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Toxic Oil Syndrome (TOS) was an epidemic disease related to the consumption of rapeseed oil denatured with aniline that made its sudden appearance in Spain in 1981. The fatty acid esters of 3-(N-phenylamino)-1,2-propanediol (PAP), which is a chemical class of by-products resulting from the reaction of aniline with oil components, have shown a strong association with TOS-related oils. These compounds also show some structural similarities to platelet-activating factor (PAF). In search of a toxic agent that could explain the widespread systemic effects observed in TOS patients, we investigated the intestinal absorption and biotransformation of the different PAP esters found in TOS-related oil samples and the possible pathophysiological effect of these mediators and their metabolic products if acting as PAF analogs. Results indicate that PAP esters are absorbed in the gastrointestinal tract and are distributed and stored in different organs, particularly in the liver and brown adipose tissue. PAP in these organs showed different patterns of fatty acids, indicating the ability of the gastrointestinal tract to modify the fatty acid composition of the parent PAP. Thus, the fatty acid profile of the PAP esters found in intestine appears to be related to the type of oil used as vehicle. Some of these PAP esters, when a long acyl chain was present in the sn-1 position of the molecule, showed an inhibitory effect on the PAF synthesis. This is an important observation in line with the systemic nature of the disease.

In 1981, an unknown disease appeared in Spain, the Spanish Toxic Oil Syndrome. Nowadays and despite all efforts, the etiological agent is still unknown. Early studies showed a link between this illness and the consumption of denatured rapeseed oil fraudulently processed and marketed as edible oil. Two families of aniline derivatives present in these oils (fatty acid anilides and acylated phenyl amino propanediol derivatives or PAPs) were found to be good chemical markers of toxic oils. In this work, a new method has been developed to analyze these aniline derivatives in oil samples by HPLC-MS and HPLC-MS/MS with an API source. For their quantification, three different internal standards were used, one for anilides and two for PAPs. Quantification limits were 8 ppm for anilides and 0.2 ppm for PAPs. Anilides and PAPs were found in marker-positive samples at levels up to 50,000 and 330 ppm, respectively. The relative abundance of the different fatty acid anilides and PAPs correlates with the fatty acid composition of the oils. More than 2,600 different samples were analyzed by this method in the most exhaustive screening of suspected toxic oils carried out to date.

In 1981 an epidemic, named Toxic Oil Syndrome, occurred in Spain as a result of ingestion of rapeseed oil denatured with 2% aniline, which had been imported for industrial use but was fraudulently diverted and processed for human consumption. Two groups of chemical compounds have been identified in the ingested toxic oil: fatty acid anilides and amino-propanediol derivatives. The objective of this work was to assess the effect of several refining process variables on the formation of 3-(N-phenylamino)-1,2-propanediol (PAP) esters. The amount of PAP esters in aniline-denatured oil increased dramatically when oil was heated from 250 degrees C to 300 degrees C. However, the ones formed when 300 degrees C was reached were lost during processing at that temperature. The level maintained during the operation time at 300 degrees C was higher in denatured samples stored for 3 weeks before refining than in denatured samples stored only for 1 week. Anilides were also analyzed. We found that anilides decreased very little with distillation time. In this paper we discuss the influence of storage time prior to refining and of elevated refining temperature, such as temperatures that might occur in close proximity to a deodorizer coil.