piperine
piperine, an organic compound classed either with the lipid family (a group consisting of fats and fatlike substances) or with the alkaloids, a family of nitrogenous compounds with marked physiological properties. It is one of the sharp-tasting constituents of the fruit of the pepper vine (Piper nigrum).
Piperine constitutes approximately 5 to 9 percent of commercial black or white pepper. Danish chemist Hans Christian Ørsted described the isolation of piperine in a publication in 1820. Its chemical constitution was established by laboratory syntheses in 1882 and 1894.
The sharp flavor of freshly ground pepper is attributed to the compound chavicine, a geometric isomer (having the same molecular formula but differing in structure) of piperine. Ground pepper loses its pungency when stored, due to the slow transformation of chavicine into piperine.