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Kinetic evaluation of 3β‐hydroxycholest‐5‐en‐7‐one (7‐ketocholesterol) stability during saponification
Author(s) -
Park Peter W.,
Guardiola Francesc,
Park Susan H.,
Addis Paul B.
Publication year - 1996
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/bf02518118
Subject(s) - saponification , chemistry , derivatization , reagent , enol , chromatography , gas chromatography , kinetics , organic chemistry , high performance liquid chromatography , catalysis , physics , quantum mechanics
To clarify conflicting information regarding 7‐ketocholesterol (7‐KC) recovery from saponification, we evaluated the stability of 7‐KC in methanolic alkaline medium. We added 1 N alcoholic KOH to 7‐KC or lard spiked with 7‐KC and held the mixtures at 45, 55, 65, and 75°C for different times to simulate various saponification conditions. Gas‐chromatographic determination of residual 7‐KC with 5α‐cholestane as the internal standard (IS) showed that the higher the saponification temperature, the greater the 7‐KC degradation. Hot saponification at 75°C for 30 min caused extensive destruction and left only 31% 7‐KC. 7‐KC loss during saponification could be described by pseudo first‐order kinetics, and the dependence of degradation rate on temperature ( T , K) by k (h −1 )=(2.6×10 17 ) exp (−1.36×10 4 /T). As predicted by the kinetic equation, 7‐KC loss during room‐temperature saponification (21°C) was practically negligible; following the exposure of 7‐KC or lard spiked with 7‐KC to 1 N alcoholic KOH for 18 h, about 97% 7‐KC was recovered. 6‐Ketocholestanol, when used as an IS, should be looked at carefully because of potential tautomerization, leading to the formation of two enol isomers when in extended contact with trimethylsilyl derivatization reagents.