Phytosterols in Cucurbita pepo convar. citrullina seed oil were analyzed by GC–MS after extraction by the organic solvents, hexane and petroleum ether, and by supercritical carbon dioxide at 400 bar and 40°C. Desmosterol, campesterol, stigmasterol, β-sitosterol, spinasterol, Δ7,22,25-stigmastatrienol, Δ7-stigmastenol, Δ7,25-stigmastadienol, and Δ7-avenasterol were identified mass spectrometrically via detection of the parent molecular ions and fragmentation patterns of corresponding trimethylsilyl derivatives. The used derivatizing agents N-methyl-N-(trimethylsilyl)trifluoroacetamide (MSTFA) and N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) are equally effective for phytosterol content determination. As expected, the predominant phytosterols were Δ7-sterols that ranged from 91.0 to 94.2% of the total phytosterol content given as sum of free sterols and steryl esters. Comparison of extraction methods revealed that, although the oil yields obtained by extraction with hexane, petroleum ether and supercritical CO2 were 43.37, 44.65, and 36.17%, respectively, the total phytosterol content in supercritical CO2 extract (294 mg/100 g oil, for both MSTFA and BSTFA) was about 30% higher than in hexane and about 20% higher than in petroleum ether extract.
Practical applications: Extraction with the application of fluids in supercritical state opens a new approach to the production of edible vegetable oils. Many economical, health, and environmental aspects are interlaced in this modern approach. By applying the supercritical extraction, the selectivity of the extraction can be significantly improved compared to traditional methods of extraction. Thus, depending on the operating conditions of supercritical CO2 extraction higher total phytosterol content can be achieved resulting in improved nutritional value of the pumpkin seed oil.