The Geography of Phytochemical Races

122 2 Examples Within Continents
undeca-2E,4Z-diene-8,10-diynoic acid isobutylamide. Other members of this group
differ in length of chain, degree of unsaturation, and constitution of the amine
function. Caffeic-acid derivatives include the widely distributed chlorogenic acid
(3-caffeoylquinic acid), cynarin (dicaffeoyl quinic acid), caftaric acid [247], and
cichoric acid [248], which are mono- and diesters of tartaric acid and caffeic acid,
respectively, and echinacoside [249].
In addition to chemotype patterning revealed by statistical analysis of the
data, latitudinal relationships emerged as well. Concentrations of cichoric acid
and echinacoside and one of the amides, undeca-2Z,4Z-diene-8,10-diynoic acid
2-methylbutyl amide [246], with a larger amine-bearing group increased with latitude.
The inverse relationship was observed for caftaric acid and hexadeca-2E,9Z-diene-
12,14-diynoic acid isobutylamide. The latitudinal differences may be of importance
in helping to identify populations for selection of seed for propagation.
2.7.26 Lippia dulcis (Verbenaceae)
The last example in this section features Lippia dulcis Trev., whose range extends
from southern Mexico to Panama and Colombia and on the Caribbean islands of
Puerto Rico, Cuba, and Hispaniola, among others. This example underlines a fundamental
question that must always be borne in mind: is the taxonomy of the subject
species correct? The plant has long been used in traditional medicine for a variety
of illnesses and is characterized by having intensely sweet-tasting leaves and fl owers,
and a highly aromatic scent. Earlier work by Compadre et al. (1985) described
identifi cation of the bisabolene sesquiterpenoid hernandulin as the sweet principle
of plants collected in Mexico (known locally as “hierba dulce”). Subsequent studies
from the same laboratory (Compadre et al., 1985, 1987) resulted in contradictory
fi ndings, in that some specimens had very little hernandulin, while others, in fact,
had substantial quantities of camphor (up to 53%) who’s bitter taste is not at all in
accord with the various names by which the plant is known, as well as accounts in
older literature that the plant is “sweeter than honey” (Souto-Bachiller et al., 1997).
These last named workers subjected plant material from Puerto Rico to detailed
chemical analysis with particular emphasis on identifying the camphoraceous component.
(+)-Hernandulcin [250] and its epimer (−)-epi-hernandulcin [251] (see
Fig. 2.77) were found to be the major components of the herb. The level of camphor,
if present, was less than 0.01%. In addition to the hernandulcin epimers, numerous
other volatile components of the Puerto Rican material were detected, almost none
of which were detected in extracts of the Mexican material analyzed under identical
conditions. Moreover, those compounds that are held in common are present in
often very different proportions. Differences in summed volatiles are also signifi -
cantly different: 8.14% total monoterpenoids in Puerto Rican material opposed to
86.29% in Mexican and 79.52% versus 6.00% total sesquiterpenoids, respectively.
Differences in total volatile fractions were of the same magnitude.