The effect of alkaline hydrolysis of maize on the availability of its nicotinic acid to the pig.

The connexion between pellagra and maize consumption has occupied the interest of many workers for a number of years. It has been suggested that maize owes its pellagragenic property to an imbalance of amino-acids, tryptophan being especially low. This imbalance was said to increase the need for nicotinic acid (Krehl, Henderson, de la Huerga & Elvehjem, 1946; Krehl, 1949). The presence of a ‘toxic’ factor in maize has also been postulated (Woolley, 1946 ; Borrow, Fowden, Stedman, Waterlow & Webb, 1948). Though this postulate cannot be entirely disregarded, it has not received experimental support in recent years. It is the purpose of this paper to present further evidence for another factor that may contribute to the pellagragenic property of maize, namely the unavailability of the nicotinic acid present in the cereal in ‘bound’ form. The observation that ‘an unknown substance is present in cereals, giving the CNBr-p-aminoacetophenone reaction and which is more strongly bound than free nicotinic acid and liberated only after hydrolysis with NaOH’ (Kodicek, 1940) has been confirmed by a number of workers (see review by Kodicek, 195 I a) . This ‘bound’ form of nicotinic acid is only partly available to Lactobacillus arabinosus and Lactobacillus casei (Krehl & Strong, 1944; Kodicek & Pepper, 1948; Clegg, Kodicek & Mistry, 1952). Microbiological and chemical evidence indicates that almost all the nicotinic acid in cereals, such as maize, wheat, barley, rye and rice, is present in this alkali-labile, ‘bound’ form, that differs from the known nicotinoyl derivatives (see Kodicek, I 95 I a). This ‘bound’ form of nicotinic acid does not appear to serve as a source of the vitamin for the nicotinic acid-deficient rat (Chaudhuri & Kodicek, 1950a; Kodicek, 1951b), chick (Krehl, Elvehjem & Strong, 1944; Coates, Ford, Harrison, Kon, Shepheard & Wilby, 1952) and duck (Heuser & Scott, 1953). Experiments with pigs, in which a deficiency of nicotinic acid was produced on diets containing a large proportion of maize (Birch, Chick & Martin, 1937; Chick, Macrae, Martin & Martin, 1938a, b ; Braude, Kon & White, 1946) suggest, by implication, that the ‘bound’ form is equally unavailable to the pig. On the other hand, dogs seemed to utilize a charcoal adsorbate of a partly purified preparation from wheat bran (Krehl et al. 1944). There is no direct evidence about the availability to man of the ‘bound’ form. Holman (1954)