The Geography of Phytochemical Races

200 4 Intercontinental Disjunctions
Baillon. and E. milliganii Hook. f. occur in Tasmania, and E. moorei F. Muell.,
E. jinksii P. I. Forst., and E. wilkiei B. Hyland occur in Australia. The fi rst two
named Australian species are temperate rainforest species; E. wilkiei is an outlier
known from higher elevations in tropical northeastern Queensland.
The genus has attracted a good deal more chemical attention than might have been
expected for a group its size, including a study of the principal aroma constituent of
leatherwood (E. lucida) honey, which was shown to be 3,7-dimethyl-1,5,7- octatrien-
3-ol [347] (Rowland et al., 1995) (see Fig. 4.12 for structures 347–356). Our concern
with the genus, however, lies with the patterns of distribution of fl avonoids,
including several structurally uncommon ones. The earliest interest in fl avonoids of
Eucryphia appears to have been that of E. C. Bate-Smith (1962), who observed an
unusual yellow-fl uorescent spot in an extract of E. glutinosa examined as part of his
chemotaxonomic survey of the dicots. Subsequent work established the structure of
the compound responsible as quercetin 5-methyl ether (azaleatin) [348] (Bate-Smith
et al., 1966). In the following year, these workers (Bate-Smith et al., 1967) described
a survey of the two Chilean species and three Australian species. (Note: the earlier
workers considered the genus to consist of fi ve species.) Reference to Table 4.5
illustrates the striking differences among the species. The capacity to synthesize
both azaleatin and caryotin (quercetin 3,5-dimethyl ether) [349], the rare 5-methyl
ethers of quercetin, as well as very similar arrays of quercetin glycosides, plus the
two unidentifi ed fl avonoids, by both Chilean species speaks clearly for their close
Fig. 4.12 Compounds 347–356, a terpene alcohol and fl avonoids from Eucryphia