Disclosed are methods, compositions, proteins, nucleic acids, cells, vectors, compounds, reagents, and systems for the preparation of kavalactones, flavokavains, and kavalactone and flavokavain biosynthetic intermediates using enzymes expressed in heterologous host cells, such as microorganisms or plants, or using in vitro enzymatic reactions. This invention also provides for the expression of the enzymes by recombinant cell lines and vectors. Furthermore, the enzymes can be components of constructs such as fusion proteins. The kavalactones produced can be utilized to treat anxiety disorder, insomnia, and other psychological and neurological disorders. The flavokavains produced can be utilized to treat various cancers including colon, bladder, and breast cancers.