抄録
In the previous paper* we have established that the nutritive value of highly unsaturated fatty acids is not much lower than that of oleic acid, and that long-believed toxicity of highly unsaturated acids is not produced by the acids themselves but actually by formation of autoxidized matters.
The observation led us to an assumption that natural unsaturated fatty cids around C18, even if different in the autoxidation degree, would always become less nutritious by some autoxidation.
The assumption was confirmed by examining the toxic effect on rats of the autoxidized product which was prepared from the ethyl ester of liquid acids of linseed oil, as the rats were all died in a few days after the feeding.
On the basis of these findings our efforts have been extended to throwing light on the structure of the toxic product of the above description. The methods used for and the result obtained from the present test are as follows:
(1) The autoxidized products were prepared by leaving the original ethyl ester of liquid acids of linseed oil, about 3mm. deep in basin, open to atmospheric oxygen under 30°C, 50 hours.
(2) As shown in Table 1, the autoxidized products are fractionated by urea adduct formation, and the nutritive or retarding effects of each fractions are examined.
(3) Fraction 1 separated from the autoxidized products (consist mainly of un-autoxidized esters) does not give any retarding actions to the rats, however, fraction 2 and 3 which do not form urea adducts show the toxic effects on the animals (Table 5). From these results it is apparent that aldehydes have no harmful effect upon the rats.
(4) On the other hand, , polymerized highly unsaturated fatty acids which contain small proportion of peroxide show the nutritive effects to the rats (Table 6) and no retarding effects are noticed.
(5) Judging from these results, the toxic effects which yield from the autoxidized acids should certainly be attributable mainly to production of peroxide-structure.
In oder to prove this assumption, we liberated the peroxide of autoxidized products by Lea's peroxide-determination method. 11) In consequence, peroxide liberated products became “not-toxic” (Table7).
On the basis of this result we have come to conclusion that the most toxic structure in autoxidized unsaturated fatty acids is peroxide which has been produced at the beginning of autoxidatron.
* Bull. Jap. Soc. Sci. Fisheries Vol. 19, 171 (1953)
