Cinnapine (1), a new pyridine alkaloid, has been isolated from the roots of Cinnamomum philippinense (Lauraceae). The structure was characterized and identified by spectral analysis.Cinnamomum philippinense (Merr.) C. E. Chang (Lauraceae) is a medium-sized tree distributed widely in the Philippines and the southern part of Taiwan. The chemical constituents of this species have been studied by [1]. In the course of screening for biologically and chemically novel agents from Formosan plants in the family Lauraceae [2-18], C. philippinense was chosen for further phytochemical investigation. Previously, we have isolated a new pyridine alkaloid, 2-(4c-hydroxypyridin3c-yl)-acetic acid, and one amide, one benzylisoquinoline, one isoquinolone, one proaporphine and one aporphine from this plant [19]. In this paper, we report the isolation and structural elucidation of the new alkaloid.Cinnapine (1) was obtained as a white amorphous powder, and its molecular formula was deduced as C 8 H 9 NO 3 by HR-ESI-MS (m/z 191.0556 [M + Na + H] + ; calcd 191.0558). The UV spectrum of 1 showed intense absorption bands at 220, 265, and 280 nm, which were typical of a pyridine skeleton [20]. The IR spectrum of 1 exhibited absorption bands at O 3100 and 1660 cm -1 , indicating hydroxyl and carbonyl groups, respectively. The structure was confirmed from the 1 H NMR spectrum, which contained signals at G 6.37 (1H, d, J = 6.0 Hz, H-5c), 7.74 (1H, d, J = 6.0 Hz, H-6c), and 7.84 (1H, br.d, H-2c) of the pyridine ring; G 3.39 (2H, s, H-2) and 3.72 (3H, s, OMe) of the side chain. The 13 C NMR and DEPT experiments for 1 showed eight resonance lines consisting of one methyl, one methylene, three methines, and three quaternary carbons (including a carbonyl signal at G 170.7). The structure of 1 was also confirmed by 2D NMR experiments. A COSY correlation was observed between H-5c and H-6c (Fig. 1). The HETCOR experiment showed that the carbon signals at G 116.8 for C-5c, 153.8 for C-2c, 155.4 for C-6c, 30.5 for C-2, and 52.3 for OMe were correlated to the proton signals at G 6.37 for H-5c, 7.84 for H-2c, 7.74 for H-6c, 3.39 for H-2, and 3.72 for OMe, respectively. The NOESY correlations between H-5c and H-6c and between H-2c and H-2 established the connective sites as shown in structure 1 (Fig. 1). Thus, 1 is a new pyridine alkaloid, which was further confirmed by an HMBC experiment (Fig. 1). The above results support the structure of 1 as a new pyridine alkaloid, methyl 2-(4c-hydroxypyridin-3c-yl)-acetate, which we name cinnapine. This compound shows the possibility of methylation of the precursor acid [2-(4c-hydroxypyridin-3c-yl)-acetic acid] by MeOH [19].General. IR, Hitachi 260-30 spectrophotometer; 1D and 2D NMR, Varian (Unity Plus) NMR spectrometer; low-resolution ESI-MS, API 3000 (Applied Biosystems); high-resolution ESI-MS, Bruker Daltonics APEX II 30e spectrometer; silica gel 60 for CC and precoated silica gel plates (Merck) were used for TLC, visualized with 10% H 2 SO 4 . Extraction and Isolation. The air-dried roots of C. philippinense (...
