| Abstract: | In extracts of senescent leaves of spinach (Spinacia oleracea) that had degreened naturally after the onset of flowering, four colorless compounds, which had characteristic UV/VIS properties of nonfluorescent chlorophyll catabolites (NCCs), were detected by HPLC. From the extracts of 58.7 g of senescent leaves of Sp. oleracea, a two‐stage HPLC purification procedure provided ca. 15 μmol of So‐NCC‐2, the most abundant polar NCC in the leaves of this vegetable. So‐NCC‐2 was isolated as a slightly yellow powder and analyzed by spectroscopic means. The high‐resolution mass spectra indicated that So‐NCC‐2 has the same molecular formula as Hv‐NCC‐1 from barley (Hordeum vulgare), the first non‐green chlorophyll catabolite from a higher plant to be structurally analyzed. Homo‐ and hetero‐nuclear NMR spectroscopy indicated So‐NCC‐2 to have the same constitution as its epimer Hv‐NCC‐1, and to differ from the latter by the configuration at C(1). The catabolite from spinach could be identified with one of the products from OsO4 dihydroxylation at the vinyl group of the main NCC from Cercidiphyllum japonicum. Chlorophyll breakdown in spinach and in C. japonicum apparently involves an enzyme‐catalyzed reduction that occurs with the same stereochemical sense at C(1), but opposite to that in barley. |
