The Geography of Phytochemical Races

2.6 South America 77
Fig. 2.48 Compounds
173–175, sesquiterpenes
from Hymenaea verrucosa.
Compounds 176 and 177,
terpenes from Minthostachys
verticillata
isomers accounted for about 60% of the resin sesquiterpenes in most of the specimens
examined. Detailed statistical analysis revealed that South American populations
often exhibited complex patterns of variation, in line with the recognition of
several varieties in the region. Much lower levels of variation, by contrast, characterized
populations from Mexico and Central America. The extent of sesquiterpene
variation observed in H. courbaril is similar to patterns of variation observed in
other members of the genus.
2.6.8 Minthostachys verticillata (Lamiaceae)
Minthostachys verticillata (Griseb.) Epl. is a labiate native to the central and northwestern
parts of Argentina. Known locally as “peperina,” leaves of this species are
and have been used as fl avoring agent for beverages, notably maté. It is unlikely,
however, that this species has been subjected to the level of selection experienced by
Mediterranean plants that we discussed above, such as thyme and oregano. A recent
study of M. verticillata collected from the fi eld documented the existence of chemically
unique geographical races (Zygadlo et al., 1996). Ten sites were sampled from
four provinces representing much of the range of this species. Most plants had at least
traces of most compounds but some notable differences were observed, for example,
thymol [105] and carvacrol [89] were major constituents in the oil from two sites in
Catamarca Province (Potero and Sebastian) but absent from another in that province
(Balcosna) and from all other sites visited. Another variant, although less dramatic,
was β-pinene [23], which was present to the level of 5.1% and 6.1% in both sites in
Tucumán Province but made a much smaller contribution to the oils from all other
sites. Similarly, menthone [176] and pulegone [177] (see Fig. 2.48) were present in
widely differing amounts from different sites both within and between provinces.
These results and selected others are summarized in Table 2.15.