Piperine
Specific molecules
The alkaloid that stings in black pepper — and nothing but pepper contains it.
It multiplies the absorption of curcumin several dozen times. The pepper in a curry is not there for taste alone.
Effects and benefits
The bite of black pepper activates the same heat receptor as chili, more gently. And it has a rare talent: slowing the elimination of other molecules by the liver and the gut.
Piperine makes up 5 to 9% of black pepper. It activates TRPV1, like capsaicin, and another receptor, TRPA1 (McNamara et al., 2005).
It slows liver and gut enzymes that eliminate foreign substances: that is what makes it raise curcumin in the blood (Shoba et al., 1998). The same mechanism can change the effect of certain medicines; at the doses of a peppered plate it stays weak, but a concentrated supplement should be mentioned to the pharmacist.
Sources: McNamara et al., Br J Pharmacol, 2005 · Shoba et al., Planta Med, 1998