Evaluation of oxidative degradation of cholesterol in food and food ingredients: identification and quantification of cholesterol oxides

Abstract

Cholesterol oxidation derivatives display a wide range of undesirable biological properties, and their presence in foodstuffs has raised much concern and attention. We have developed a method allowing quick, simple, and reliable quantification of cholesterol oxidative degradation in food. After lipid extraction and mild saponification, the unsaponifiable fractions from food samples are deposited on thin-layer chromatography plates and developed in hexane-ether (70:30); cholesterol oxides, migrating in a single band, are resolved from cholesterol, and both areas are scraped and analyzed as trimethylsilyl derivatives by capillary gas chromatography. 19-Hydroxycholesterol and cholestanol are used as internal standards for the quantification of cholesterol oxides and of cholesterol, respectively. We have shown that moderate heating of butter leads to the formation of cholesterol oxides, in amounts increasing with temperature, length of heating, and storage times. Cholesterol oxides are also present in commercial egg powder, egg mixes, and butter cookies or cakes. This method is a useful tool in assessing the quantitative importance of cholesterol oxides in the human diet and their formation during food processing or storing.Cholesterol can easily undergo oxidation in air, and the many substances derived from this oxidation, the so-called cholesterol oxides or oxysterols, have recently received much attention in view of their biological activities (Smith, 1981). Some cholesterol oxides display angiotoxic properties both in vivo and in vitro (Imai et al., 1976;Jacobson et al., 1985;Matthias et al., 1987) or act as mutagenic or carcinogenic compounds (Sevanian and Peterson, 1986;Raaphorst et al., 1987). Their presence in processed food has attracted much concern since cholesterol oxides have been detected in several food ingredients such as egg powder, milk powder, or heated tallow (Nourooz-Zadeh and Appelqvist, 1988; Park and Addis, 1986), and they are readily absorbed and incorporated into circulating lipoproteins (Peng et al., 1987). Thus, it is important to assess the daily ingestion of oxysterols from the diet. However, progress in this field has been hampered by difficulties associated with the isolation and analysis of these compounds. Gas-liquid chromatography (GLC) has been used in several studies (Park and Addis, 1985; Nourooz-Zadeh and Appelqvist, 1987; de Bovenkamp et al., 1988), but complete resolution of major cholesterol oxides is not always achieved; highperformance liquid chromatography methods have been developed (Csiky, 1982;Kou and Holmes, 1985;Sugino et al., 1986), but oxysterols are poorly detected by UV spectrometry. Moreover, because of their low concentrations in lipid extracts from food samples rich in cholesterol, it is necessary to separate the oxysterols from cholesterol to facilitate proper quantification: the isolation and concentration steps are long and tedious procedures that generally include several steps of liquid chromatography (Csiky, 1982; Higley et al, 1986; van de Bovenkamp et a...

Estabilidade oxidativa do colesterol em ovo integral em pó

“…Desta forma, a suspeita recai sobre o tipo de processo, pelos antecedentes conhecidos indicados na literatura, em razão de a matéria-prima, no caso o ovo, não apresentar TABELA III -7-cetocolesterol livre e total em ovo integral em pó Penazzi et al (1995) 38,4 -83,7 (total) Sarantinos, O´Dea, Sinclair (1993) 30,2 -44,1 (total) Pie, Spahis, Seillan et al (1990) 29,0 -104,0 (total)…”

“…Muitos óxidos de colesterol (OsC) têm sido identificados (Tai et al, 1999), mas somente oito deles são os mais freqüentemente encontrados em alimentos: 7-cetocolesterol (7-ceto), 20-hidroxicolesterol (20-OH), 25-hidroxicolesterol (25-OH), 7 -hidroxicolesterol (7 -OH), 7 -hidroxicolesterol (7 -OH), colesterol-5,6 -epóxido (5,6 -epóxido), colesterol-5,6 -epóxido (5,6 -epóxido) e colestanotriol (Triol) Lercker, Rodriguez-Estrada, 2000;Pie, Spahis, Seillan, 1990;Tai, Chen, Chen, 1999). O 7-ceto tem sido proposto como indicador da oxidação do colesterol, por ser o de maior ocorrência em muitos alimentos.…”

“…O processo de obtenção do ovo integral em pó ou gema em pó é feito por atomização, concentrando-se os teores de colesterol por desidratação em 929 a 1918 mg/100 g (Pie et al, 1990;Sarantinos, O'Dea, Sinclair, 1993). Diversos estudos têm relatado a formação de OsC em ovo integral em pó obtido por atomização, relacionada com o tipo do equipamento e temperatura do processo, além das condições de estocagem (Guardiola et al,1997;Huber, Pike, Huber, 1995;Lai et al, 1995;Sander et al, 1989;Sarantinos, O´Dea, Sinclair, 1993;Zunin et al, 1995).…”

“…

INTRODUÇÃOEstudos sobre a oxidação do colesterol em alimentos têm sido motivados principalmente pelas característi-cas biológicas dos óxidos formados, interferindo na morfologia e função da membrana celular, inibindo a biossíntese do próprio colesterol e sendo aterogênicos (Brown, Jessup,1999; Peng, Hu, Morin,1991), citotóxicos (Osada, 2002;Ohtani et al, 1996;Sevanian, Peterson, 1986;Smith, Johnson, 1989), mutagênicos e carcinogênicos Sevanian, Peterson, 1986).Muitos óxidos de colesterol (OsC) têm sido identificados (Tai et al, 1999), mas somente oito deles são os mais freqüentemente encontrados em alimentos: 7-cetocolesterol (7-ceto), 20-hidroxicolesterol (20-OH), 25-hidroxicolesterol (25-OH), 7 -hidroxicolesterol (7 -OH), 7 -hidroxicolesterol (7 -OH), colesterol-5,6 -epóxido (5,6 -epóxido), colesterol-5,6 -epóxido (5,6 -epóxido) e colestanotriol (Triol) Lercker, Rodriguez-Estrada, 2000;Pie, Spahis, Seillan, 1990;Tai, Chen, Chen, 1999). O 7-ceto tem sido proposto como indicador da oxidação do colesterol, por ser o de maior ocorrência em muitos alimentos.

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Óxidos de colesterol: ocorrência em alimentos, formação e efeitos biológicos

“…A presença de OsC em alimentos tem sido observada, destacando-se aqueles com maior conteúdo de colesterol, em ordem decrescente, os produtos de ovos (Pie et al, 1990;Sarantinos et al, 1993;Zunin et al, 1995;Morales-Aizpurúa, 2001), cárneos (Csallany et al, 1989;Pie et al, 1991), lácteos (Sander et al, 1989a;Pie et al, 1990;Sarantinos et al, 1993) e marinhos (Osada et al, 1993;Moura, 1999). O somatório dos OsC quantificados nesses produtos revelou ser de até 443 µg/g (Tai et al, 2000).…”