ABSTRACT
Endophytic fungi, like fungi adapted to other ecological niches, are capable of producing a variety of relatively low molecular weight (less than 1500) metabolites that have no apparent role in their primary metabolism or growth in vitro and that have come to be known as secondary metabolites. Although these compounds display an extraordinary degree of structural diversity, they can be categorized according to their biosynthetic origins (Turner and Aldridge, 1983; Campbell, 1984). By far the largest groups are those made from acetate equivalents (the polyketides), those formed from mevalonate-derived C5 units (the isoprenoids, also called terpenoids), and amino acid-derived compounds. Examples are shown in Table 1. The boundaries between these classes are not entirely distinct, however. Some compounds represent fusions of polyketides and peptides or amino acids. Others are composed of both amino acids and isoprenyl units. Less populated groups of fungal compounds derive more directly from glucose, shikimic acid, fatty acids, or tricarboxylic acid cycle intermediates.
