THE CAROTENOID AND PROVITAMIN A CONTENT OF THE WATERMELON

10 years ago lycopene, C40H56, and carotene, C40H56, were isolated from the pulp of the European watermelon (Citrullus vulgaris, Schrad. = Cucumis citrullus, L.) by Zechmeister and Tuzson (l), and it was shown that the chief pigment, lycopene, is responsible for the red color. As the chromatographic method was not available at that time, no precise information as to the composition of the pigment was obtained. In some new experiments described below we have carried out a quantitative analysis of the components and have estimated the provitamin A content of the California watermelon. 1 kilo of the pulp examined contained 1.0 mg. of a complicated xanthophyll mixture, 6.1 mg. of lycopene, 0.06 mg. of γ-carotene, 0.16 mg. of unknown carotenoids (located in the column between γ- and β-carotene), 0.46 mg. of β-carotene, 0.01 mg. of α-carotene. The figures include the fractions of lycopene, and γ- and β-carotene which underwent isomerization during the experimental procedure (2). \n \nThe calorimetric value of the total extract of 1 kilo of pulp corresponded to 7 to 8 mg. of “lycopene”; some samples were, however, considerably richer in pigment. Our material, picked in California in September, contained, according to the above figures, 0.5 mg. of provitamin A in 1 kilo of pulp, or about one-fifth to one-sixth of the daily β-carotene requirement of an adult person. \n \nIt is interesting to note that a considerable number of yellow and pink unidentified oxygen-containing carotenoids were found in minute quantities; i.e., to the extent of about 0.01 mg. per kilo of pulp. Even with the use of chromatography 1000 or more kilos of melon would be needed for a satisfactory study of these pigments. One of them is spectroscopically identical with torulene, detected by Lederer in red yeast (3).