The Geography of Phytochemical Races

7.7 Larrea (Zygophyllaceae) 293
Extraction of the surface of fresh leaves of creosote bush gave a rich array of
fl avonoid aglycones based on the fl avonols such as kaempferol, quercetin, herbacetin,
and gossypetin, and on the fl avones such as apigenin and luteolin. An unusual
dihydrofl avonol was also obtained. Representative members of this array are illustrated
in Fig. 7.4: luteolin 7,3′-dimethyl ether [602], kaempferol 3,7-dimethyl ether
[603], quercetin 7,3′,4′-trimethyl ether [604], herbacetin 3,7-dimethyl ether [605],
gossypetin 3,7,3′-trimethyl ether [606], and dihydromyricetin 3′,5′-dimethyl ether
[607]. The array of leaf-surface fl avonoids of L. tridentata was the most complex of
any of the fi ve species and, signifi cantly, there were no differences among populations
that exhibit different ploidy levels. In contrast, L. divaricata exhibited two fl avonoid
profi les, the more complex of which was observed in plants from Argentina;
plants from Peru exhibited a decidedly simpler profi le. The distribution of nonpolar
compounds identifi ed from these taxa is presented in Table 7.1.
The similarity between the profi les of the North American and Argentinean species
suggests the possibility of a closer relationship between them than between any
other pair of taxa in the genus, including between the Argentinean and Peruvian
Fig. 7.4 Compounds 602–607, fl avonoids from Larrea tridentata