Letter	Planta Med 2004; 70: 1228-1230 DOI: 10.1055/s-2004-835856
© Georg Thieme Verlag KG Stuttgart · New York
Prolyl Endopeptidase Inhibitors from the Leaves of Ginkgo biloba
Jung-Han Lee1, Si-Young Lee1, Kyung-Seok Lee1, Hyun-Jung Jang1, Kyung-Ho Lee1, Tae-Ryong Hahn2, Young-Sook Paik1,2
1 College of Environment and Applied Chemistry, Kyung Hee University, Suwon, Korea 2 Plant Metabolism Research Center, Kyung Hee University, Suwon, Korea

Abstract

Prolyl endopeptidase (PEP, EC 3.4.21.26) hydrolyzes proline-containing neuropeptides, such as vasopressin, substance P, and thyrotropin-releasing hormone (TRH), and is suggested to participate in learning and memory processes. Ginkgo biloba leaves, upon examination for anti-amnestic constituents as new types of PEP inhibitors, showed significant PEP inhibition. PEP activity-guided fractionation and column chromatography of the MeOH extracts of G. biloba leaves resulted in the isolation of 6-(8′Z-pentadecenyl)salicylic acid (1) and 6-(10′Z-heptadecenyl)salicylic acid (2). The kinetic study indicated that compounds 1 and 2 are non-competitive inhibitors of prolyl endopeptidase with Ki values of 0.87 and 0.80 μM, respectively.