The effect of bromfenvinphos, its impurities and chlorfenvinphos on acetylcholinesterase activity.

The aim of this work was to examine the effect of two organophosphorous compounds i.e. bromfenvinphos (BFVF) and chlorfenvinphos (CFVF) possessing acaricidal and insecticidal properties, on the activity of human erythrocytes acetylcholinesterase (AChE, EC 3.1.1.7). Moreover, the effect of five bromfenvinphos production impurities on AChE activity was studied. The erythrocytes were incubated with the compounds studied in the concentrations range from 0.05 to 250 μM for 1h. The organophosphorous compounds studied in low concentrations increased Km value but they did not change Vmax value (competitive inhibition). Higher concentrations of the compounds studied decreased Vmax value and increased Km value, what revealed a mixed type of AChE inhibition by these xenobiotics. Basic significance in AChE activity inhibition has the type of halogen in vinyl group. Chlorfenvinphos (insecticide) exhibited stronger enzyme inhibition than bromfenvinphos. CFVF and dibromo-bromfenvinphos possessed the lowest Ki and Ki' values among all the compounds studied. The presence of Cl atom (chlorfenvinphos) instead of Br atom (bromfenvinphos) considerably increases antiesterase activity of the individual compound. Three impurities like 2,4-dichlorophenacyl bromide, 2,4-dichlorophenacylidene bromide and 2,4-dichlorophenacylidyne bromide did not induce any statistically changes in AChE activity. Two impurities of bromfenvinphos such as: dihydro-bromfenvinphos and dibromo-bromfenvinphos revealed significant effect on the AChE activity, which may be connected with the presence a phosphate group in these substances. It was proven that an increase in antiesterase activitiy of the compounds studied corresponded with the increase in the number of Br atoms at carbon of their vinyl group: dibromo-bromfenvinphos>bromfenvinphos>dihydro-bromfenvinphos.