Podocarpus macrophyllus D. DON (Podocarpaceae) (Japanese name: Inumaki) is a dioecious evergreen tree distributed in the subtropical areas of south eastern China, Taiwan, and Japan. From this plant, flavonoids, bisflavonoids, norditerpenoids, and ecdysons have been obtained. [1][2][3][4] In our recent study, several bisnor-and norditerpenoids having potent cytotoxic activities against P388 murine leukemia cells were isolated and their structures were determined. [5][6][7] In the present study, from the root and bark of this plant, we isolated fourteen new bisnor-and norditerpenoides, makilactones E-R, along with thirteen known ones. This paper describes the isolation and structural elucidation of those new bisnor-and norditerpenoides, revision of the structures of two of the thirteen known ones isolated and their cytotoxic activities.
Results and DiscussionDried root of Podocarpus macrophyllus D. DON (22.66 kg) was extracted with MeOH (45 lϫ3) at room temperature. The combined MeOH extract was concentrated and the residue (614 g) was subjected to Diaion ® HP-20 resin column chromatography (10 cmϫ40 cm) eluting sequentially with [ (18) Table 2, the 13 C-NMR spectrum of 1 was very similar to that of nagilactone G (17), a known norditerpenoid also isolated from the bark of this plant, excepting for the signals due to the C-14 side chain and C-1, C-2, and C-3 of ring A substructures. Two of the three methyl carbon signals at d C 22.3 and d C 26.1 correlating with the singlet proton signals at d H 1.64 and 2.00, respectively, in the heteronuclear multiple quantum correlation (HMQC) spectrum, were assigned to C-18 and C-20, respectively. The other methyl carbon signal (d C 21.0) correlating with the doublet methyl signal at d H 1.57 was assigned to C-17 of the side chain in the HMQC spectrum. The proton signal of Me-20 (d H 2.00) correlated with C-1 (d C 63.6) and that of Me-18 (d H 1.64) with C-3 (d C 71.4) in heteronuclear multiple bond connectivity (HMBC). In the nuclear Overhauser effect spectroscopy (NOESY) spectrum, the proton signal of Me-20 (d H 2.00) correlated with H-7 (d H 5.18). These observations showed that when C-14 side chain is removed, 1 had the same carbon skeleton structure as 17 8) (hereafter, this basic carbon skeleton structure is referred to as "desisopropylnagilactone G unit"). The 13 C-NMR spectrum showed that none of C-1, C-2 and C-3 was methylene carbon. In the correlation spectroscopy (COSY) spectrum, the proton signals H- Fourteen new bisnor-and norditerpene dilactones, makilactones E-R, having a 7a a : 8a a-epoxy-9,11-enolide substructure, were isolated from a methanolic extract of the root and the bark of Podocarpus macrophyllus D. DON (Podocarpaceae) with thirteen known bisnor-and norditerpenoids, and the structures of those new bisnorand norditerpenoids were determined on the basis of their spectroscopic studies. Of the thirteen known ones isolated, the structures of two, i.e., podolactone B and inumakilactone B, were revised on the basis of X-ray crystallographic analysis and spectro...
