Asteraceae groups

Most of the new source reports concern species from the Asteraceae, with many of the flavonols being isolated from aerial parts, where they are accumulated externally. They range from simple to more complex structures. There appears to be a tendency towards 6-methox-ylation rather than towards 8-methoxylation, in addition to possible OMe-substitution of other positions of the flavonol molecule. Flavonols with 6,8-di-O-methylation and additional OMe-groups are also found in several genera such as Senecio, Psiadia, or Inula, to cite but a few examples. 

Predominantly, this substitution occurs in the 3, 4 -position of ring B, rarely between neighboring OH-groups in ring A. Such compounds were reported from Fabaceae, Rutaceae, and some Asteraceae, from all parts of the plants. Only in rare cases, their accumulation as exudate constituents was documented (Ozothamnus, Asteraceae). ... 

These compounds are almost exclusively accumulated in aerial parts and leaves from genera of the Rutaceae such as Bosistoa, Boronia, and Melicope, and rarely in Euodia and Zanthox-ylum. There is a strong tendency towards prenylation at the 7-OH or 4 -OH group. From aerial parts of Boronia coerulescens, a derivative with 3,4 -(9-prenylation was also described (compound 130, Table 12.4). Similarly, only one C-6-(9-derivative was reported from the aerial parts of Melicope. Two 7-epoxy derivatives have already been listed in the previous survey. Combination with methylenedioxy substitution is less frequent, concerning a few sources of Rutaceae and Asteraceae only. Probably, these constituents are partly accumulated externally. 

The other major group of irregular monoterpenes is formed by non-head-to-tail fusion of isoprene units. Important members include artemisia ketone 64, santolinatriene 65, chrysanthemol 66, yomogi alcohol 67 and lavandulol 68 (Structure 4.15). Lavandulane-type compounds occur in the families Lamiaceae (Labiatae) and Apiaceae (Umbelliferae), while chrysanthemane, artemisane and santolinane types occur in the family Asteraceae (Compositae) [47,48]. 

The lignans are a large group of plant phenolics, biosynthesized from the union of two phenylpropane molecules e.g., both matairesinol (Centaurea species, family Asteraceae) and podophyllotoxin Podophyllum peltatum, family Berberidaceae) are formed from the phenylpropane coniferyl alcohol. Lignans are essentially cinnamoyl alcohol dimers, though further cyclization and other structural modifications result in various structural types, e.g. dibenzylbutyrolactone and epoxy lignan. 

Many plant families have different biosynthetic groups of secondary metabolite defenses, and their possible interaction in plant defense has received little attention. The Asteraceae (daisy family) presents several characteristic groups of widely... 

The classification of plants is primarily based on the similarities and differences that are displayed by their morphological and anatomical characteristics. In some instances this does not suffice since the morphological differences may not be genetically defined but have been caused by local bio-climatic factors. Nevertheless is apparent that secondary metabolites can contribute to the taxonomy of plants and their systematic evolution. There are many examples of cases where the morphological features are not clear and secondary metabolites serve to clarify the morphological classification (e.g. classification of the tribes of the family Asteraceae). It has also been proved to be significant to use all the secondary metabolites for the above purpose and not only one of their chemical groups [4]. 

Many unsaturated compounds found in nature contain one or more acetylenic bonds, and these are predominantly produced by further desaturation of olefinic systems in fatty acid-derived molecules. They are surprisingly widespread in nature, and are found in many organisms, but are especially common in plants of the Compositae/Asteraceae, the Umbelliferae/Apiaceae, and fungi of the group... 

PAs are found widely in the families Asteraceae, Boraginaceae, Fabaceae, and Apocynaceae. About 360 diverse structures have been characterized,23 and these widespread alkaloids are produced by at least 3% of all flowering plants. It is remarkable that one group of animals-the insects-have broken through the formidable alkaloidal defenses represented by the highly toxic pyrrolizidine alkaloids. This evolutionary adaptation has provided a large resource for these insects that is not available to PA-intolerant species, which constitute most of the herbivores. 

The family for Jerusalem artichoke is therefore frequently written as Asteraceae (Compositae). The modem names were introduced as a way of standardizing taxonomic terms (e.g., all family names now end in aceae for ease of recognition), and to realign certain groupings so that each family has a nomenclatural-type specimen. The family Asteraceae contains 476 genera in total. The genus Helianthus has sometimes been placed in the subtribe Helianthinae of the family Asteraceae (e.g., Robinson, 1981). 

The best-studied group of acquired alkaloids are the pyrrolizidines, which are produced by plants, especially in the families Asteraceae and Boraginaceae (502). Some arctiid larvae of Tyria Jacobaea, Cycnia men-dica, Amphicallia bellafrix, Arginia cribaria, and Arctia caja were shown... 

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