The Geography of Phytochemical Races

2.4 The Mediterranean Basin 51
intermediate, and low levels of quercetin, respectively, the authors calculated
values for p, the frequency of the a allele. Their results also appear in the table.
This method of analysis, which has also been used quite successfully in the discussion
of monoterpene differences, which will appear below, provides a means
to convert descriptive secondary metabolite data into a potentially more meaningful
format. In this instance, it clearly demonstrates differences in the genetic
composition of the respective populations of P. uncinata, although no easily
interpreted pattern has emerged.
One point should be raised that was not dealt with in the Lauranson and Lebreton
(1991) paper. It would appear that the authors examined the concentration values
of the individual fl avonols at face value without considering likely or possible
biosynthetic relationships. In particular, isorhamnetin is produced by O-methylation
of quercetin. Total quercetin produced would then be the sum of quercetin per se plus
the amount of isorhamnetin present. This value, refl ecting total 3′,4′- dioxygenated
fl avonols, would be the more accurate measure of allele frequency.
2.4 The Mediterranean Basin
2.4.1 Withania somnifera (Solanaceae)
Several literature reports describe efforts to identify the component(s) of Withania
somnifera (L.) Dun. responsible for the sedative, hypnotic, and antiseptic properties
of the plant. Those studies included material collected in South Africa and in
different parts of India. Although none of the earlier studies resulted in the establishment
of a detailed structure, it did become evident that plants from different
areas exhibited different chemistries. Examination of the nonalkaloidal components
of W. somnifera from different regions of Israel also revealed chemical
heterogeneity, leading to a more detailed study of this species (Abraham et al.,
1968). The study, which involved 24 populations, showed that three well-defi ned
chemotypes exist in Israel (Fig. 2.30). Chemotype 1, the most widespread of the
three, consists of three compounds [111], known as “withaferin-A”, its dihydro
derivative [112], and the hydroxyl derivative [113]. Chemotype 2, confi ned to
northern Israel, consists of the single compound [114]. Chemotype 3, found in
fi ve sites along the southern coastal plain, consists of the most complex array of
compounds (at least seven) of the sort represented by structures [115 and 116]
(see Fig. 2.31 for structures 111–116). Examination of eight individual plants
of chemotype III showed identical profi les. Common garden studies revealed
that the withanolide profi les of plants grown from seed were identical to those
of plants in the wild and cultivated plants of all three types sampled at intervals
throughout their growth showed only quantitative changes in withanolide
content. The authors did not speculate as to how these populations had become
differentiated.