The Geography of Phytochemical Races

62 2 Examples Within Continents
Table 2.12 Alkaloid variation with elevation in Datura metel (from Karnick and Saxena, 1970)
Source (Elevation) Tissue Analyzed
Root Stem Leaf Floral Fruit Seed
Bombay (sealevel) 0.27a 0.19 0.25 0.69 0.060 0.09
Poona (563 m) 0.52 0.29 0.32 0.86 0.079 0.10
Pachmari (716 m) 0.71 0.43 0.54 0.95 0.089 0.14
Darjeeling (2166 m) 0.89 0.46 0.58 0.99 0.097 0.19
a Total alkaloid expressed as percent hyoscyamine.
and related compounds. Specimens were collected from the fi eld at four different
elevations ranging from sea level (Bombay) to 2166 m (Darjeeling). Plants were
separated into their constituent organs and analyzed for total alkaloid content. The
results are displayed in Table 2.12. Although the report contained no statistical information,
the trend of increasing alkaloid content with increasing elevation is clear.
It is interesting to note that the concentration of compounds increases rather than
decreases with elevation, opposite to the trend seen with the cyanogenic compounds
from legumes (see above). It would be of interest to learn if herbivore pressure is
higher at the upper elevation sites, or whether there is some other factor infl uencing
alkaloid synthesis in this species.
In contrast to the increasing alkaloid concentration with elevation in the above
case, Chandra and Purohit (1980) demonstrated the reverse trend in a study of
Berberis lycium Royle (Berberidaceae) from different elevations in Garhwal, India.
Roots, stems, and leaves were collected at sites ranging from 750 m to 3700 m.
A clear-cut trend was noted in all three tissue types with regard to berberine [85]
content with lower levels present at the higher sites. For example, roots of B. lycium
collected at 750 m, 1400 m, 1800 m, and 2500 m gave values of 18.60%, 17.18%,
13.08%, and 11.05% dry weight berberine, respectively. Study of Berberis asiatica
Griff. revealed a decrease in root alkaloid content, from 19.25% to 16.40%, in material
collected at 1400 m and 1800 m, respectively, but an increase in the contents
in both stems and leaves. Collections of B. jaeschkeana Schneider at 3200 m had
nearly three times the alkaloid content in roots as did material from 3700 m. Stems
of this species showed a slight reduction at the higher elevation, but alkaloid content
of leaves was higher at the higher elevation. The overall conclusion reached by these
workers was that toxic alkaloid production is reduced at the higher elevations, but
no reason for this phenomenon was offered.
A recent study of secondary metabolites in Swertia franchetiana H. Smith (Gentianaceae)
involved collections of plant material over a distance of approximately
1100 km from the area of Xining, China (36.35 N, 101.55 E) at 2200 m southwestward
to the area near Lhasa, Tibet (29.41 N, 91.10 E) at an elevation of 3960 m (H. Yang
et al., 2004). They reported a lack of “altitudinal trends in phytochemical constituents”
of the taxon having identifi ed the bitter principle swertiamarin, the triterpene oleanolic
acid, the C-glucosyl xanthone mangiferin, and several other xanthone derivatives
(see Fig. 2.38 for structures). The only compound for which altitudinal variation was
detected in this work was 1,8- dihydroxy-3,7-dimethoxyxanthone (positional isomer
of the compound shown in the Figure), which showed a negative correlation with