The Geography of Phytochemical Races

2.5 Asia 67
ether) [148], a C-glucosylluteolin derivative, and quercetin 7-O-glucoside [149]
from the Tibetan species B. heterostemon Maxim. A recent study of B. ophanidis
Boiss by Greenham et al. (2001). revealed a very different picture again, particularly
with regard to fl avone aglycones obtained from the leaf surface. Six of the identifi ed
compounds are based on the tetrasubstituted A-ring: 5,7,4′-trihydroxy-6,8-dimethoxyfl
avone [150]; 5,7-dihydroxy-6,8,4′-trimethoxyfl avone [151] (nevadensin);
5,7,3′-trihydroxy-6,8,4′-trimethoxyfl avone [152] (acerosin); 5,7,4′-dihydroxy-
6,8,3′-trimethoxyfl avone [153] (sudachitin); 5,7-dihydroxy-6,8,3′,4′-dimethoxyfl
avone [154] (hymenoxin); and 5-hydroxy-6,7,8,4′-tetramethoxyfl avone [155]
(gardenin-B). Other compounds identifi ed in the aglycone fraction included apigenin
[156], apigenin 4′-methyl ether (acacetin) [157], luteolin, and the coumarin
umbelliferone [159]. Vacuolar fl avonoids identifi ed were the 7-O-rutinosides of
apigenin and luteolin, and the 7-O-glucosides of apigenin, luteolin, and tricetin
[158]. Greenham et al. (2001) did not speculate on the evolutionary signifi cance
of these fl avonoid differences; detailed sequence studies would likely be needed
before relationships among these species could be discussed.
Returning to the chemotaxonomic aspect of the study, however, it is interesting to
note that recent work by Bakker et al. (1998) on rbcL and atpB sequences of Biebersteinia
place the genus close to Rutaceae. This position is fully supported by the fl avonoids
reported by Greenham et al. (2001), which are very similar to O-methylated
fl avones known from well-studied members of Rutaceae, such as Citrus.
2.5.6 Rhodiola crenulata (Crassulaceae)
Rhodiola crenulata (Hook. F. et Thomas) S. H. Fu occurs in southwestern China
(Yunnan and Sichuan provinces) and in the Tibetan Autonomous Region. Y. Li et al.
(2004) examined rhizomes of plants from these areas for their essential oils. Material
from the two areas (Yunnan and Sichuan taken as one source area) shared a suite
of ten compounds but differed in the relative amounts of certain individual components.
The most striking differences were recorded for n-octanol (eight- carbon
straight chain alcohol), whose content ranged from 13.4% to 21.0% of total oils for
the three Tibetan populations, and from 29.6% to 33.6% for the four populations
sampled in China. Levels of geraniol [18] ranged between 45.5% and 55.1% for
Tibetan material, and between 14.8% and 26.9% for plants from the Chinese sites.
No discussion of the signifi cance of these results was forthcoming.
2.5.7 Hippophae rhamnoides (Elaeagnaceae)
Hippophae rhamnoides L., known as buckthorn or sallowthorn, occurs from Europe
to northern China (Mabberley, 1997, p. 342). Of the nine subspecies recognized
within this species, two occur only in China, subsp. yunnanensis Rousi and subsp.
sinensis Rousi., subsp. yunnanensis occurs more to the south and west in China with