methoxybenzoic acid was also isolated from plants growing 2500 m above sea level. The taxonomic situation of both species is discussed.

GLAUCOLIDES AND RELATED SESQUITERPENE LACTONES FROM VERNONIA CHAMAEDRYS

Abstract Chemical investigation of the aerial parts of Vernonia chamaedrys resulted in the isolation of 15 glaucolides and related sesquiterpene lactones, six of them new, as well as a number of common plant constituents. The C-8 stereochemistry of the piptocarphins is corrected.

Melampolides from Mikania cordifolia

Abstract Aerial parts of two collections of Mikania cordifolia from northern Argentina afforded eight new melampolides whose structures were established by chemical and spectroscopic means. Two of these appear to be mixtures of ester side chain epimers.

Terpenoid constituents of Viguiera tucumanensis

Abstract Two varieties of Viguiera tucumanensis , collected in two different geographical regions of Argentina, were shown to have a very close chemical constitution. They all gave the new diterpene clerod-14-ene-3α,4β,13ζ-triol. The taxonomic implications are discussed briefly.