Stability of Cholesterol, 7-Ketocholesterol and β-Sitosterol during Saponification: Ramifications for Artifact Monitoring of Sterol Oxide Products.
Cholesterol has been used to monitor artifact generation. Stability differences among cholesterol oxide products (COPs) and cholesterol in thermal and alkaline conditions are theorized. Thus, use of cholesterol may be unsuitable for detection of artifacts generated from COPs. Stability of cholesterol was compared to that of 7-ketocholesterol (7-keto) and β-sitosterol (βS) under various thermal and alkaline saponification conditions: 1 M methanolic KOH for 18 h at 24 °C (1 M18hr24°C, Control), 18 h at 37 °C (1M18hr37°C), 3 h at 45 °C (1M3hr45°C), and 3.6 M methanolic KOH for 3 h at 24 °C (3.6M3hr24°C). Trends indicated that cholesterol in solution was more stable than 7-keto under all conditions. Compared to βS, cholesterol was more stable under all conditions except for 1M18hr37°C for which stabilities were similar. Compounds were more labile in heat than alkalinity. Poor recoveries of 7-keto during cold saponification with high alkalinity were attributed to alkaline instability. 7-Keto, less stable than cholesterol, should be used to monitor artifact generation during screening of various methods that include thermal and alkaline conditions. In a preliminary analysis of turkey meat, more 3,5-7-one was generated from spiking with cholesterol than with 7-keto.
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