Japanese butterbur (fuki)

Fuki (Petasites japonicus) is a daisy-family plant native to Japan. Both its flower buds, fukinoto, which emerge in early spring, and its elongated leaf stalks, fuki, are treated as traditional food ingredients. However, the evidence currently available for this entry concerns not records of bitterness itself but a different naturally occurring group of constituents in this plant, pyrrolizidine alkaloids (PA).

A public information page from Japan's Ministry of Agriculture, Forestry and Fisheries states that PA was detected in most commercially available fuki and fukinotō, that concentrations were higher in fukinotō than in fuki, and that no PA-related health harm suspected to result from eating fuki or fukinotō has been reported in Japan. A 2023 review refers to this ministry survey from Heisei 27-29 (2015-2017) and says that its authors themselves quantified petasin and PA (petasitenine, neopetasitenine, and senkirkine) in fukinotō extracts, finding that nonpolar hexane extraction could retain a high amount of petasin while keeping PA content low. The public page itself gives neither individual concentration values nor details of the survey design, and the extract findings do not give concentrations in fuki or fukinotō as foods.