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

Abstract

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.

Determination of non-polar and mid-polar monomeric oxidation products of stigmasterol during thermo-oxidation

“…The total amount of polar oxidation products accounted thus only for 18% of the initial stigmasterol indicating that other types of products had to be formed. The polar oxides may have been suffered further reactions, such as polymerization (Kemmo, Soupas, Lampi & Piironen, 2005;Soupas et al, 2006) or dehydration, giving rise to other types of non polar products (Bortolomeazzi, De Zan, Pizzale & Lanfranco, 2000). These results are in agreement with those obtained by Lampi, Juntunen, Toivo and Piironen (2002), with a maximum content of polar oxidation products after 1 hour heating of stigmaterol at 180 ºC 7-ketostigmasterol was the only product whose content increased statistically during the whole course of the experiment.…”

“…The molecular ion corresponded to the peak with the m/z 392 and the peaks at m/z 253 and 211 were due to loss of side chain and of the chain plus ring D, supporting the presence of three double bonds in the ring system (Bortolomeazzi, De Zan, Pizzale & Lanfranco, 2000). The formation of these double bonds, being located at the 2, 4 and 6 positions, can be explained by the loss of two molecules of water from a hydroxyl derivative of sterol (Bortolomeazzi Pizzale, Novelli & Conte, 1996).…”

“…Bortolomeazzi, De Zan, Pizzale and Lanfranco (2000) also found sterenes with double bonds located at C2, C4, and C6 positions in refined vegetable oil. The sterenes were synthesized from the dehydration of hydroxysterols during the refining.…”

Oxysterols formation: A review of a multifactorial process

“…These compounds may consist of high molecular weight compounds, such as di-and oligomers (of hydroxy, epoxy and keto derivatives) linked by ether bonds or by combining radicals (37)(38)(39). They can also consist on steradienes and steratrienes, compounds formed from sterols, 7-ketosterols or 7-hydroxysterols (40). Using a model system consisting on pure stigmasterol heated at 180 °C for 180 min, Menéndez-Carreño et al (32), in agreement with Lampi et al (37), reported that dimeric and polymeric products contributed to 30% of stigmasterol degradation.…”

Structural Analysis of Mogrol and its Glycosides as Inhibitors of Animal DNA Polymerase and Human Cancer Cell Growth

“…Some studies suggest that phytosteroids such as mogrol (compound 1) affect the reproductive system in animals, and in particular, that they have estrogenic effects [33,34]. Phytosteroids such as compounds 1 and 3 are very stable, and intense processes (such as boiling, neutralization, bleaching, and deodorization) do not affect the phytosteroid content of vegetables and fruits [35,36]. Dietary phytosteroids reduce cholesterol absorption and plasma cholesterol levels and prevent cardiovascular events [37,38].…”