Absorption spectra in relation to the constituents of fish oils

Abstract

Vitamins A and D, ergosterol, and a carotenoid pigment are the only non-saponifiable constituents of fish oils which show appreciable selective absorption, and of these only vitamin A, and" occasionally the pigment, can be detected spectrographically in solns. of the oils. Most naturally occurring glycerides, animal and vegetable, saturated and unsaturated, are relatively diactinic, but the acids derived from them by prolonged saponification (cf. Gil-lam, Heilbron, Hilditch and Morton, (1931) Biochem. J., 25, 30), or slowly and spontaneously, without hydrolysis, especially in fish-liver oils, often show highly selective absorption, with narrow bands near (235, 259), 270, 282, 290 (inflexion), 301.5, 316.5, 332, 348, 360 (infl.), 377, 401, (422, 445, 460) m[mu], the figures in parentheses being not always strictly reproducible. The bands owe their origin to unsaturation, but the hypothesis that they are straight chain acids is not in harmony with the evidence. Cyclization to form polycyclic hydroaromatic bodies is the most plausible explanation of the change.