Steroidal alkaloid, biotransformation

Biotransformations are carried out by either whole cells (microbial, plant, or animal) or by isolated enzymes. Both methods have advantages and disadvantages. In general, multistep transformations, such as hydroxylations of steroids, or the synthesis of amino acids, riboflavin, vitamins, and alkaloids that require the presence of several enzymes and cofactors are carried out by whole cells. Simple one- or two-step transformations, on the other hand, are usually carried out by isolated enzymes. Compared to fermentations, enzymatic reactions have a number of advantages including simple instmmentation reduced side reactions, easy control, and product isolation. 

In Table 2 antibiotic and steroid biotransformations are only poorly represented compared to their actual frequency more than 50 examples of antibiotic transformations were already reported in 1975 [9, 38, 39] a hsting of steroid microbial transformations, published in 1981, covers 853 substrates [40], while more than 1000 examples have been hsted for the 1979-1992 period [41-44]. However, most of the examples reported in those areas have been essentially oriented towards the preparation of new active compounds rather than towards a study of detoxification metabohtes derived from drugs. Alkaloids represent another group of biologically active natural substances where microbial metabolism was explored relatively early and exhaustively [40,45-47]. 

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