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

Abstract

Oxidation products of stigmasterol were characterized by their polarity and molecular size using solid phase extraction (SPE) and high performance size exclusion (HPSEC) methods. Monomeric oxides were studied further by GC-MS and GC-FID. The focus was on identifying and quantificating non-polar and mid-polar monomeric oxides after SPE fractionation. Commercial stigmasterol was subjected to 180 ºC up to 3 hours. Six oxidation products were identified by GC-MS in the nonpolar and mid-polar monomeric fractions, and they appeared already after the first hour of heating. Quantification by GC-FID showed an increase in the non-polar and mid-polar oxidation products during heating time, and their amounts reached values of 6.1 and 47.0 μg/mg of commercial stigmasterol, respectively. Polar oxidation products commonly measured reached a value of 193 μg/mg after 1 hour of heating, while after 3-hour heating, the amount was only 164 μg/mg. Since as much as 550 μg/mg of stigmasterol was decomposed, the monomeric products explained only partly the stigmasterol loss. Dimeric and polymeric products contributed to 165 µg/g of gap showing the importance of polymerization reactions at 180 ºC.2

Oxysterols formation: A review of a multifactorial process

“…In this sense, Soupas et al (35) proposed 140 °C as the key temperature in the process, since sterols behaved differently below and above this temperature. At 175-180 °C, whereas Xu et al (30) found the maximum amount of COPs at similar times as in our experiment, some other works, (14,32,36) obtained that SOPs decreased only after 40, 60 and 90 min, respectively.…”

“…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. Menéndez-Carreño's group also described a strong relationship between non-polar/mid polar and the other indicators of oxidation reactions.…”

“…Regarding experiments attained using thermo-oxidation treatments similar to ours, Xu et al (30) found 61% of cholesterol degradation after 10 min heating at 175 °C. Nevertheless, percentages of just 50% degradation of cholesterol, β-sitosterol and stigmasterol were detected after 60 min heating in some other works (17,32).…”

A review of analytical methods measuring lipid oxidation status in foods: a challenging task

“…Morales et al [33] applied it for the determination of advanced oxidation in vegetable oils through the detection of fatty acids polymers. Oligomers formation during thermo-oxidation of phytosterols has also been reported [89][90][91][92] by means of HPSEC analysis.…”

Oxidation of β-sitosterol and campesterol in sunflower oil upon deep- and pan-frying of French fries

“…PS are regarded to have health-promoting properties in preventing cardiovascular diseases by inhibiting the intestinal absorption of cholesterol, accordingly, the consumption of 2 g/day of PS could reduce the risk of heart diseases by about 25 % (Kritchevsky and Chen 2005). Therefore, PS have been recently incorporated into novel foods (Koschutnig et al 2010;Menéndez-Carreño et al 2010;Lehtonen et al 2011).…”