Piperine

Piperine, possibly along with its isomer chavicine, is the compound responsible for the pungency of black pepper and long pepper via activation of TRPV1. It has been used in some forms of traditional medicine.

Due to its poor solubility in water, piperine is typically extracted from black pepper by using organic solvents like dichloromethane or ethanol. The amount of piperine varies from 1–2% in long pepper, to 5–10% in commercial white and black peppers.

Piperine can also be prepared by treating the solvent-free residue from a concentrated alcoholic extract of black pepper with a solution of potassium hydroxide to remove resin (said to contain chavicine, an isomer of piperine). The solution is decanted from the insoluble residue and left to stand overnight in alcohol. During this period, the alkaloid slowly crystallizes from the solution.

Piperine has been synthesized by the reaction of piperonoyl chloride with piperidine.

The biosynthesis of piperine is only partially known.

In addition to piperine synthase PipBAHD2, there is an orthologous enzyme with broader substract specificity in Piper nigrum with gene symbol PipBAHD1, called a "piperamide synthase". This other enzyme is responsible for the many piperamide compounds (see ) besides piperine found in black pepper. Both enzymes are BAHD acyltransferases.

Piperine forms salts only with strong acids. The platinichloride B₄·H₂PtCl₆ forms orange-red needles ("B" denotes one mole of the alkaloid base in this and the following formula). Iodine in potassium iodide added to an alcoholic solution of the base in the presence of a little hydrochloric acid gives a characteristic periodide, B₂·HI·I₂, crystallizing in steel-blue needles with melting point 145 °C.

Piperine can be hydrolyzed by an alkali into piperidine and piperic acid.