Fungi metabolites derived from aromatic

It is remarkable in view of the ability of fungi to produce pigments by condensation of cinnamic, /7-coumaric and caffeic acid derivatives with one, two, five, and six acetate units that they appear essentially devoid of metabolites involving side chain extension of the same aromatic starter units by three and by four acetate units. This situation is in marked contrast to that prevailing in higher plants where secondary metabolites derived from triketide extension of cinnamoyl derivatives are abundant and widespread. 

Aromatic compounds derived from six, seven and eight or more acetate units are also found as metabolites of these fungi. These metabolites include a series of anthraquinone pigments, which are discussed later in Chapter 7. 

Compounds derived from phenylalanine and/or tyrosine are among the most common of all secondary metabolites in plants, bacteria, and fungi. These include phenylpropanoid compounds as well as many C -Ci compounds (Fig. 8.1) (Gross, 1981). Relatively simple Ce-Cs compounds, such as cinnamic (1) and p-coumaric acids (2), are modified to produce more complex derivatives (Fig. 8.2) (Conn, 1981, 1986). The term phenylpropanoid is sometimes used to refer to any compound bearing a 3-carbon chain attached to 6-carbon aromatic ring (C6-C3 compounds). Most phenylpropanoids are formed from cinnamic or p-coumaric acids. 

A wide range of aromatic products in the plant kingdom originate from intermediates of the shikimic acid pathway. These include amino acids and ubiquinone among important primary metabolites and also many other compounds (in contrast fo fungi which possess many acetate-derived products), such as lignins, alkaloids, and phenolic acids. Flavonoids (and stilbenes) also arise in part by this route but additionally utilize acetate in the course of their biosynthesis, which will therefore be described in this chapter. 

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