*3.3.2. Indole diterpenes*

in survival, maintenance, and regeneration of specific neuronal populations in the adult brain [95]. Therefore, the metabolites extracted from *Hericium* are important source of metabolites and source as remedy in the fight against neurodegenerative diseases such as Parkinson's, Alzheimer's, and Huntington's diseases, which are accompanied by decreased neurotrophic factor expression [102]. Two new potential metabolites have been isolated from *H. erinaceus* (strain STMA 06157B) and *H. flagellum* (strain CBS 103681) [96] (**Figure 14**).

**Figure 14.** Structural elucidation of metabolites isolated from *H. erinaceus* and *H. flagellum* [96].

**Figure 13.** Structures of metabolites isolated from *C. africanus* [90].

128 Terpenes and Terpenoids

Indole diterpenes are the broad class of secondary metabolites with enormous structural and functional diversity. They mostly occur in filamentous fungal members having most abundance in *Penicillium*, *Aspergillus*, *Neotyphodium*, and *Claviceps* [97, 98]. This class of diterpenes is generally divided into two main groups, paxilline type and non-paxilline type [98], though it mainly consists of cyclic diterpenoid backbone in addition to an indole moiety.
