Effects of various esterase inhibitors on dl-PHPB conversion in rat plasma. The conversion of dl-PHPB to dl-NBP was highly effectively inhibited by NaF (200 mmol/L, a general esterase inhibitor) (A), and EDTA or EGTA (10 mmol/L, metal ion chelating agents) (B); partly inhibited by teicoplanin (1 mmol/L, a paraoxonase inhibitor) (C), donepezil (1 mmol/L, a cholinesterase inhibitor) (D); and negligibly inhibited by DTNB (1 mmol/L, an arylesterase inhibitor) (E), BNPP (1 mmol/L, a carboxylesterase inhibitor) (F) or PMSF (1 mmol/L, a serine esterase inhibitor) (G) (values are the mean±standard error of triplicate determinations). *P<0.05, **P<0.01 compared with control group.