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The absolute configuration of naturally occurring lippifoliane derivatives isolated from the widely used plant Lippia integrifolia was assigned by analysis of the circular dichroism data in combination with density functional theory minimum energy molecular models of (1S,4R,6S,9S,10R)-lippifolian-1-ol-5-one (1), (4R,9S,10R)-lippifoli-1(6)-en-5-one (2), and (4S,9S,10R)-lippifoli-1(6)-en-4-ol-5-one (3) and application of the octant rule for saturated ketone 1 and the helicity rules for alpha,beta-unsaturated ketones 2 and 3. The results were reinforced by the anomalous dispersion effect observed in the X-ray diffraction analysis of (4S,9S,10R)-4,10,11-tribromo-10,11-seco-lippifoli-1(6)-en-5-one (4) prepared from 2. The biogenetic relationships between lippifolianes 1-3 and africanane derivatives 7-9 and 13 isolated from the same species, together with chiroptical data for africananes isolated from the Hepaticae family, complete a stereochemical scenario in relation to the absolute configuration of africananes from L. integrifolia.

Three new sesquiterpenes (1-3) possessing the 2,6,6,9-tetramethyltricyclo[5 .4.0.0Z'*]undecane (lippifoliane) skeleton were isolated as minor constituents of Lippia integrifolia. Their structures and stereochemistry were elucidated from nmr data including double resonance experiments, COSY, and nOe, and by comparison of their "C-nmr spectra with those of lippifoli-1 (6)-en-5 -one.Following the studies on the chemical constituents of the aromatic shrub Lippiu integrifoo(iu (Griseb.) Hieron (Verbenaceae) (1-5), we report herein the isolation, structure elucidation, and full spectral analyses of three new substances 1-3 found as minor components in the essential oil of this plant. These tricyclic sesquiterpenes are structurally related to lippifoli-1(6)-en-5-one 141, previously isolated as one of the major constituents (2,3). RESULTS AND DISCUSSIONCompounds 1 and 2 showed [MI' at mlz 236 in agreement with the molecular formula CI5H2*O2. The 'H-nmr spectra of 1 (Table 1) showed H-6 as a doublet (J=ca.

The aerial parts of lemon verbena (Aloysia citriodora PALÁU) are worldwide used due to their medicinal and aromatic properties. The essential-oil and acteoside contents have been proposed as the main quality markers for their pharmacological and organoleptic features. The northwestern region of Argentina has been repeatedly proposed as the place of origin for this species. For this reason, the essential-oil yields and chemical compositions of leaves of 25 populations of lemon verbena from both wild collections and experimental crops from this region were studied. Plants from six different collections were subsequently grown on the same experimental parcel located at Cerrillos, Salta province, during more than seven years. In addition, the acteoside contents determined in all the samples collected in 2010 showed significant variations (from 0.5 to 4.0%). Large differences were observed in the essential-oil composition and yields, which ranged from 0.4 to 2.1% (v/w). Nevertheless, most of the samples complied with the European Pharmacopoeia specifications. A remarkable chemical diversity with at least four clearly defined chemotypes was detected in this region. Therefore, it would be urgent to encourage actions to protect these genotypes of lemon verbena in the northwestern Argentina.