Endophytic Fungi Are Multifunctional Biosynthesizers 57Figure 2. Chemical structures of endophytic metabolites: Cryptocandin, (R)-(-)-
mellein, Subglutinols A, and Cytochalasin, displaying antibiotic, antiviral,
immunosuppressive, and antitumor activities respectively.
The alkaloids are commonly found in endophytic fungi. Fungal genera
such as Xylaria, Phoma, Hypoxylon and Chalara are representative producers
of a relatively large group of substances known as the cytochalasins of which
over 20 are now known (Figure 2) (Wagenaar et al., 2000). Many of these
compounds possess antitumor and antibiotic activities but, because of their
cellular toxicity they have not been developed into pharmaceuticals. Three
novel cytochalasins have recently been reported from Rhinocladiella sp. as an
endophyte on T. wilfordii (Wagenaar et al., 2000). These compounds have
antitumor activity and have been identified as 22-oxa-(12)-cytochalasins.
Thus, it is not uncommon to find the cytochalasins in endophytic fungi and
workers in this field need to be alert to the fact that redundancy in discovery
does occur. Chemical redundancy usually occurs with certain groups of
organisms in which previous studies have already established the chemical
identity of major biologically active compounds. For instance, as with the
cytochalasins they are commonly associated with the Xylariaceaous fungi.
Moreover, endophytes were reported for production of antioxidants and
butyryl cholinesterase inhibitors, one of neuro hydrolase that is involved in