Über die Bildung und Beseitigung verschiedener Steroid‐Derivate während der Raffination der Speiseöle

Zan

et al. 2000

The dehydration of sterols during the refining process of vegetable oils results in the formation of steroidal hydrocarbons (sterenes or steradienes) with two double bonds in the ring system. Other steroidal hydrocarbons whose structures were in agreement with the presence of three double bonds in the ring system were detected in the sterene fractions of refined vegetable oils. The 5alpha-, 7alpha-, and 7beta-hydroxy derivatives of cholesterol and phytosterols have been dehydrated in n-butanol/H(3)PO(4) to form steroidal hydrocarbons with three double bonds at the 2, 4, and 6 positions in the ring system. These hydrocarbons had the same relative retention time and mass spectra as those present in the sterene fractions of refined oils. The dehydration of the hydroxy sterols dissolved in extra virgin olive oil and in the presence of 1% bleaching earths at 80 degrees C for 1 h results in the formation of the same steroidal hydrocarbons found in the refined oils.

Section: Introductionmentioning

confidence: 61%

Identification of New Steroidal Hydrocarbons in Refined Oils and the Role of Hydroxy Sterols as Possible Precursors

Zan

et al. 2000

“…In particular, bleaching with acidic earths and deodorization at high temperatures can cause major changes, which are related to the conditions used, to the minor components present in the unsaponifiable matter of oils. In the case of sterols, isomerization with a shift of the double bonds and dehydration with formation of steroidal hydrocarbons (steradienes) and disteryl ethers have been reported (1)(2)(3)(4)(5)(6)(7)(8). The analysis of steradienes represents, in fact, a useful method for detecting the addition of refined oil to extra virgin olive oils and is one of the official methods in the European Union (9)(10)(11)(12)(13).…”

Section: Introductionmentioning

confidence: 99%

Presence of Phytosterol Oxides in Crude Vegetable Oils and Their Fate during Refining

Cordaro

et al. 2003

The content of phytosterol oxidation products was determined in samples of crude vegetable oils: peanut, sunflower, maize, palm nut, and lampante olive oils that were intended for refining and not for direct consumption. The 7 alpha- and 7 beta-hydroxy derivatives of beta-sitosterol, stigmasterol, and campesterol and the 7-keto-beta-sitosterol were the principal phytosterol oxides found in almost all of the oils analyzed. In some oils, the epoxy and dihydroxy derivatives of beta-sitosterol were also found at very low levels. The highest total concentrations of phytosterol oxides, ranging from 4.5 to 67.5 and from 4.1 to 60.1 ppm, were found in sunflower and maize oils, respectively. Lower concentrations were present in the peanut oils, 2.7-9.6 ppm, and in the palm nut oil, 5.5 ppm, whereas in the lampante olive oils, only three samples of the six analyzed contained a low concentration (1.5-2.5 ppm) of oxyphytosterols. No detectable levels of phytosterol oxides were found in the samples of palm and coconut oils. Bleaching experiments were carried out on a sample of sunflower oil at 80 degrees C for 1 h with 1 and 2% of both acidic and neutral earths. The bleaching caused a reduction of the hydroxyphytosterol with partial formation of steroidal hydrocarbons with three double bonds in the ring system at the 2-, 4-, and 6-positions (steratrienes). The same sunflower oil was deodorized at 180 degrees C under vacuum for 1 h, and no dehydration products were formed with a complete recovery of the hydroxyphytosterols. A bleaching test with acidic earths was carried out also with an extra virgin olive oil fortified with 7-keto-cholesterol, dihydroxycholesterol, and alpha-epoxy-cholesterol. There was no formation of steratrienes from these compounds, but dihydroxycholesterol underwent considerable decomposition and alpha-epoxycholesterol underwent ring opening with formation of the dihydroxy derivative, whereas 7-ketocholesterol was rather stable

“…Little is known of the fate of sterol oxides eventually present in the oil during the refining processes (Niewiadomski et al, 1964;Grob et al, 1994;Bortolomeazzi et al, 1996).…”

Section: Introductionmentioning

confidence: 99%

“…Phytosterols can undergo transformation during the refining process of oils with the formation of isomers and dehydrated products (Niewiadomski et al, 1966;Grob et al, 1994;Mennie et al, 1994), which in turn can be analyzed to evaluate the quality of the oil and of other products (Lanzon et al, 1989;Cert et al,1994;Grob et al, 1995;Biedermann et al, 1996;Crews et al, 1997). Little is known of the fate of sterol oxides eventually present in the oil during the refining processes (Niewiadomski et al, 1964;Grob et al, 1994;Bortolomeazzi et al, 1996).…”

Section: Introductionmentioning

confidence: 99%

Mass Spectrometry Characterization of the 5α-, 7α-, and 7β-Hydroxy Derivatives of β-Sitosterol, Campesterol, Stigmasterol, and Brassicasterol

Zan

et al. 1999

The 5alpha-hydroperoxides of beta-sitosterol, campesterol, stigmasterol, and brassicasterol were obtained by photooxidation of the respective sterols in pyridine in the presence of hematoporphyrine as sensitizer. The reduction of the hydroperoxides gives the corresponding 5alpha-hydroxy derivatives. The 7alpha- and 7beta-hydroperoxides of the sterols were obtained by allowing an aliquot of the 5alpha-hydroperoxides to isomerize to 7alpha-hydroperoxides, which in turn epimerize to 7beta-hydroperoxides. The reduction gave the corresponding 7alpha- and 7beta-hydroxy derivatives. The 5alpha-, 7alpha-, and 7beta-hydroxy derivatives of beta-sitosterol, campesterol, stigmasterol, and brassicasterol were identified by comparing thin-layer chromatography mobilities, specific color reactions, and mass spectral data with those of the corresponding hydroxy derivatives of cholesterol, which were synthesized in the same manner. The phytosterols had the same behavior to photooxidation as cholesterol and, moreover, the different phytosterols photooxidized at about the same rate. The mass spectra of the trimethylsilyl ethers of the hydroxy derivatives of the phytosterols investigated and of the corresponding hydroxy derivatives of cholesterol have the same fragmentation patterns and similar relative ion abundances.