title: Prolyl endopeptidase inhibitors from Syzygium samarangense (Blume) Merr. & L. M. Perry.
abstract: Compounds isolated from the hexane extract of the leaves of Syzygium samarangense (Blume) Merr. & L. M. Perry were tested for inhibitory activity against the following serine proteases: trypsin, thrombin and prolyl endopeptidase. The compounds were identified as an intractable mixture of alpha-carotene and beta-carotene (1), lupeol (2), betulin (3), epi-betulinic acid (4), 2',4'-dihydroxy-6'-methoxy-3'-methylchalcone (5), 2'-hydroxy-4',6'-dimethoxy-3'-methylchalcone (6), 2',4'-dihydroxy-6'-methoxy-3',5'-dimethylchalcone (7), 2',4'-dihydroxy-6'-methoxy-3'-methyldihydrochalcone (8) and 7-hydroxy-5-methoxy-6,8-dimethylflavanone (9). Hydrogenation of compounds 5, 6 and 7 yielded compound 8, 2'-hydroxy-4',6'-dimethoxy-3'-methyldihydrochalcone (10) and 2',4'-dihydroxy-6'-methoxy-3',5'-dimethyldihydrochalcone (11), respectively. The hydrogenated products of compounds 6 and 7 were also tested for enzyme inhibitory activity. In addition, beta-sitosterol (12) and beta-D-sitosterylglucoside (13) were also isolated. This is the first report of the isolation of compounds 1-6, 8 and 13 from this plant. Compounds 3-8 and 10 exhibited significant and selective inhibition against prolyl endopeptidase among three serine proteases. This is the first report of this kind of activity for all these compounds.
authors.affiliation: Institute of Chemistry, College of Science, University of the Philippines, Diliman 1101 Quezon City, Philippines. evangeline.amor@up.edu.ph
authors.forename: Evangeline C
authors.initials: EC
authors.lastname: Amor
authors.forename: Irene M
authors.initials: IM
authors.lastname: Villaseñor
authors.forename: Amsha
authors.initials: A
authors.lastname: Yasin
authors.forename: M Iqbal
authors.initials: MI
authors.lastname: Choudhary
mesh_terms: D006586:Hexanes; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D010936:Plant Extracts / Q000737:chemistry / Q000302:isolation & purification*; D018515:Plant Leaves / Q000737:chemistry; D000085822:Prolyl Oligopeptidases; D011480:Protease Inhibitors / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D012697:Serine Endopeptidases / Q000378:metabolism; D027842:Syzygium / Q000737:chemistry*; D013917:Thrombin / Q000378:metabolism; D014357:Trypsin / Q000378:metabolism
chemical_list: D006586:Hexanes; D010936:Plant Extracts; D011480:Protease Inhibitors; C026385:n-hexane; D012697:Serine Endopeptidases; D000085822:Prolyl Oligopeptidases; D014357:Trypsin; D013917:Thrombin