Terpenoids classification

Termination step (radical), 141 Terpenoid. 202-204, 1070-1078 biosynthesis of, 1071-1078 classification of, 1071 DXP biosynthetic pathway of, 1071... 

G.l.c. papers of interest include the classification of 22 acyclic monoterpenoid alcohols according to retention indexes, resolution of cyclic ketones [e.g. ( )-menthone, ( )-isomenthone] as diethyl (+)-tartrate acetals, and the use of lanthanide shift reagents to resolve non-terpenoid racemic epoxides.The occurrence and prevention of monoterpenoid hydrocarbon isomerization during silica gel chromatography has been examined and the separation of monoterpenoids and sesquiterpenoids by gel permeation chromatography is reported. Monoterpenoid hydrocarbons have been selectively extracted from essential oils using dimethylsilicone. ... 

Significant amounts of larger hydrocarbons are also generated by plants and emitted to the atmosphere. The larger hydrocarbon compounds generally fall under the classification of isoprenoids, or terpenoids, con-... 

Camara, J. S., Alves, M. A., and Marques, J. C. (2007). Classification of Boal, Malvazia. Sercial and Verdelho wines based on terpenoid patterns. Food Chem. 101,475 84. 

Many chemotaxonomic studies have been published that consists of lists of phytochemical data, but a significant number of studies are now appearing that probe such questions as the genetics of terpenoid formation, hybridization and clonal variation, and biochemical evolution. Reviews have appeared on the chemotaxonomy of flowering plants,435 and of terpenoid formation in particular,436 on chemistry in botanical classification,437 on leaf oils of conifers,438 and on biochemical evolution in plants 439 the last named is comprehensive and quite outstanding. 

Table 5.1 The classification of terpenoids is based on the number of C isoprenoid units in their structures...

Jux A, Gleixner G, Boland W. Classification of terpenoids according to the methylerythritol phosphate or the mevalonate pathway with natural C/ C ratios dynamic allocation of resources in induced plants. Angew. Chem. Int. Ed. 2001 40 2091-2093. 

Tanacetum species contain mainly sesquiterpenoids and flavonoids, whereas the other terpenoids and phenolic compounds are rarely found. Sesquiterpenoids which are the main constituents of the genus, supposed to be bioactive principles of the plants. Flavonoids and essential oils are also pointed out as active substances in some species. On the other hand, there is a confusion on the systematic position and classification of several species of Asteraceae, therefore chemotaxonomy of the species will help the systematic studies. 

In Part I the choice of the most suitable system of classification posed a problem. The two different solutions adopted, one based on structural relationships (monoterpenoids and carotenoids) and the other on biogenetic relationships (sesqui-, di- and tri-terpenoids) in part reflects current practice. 

Individual secondary metabolites may be common to a number of species or may be produced by only one organism. Related species often have related patterns of secondary metabolite production and so a species can be classified according to the secondary metabolites they produce. Such a classification is known as chemical taxonomy. Occasionally, two plants are found to have identical physical aspects which botanists use for classification, but differ in the secondary metabolites they produce. For example, two flowers may look identical but one is odourless whilst the other possesses a strong scent due to the production of a fragrant terpenoid chemical. Such different strains are known as chemotypes. 

The generic name terpene was originally applied to the hydrocarbons found in turpentine, the suffix ene indicating the presence of olefinic bonds. Each of these materials contain two isoprene units, hence ten carbon atoms. Related materials containing 20 carbon atoms are named as diterpenes. The relationship to isoprene was discovered later, by which time the terms monoterpene and diterpene were well established. Hence the most basic members of the family, i.e. those containing only one isoprene unit, came to be known as hemiterpenoids. Table 1.1 shows various sub-divisions of the terpenoid family based on this classification. It also shows two specific sub-groups of terpenoid materials, namely, the carotenoids and the steroids. Steroids and carotenoids are sub-groups of the triterpenoids and tetraterpenoids, respectively, as will be explained later. 

The terpenoids are divided into groups and sub-groups according to the pathway by which nature synthesised them and hence, by their skeletal structures since these arise directly from the biosynthesis. As described above, the first basis for classification is the number of isoprene units which make up the terpenoid. The names for these groups are shown in Table 1.1. The next classification depends on whether the skeleta remain as open chains or have been cyclised giving one, two or more rings. Families of terpenoids possessing the same skeleton are named after a principal member of that family, usually either the most common or... 

It is usual to classify alkaloids (basic nitrogenous metabolites) according to the amino acids (or their derivatives) from which they arise. Thus, the most important classes are derived from the amino acids ornithine, lysine, phenylalanine, tyrosine and tryptophan, and the skeletons of these amino acids are retained largely intact in the alkaloids derived from them. However, this type of classification is often criticized because it fails to include those alkaloids that are derived from a mixed biogenetic pathway (e.g. polyketide or terpenoid) with incorporation of a nitrogen atom, ultimately from ammonia. The alkaloids that are the subject of this review are excellent examples of such compounds and they are often known as pseudoalkaloids. 

Classi ation A rough classification into the following groups of compounds can be made (approximate economic value in %) terpenoids (40%), brenzcate-chol derivatives (17%), phenol derivatives (13%),... 

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