Serum cholinesterase inhibitors in the commercial hexane impurities.

Commercial hexane was concentrated by distillation. The distillation residue (0.43 ml/l original solvent) contains material which inhibits human serum cholinesterase (ChE) "in vitro" with a slight effect on acetylcholinesterase. Phosphorus was detected equivalent to 0.33 mumol monophosphorus compound/litre original solvent. The inhibition was progressive with the enzyme-inhibitor preincubation time. A partial reactivation of the inhibited enzyme was obtained by treatment with hydroxylamine and 2-PAM. The results are coherent with a covalent inactivation by more than one inhibitor which acylate (probably phosphorylate) ChE, although it seems likely that a reversible but unstable inhibitor could also be present in the hexane residue. The results are discussed in the context of the known neurotoxic effects of n-hexane and some organophosphorus esters.