2.1. Podophyllotoxin biosynthesis
The first step in the production of PPT is the deamination of phenylalanine by phenylalanine ammonia-lyase to cinnamic acid, which is converted into feruloyl-CoA by caffeoyl-CoA O-methyl transferase. Feruloyl-CoA further undergoes a series of formation of intermediates such as coniferyl alcohol to produce pinoresinol and lariciresinol. These compounds lead to the production of secoisolariciresinol in the presence of pinoresinol-lariciresinol reductase leading to the synthesis of matairesinol, which eventually yields PPT (Fig. 2 ) (Bahabadi et al., 2012; Javadian et al., 2017).