Coumarins and Alkaloids from the Stems of Metrodorea Flavida

In a previous paper, we reported the characterization of a new coumarin, 8-(2,3-dihydroxy-3-methylbutyloxy)-6,7methylenedioxycoumarin, together with known furocoumarins and a furofuran lignan, which were isolated from the leaves of Metrodorea flavida. In continuation of our phytochemical studies on the constituents of this species, we report from the stem the isolation and structural elucidation of a new coumarin 5,6-methylenedioxy-7,8-dimethoxycoumarin (1) , in addition to the known compounds: scoparone (2); 6,7-methylenedioxy-8methoxycoumarin (3); xanthotoxin (4); isopimpinellin (5); imperatorin (6); braylin (7); γ-fagarine (8); kokusaginine (9) ; maculin (10); syringic aldehyde (11); rutaecarpine (12); sitosterol and lupeol. All the compounds were isolated by chromatographic techniques. The structural elucidation of these compounds were based on spectrometric data, especially IR, H NMR and C NMR, involving comparison with the literature data.

All the compounds were isolated by chromatographic techniques.The structural elucidation of these compounds were based on spectrometric data, especially IR, 1 H NMR and 13 C NMR, involving comparison with the literature data.

Equipment
Mps uncorr.IR were recorded in KBr discs. 1 H and 13 C-NMR spectra were recorded at 300 and 75 MHz, respectively, in CDCl 3 on a Varian GEMINI 300 instrument and at 400 and 100 MHz, in DMSO, on a Brucker ARX 400 instrument.EIMS were obtained by direct probe insertion at 70 eV.

Plant material
Metrodorea flavida was collected in Paragominas, State of Pará, Brazil, in December 1991.A voucher specimen is deposited at the Herbarium of the CPATU-EM-BRAPA, Belém, Brazil.

Results and Discussion
The new coumarin 1 was obtained from the dichloromethane extract of M. flavida and showed as a blue color on TLC under UV light 336 nm.Its 1 H NMR spectrum exhibited resonances typical of H-3 and H-4 (δ 6.20 and 7.91) of the coumarin nucleus in which C-5 was oxygenated 11 .The presence of a methylenedioxy group was indicated from the methylene hydrogens signal at δ 6.01 (s) and two methoxy groups from the signals at δ 4.04 and 3.99 (s, 3H each one).These groups were located at the positions 5, 6, 7 and 8 suggesting one of the possible structures 1, 1a or 1b.Further information concerning the actual positions of the methoxy groups was obtained by analysis of the 1D-NOE difference spectrum.Irradiation of the signal at δ 7.91 (d, H-4) didn't enhance the signals at δ 4.04 and 3.99 (2x OMe), which confirmed the placement of the methylenedioxy group at C-5/C-6.This result is consistent with the structure 1.The assignments of the signals of carbons 3,4 and -OCH 2 O-moiety in the 13 C-NMR spectrum were established by HETCOR ( 13 C, 1 H-COSY-1 J CH ) spectrum and the attribution of the quaternary carbons was made by COLOC ( 13 C, 1 H-COSY-n J CH , n = 2 and 3) experiment (Table 1).This is the first report of the occurrence of one indolopiridoquinazoline alkaloid (rutaecarpine) from the genus Metrodorea.This fact reinforces the taxonomic position of the Metrodorea flavida into the Cusparieae tribe, due to the occurrence of this type of alkaloid in the tribes Cusparieae and Xanthoxyleae.8a 8

Table 1 .
NMR data for compound 1 (CDCl3, J values, in Hz, are given in parentheses).Hydrogens correlating with carbon resonance.