Piceid can be isolated from the Japanese knotweed through the process resveratrol.
Resveratrol can be produced from piceid via the mold Aspergillus oryzae. Resveratrol (3,5,4-trihydroxy-trans-stilbene) is a stilbenoid, a type of natural phenol, and a phytoalexin produced by several plants in response to injury or when the plant is under attack by pathogens, such as bacteria or fungi. 
