TERPENOID COMPOSITION OF LIPPIA-DULCIS

The composition of Lippia dulcis, an intensely sweet herb endemic to t ropical America, was investigated using plants collected in Puerto Ric o. Contrary to previous reports, it is characterized by the presence o f a high percentage of sesquiterpenoids (79%). Isolation experiments a nd gas chromatographic charac terization using direct injection, show that the intensely sweet sesquiterpenoid (+)-hernandulcin (36%) and it s epimer (-)-epi-hernandulcin (22%) are the main constituents of these herbs. The oil contains, if any, undetectable amounts of camphor (muc h less than 0.01%). These findings are in sharp contrast with the comp osition reported earlier for 'Hierba dulce', a pungent Mexican plant i dentified as L. dulcis. Only trace amounts of hernandulcin (40 ppm wt/ wt, dry weight) were reported in the plants from Mexico. The volatile oil isolated from these plants by steam distillation consisted mainly of monoterpenoids (86%). A bitter monoterpenoid, camphor, made up as m uch as 53% of the essential oil of the Mexican plants. If the identity of the Mexican plants is confirmed, these results may reveal the exis tence of two chemotypes of this herb, i.e. an hernandulcin type and a camphor type. Copyright (C) 1997 Elsevier Science Ltd.