Synthetic compounds compared with natural

Chelators of iron, which are now widely applied for the treatment of patients with thalassemia and other pathologies associated with iron overload, are the intravenous chelator desferal (desferrioxamine) and oral chelator deferiprone (LI) (Figure 19.23, see also Chapter 31). Desferrioxamine (DFO) belongs to a class of natural compounds called siderophores produced by microorganisms. The antioxidant activity of DFO has been studied and compared with that of synthetic hydroxypyrid-4-nones (LI) and classic antioxidants (vitamin E). It is known that chronic iron overload in humans is associated with hepatocellular damage. Therefore, Morel et al. [370] studied the antioxidant effects of DFO, another siderophore pyoverdin, and hydroxypyrid-4-ones on lipid peroxidation in primary hepatocyte culture. These authors found that the efficacy of chelators to inhibit iron-stimulated lipid peroxidation in hepatocytes decreased in the range of DFO > hydroxypyrid-4-ones > pyoverdin. It seems that other siderophores are also less effective inhibitors of lipid peroxidation than DFO [371],... 

There are limitations beyond the difficulty of measuring small peaks The 13C/12C ratio differs with the source of the compound—synthetic compared with a natural source. A natural product from different organisms or regions may show differences. Furthermore, isotope peaks may be more intense than the calculated value because of ion-molecule interactions that vary with the sample concentration or with the class of compound involved. For example ... 

The second group comprises fully synthetic compounds which often have a totally different chemical structure as compared to the semi-synthetic analogs, but interact with the same opioid receptors and show the same spectrum of analgesia and side-effects as the natural compounds. The older name opiates is still in use to describe both groups... 

Pyridazine (1,2-diazine) (1) and its benzo analogs cinnoline (1,2-diazanaphthalene) or benzo[c]pyridazine (2) and phthalazine (benzo[rf]pyridazine) (3) have been known since the nineteenth century. Although the basic synthetic principles and reactivity were investigated in the early years, interest in these compounds was not very intense, compared with pyrimidines and their bicyclic analogs, as they were not found in nature. However, during the last three decades intensive research has been stimulated because many derivatives have found application as a result of their biological activity. 

Butyl Rubber. A synthetic rubber produced by copolymerization of isobutene(98%) with a small proportion(ca 2%) of isoprene or butadiene. Polymerization is conducted at-50 to 100° in a liquid hydrocarbon, with A1C13 as catalyst. Its outstanding property compared with other rubbers is impermeability to gases. The uncured rubber is tacky, but it may be compounded like natural rubber and vulcanized. Butyl rubber has good resistance to chemical attack and to aging even at high temps. It has superior vibration insulation characteristics and abrasion resistance, but relatively low tensile strength and poor flame resistance... 

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