Identification and determination of phytosterols in pharmaceutical preparations

For decades sterol containing plant extracts have found wide applications in the treatment of benign prostate enlargement. Especially in Germany, the extracts of Cucurbita spec. (pumpkin seeds), Sabal fructus and Urtica dioica, as well as other poorly defined „phytosterol“ preparations are widely used. In contrast to phytosterols from other plants of interest, the extracts of pumkin seeds contain significant amounts of Δ⁷-phytosterols and their glucosides, which are claimed to be responsible for the therapeutic effects due to their structural similarity to 5α-dihydrotestosteron.

In continuation of our research on sterol analysis we worked out a methodology for the determination of phytosterols in different pharmaceutical formulations. The method includes a sample cleanup of the unsaponifiables and the glucoside hydrolysates by a modified QuEChERS approach and the identification and determination of the sterol aglyca by GC-MS analysis of the corresponding trimethylsilyl ethers.

In a number of phytosterol preparations from local pharmacies, supermarkets and internet shops the sterol patterns were analyzed with special attention to the content of Δ⁵- and Δ⁷-phytosterols. Only in two pharmacy products (GRANU FINK PROSTA and PROSTA FINK FORTE) we found relevant amounts of Δ⁷-phytosterols. All other products without pumpkin seed contained no Δ⁷-phytosterols. Lowest content of phytosterols were found in a pumpkinseed oil product from a discounter.