Camptothecin biosynthetic pathway

Figure 8.8 Camptothecin biosynthetic pathway. TDC tryptophan decarboxylase STR stric-tosidine synthase. The double arrows indicate multiple reactions, and the dashed arrows...

Among the worldwide total of 30000 known natural products, about 80% stems from plant resources. The number of known chemical structures of plant secondary metabolites is four times the number of known microbial secondary metabolites. Plant secondary metabolites are widely used as valuable medicines (such as paclitaxel, vinblastine, camptothecin, ginsenosides, and artemisinin), food additives, flavors, spices (such as rose oil, vanillin), pigments (such as Sin red and anthocyanins), cosmetics (such as aloe polysaccharides), and bio-pesticides (such as pyrethrins). Currently, a quarter of all prescribed pharmaceuticals compounds in industrialized countries are directly or indirectly derived from plants, or via semi-synthesis. Furthermore, 11% of the 252 drugs considered as basic and essential by the WHO are exclusively derived from plants. According to their biosynthetic pathways, secondary metabolites are usually classified into three large molecule families phenolics, terpenes, and steroids. Some known plant-derived pharmaceuticals are shown in Table 6.1. 

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