The Geography of Phytochemical Races

2.5 Asia 63
Fig. 2.38 Compounds from Swertia franchetiana
altitude. There was a statistically signifi cant relationship between 1,8- dihydroxy-3,7dimethoxyxanthone
and mangiferin and latitude and longitude, however.
The authors suggest that altitudinal variation in “phytochemical constituents
remains unknown.” That this is factually incorrect is revealed by the well-known
work on the effect of elevation on cyanogenic glycosides, as shown in the case of the
clovers above, as well as in the case of alkaloid variation in Berberis just described.
2.5.2 Cymbopogon distans (Poaceae)
Cymbopogon is a genus of aromatic grasses native to tropical and warm regions of
the Old World. Lemongrass, a common ingredient in southeastern Asian cooking,
is C. citratus (DC.) Stapf. The species of interest to us here, C. distans (Stend.)
Wats., occurs in the northwestern region of Uttar Pradesh, India, northeast of Delhi.
Mathela et al. (1988) described the existence of four chemotypes of this taxon based
upon different combinations of mono- and sesquiterpene derivatives. Chemotype 1,
the α-oxobisabolene [131] type (see Fig. 2.39 for structures 131–138), was characterized
by high percentages of the title compound, often reaching levels as high as
68%. Geranial [132], geraniol [133], geranyl acetate [134], neral [135], and piperitone
[136], all of which play major roles in the other chemotypes, were not observed.
This population was collected near Hanumangarh (Naintal, 1900 m). Chemotype
2, referred to as the “lemon-grass oil chemotype,” was obtained from Munsiyari
(Pithoragarh, 2200 m). This form had signifi cant amounts of geraniol, geranyl acetate,
and the two aldehydes geranial and neral. Chemotype 3, the piperitone type,
was collected on Naina Peak at 2600 m (Nainital). Its volatile oils consisted of up