Identification of a new tadalafil analogue in commercial dietary supplements: isopropylnortadalafil

ABSTRACT

A new tadalafil analogue was found in a commercial dietary supplement for enhancing sexual performance. The compound was detected by a high-performance liquid chromatography-diode array detector (HPLC-DAD). The analogue was isolated using semi-preparative HPLC, and its accurate mass was established by two LC-high-resolution-mass spectrometers (LC-HRMS). The structure was determined by nuclear magnetic resonance (NMR) spectroscopy. The accurate mass of the compound corresponded to a molecular formula of C₂₄H₂₃N₃O₄. The compound was identified as a structural analogue of tadalafil in which the N-methyl group of tadalafil was replaced with an N-isopropyl group. We have named the new analogue isopropylnortadalafil and it is first reported herein.

GRAPHICAL ABSTRACT

KEYWORDS:

• PDE-5 inhibitor
• adulterated dietary supplement
• tadalafil analogue
• isopropylnortadalafil
• LC-HRMS
• NMR

Acknowledgment

The authors thank the Central Laboratory of Kangwon National University for providing them with technical assistance for the spectroscopic experiments. Han Na Park and Ji Hyun Lee contributed equally to this work.

Disclosure statement

No potential conflict of interest was reported by the authors.

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Additional information

Funding

This work was supported by the Ministry of Food and Drug Safety [grant numbers MFDSAAT2016 and 15182MFDS523]; and Kangwon National University.