Stability assessment of tamsulosin and tadalafil co-formulated in capsules by two validated chromatographic methods.

The advent of a new pharmaceutical formulation evokes the need for examining the chemical stability of their constituents and establishing proper stability-indicating methods. Herein, the stability of the newly co-formulated Tamsulosin and Tadalafil were examined under different stress conditions. The acidic degradation of Tamsulosin yielded its sulfonated derivative, while Tadalafil was susceptible to both acidic and basic degradation. Two stability-indicating chromatographic methods, namely; high-performance thin-layer chromatography and high-performance liquid chromatography, have been developed. Significant high-performance thin-layer chromatography-fractionation could be achieved by utilizing a stationary phase of silica gel 60 F254 and a mobile phase composed of ethyl acetate/toluene/methanol/ammonia (4:2:4:0.6, by volumes) with densitometric recording at 280 nm over a concentration range of 0.5-25 µg/band for both drugs. The HPLC-separation could be reached on XBridge® C18 column isocraticaly by using a mobile phase having acetonitrile/phosphate buffer, pH 6.0 (45:55, v/v) pumped at a flow rate of 1.7 mL/min and applying diode array ultraviolet-detection at 210 nm over a linearity range of 3-70 µg/mL for each drug. Specificity of the two methods was additionally assured via peak purity assessment. Moreover, the methods were distinctly exploited for evaluating the drugs' stability in accelerated stability-studied samples of Tamplus® capsules.

Isolation and characterisation of N-benzyl tadalafil as a novel adulterant in a coffee-based dietary supplement.

A new tadalafil analogue was detected via high-performance liquid chromatography (HPLC)-diode array detection (DAD) during routine screening of health foods suspected of adulteration with erectile dysfunction drugs. The UV absorption spectrum of the unknown was almost identical to that of tadalafil. The analogue was purified by preparative HPLC and structural elucidation carried out by mass spectrometric and NMR spectroscopic experiments. The spectral data revealed that this tadalafil analogue bears a benzyl group instead of the methyl group. The isolated compound was identified as N-benzyl tadalafil. Considering the risk it poses to public health, this new PDE-5 analogues for ED should be included on the inspection list for illegal products.

Isolation and structural characterization of a new tadalafil analog (chloropropanoylpretadalafil) found in a dietary supplement.

A screen for known PDE-5 inhibitors in a dietary supplement product marketed for "enhanced sexual performance" detected a compound that structurally resembled chloropretadalafil, a known analog of tadalafil. The compound was isolated from the supplement matrix using high performance liquid chromatography with ultraviolet detection (HPLC-UV) and a fraction collector, and was further characterized using gas chromatography with Fourier Transform infrared detection and mass spectral detection (GC/FT-IR/MS), as well as high resolution mass spectrometry (HRMS). The analog had an accurate mass of m/z 441.1216 (error is 0.8706ppm) for the protonated species [M+H](+), corresponding to a molecular formula of C23H22ClN2O5. HRAM and GC/FT-IR/MS mass spectral fragmentation data suggested that the modification is a chloropropanoyl moiety extending from the nitrogen on the piperidine ring of chloropretadalafil. The proposed new analog has been named chloropropanoylpretadalafil.

Separation and identification of a novel tadalafil analogue adulterant in a dietary supplement.

A novel tadalafil analogue found in a dietary supplement by routine drug-adulteration screening was isolated by column chromatography and HPLC. On the basis of extensive 1D- and 2D-nuclear magnetic resonance (NMR), infrared (IR) and mass spectral analyses, the structure of the new compound YJ-02 was established as 6-(benzo[d][1,3]dioxol-5-yl)-2,3,6,7,12,12a-hexahydro-2-(1E,2E)-3-phenylallylidene)amino)pyrazino[1',2':1,6]pyrido[3,4-b]indole-1,4-dione. Its common name is N-phenylpropenyltadalafil.

Isolation and characterization of a tadalafil analogue, N-cyclopentyl nortadalafil in health supplement.

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.

Simultaneous Detection of Three Phosphodiesterase Type 5 Inhibitors and Eight of Their Analogs in Lifestyle Products and Screening for Adulterants by High-Performance Thin-Layer Chromatography.

An HPTLC method is proposed to permit effective screening for the presence of three phosphodiesterase type 5 inhibitors (PDE5-Is; sildenafil, vardenafil, and tadalafil) and eight of their analogs (hydroxyacetildenafil, homosildenafil, thiohomosildenafil, acetildenafil, acetaminotadalafil, propoxyphenyl hydroxyhomosildenafil, hydroxyhomosildenafil, and hydroxythiohomosildenafil) in finished products, including tablets, capsules, chocolate, instant coffee, syrup, and chewing gum. For all the finished products, the same simple sample preparation may be applied: ultrasound-assisted extraction in 10 mL methanol for 30 min followed by centrifugation. The Rf values of individual HPTLC bands afford preliminary identification of potential PDE5-Is. Scanning densitometry capabilities enable comparison of the unknown UV spectra with those of known standard compounds and allow further structural insight. Mass spectrometric analysis of the material derived from individual zones supplies an additional degree of confidence. Significantly, the proposed screening technique allows focus on the already known PDE5 Is and provides a platform for isolation and chemical categorization of the newly-synthesized analogs. Furthermore, the scope could be expanded to other therapeutic categories (e.g., analgesics, antidiabetics, and anorexiants) that are occasionally coadulterated along with the PDE5-Is. The method was successfully applied to screening of 45 commercial lifestyle products. Of those, 31 products tested positive for at least one illegal component (sildenafil, tadalafil, propoxyphenyl hydroxyhomosildenafil, or dimethylsildenafil).

Isolation and structural characterization of a new tadalafil analog (2-hydroxyethylnortadalafil) found in a dietary supplement.

A screen for known PDE-5 inhibitors in a dietary supplement product marketed for "enhanced sexual performance" detected a compound that structurally resembled tadalafil. The compound was isolated from the supplement matrix using high-performance liquid chromatography with ultraviolet detection (HPLC-UV) and a fraction collector, and was further characterized using nuclear magnetic resonance (NMR), liquid chromatography-mass spectrometry (LC-MS), as well as high-resolution accurate mass mass spectrometry (HRAM-MS). The analog had an accurate mass of m/z 420.15614 (error is 1.77235ppm) for the protonated species [M+H](+), corresponding to a molecular formula of C23H22N3O5. Mass spectral fragmentation data suggested that the modification occurred in place of the CH3 located on the pyrazinopyridoindole-1,4-dione of tadalafil. NMR was utilized to further elucidate the configuration of the substitution. The analysis indicated that the moiety is a CH2CH2OH, hydroxyethyl group. The new analog has been named 2-hydroxyethylnortadalafil.