Terpenoids Isoprenoids

Although far less numerous than the terpenoid/isoprenoid or polyketide NPs, the alkaloids (with an estimated 20,000 different structures) have a special place in NP research because a few are of great value to humans—for example, morphine, theobromine, caffeine, vincristine, quinine, codeine, cocaine, nicotine and strychnine. These often complex chemicals are found in about 20% of vascular plants and a smaller number of fungi, marine invertebrates and a few bacteria. ... 

The terpenoids (isoprenoids) are a class of secondary metabolites that may be formally considered to be constructed from the five-carbon isoprene unit [1]. The terpenes have been classified primarily on the basis of their number of isoprene units (monoterpenes Cio. sesquiterpenes C15, diterpenes 20, sesterterpenes C25. triterpenes C30 and carotenoids C40) and then on their carbon skeleton. The monoterpenes, sesquiterpenes, diterpenes and sesterterpenes contain the isoprene units linked head to tail, while the triterpenes and carotenoids contain two C15 and C20 units, respectively linked in the middle tail to tail. Several thousand terpenes... 

Fig. 117.9 An overview of the cytosolic mevalonate pathway and plastidial mevalonate-independent pathway for the biosynthesis of terpenoids (isoprenoids) in plant cells [99] (DMAPP, dimethylallyl diphosphate DXP, l-deoxy-D-xylulose-5-phosphate DXS, DXP synthase DXR, DXP reductoisomerase MEP, 2-C-methyl-D-erythritol 4-phosphate GASP, gfyc-eraldehyde-3-phosphate HMG-CoA, 3-hydroxy-3-methylglutaryl-CoA HMGR, HMGR-CoA reductase IPP, isopentenyl diphosphate. Mevinolin and fosmidomycin are inhibitors of HMGR and DXR, respectively)...

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