Alkaloids from Annona dioica

Article J. Braz. Chem. Soc., Vol. 14, No. 3, 396-400, 2003. Printed in Brazil - ©2003 Sociedade Brasileira de Química 0103 - 5053 $6.00+0.00 Alkaloids from Annona dioica a a Paulo R. D. dos Santos , Anselmo A. Morais and Raimundo Braz-Filho b a Curso de Pós-graduação em Química Orgânica, Departamento de Química, ICE, UFRRJ, 23851-970 Seropédica - RJ, Brazil b Setor de Química de Produtos Naturais, LCQUI, CCT, Universidade Estadual do Norte Fluminense, 28015-620 Campos - RJ, Brazil Do extrato etanólico da madeira de Annona dióica foram isoladas as conhecidas 1-aza-4metilantraquinona, lasiodiplodina, liriodenina, uma mistura de 1-aza-5,9,10-trimetoxi-4-metil-2-oxo1,2-diidroantraceno e 1-aza-8,9,10-trimetoxi-4-metil-2-oxo-1,2-diidroantraceno (geovanina) e o novo alcalóide 1,2-metilenodioxi-6α,7-desidroaporfina-4(S)-(4-hidroxi-3,5-dimetoxifenil)-3,4-diidro2(1H)-piridinona. As estruturas destes produtos naturais foram elucidadas com base em seus dados espectrais, inclusive experiências de NOE e espectros de RMN 2D de correlação homonuclear 1H1 H-COSY e heteronuclear 1H-13C-COSY-nJCH (HMQC, n=1 e HMBC, n=2 e 3). From the ethanolic extract of the wood of Annona dioica were isolated the known 1-aza-4methylanthraquinone, lasiodiplodin, liriodenine, a mixture of 1-aza-5,9,10-trimethoxy-4-methyl-2oxo-1,2-dihydroanthracene and 1-aza-8,9,10-trimethoxy-4-methyl-2-oxo-1,2-dihydroanthracene (geovanine) and the new alkaloid 1,2-methylenedioxy-6α,7-dehydroaporphine-4(S)-(4-hydroxy3,5-dimethoxyphenyl)-3,4-dihydro-2(1H)-pyridinone. The structures of these natural products were elucidated on the basis of their spectral data, including NOE experiments and homonuclear 1H-1HCOSY e heteronuclear 1H-13C-COSY-nJCH (HMQC, n=1 and HMBC, n=2 and 3) 2D-shift-correlated NMR spectra. Keywords: Annona dioica, Annonaceae, quinoline alkaloids, lignoaporphine, lasiodiplodin Introduction Annona dioica, Annonaceae, is a shrub distributed throughout the States of São Paulo, Minas Gerais, Paraná and Mato Grosso, Brazil, commonly called “ceraticum (do campo, or grande)”, “arixicum” and “ariticum”. The fruits and leaves are used against rheumatism and the seeds to heal diarrhea.1 This paper reports the isolation of the known 1-aza-4methylanthraquinone (1), lasiodiplodin (2), liriodenine (3), along with a mixture of 1-aza-8,9,10-trimethoxy-4methyl-2-oxo-1,2-dihydroanthracene (4, geovanine) and 1-aza-5,9,10-trimethoxy-4-methyl-2-oxo-1,2-dihydroanthracene (5), and the new alkaloid 1,2-methylenedioxy6α,7-dehydroaporphine-4(S)-(4-hydroxy-3,5-dimethoxyphenyl)-3,4-dihydro-2(1H)-pyridinone (6). The structures were established by spectral analysis, mainly 1H and 13C * e-mail: NMR including homonuclear 2D 1 H- 1H-COSY and heteronuclear 2D 1H-13C-COSY-nJCH (HMQC, n=1 and HMBC, n=2 and 3) and NOE experiments. To the best of our knowledge, the compound 6 is hitherto unreported in the literature. Results and Discussion Comparative analysis of HBBD- and DEPT-13C NMR spectra of each natural product (1 to 6) was used to identify signals corresponding to quaternary, methine, methylene and methyl carbon atoms. Compound 1 was previously isolated from Cleistopholis patens,2,3 2 from Lasiodiplodia theobromae 4 and Euphorbia splendens, 5 3 from Atherosperma moschatum, Liriodendron tulipifera,6 Fusea longifolia, Siparuna guianensis,7 Thalictrum sessile8 and many other plants species, and 4 (geovanine) from Annona ambotay.9 The structural identification of these compounds was based on their spectral data, including homonuclear 2D 1H-1H-COSY and heteronuclear 2D 13C-1H-COSY-nJCH Vol. 14, No. 3, 2003 Alkaloids from Annona dioica (n=1; n=2 and 3, COLOC) experiments and differential NOE data, together with comparison with literature values of 1H and 13C NMR (vide supra). The mixture of 4 and 5 showed IR absorption for conjugated carbonyl function (νmax 1650 cm-1) and aromatic ring (νmax 1560 and 1520 cm-1). The multiplicity of each carbon signal of the two components 4 and 5 was deduced by comparative analysis of the HBBD- and DEPT-13C NMR spectra (Table 1). This analysis in combination with GCEIMS {Rt=2.41min (40%): m/z 299 ([M]+ of 5, 65%; Rt=3.08 min (60%): m/z 299 ([M]+ of 4, 63%)} and 1D 1H and 2D 1H-1H-COSY NMR spectra (Table 1) allowed the deduction of the same molecular formula C17H17NO4 for 4 and 5. Comparison of 1H NMR spectral data of 4 and of geovanine (isolated from Annona ambotay9) was used to characterize it as the same compound (Table 1) and consequently to establish the structure of 4 as 1-aza-8,9,10trimethoxy-4-methyl-2-oxo-1,2-dihydroanthracene. This structure was confirmed by NOE difference experiments performed with irradiation at MeO-10 (δH 3.90) which Table 1. 1H (200 MHz) and 13C (50 MHz) NMR for 4, in CDCl3 and TMS as internal standard, compared with geovanine in CDCl 3. 9 Chemical shifts in δ (δH and δC) and coupling constants (J, in parenthesis) 13 4a C-1H-COSY-1JCH δC Geovanine (4) 9 δH C 2 4 4a 8 8a 9 9a 10 10a δH - 161.82 148.48 114.27 155.27 117.25 151.08 129.02 136.53 126.85 - - 123.36 115.87 124.68 106.79 6.45 (s) 7.75 (d, 8.8) 7.32 (t, 8.8) 6.88 (d, 8.8) 6.48 (s) 7.77 (d, 8.0) 7.35 (t, 8.0) 6.91 (d, 8.0) 23.22 56.16 62.70 62.70 2.75 (s) 4.02 (s) 3.88 (s) 3.90 (s) 2.78 (s) 4.04 (s) 3.93 (s) 3.91 (s) CH 3 5 6 7 CH 3 Me-4 MeO-8 MeO-9 MeO-10 a Number of hydrogen bound to carbon atoms deduced by comparative analysis of HBBD- and DEPT- 13C NMR spectra. Homonuclear 2D 1 H- 1H-COSY spectrum and { 1H}- 1H-NOE difference spectra were also used in these assignments. Chemical shifts (δH) and coupling constants (J) of hydrogen atoms deduced from 1D 1 H NMR spectrum. 397 resulted in signal enhancements at δH 2.75 (Me-4) and 7.75 (H-5) and irradiation at MeO-8 (δH 4.02) which showed NOE at δH 6.88 (H-7). The remaining signals observed in the 1H (δH 7.82, t, J 8.2 Hz, H-7, position conjugated with carbonyl group; partial superimposition with signal at 7.75 of the H-5 of 4), 6.59 (s, H-3), 2.65 (s, Me-4), 4.04 (s, MeO)] and 13C (δC 63.79, MeO)] NMR and GC/MS (vide supra) spectra were speculatively used to propose the structure 5 (1-aza-5,9,10-trimethoxy-4-methyl-2-oxo-1,2-dihydroanthracene) for the other component present in the mixture, probably a new alkaloid. The lignoaporphine alkaloid 6 showed IR absorption bands for a carbonyl group (ν max 1660 cm -1) and for aromatic ring (νmax 1630, 1610, 1520 and 1500 cm-1). The number of hydrogen atoms bound to each carbon atom was deduced by comparative analysis of the HBBD - (25 signals corresponding to 28 carbon atoms) and DEPT13 CNMR (Table 2) in combination with 1H NMR spectral data (1D and 2D 1H-1H-COSY) and low resolution mass spectrum (m/z 469 [M]+, 100%, C28H23NO6), allowing to establish the formula (C)13(C=O)(CH)8(CH2)3(OCH2O) (MeO)2(OH)= C28H23O6 (455 daltons) + N = C28H23NO6 (m/z 469, [M]+). This molecular formula is compatible with an aporphine skeleton (C16H9N) sustaining one methylenedioxy group and one 4’-hydroxy-3’,5’-dimet (...truncated)