Chem. Pharm. Bull., 53(7),832-835, July 2005

Notes

Piperine from the Fruits of Piper longum with Inhibitory Effect on Monoamine Oxidase and Antidepressant-Like Activity

Seon A LEE,^a Seong Su HONG,^a Xiang Hua HAN,^a Ji Sang HWANG,^a Gab Jin OH,^b Kyong Soon LEE,^a Myung Koo LEE,^a,c Bang Yeon HWANG,^a and Jai Seup RO^*,a

^a College of Pharmacy, Chungbuk National University; Cheongju 361-763, Korea: ^b Samjin Pharm. Co. Ltd.; Hwasung 445-920, Korea: and ^c Research Center for Bioresource and Health, Chungbuk National University; Cheongju 361-763, Korea. * To whom correspondence should be addressed. e-mail: jsroh@chungbuk.ac.kr

A bioassay-guided isolation of the ethanol extract from the fruits of Piper longum yielded a known piperidine alkaloid, piperine, as a monoamine oxidase (MAO) inhibitor. Piperine showed an inhibitory effect against MAO-A (IC₅₀ value: 20.9 μM) and MAO-B (IC₅₀ value: 7.0 μM). Kinetic analyses by a Lineweaver-Burk plot clearly indicated that piperine competitively inhibited MAO-A and MAO-B with K_i values of 19.0±0.9 μM and 3.19±0.5 μM, respectively. The inhibition by piperine was found to be reversible by dialysis of the incubation mixture. In addition, the immobility times in the tail suspension test were significantly reduced by piperine, similar to that of the reference antidepressant fluoxetine, without accompanying changes in ambulation when assessed in an open-field. These results suggest that piperine possesses potent antidepressant-like properties that are mediated in part through the inhibition of MAO activity, and therefore represent a promising pharmacotherapeutic candidate as an antidepressant agent.

Key words Piper longum; piperine; monoamine oxidase inhibitor; antidepressant agent