DIOXOAPORPHINE ALKALOID AND FLAVONE from piper manausense YUNK

l,2Methylenedloxy-6-methyl-4H-dibenzo [de,g] quinoline -4,5(6H)-dione together with 5-hydroxy-4',7-dimethoxyflavone; /J-sitosterol, stigmasterol and esters from the lauric and stearic acids, were isolated from the stem of Piper manausense Yunk (Piperaceae). INTRODUCCIÓN Aporphine alkaloids have been studied extenslvely because these compounds are of pharmacological significant importance (1). The presence of these constituents in the Piperaceae family has been reported in Piper longum,P. auritum and P. sanctum (2). In the present study, an investigation of the benzene extract of the stem o^ Piper manausense Yunk (Piperaceae) yielded 1,2-methylenedioxy6-methyl-4H-dibenzo [de, g] quinoline-4,5(6H)-dione (Cepharadione-A) 1, together with 5-hydroxy-4',7-dimethoxyflavone 2, ^sitosterol, stigmasterol and esters from lauric and stearic acids. RESULTS AND DISCUSSION Cepharadione-A 1 was obtained from P. manausense as orange needles. Its EI-MS showed a molecular ion peak at am/z 305 and fragments at m/z 277(IVf-CO) and 249(IVf-2CO). The IR absorption bands at 1660 and 1595 cm-' and the UV (237, REVISTACOLOMBIANADEQUIMICAVOL 19 No. 2 (1990) 63 278, 285 sh, 302, 314 and 432) absorptions are similars to that 4,5-dioxoaphorphines (3). The ^H NMR spectrum revealed the presence of oneN-nethyl and one methylenedioxy group with the singlets at 5 3.85 and 5 6.46 respectively; two singlets ató 8.14 and 67.51 wereattributed tounusually poorly shielded hydrogen atoms placed at C-3 and C-7, respectively; this fact suggested that the B ring of the alkaloid was highiy strained as expected for 4,5-dioxoaporphines (3). The other coupled aromatic protons in 1 cause three groups of PMR bands at 5 8.999.01 (m, H-11), 5 7.90-7.92 (m, H-8) and 5 7.66-7.73 (m, H-9 and H-10). Irradiation experiments of the most downfield aromatic absorption at 6 8.999.01, led to a 2 5 % enhancement of the protón signal at 5 7.51 indicating the transannular coupllng between H-11 and H-7, which confirmed the assignment for 1 (4). Cepharadione-A was previously isolated from Piper longum (2) and P. sanctum (5) in the Piperaceae family. 5-Hydroxy-4',7-d¡methoxyflavone2 is a known constituent of Piper peepuloides Roxb (6). This compound exhibited UV máxima at 328 and 270 nm, and IR absorption bands at 3400 cm-l (OH) and 1630 cm-l(CO). This Information together with a study of its ^H NMR spectrum indicated it to be a flavone. The signal at 5 3.85 was assigned to OMe-7 and OMe-4'. The two doublets (] = 3.0 Hz) at 8 6,36 and 5 6.48 were attributed to H-6 and H-8, respecitvely; the singlet at 5 6.00 corresponds to H-3. The pesence of an AA'BB' system was suggested by the two doublets (J = 8.0 Hz) at 5 7.00 and 5 7.85. This structure was confirmed by comparison with published spectral data (7) and by MS, which exhibited the molecular ion peak at m/z 298 in accord with a flavone containing one hydroxyl and two methoxyl groups. The retro-Diels Alder fragments (m/z 132 and m/z 166) showed the presence of one methoxyl group on B ring.