P. longum, sometimes called long pepper, is closely related to black pepper, Piper nigrum, but generally has a hotter flavor. Fruits of the Piper genus contain the same active constituent, piperine—an alkaloid largely responsible for these peppers’ pungent flavor and physiologic effects. Animal studies suggest that P. longum has antioxidant, anti-inflammatory, analgesic, anti-microbial, and immunomodulatory activities. It has also been shown to reduce high cholesterol levels, prevent blood clot formation in blood vessels, and protect liver and heart tissue from toxic damage. In addition, it is used to stimulate appetite and relieve indigestion.
P. longum and piperine have been found to enhance the bioavailability of other herbs and medications by inhibiting a transport protein in the cells lining the intestinal wall that returns certain compounds back into the intestine. P. longum alkaloids have also been shown to inhibit the clearance of certain drugs and plant compounds in the liver, further enhancing their activity in the body; therefore, it should be used cautiously by individuals taking medications.
Source: Journal of Acupuncture and Meridian Studies