Terpenoids triterpenoids

Terpenes (and terpenoids) are further classified according to the number of 5-carbon units they contain. Thus, monoterpenes are 10-carbon substances biosynthesized from two isoprene units, sesquiterpenes are 15-carbon molecules from three isoprene units, diterpenes are 20-carbon substances from four isoprene units, and so on. Monoterpenes and sesquiterpenes are found primarily in plants, but the higher terpenoids occur in both plants and animals, and many have important biological roles. The triterpenoid lanosterol, for example, is the precursor from which all steroid hormones are made. 

The terpenoid precursor isopentenyl diphosphate, formerly called isopentenyl pyrophosphate and abbreviated IPP, is biosynthesized by two different pathways depending on the organism and the structure of the final product. In animals and higher plants, sesquiterpenoids and triterpenoids arise primarily from the mevalonate pathway, whereas monoterpenoids, diterpenoids, and tetraterpenoids are biosynthesized by the 1-deoxyxylulose 5-phosphate (DXP) pathway. In bacteria,... 

Further combination of GPP with another IPP gives the C15 unit farnesyl diphosphate (FPP), and so on, up to C25. Terpenoids with more than 25 carbons—that is, triterpenoids (C30) and tetraterpenoids (C40)—ate synthesized by dimerization of Cj5 and C2q units, respectively (Figure 27.8). Triterpenoids and... 

Sengupta P, Mukhopadhyay J. Terpenoids and related compounds—VII triterpenoids of Phyllanthus acidus Skeels. Phytochemistry 1966 5 531-534. 

Triterpenoids (C30 compounds) are the most ubiquitous of the terpenoids and are found in both terrestrial and marine flora and fauna (Mahato et al., 1992). Diterpenoids and triterpenoids rarely occur together in the same tissue. In higher plants, triterpenoid resins are found in numerous genera of broad-leaved trees, predominantly but not exclusively tropical (Mills and White, 1994 105). They show considerable diversity in the carbon skeleton (both tetracyclic and pentacyclic structures are found) which occur in nature either in the free state or as glycosides, although many have either a keto or a hydroxyl group at C-3, with possible further functional groups and/or double bonds in the side-chains. 

In this presentation, bioactivity-directed isolation and stmcture elucidation of the active constituents will be given. Structures of the constituents, which form namely terpenoids (sesqni, di- and triterpenoids) were based on spectroscopic tech-niqnes, particnlarly intensive NMR and Mass spectroscopies. 

Streibl M, Herout V, Terpenoids-especially oxygenated mono-, sesqui-, di-, and triterpenoids, in Eglinton G, Murphy MTJ (eds.). Organic Geochemistry Methods and Results, Springer-Verlag, Berlin, pp. 401—424, 1969. 

The interaction between Drosophila, yeasts and columnar cacti of the Sonoran Desert has been the subject of much recent interest (37) As a coevolved system, perhaps more is known about this interaction than any other. The chemistry of the cacti (70 spp.) has been postulated to play a significant role in the establishment of this system (38 ), but this was based upon reports of a relatively small number of relatively simple alkaloids, and a small number of terpenoid compounds. Only recently, the diversification of plant compounds has been discovered to be much greater (5). In their section on alkaloids in the above work, BajaJ and McLaughlin report the presence of some thirty-five structures. In addition, I have been able to isolate some sixty triterpenoid glycosides (structures were not determined) and more were detected but not Isolated. 

Terpenoids are structurally based on the isoprenoid (C5) unit and include monoterpenoids, sesquiterpenoids, diterpenoids, triterpenoids, steroids and carotenoids. These compounds can be further modified to generate greater structural complexity. Thus the saponins are surface active amphiphiles deriving from the glycosylation of steroid (C27) or triterpenoid (C30) entities. Plant triterpenoids with very specific biochemical effects include those that mimic the effects of mammalian steroid hormones or of insect developmental hormones. 

Biosynthesis of Polyketides Phenolic Compounds derived from Shikimate The Biosynthesis of C5—C20 Terpenoid Compounds Triterpenoids, Steroids, and Carotenoids Non-protein Amino-acids, Cyanogenic Glycosides, and Glucosinolates Biosynthesis of Alkaloids. 

Terpenoids Sesquiterpenoids Diterpenoids Triterpenoids Carotenoids and Polyter-penoids Steroids Physical Methods Steroid Reactions and Partial Synthesis. 

The lipophilic fraction, extractable with nonpolar solvents (ethyl ether, dichloromethane, etc.) consists mainly of fats, waxes, terpenes and terpenoids, and higher aliphatic alcohols (cf. Sections 5.3.1 and 5.3.2). Terpenes, resin acids, and sterols are located in the resin canals present in the bark and also occur in the cork cells and in the pathological exudate (oleore-sin) of wounded bark. Triterpenoids are abundant in bark /3-sitosterol occurs in waxes, as an alcohol component, and the cork cells in the outer bark (periderm) of birch contain large amounts of betulinol (cf. Fig. 5-6). 

Wood resin is considerably changed during the pulping process. The fatty acid esters of sterols and triterpenoid alcohols in hardwoods (waxes) are saponified very slowly. Unsaturated compounds, e.g., fatty acids, resin acids, and other higher terpenoids, are polymerized to high molecular weight compounds, which also give rise to "pitch problems."... 

Various studies have also been reported on sesquiterpenoid lactones in Xanthium strumarium and Vemonia species,452,453 diterpenoids of Isodon species,454 and triterpenoids in Lycopodium species.455 Analyses of the carotenoids of Medicago species and of berries from a range of sources reinforce previously held views that the distribution of carotenoids in these sources has no taxonomic significance.456,457 Although most higher plants that have been investigated do not retain the capacity to biosynthesize the normal pattern of terpenoids when in tissue culture, it has been reported that Ruta graveolens did retain this ability.458... 

Which of the following terpenoids might have been formed by a tail-to-tail coupling (a) monoterpenoid (b) sesquiterpenoid (c) diterpenoid (d) triterpenoid... 

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