Benzoquinones, prenylated

Quinones represent a very large and heterogeneous class of biomolecules. Three major biosynthetic pathways contribute to the formations of various quinones. The aromatic skeletons of quinones can be synthesized by the polyketide pathway and by the shikimate pathway. The isoprenoid pathways are involved in the biosynthesis of the prenyl chain and in the formation of some benzoquinones and naphthoquinones. ... 

In 1955, R. A. Morton and associates in Liverpool announced the isolation of a quinone which they named ubiquinone for its ubiquitous occurrence.484 485 It was characterized as a derivative of benzoquinone attached to an unsaturated polyprenyl (isoprenoid) side chain (Fig. 15-24). In fact, there is a family of ubiquinones that from bacteria typically contains six prenyl units in its side chain, while most ubiquinones from mammalian mitochondria contain ten. Ubiquinone was also isolated by F. L. Crane and associates using isooctane extraction of mitochondria. These workers proposed that the new quinone, which they called coenzyme Q, might participate in electron transport. As is described in Chapter 18, this function has been fully established. Both the name ubiquinone and the abbreviation Q are in general use. A subscript indicates the number of prenyl units, e.g., Q10. Ubiquinones can be reversibly reduced to the hydro-quinone forms (Fig. 15-24), providing a basis for their function in electron transport within mitochondria and chloroplasts.486 490... 

Benzoquinones such as (227) have been prepared by regiospecific oxidative prenylation of the corresponding methylhydroquinone with Me2C=CHCH2Br in the presence of /3-cyclodextrin. Detailed descriptions are available of methods for the preparation of ubiquinone analogues,and the synthesis of some new ubiquinone analogues, e.g. (228), has been reported. ... 

Of the nine complementation groups, coq2—coq8 are involved in the synthesis of the benzoquinone, while coql participates in the synthesis of the prenyl side chain. The isopentenyl diphosphate (IPP), required for the biosynthesis of the side chain precursor, hexaprenyl diphosphate (HexPP), for the yeast Q 6 unlike that of E. coli, is derived from the mevalonate pathway. " ... 

Marine invertebrates have proved to be a rich source of biologically active prenylated heterocyclic natural products, with several prenylated quinones and chromenols having been discovered from ascidian species (sea squirts). Conicaquinones A and B (Figure 8) were isolated from the marine ascidian Aplidium conicum in 2003 (03EJO898), and are clearly related to the previously mentioned benzoquinone thiazine counterparts, the aplidinones (05EJ(35024). However, unlike the aplidinones, these... 

Ubiquinones are prenylated benzoquinone derivatives carrying a side chain of 5-10 isoprene residues. Ubiquinone 50 (coenzyme Qio) for instance, has a side chain of fifty carbon atoms (=10 isoprene units). 

A family of 2,3-dimethyl-5-polyprenyl-l,4-benzoquinones found in plant tissues. R represents a prenyl side-chain which may be unsubstituted (Plastoquinones), monohydroxylated (Plastoquinone C), monoacylated (Plastoquinone B), or monohydroxylated and monoacylated (Plastoquinone Z).The latter classes appear to be confined to higher plant tissues. 

Com oil generally is considered to be fairly stable to oxidation. The quality of its flavor is very good. Com oil is the only oil containing a significant amount of ubiquinone (200 mgxkg" a benzoquinone with a side chain of 6-10 prenyl units), an excellent antioxidant that helps protect oils against oxidative rancidity (Petillo Hultin, 2008 Shahidi, 1997). 

Cimino, G., De Stefano, S., and Minale, L. (1972c) Polyprenyl derivatives from the sponge Ircinia spirwsula, 2-polyprenyl-benzoquinones, 2-polyprenylbenzoquinols, prenylated furans and a C-31 difuranoterpene. Tetrahedron, 28,1315-1324. 

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