Chemotypes 435

There are a number of practical problems involved with using polysaccharides as vaccines as there are frequently too many different chemotypes for it to be practicable to prepare a vaccine. In some cases a limited number of serotypes are the dominant cause of infection and it may then be possible to produce vaccines. A major problem is the poor immune response elicited by polysaccharide antigens, which may in some cases be improved by chemical modification. This is (fie case for vaccines for Haemophilus influenzae type b (a causative agent of meningitis), where the antigenicity of the polysaccharide can be increased by coupling to proteins. 

Three 3-amino-3,6-dideoxyhexoses, having the d- and L gluco and D-ga-lacto configurations, have been found. The two D-sugars are not very common, but occur in some 0-antigens for example, those from E. coli 0114 (Ref. 60) and E. coli 02 (Ref 61), respectively. The D-galacto isomer has also been found in the cell-wall polysaccharide from Eubacterium saburreum strain L13.3-Amino-3,6-dideoxy-L-glucose has been found in the core part of the Aeromonas hydrophila chemotype 111 LPS. 

New Zealand showing general locations of the three chemotypes of Leptospermum scoparium... 

Myrtaceae), known locally as kanuka. Fifty-one specimens from New Zealand along with six from Australia (and other species of Kunzea) were included in the study. Oils from Australian and New Zealand specimens were quite similar with a-pinene as the most prominent component in both, along with lower but similar levels of p-cymene and 1,8-cineole. Although two chemotypes can be defined within this taxon, they occur within populations and do not show the geographic patterning seen in manuka. 

An interesting dispersal scenario was described by the authors on the basis of the similarity of southern Finnish chemotypes to chemotypes found in the Netherlands, and other parts of Northern Europe. They suggest that tansy seeds, known to be common components of shipping ballast (Jutila, 1996), may have been transported to... 

The next example involves a recent study of essential oil polymorphism in Thymus praecox Opiz subsp. arcticus (E. Durand) Jalas (syn. T. drucei Ronn.) on the British Isles (Schmidt et al., 2004). More than 700 specimens of the plant were collected in Ireland, Scotland, and southern England and subjected to gas chromatographic analysis (coupled with mass spectroscopy). Sixty-nine constituents were identified, the majority of which were mono- and sesquiterpenoids. Analysis of the data revealed a highly polymorphic assemblage with 13 chemotypes in Scotland, 11 in Ireland, and 17 in the south of England. Polymorphism seems to... 

The north-south gradient was also evident in the concentration of the most abundant chemotype, which was shown to consist of linalool [19] and its acetate. Most frequent in Greenland, Iceland, and Norway (90-100%), it was present in only 40% of plants collected in Scotland, and in only ca. 5% of plants from southern sites. This finding paralleled the observations of Stahl-Biskup and Laakso (1990) that a similar north-south trend exists in the oils of Thymus ser-pyllum subspecies serpyllum and tanaensis in Finland. The opposite trend was observed with y-terpinene, which was present in southern populations but absent from those from the northern sites. 

Kirch et al. (1995) examined individual plants collected in Corsica, Elba, Sardinia, Liguria, and Provence for alkaloids and observed four groups, one characterized by sparteine [119] (see Fig. 2.34 for structures 119-124), one characterized by lupanine-based alkaloids [120 and 121], one that had a very low level of alkaloid production, and one that lacked sparteine and lupanine-based compounds, but did accumulate other alkaloids such as anagyrine [122], ammodendrine [123], and compounds based on cytisine [124], their outlier group. The distribution of these four chemotypes is presented in Table 2.10. 

Studies of the essential oils of Thymus species have documented the existence of several chemotypes with greater or lesser geographical distinctions among them. In an examination of the essential oils of T. vulgaris L. native to France, Granger and Passet (1973) described six chemical phenotypes based upon the occurrence of a number... 

The earlier alkaloid literature contains numerous reports of studies aimed at discovering the existence of chemotypes involving these pharmacologically important compounds. An example of this sort of study comes from the work of Karnick and Saxena (1970) who were interested in the effect of elevation on total alkaloid content of Datura metel L. (Solanaceae), an important source of hyoscyamine [26]... 

Fig. 2.67 Map showing range of occurrence of Satureja douglasii chemotypes...

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