,5-Dicarbonyl derivatives of 2, can reduce Fe J" to Fe 2 depending o11 the nature of the substituents at position 4 and in the 3, 5-ester group. This ability is less pronounced for the 1,4-DHP derivatives investigated than for ascorbic acid, but among derivatives possessing antioxidant activity it is less than that of the known antioxidants ionol (BOT) and trolox.Iron ions are initiators and accelerators of the peroxide oxidation of lipids [1,2], including fats and oils [3], and also of the degradation of biosubstrates [4]. Antioxidants, natural and synthetic, inhibit these processes, however a large majority of them are also good reducing agents. For successful use of antioxidants it is necessary to know their undesirable ability to reduce ions of trivalent iron, which affect peroxide oxidation less actively, to the significantly more active divalent state, i.e. weaker reducing agents in relation to ions with variable valency are the better antioxidants.Derivatives of 1,4-dihydropyridine (1,4-DHP) of the type of I, particularly those unsubstituted at position 4, are good hydrogen donors [5], antioxidants [6,7] and are synergists of natural antioxidants [8,9]. The present report is devoted to a study of the ability of compounds Ia-e, possessing antioxidant activity, including the physiologically active derivative of 1,4-dihydroisonicotinic acid (Id), to reduce ions of Fe 3+ to Fe 2 § The known cardiovascular preparation nifedipine (If) and the synthetic antioxidants ionol (BOT) and trolox were also investigated for comparison.The formation of the complex with 1,10-phenanthroline, which has a characteristic absorption maximum at 520 nm, was used to determine the presence of the Fe 2 § [10].The results obtained, given in Table 1, show that the 1,4-DHP derivatives investigated, with the exception of nifedipine, can to some extent reduce Fe 3+ to Fe 2 § This ability is significantly less for the studied compounds than for the natural reducing agent ascorbic acid which reacts very rapidly. For the latter the optical density reaches a value of 2.0 arbitrary units a few seconds after mixing the reactants.