The nature of the vitamin A constituent of green leaves

Abstract

The vitamin A activity of the unsaponifiable fraction from white cabbage is very small though definite compared with that derived from green leaves. The respective minimal doses are about 10 and 0.25 mgm. The vitamin A substance of green spinach and cabbage leaves and of carrots is contained in the most highly unsaturated fraction of the unsaponifiable matter and, as far as the process of purification here employed extends, remains associated with the carotene crystals. These crystals from cabbage softened at 174[degree] and melted at 178[degree], those from spinach at 163-4[degree] and from carrots at 164-9[degree]. The vitamin A activity is certainly not diminished in the specimen of higher melting point and therefore of presumably greater purity; in this specimen the active dose lies between 0.002 and 0.005 mgm. No claim is made for great purity of the specimens of carotene, since the work was carried out on too small a scale to admit of sufficient recrystallizations to ensure the separation of all impurities. It is possible that the crystals of carotene may themselves be homogeneous and active or that they may (consist of 2 or more closely related substances only 1 of which possesses vitamin A activity.