Chlorophyll breakdown - On a nonfluorescent chlorophyll catabolite from spinach

In extracts of senescent leaves of spinach (Spinacia oleracea) that had deg reened naturally after the onset of flowering. four colorless compounds. wh ich had characteristic UV/VIS properties of nonfluorescent chlorophyll cata bolites (NCCs). were detected by HPLC. From the extracts of 58.7 g of senes cent leaves of Sp, oleracea, a two-stage HPLC purification procedure provid ed ca. 15 mu mol 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 analy zed 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 v ulgare), the first non-green chlorophyll catabolite from a higher plant to be structurally analyzed. Homo- and hetero-nuclear NMR spectroscopy indicat ed So-NCC-2 to have the same constitution as its epimer Hv-NCC-1, and to di ffer from the latter by the configuration at C(1). The catabolite from spin ach could be identified with one of the products from OsO4 dihydroxylation at the vinyl group of the main NCC from Cercidiphyllum japonicum. Chlorophy ll breakdown in spinach and in C japonicum apparently involves an enzyme-ca talyzed reduction that occurs with the same stereochemical sense at C(1), b ut opposite to that in barley.