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.

Preparation

Extraction

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. 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.

Chemical synthesis

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

Biosynthesis

The biosynthesis of piperine is only partially known.

The last step is catalyzed by piperine synthase. As suggested by its systematic name, it converts piperoyl-CoA and piperidine into piperine.
Piperoyl-CoA is made by piperoyl-CoA ligase from piperic acid, which is in turn made from feruperic acid by CYP719A37.
Feruperic acid is presumably made from ferulic acid. Piperine is presumably made from lysine.

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 besides piperine found in black pepper. Both enzymes are BAHD acyltransferases.

Reactions

Piperine forms salts only with strong acids. The platinichloride B₄·H₂PtCl₆ forms orange-red needles. 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.
In light, especially ultraviolet light, piperine is changed into its isomers chavicine, isochavicine and isopiperine, which are tasteless.

History

Piperine was discovered in 1819 by Hans Christian Ørsted, who isolated it from the fruits of Piper nigrum, the source plant of both black and white pepper. Piperine was also found in Piper longum and Piper officinarum C. DC., two species called "long pepper".

Uses

Piperine is widely used in the supplements industry for its effect on enhancing absorption and bioavailability of other compounds such as curcumin, resveratrol, ashwaganda, amino acids, vitamins and several minerals including selenium. It has been reported to inhibit several enzymes that participate in xenobiotic metabolism, including CYP3A4, P-gp, UDP-glucose 6-dehydrogenase, and glucuronosyltransferase. The last two activities are most relevant for curcumin.