Methyl Proline in Young Apple Fruits

Abstract

IT was recently suggested that a ‘new’ amino-acid isolated from the apple fruit was a methyl proline¹. This acid (called D ₁ in the original communication) has now been compared with an authentic specimen of γ-methyl proline kindly supplied by Prof. F. C. Steward, of Cornell University. The positions occupied by these two acids on two-dimensional chromatograms (phenol ammonia–butanol–acetic acid–water) were found to be identical. Mr. J. K. Pollard in Prof. Steward's laboratory has also found the two compounds to superimpose on collidine–lutidine: phenol chromatograms. The two compounds (D ₁ and γ-methyl proline) give identical colour reactions on paper chromatograms with ninhydrin (a yellow-orange colour) and with isatin (a pure blue colour developing at the same rate with both acids). Not more than ∼ 17 mgm. of D ₁ were obtained from 70 kgm. of young Worcester Pearmain apples, and elementary analysis on a sample containing traces of inorganic salt gave the following: C, 53.6 per cent; H, 8.17 per cent ; N, 9.7 per cent. Assuming this indicates a C₆ compound with an empirical formula of C₆H₁₁O₂N, and correcting the analyses for ash gives: C, 55.8; H, 8.5; N, 10.1; methyl proline requires : C, 55.8; H, 8.5; N, 10.8 per cent.