Evaluation of the organophosphorus hydrolase enzyme activity in creams and investigation of its stability

Organophosphate compounds (OPs) are esters of phosphoric acid that are extremely toxic compounds that act as acetylcholinesterase (AChE) inhibitors in the external and central nervous system (1, 2). These compounds are widely used in agriculture and are toxic insecticides, pesticides and chemical nerve agents and military applications (3-5). OP insecticides are degraded when exposed to sunlight, water and microbial hydrolysis in the soil (6). Most OPs are nearly lipophilic (7). Organophosphate pesticide poisoning of humans and animals is caused by skin contact, inhalation and body ingestion. The toxic compounds in the form of vapor or liquid are easily absorbed through transcutaneous contact (8). With Abstract The main purpose of this project is investigation of the organophosphorus hydrolase (OPH) enzyme activity in water in oil (w/o) and oil in water (o/w) creams and investigation of the OPH enzyme stability in formulated creams. OPH enzyme was extracted and purified from strain flavobacterium. The w/o and o/w creams were prepared using different formulations. In order to achieve an emulsion with maximum stability, appropriate percentage of the cream components was selected by studying different formulations and the physical and chemical stability of the produced cream were considered. 5Uenzyme/90gcream enzyme was used for each formulation. To measure the enzyme activity in creams, extraction method was used and enzyme activity was determined based on parathion hydrolysis. The thermal stability of OPH in both types of w/o and o/w creams was studied at 4 and 30 °C for various time periods. The average enzyme activity was about 0.0065 U/gcream and 0.018 U/gcream for w/o and o/w creams respectivly. According to the results, the relative activity at 4 °C was reduced to 50% after 26 and 45 days in w/o and o/w creams, respectivly. The results showed that the OPH enzyme activity in o/w cream was 2.6 times more than that of w/o cream, because of the higher hydrophobicity of o/w cream compared to w/o. The OPH enzyme stability in o/w cream was greater in comparison to w/o cream. The OPH enzyme was active for nearly 2 months on o/w creams at 4 °C .