35 ナデシコ科Pseudostellaria及びStellaria属植物に含有される新規環状ペプチドに関する研究(口頭発表の部)

抄録

On the basis of the existence of many naturally occurring cyclic peptides with unique structures and biological activities, we have focused our attention on various cyclic peptides, such as RA and Astin series, with antitumor activities, from higher plants. Despite their importance, surprisingly few studies of higher plants occurring cyclic peptides exist in the literature. As a part of our continuing studies in search of new bioactive cyclic peptides from higher plants, we have isolated 16 novel cyclic peptides, named pseudostellarins A-H (1-8), from the roots of Pseudostellaria heterophylla, named dichotomin A-E (9-13), from the roots of Stellaria dichotoma L. var. lanceolata Bge., and named yunnanins A-C (14-16), from the roots of Stellaria yunnanensis, all of them belonging to Caryophyllaceae family. Some of them showed tyrosinase inhibitory and cell growth inhibitory activities. These structures were elucidated by extensive 2D NMR such as COSY, HOHAHA, HMBC, HMQC, phase sensitive NOESY and ROESY spectra, chemical degradation and ESI MS/MS methods. Synthetic and naturally occurring cyclic peptides have been the subject of many conformational studies with the cyclic pentapeptides, hexapeptides and octapeptides, receiving the most attention. However there have been no systematic examinations of cyclic heptapeptides. In order to determine the importance of the specific functional groups for the overall conformation of cyclic heptapeptides, and in an attempt to understand the relationships between chemical composition and three-dimensional structure, conformational analyses of cyclic heptapeptides, pseudostellarin D (4), yunnanins A and C (14 and 16) using X-ray crystallography, high field NMR and MD calculations were undertaken. The dominant solution conformations of 4, 14 and 16 analyzed by high field NMR and MD calculations employing distance constraints were, on the whole, homologous to thoes observed in the solid state.