Studies on the Constituents of Pueraria lobata. V.1) A Tryptophan Derivative from Puerariae Flos

Puerariae Flos, the flowers of Pueraria. lobata (WILLD.) OHWI, is an important oriental crude drug used to ameliorate crapulence. In the preceding paper,' we described two triterpenoidal glycosides of the sophoradiol glucuronides, along with the known six aromatic compounds, kakkalide, daidzin, genistin, rutin, robinin and nicotiflorin. This paper further deals with a tryptophan derivative, tentatively named PF-P, obtained from this plant. PF-P (1), an amorphous powder, [ƒ¿]D + 19.7•‹ (dimethyl sulfoxide (DMSO)), was isolated by MCI-gel CHP 20P (solvent, H2O-Me0H) and silica gel (solvent, CHCl3 : MeOH : H2O = 7 : 3 : 0.5) column chromatographies of the aqueous layer. PF-P (1), C23H32N2O8¥2H2CO3, showed absorptions due to ƒËOH (3400 cm -1) and ƒËC = O and ƒÂN-H (1640-1580 cm-1) in the infrared (IR) spectrum, and gave a characteristic ultraviolet (UV) curve (E 25800 at 223 nm, E 5500 at 273, c 5400 at 279 and E 4300 at 290) due to an indole skeleton. It was negative to the Dragendorff, ninhydrin and diazobenzidine color reactions. Negative fast atom bombardment mass spectrometry (FAB-MS) of 1 gave a cluster ion (M H) at m/z 463. The 1H-1H and 1H-13C correlation spectroscopy (COSY) nuclear magnetic resonance (NMR) spectra (Figs. 1 and 2) of 1 disclosed that 1 was constituted of the following three partial structures: a caproic acid moiety, 1H-NMR (DMSO-d6+D2O): ƒÂ2.00 (2H, t, J=7 .7 Hz, H-2"), 1.42 (2H, quintet, J=7 .1 Hz, H-3"), 1.18 (2H, m, H-4"), 1,23 (2H, m, H-5"), 0.83 (3H, t, J=7.0 Hz, H-6"); 13C-NMR (DMSO-d6): ƒÂ171.2 (s, C-1"), 35.5 (t, C2"), 24.8 (t, C-3"), 30.9 (t, C-4"), 21.8 (t, C-5"), 13.7 (q, C-6"), an ƒÀ-D-glucopyranosyl moiety, 'H-NMR: 65.35 (1H, d, J=9.2 Hz, H-1'), 3.78 (1H, t, J=9.0 Hz, H-2'), 3.42-3.48