title: Isolation and characterization of a tadalafil analogue, N-cyclopentyl nortadalafil in health supplement.
abstract: A tadalafil analogue was detected for the first time during the screening of a health supplement for undeclared sexual enhancement drugs. The compound had been isolated and purified by preparative high-pressure liquid chromatography (HPLC). Its chemical structure was elucidated using high-resolution mass spectrometry (HRMS), electrospray ionization tandem mass spectrometry (ESI-MS/MS) and nuclear magnetic resonance (NMR) spectroscopy. The compound had a protonated molecular ion at m/z 444 with a chemical formula of C26H25N3O4. The data obtained from the MS analysis of the compound suggested that the N-methyl group on the piperazinedione moiety of tadalafil was substituted with a -C5H9 group. Analysis using NMR was performed and the -C5H9 group was characterized as a cyclopentyl moiety. The analogue was named N-cyclopentyl nortadalafil.
authors.affiliation: Pharmaceutical Laboratory, Applied Sciences Group, Health Sciences Authority, 11 Outram Road, Singapore 160978, Singapore; Department of Pharmacy, Faculty of Science, National University of Singapore, 18 Science Drive 4, Singapore 117543, Singapore. Electronic address: xu_yimin@hsa.gov.sg.
authors.forename: Yimin
authors.initials: Y
authors.lastname: Xu
authors.affiliation: Pharmaceutical Laboratory, Applied Sciences Group, Health Sciences Authority, 11 Outram Road, Singapore 160978, Singapore.
authors.forename: Chee-Leong
authors.initials: CL
authors.lastname: Kee
authors.affiliation: Pharmaceutical Laboratory, Applied Sciences Group, Health Sciences Authority, 11 Outram Road, Singapore 160978, Singapore.
authors.forename: Xiaowei
authors.initials: X
authors.lastname: Ge
authors.affiliation: Pharmaceutical Laboratory, Applied Sciences Group, Health Sciences Authority, 11 Outram Road, Singapore 160978, Singapore.
authors.forename: Min-Yong
authors.initials: MY
authors.lastname: Low
authors.affiliation: Department of Pharmacy, Faculty of Science, National University of Singapore, 18 Science Drive 4, Singapore 117543, Singapore.
authors.forename: Hwee-Ling
authors.initials: HL
authors.lastname: Koh
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods; D019587:Dietary Supplements; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D000068581:Tadalafil / Q000031:analogs & derivatives* / Q000302:isolation & purification*; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D000068581:Tadalafil
keywords: HRMS; Health supplement; N-Cyclopentyl nortadalafil; NMR; Tadalafil analogue