Das cascas do tronco e das folhas do Hymenodictyon floribundum B. L. Rob foram isolados dois novos iridoides, floribundano A (1) e floribundano B (2), e três compostos conhecidos, lupenona (3), escopoletina (4) e 4,5-di-hidroblumenol A (5). As estruturas de todos os compostos foram estabelecidas com base nos seus dados espectroscópicos.Two new iridoids floribundane A (1) and floribundane B (2) and the known compounds lupenone (3), scopoletin (4) and 4,5-dihydroblumenol A (5) were isolated from trunk bark and leaves of Hymenodictyon floribundum B.L. Rob. The structures of all compounds were established from their spectroscopic data.
Keywords: Hymenodictyon floribundum, monoterpenes, secoiridoids, nitrogen-containing iridoid, C-9 iridoid
IntroductionThe Hymenodictyon genus comprises 22 species. Of these, 11 are endemic to Madagascar, 4 to Asia and 7 to Tropical Africa. 1 Hymenodictyon floribundum B.L. Rob. (Rubiaceae), endemic to Tropical Africa, is a small tree that grows in the mountains of the Huíla province and its traditional name is NDambi Yov`olwi, (omu)Lia-tyimeme. Its trunk bark is used in Angola folk medicine to treat fever. 2 A previous study has shown that the trunk bark of this tree contains scopoletin, hymeselsin, scopolin and 3-O-β-D-glucopyranosyl-β-sitosterol. 3 An exhaustive literature review revealed that, with the exception of an ongoing study examining the trunk bark and dried leaves of Hymendictyon floribundum (in the context of other medicinal plants of Angola), 4 other parts of the tree have not yet to be studied.In the aforementioned study, powdered trunk barks and dried leaves were extracted by maceration with methanol. The methanol extract was partitioned with hexane and chloroform. The hexane extract from trunk barks yielded lupenone (3) 5 and the chloroform extract yielded scopoletin (4). 6 The chloroform extract from dried leaves yielded floribundane A (1), 4,5-dihydroblumenol A (5) 7,8 and floribundane B (2).
Results and DiscussionFloribundane A (1) was obtained as a colourless oil with [α] 2 D 0 = +25.31º. The HR-TOF-EI-MS showed a molecular ion peak at m/z 223.0843 [M] + (in agreement with the molecular formula C 11 H 13 NO 4 ) implying 6 degrees of unsaturation. The UV maximum at 234 nm and the IR absorptions at 1724, 1633 and 1268 cm -1 suggested the presence of the chromophore -OOCC=CHO. 9 The IR also showed the presence of a lactam ring: NH band (3403 cm -1 ), and the amide band I (1690 cm -1 ) with an absence of the amide II band. 10 The 1 H NMR spectrum of compound (1) ( 16 and rat intestinal bacteria. 17 Comparison with the published data of known iridoid alkaloids, such as (6) (Figure 1), and hemiacetal-secoiridoids 11,18 like (7) ( Figure 1) and compound (1) 11,18 showed that (1) it was neither a hemiacetal nor a nitrogen-containing iridoid (N-2) but that it was compatible with a C-1(N)O-2 substitution. This was also supported by the presence of the 1 H-1 H COSY correlation between H-1/NH, rather than the H-1/NH, H-3/NH correlations expected in the iridoid alkaloids, 17 ...
