The genus Newbouldia (Bignioniaceae) comprises only one species distributed throughout the tropical and sub-tropical zones of the world. 1) Newbouldia laevis SEEM. locally called "Oogly C", is a shrub or small tree growing in West and Central Africa (Senegal, Ivory Coast, Gabon and Cameroon, Nigeria etc.). Apart from the economic uses of N. laevis such as fuel wood and as boundary tree, different parts of this plant have been used in African folk medicine as an astringent in diarrhea, dysentery and in the treatment of various diseases such as worms, malaria, sexual transmitted disease, and in the reduction of dental caries.1) Previous studies undertaken on this species have resulted in the isolation of a number of secondary metabolites which belong to the classes of furanonaphthoquinones, pyrazole alkaloids, phenylpropanoid glycosides, and benzofurans.2) The medicinal uses and the presence of different classes of compounds in the title plant, prompted the present investigation on root and seed metabolites. We isolated and characterized two new compounds, namely, newbouldiaquinone (1), a naphthoquinone-anthraquinone coupled pigment, and newbouldiamide (2), a ceramide. The bis-benzoquinones, bis-naphthoquinones and bis-anthraquinones are the most widespread groups of quinone "dimers" found in nature.3,4) By contrast, the mixed naphthoquinone-anthraquinones coupled pigments are less common. There are only three recorded examples of similar systems. In the first two examples, a pyranoanthraquinone-naphthoquinone and an furanoanthraquinonenaphthoquinone dimeric system are present. 5,6) In the third example, anthraquinone and naphthoquinone moieties are linked by a nine-membered lactone ring. 7,8) Thus, the coupled naphthoquinone-anthraquinone system presented here is unique as a natural product. The ceramides containing nonhydroxyl octadecanoic acid as a fatty acid were reported in the literature.9) The presence of the long chain base of twenty-four carbons containing hydroxyl groups at positions 3, 4, 5 make compound 2 unique among ceramides.
Results and DiscussionThe MeOH-CH 2 Cl 2 (1 : 1) extracts of seeds, stem and roots of N. laevis were fractionated by silica gel column chromatography to give 556 fractions, which were further chromatographed on silica gel to give the two new compounds 1 and 2 together with known the constituents lapachol (3), oleanolic acid, b-sitosterol, and b-sitosterol glucopyranoside.Newbouldiaquinone (1) was obtained as a yellow powder. The UV spectrum of 1 exhibited absorption maxima at 275 and 388 nm, suggesting a naphthoquinone derivative.2 , suggesting the presence of hydoxyl, methyl, and carbonyl groups. This fragmentation pattern is typical for hydroxyanthraquinones and/or naphthoquinones. 5,10) Preliminary inspection of the 1 H-NMR spectrum of newbouldiaquinone (1) showed one singlet at d 2.50 which was in a strongly deshielded environment, characteristic for attachment to an aromatic system.5) The 1 H-NMR spectrum in CDCl 3 (Table 1) also showed two double doublets and two triplet...
