Piperine

Preparation

Piperine is extracted from black pepper using dichloromethane. Aqueous hydrotropes can be used in the extraction to result in high yield and selectivity. The amount of piperine varies from 1-2% in long pepper, to 5-10% in commercial white and black peppers. Further, it may be prepared by treating the solvent-free residue from an alcoholic extract of black pepper, with a solution of potassium hydroxide to remove resin (said to contain chavicine, an isomer of piperine) and solution of the washed, insoluble residue in warm alcohol, from which the alkaloid crystallises on cooling.

Reactions

Piperine yields 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 formulae.) 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, crystallising in steel-blue needles, mp. 145 °C.

History

Piperine was discovered in 1819 by Hans Christian Ørsted, who isolated it from the fruits of Piper nigrum, the source plant of both the black and white pepper grains. Flückiger and Hanbury found piperine in Piper longum and Piper officinarum (Miq.) C. DC. (=Piper retrofractum Vahl), two species called "long pepper". West African pepper also contains piperine.

Anderson first hydrolysed piperine by alkalis into a base and an acid, which were later named piperidine and piperic acid respectively. The alkaloid was first synthesised by the action of piperoyl chloride on piperidine.

Preliminary research

A component of pungency by piperine results from activation of the heat- and acidity-sensing TRPV ion channels, TRPV1 and TRPA1, on nociceptors, the pain-sensing nerve cells.

Piperine is being studied for its potential to affect bioavailability of other compounds in food. One example investigated is the potential for piperine to enhance the bioavailability of curcumin. In laboratory studies, it inhibits human CYP3A4 and P-glycoprotein which are enzymes involved in the metabolism and transport of xenobiotics and metabolites. Other research indicates it inhibits the degradation of ABCA1, a key transporter protein involved in cholesterol efflux. In animal studies, piperine inhibited CYP450 enzymes involved in drug metabolism.