| Abstract
| - During recent years, intensive use of herbicides hasraised increasing concern mainly due to their massivepollution of the environment. As these herbicides are directlyor indirectly toxic to a wide range of organisms, theirpotential for contaminating soil, surface water, andgroundwater makes these xenobiotics of special interestfrom a health and environmental point of view. Knowledgeof the mechanisms by which they exert their toxiceffects is becoming a need. Because of the herbicides'lipophilicity, a possible site of interaction in the cell isrepresented by biomembranes. The interaction of fourherbicides, difenoxuron, diuron, linuron, and metoxuron,with model membranes constituted of dimyristoylphosphatidylcholine multilamellar vesicles was investigated by thedifferential scanning calorimetry technique. The aim was tostudy the effects exerted by an increasing amount of theexamined compounds on thermotropic behavior of the modelphospholipid membranes and to correlate the obtainedresults with structural features of the herbicides due to theirenvironmental mobility. Among the herbicides studied,linuron is the most effective in perturbing the ordinatestructure of vesicles forming phospholipids, whereasmetoxuron is the least effective and the others exert anintermediate effect. Linuron exerts its effect both on thetransition temperature of the gel to the liquid crystallinephase and on the enthalpy change. Difenoxuron, diuron,and metoxuron cause a change in the transition temperaturebut have an insignificant effect on the enthalpy change.The calorimetric results, correlated with the structural featuresof the herbicides, are consistent with their partitioncoefficient, log Kow, suggesting that the more hydrophobiccompound character causes a greater liposolubility andconsequential cellular absorption with more effectivenesson the membrane order.
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