The Geography of Phytochemical Races

38 2 Examples Within Continents
naturally in Lithuania. Although differentiation of chemotypes was indicated by the
data, the relevant observation noted by the authors (Mockute and Judzentiene, 2003)
is the existence of different chemical profi les, Portugal, Norway, and a population
from Estonia in one, another population from Estonia comprising a second, and
populations from Canada comprising yet another. Important leads to the literature
can be found in the Lithuanian work.
2.3.6 Pulicaria dysenterica (Asteraceae)
Recent work on fl avonoids of Pulicaria dysenterica (L.) Bernh. fi ts in well at this
point since it too exhibits variation in the expression of O-methylated fl avonols
(Williams et al., 2000). In addition to the use of this plant in folk medicine formalized
in its specifi c epithet, its common name in English, “fl eabane,” gives recognition
to its value as an agent to discourage fl eas and other insects from taking up
residence in human quarters. Interest in the fl avonoid chemistry of fl eabane led
to the discovery, as by the cited workers, of several chemotypes involving plants
collected from different places in England and continental Europe. Whereas
the vacuolar fl avonoid profi le, consisting of just quercetin 3-O- glucuronide,
was observed in all specimens, the leaf exudate fractions showed differences in
major components. Four chemical variants were observed based upon the major
(or in some cases sole) fl avonol derivative(s): (1) quercetagetin 3,7-dimethyl
ether [74]; (2) 6-hydroxykaempferol-3,4′-dimethyl ether [75]; (3) a mixture of
6-hydroxykaempferol-3,7-dimethyl ether [76] and quercetagetin 3,7,3′-trimethyl
ether [77]; and (4) a mixture of 6-hydroxykaempferol-3,7-dimethyl ether, quercetagetin
3,7,3′-trimethyl ether, and quercetagetin 3,7,3′,4′-tetramethyl ether [78]
(see Fig. 2.19 for structures 74–78). It is diffi cult to assess the signifi cance of
these chemical variants owing to limited sampling and the possibility that they
are responding to some environmental factor or factors. Common garden studies
coupled with more extensive collections are necessary to put the existence of
these forms on fi rm ground. Additional variation was noted with reference to the
work of Pares et al. (1981) who reported quite a different fl avonoid profi le from
material collected in Turkey.
2.3.7 Thalictrum minus (Ranunculaceae)
This example demonstrates how widely chemical profi les can differ between two
populations separated by only a matter of kilometers; in this case, populations of
halictrum minus L. in the Vojvodina area of Serbia (Popovic et al., 1992) (Fig. 2.20).
Plants collected at 500 m in the Fruska Gora Mountains (Novi Sad) afforded a
comparatively complex mixture of benzylisoquinoline alkaloids that consisted of