The nature of the vitamin A constituent of green leaves

IN spite of the fact that green leaves form one of the most potent sources of vitamin A, comparatively little work has been done on the isolation of the active substance from these leaves. The material from an ethereal extract of spinach or other green leaves has been added to a synthetic diet in order to supply vitamin A by various observers, amongst them Osborne and Mendel [1919,1, 2] and Willimott and Wokes [1927]. In some experiments which were being carried out by E. M. Hume and H. H. Smith, the unsaponifiable matter from which the sterol had been separated was used to supply the vitamin A constituent of the diet, and it seemed desirable to obtain as much knowledge as possible about the nature of the extract used.