Sildenafil / Sildenafil Citrate ≥99% — pure substance

Sildenafil / Sildenafil Citrate (research reagent)

Sildenafil is an organic heterocyclic compound from the pyrazolo[4,3-d]pyrimidine derivative class, used in laboratories as a reference reagent and analytical standard in studies of selective phosphodiesterase type 5 (PDE5) inhibitors. It is available both as the free base and as a readily soluble salt — the citrate. In a research context it acts as one of the classic model ligands of PDE5, used in experimental pharmacology, analytical chemistry and studies of cyclic-GMP-dependent signalling pathways.

Physicochemical data

Characteristics and research applications

The core of the sildenafil molecule is a pyrazolo[4,3-d]pyrimidin-7-one system, to which an ethoxyphenyl substituent and a sulfonyl group bearing a 4-methylpiperazine moiety are attached. This elaborate architecture gives the compound characteristic spectral properties (UV, MS, NMR) used for its identification and quantification. The citrate form — a salt formed with citric acid — offers better aqueous solubility than the free base, which facilitates the preparation of standard solutions and buffered experimental mixtures.

In a research context sildenafil is described as a selective inhibitor of phosphodiesterase type 5, the enzyme that hydrolyses cyclic guanosine monophosphate (cGMP). In in-vitro model systems it serves as a tool for studying PDE5 inhibition kinetics, assessing selectivity against other phosphodiesterase isoforms, and as a reference compound in enzymatic and receptor assays. Owing to its well-characterised profile it is a convenient benchmark when validating new analytical methods and studying structure–activity relationships.

As an analytical reagent, sildenafil (as the base or the citrate) is used as a reference substance in HPLC and LC-MS methods for identity control, content determination and the detection of adulteration in research samples. Its high purity (≥99%) enables the preparation of calibration curves and the use of the material as a reference in method-development studies. The product should be stored in a dry, cool place, away from light and moisture. The material is intended solely for laboratory applications carried out by qualified personnel using appropriate personal protective equipment.