The Geography of Phytochemical Races

228 5 Wide Disjunctions
also been identifi ed as a component of a collection of a different chemotype from
northern Germany. Further variations on the sesquiterpene theme were reported
by Melching et al. (1999) from a specimen collected near Vorarlberg, Austria;
two compounds of the aromadendrene type were identifi ed: (−)-aromadendran-
5-ol [432] and (+)-aromadendr-4-en-12-ol [433].
5.2.7 Adelanthus decipiens (Adelanthaceae)
Adelanthus decipiens (Hook.) Mitt. is another liverwort that exists in widely separated
locales, in this instance, northern Europe and the Southern Hemisphere
(Asakawa and Inoue, 1987). It reaches its northern limit in western Great Britain.
Rycroft et al. (1998) studied the chloroform-soluble components of three specimens
collected from different sites in Scotland and herbarium specimens representing
sites in Wales, Ireland, Colombia, and Ecuador. The procedure employed by
these workers involves extraction of the dry plant material with deuterochloroform
(CDCl 3 ) followed directly by analysis by proton NMR. This procedure yields a
“fi ngerprint” of the individual specimens as well as provides important clues to
the structure of the major component(s) (Rycroft, 1996). An added benefi t is the
capacity to work with very small amounts of plant material, often less than 100 mg.
Coupling this extraction procedure with gas chromatography coupled with mass
spectroscopy (GC-MS) analysis provides a powerful method as shown by the acquisition
of interpretable spectra from a sample of A. decipiens weighing 7 mg. The
use of small samples taken from herbarium specimens, an approach discussed by
Phillipson (1982), enables the study of material from sites otherwise diffi cult of
access.
Specimens of Adelanthus yielded a moderately complex array of phenolic
compounds based either upon acetophenone or naphthalene, although not all compounds
were seen in each specimen. Structures of the compounds identifi ed are
shown in Fig. 5.6. The geographic origin of the plant specimens from which individual
compounds came is presented in Table 5.2. Plants from all areas tested
have the capacity to make naphthalene derivatives, with these the only type seen
is the specimen from Wales. Although all other specimens exhibited acetophenone
derivatives, there is a good deal of variation with regard to which compounds are
accumulated and what their relative concentrations are. Even in specimens from
the same general area, the fi rst two listed specimens from Scotland, for example,
differences in relative concentrations of certain were noted. It is always tempting to
excuse differences (inter- as well as intrasite) on the basis of small sample size, but
that possibility is not likely to carry much weight in the present situation in view
of the array of compounds from the 7-mg sample from Wales. In short, the data
likely represent a fair appraisal of the accumulation tendencies of plants from these
areas. It would be interesting to learn how much variation there is among individuals
within populations and what variation there may be between seasons. With the
effi cient methods employed by Rycroft and his coworkers, this information should
not be diffi cult to obtain.