Phenanthrene derivatives from the stems and leaves of Dioscorea nipponica Makino

From the CHCl3-soluble portion of the 70% EtOH extract of the stems and leaves of Dioscorea nipponica Makino, two new phenanthrenes, 7-hydroxy-2,3,5-trimethoxy-9,10-dihydrophenanthrene (1) and 2,2',7,7'-tetrahydroxy-4,4',6,6'-tetramethoxy-1,1'-biphenanthrenes (2), as well as three known phenanthrenes, 6-methoxycoelonin (3), 4,7-dihydroxy-2,3,6-trimethoxyphenanthrene (4), and 3,7-dihydroxy-2,4,6-trimethoxyphenanthrene (5), were isolated. The structures were determined by means of HR-MS, 1H NMR, 13C NMR, and HMBC experiments.