Triterpenes tetra

Cyclic Monohydroxy Compounds. Triterpenic tetra- and pentacychc monohydroxy compounds are characteristic of ohve oUs (34—49). The following compounds have been shown to be present, accompanied by small amounts of lanosterol and obtusifoliol ... 

Classical examples of anti-inflammatory Asteraceae are Arnica montana and Calendula officinalis, both used in European medicine to treat bruises and contusions. There is an expanding body of evidences to suggest that Asteraceae could be a useful source of anti-inflammatories, such as sesquiterpene lactones and/or triterpene alcohols, the latter being known to inhibit 12-O-tetra-decanoylphorbol-13-acetate (TPA)-induced inflammation in mice as efficiently as commercial indomethacine by possible inhibition of phospholipase A2 (10). 

Mahato et al., 1992 Haralampidis et al, 2002 Vincken et al, 2007). In this chapter, emphasis will be laid on the formation of sterols and steroids in plants the pathways leading to the tetra- and pentacyclic triterpenes will not be considered further. 

Oligomerization of isoprenoids under elimination of pyrophosphate affords the precursors for the biosynthesis of monoterpenes, sesquiterpenes, diterpenes, triterpenes, and tetra-terpenes (93). Long-chain oligomer pyrophosphates also supply the side chains of vitamin E (99, a-tocopherol. Fig. 11), heme a (18), chlorophyll (17, Fig. 2), and the quinone type cofactors, including vitamin K (menaquinone, 98) and coenzyme QIO (ubiquinone, 97). The quinone moieties are derived from hydroxybenzoate that is synthesized from tyrosine in animals or from chorismate in microorganisms (53, 54). 

Most of sea cucumber triterpene glycosides are tetra- or pentaglycosides. The majority of tetrasaccharides show a linear chain with the most common 3-0-Me-Glc-(l—>3)-Glc-(1 4)-Qui-(l—>2)-Xyl structure. The few disaccharides that have been isolated show a Qui-(1 2)-4-0S03Na-Xyl chain attached to C-3 of the triterpenoid aglycone. Some hexasaccharides have been isolated from sea cucumbers of the order Aspidochirota Stichopus japonica, Stichopus chloronotus, Parastichopus californius and Bohadschia bivittata [55]. They are non-sulfated glycosides with a linear 3-0-Me-Glc-(1 3)-Glc-(l- 4)-Xyl chain and a branching of a linear trisaccharide at C-2 of the xylose unit. 

VHMirnols. Tetra- and pentacyclic triterpenes from leaves of the Japanese tree Viburnum dilatation (dam-marane type). More than 15 V. have been described. 

The structures of terpenes or terpenoids varies widely and are classified according to various aspects, e.g. number of isoprene units (Cio monoterpenes, C15 sesquiterpenes, C20 diterpenes, C25 sesterterpenes, C30 triterpenes, C40 tetraterpenes) or division in acyclic, mono-, hi-, tri-, tetra-, pentacyclic terpenes. Often terpenes are named by their trivial names, e.g. d-limonene. 

Ikan, R. (1965). Thin-layer chromatography of tetra-cyclic triterpenes on silica impregnated with silver nitrate. J. Chromatogr. 17 591-593. 

Triterpenes are synthesized via the MVA pathway from two molecules of FPP that are joined by tail-to-tail condensation to squalene. Cyclization of its metabolite 2,3-oxidosqualene followed by rearrangements and methyl shifts yields various structures, mostly tetra- or penta-cyclic. 2,3-Oxidosqualene is also the precursor of plant steroids. In this case, it is cyclized to the triterpene cycloartenol, which is then converted to the compound cholesterol with the loss of three methyl groups. The oxygen of 2,3-oxidosqualene is usually retained as hydroxy group at C-3 in both triterpenes and steroids. 

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