Session Speaker

Differential Heat Stability of Amphenicols and their Relationship to Antimicrobial Activity: Possible Synergism after Heating Treatments
Chi-Chung Chou, Catherine A. Franje, MingKun Hsieh, Shao-Kuang Chang, Ching-Lin Shyu
USA

Heat stability of amphenicols was investigated by correlation of the drugs’ structural degradation to their antimicrobial activity. Florfenicol (FF), thiamphenicol (TAP), and chloramphenicol (CAP) were heated at 100°C in water, sodium borate buffer and chicken meat for up to 2h. Degradations were evaluated through capillary electrophoresis (CE) with UV-DAD spectrometry and minimum inhibitory concentration (MIC) assay. FF were minimally degraded after heating in water but were extensively degraded in borate buffer for up to 98% producing 4 new peaks and 8-folds increase in MIC. Heat stability in water was ranked as FF > TAP = CAP while in sodium borate buffer ranked as TAP = CAP > FF. CAP and TAP boiled in chicken meat showed higher reductions than in water, suggesting that amphenicols in meat may not be all protected at heating. Both CE and GC/MS analysis showed that heating of FF produced TAP and significant synergistic activities against Staphylococcus aureus were discovered among amphenicols. In conclusion, despite close structural similarity; amphenicols exhibited differential degradation behavior in different matrices. The degree of structural degradation did not proportional to the increase in antimicrobial activity. Therefore, heating of amphenicol residues in food cannot always be assumed safe.