A novel indole alkaloid, nauclefolinine (1) and five known triterpenic compounds, rotundic acid (2), a-L-rhamnoquinovic acid (3), 3-O-b-D-glucopyranosyl-b-sitosterol (4), squalene (5) and sitosterol-3-O-6’-stearoyl-b-D-glucopyranoside (6) have been isolated from the roots of Nauclea latifolia. KEY WORDS: Nauclea latifolia, Rubiaceae, Indole alkaloid, Triterpenic acids, Rotundic acid, Rhamnoquinovic acid  Bull. Chem. Soc. Ethiop. 2003, 17(2), 173-176

Ayafor, J.F.

Connolly, J.D.

Ngnokam, D.

Nuzillard, J.M.

English

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Bull. Chem. Soc. Ethiop. 2003, 17(2), 173-176.                                                            ISSN 1011-3924 Printed in Ethiopia                                                                       2003 Chemical Society of Ethiopia  __________ *Corresponding author. Tel: (237) 9558830. E-mail: dngnokam@yahoo.fr NAUCLEFOLININE: A NEW ALKALOID FROM THE ROOTS OF  NAUCLEA LATIFOLIA   D. Ngnokam1*, J.F. Ayafor1, J.D. Connolly2 and J.M. Nuzillard3   1Department of Chemistry, University of Dschang, Box 67 Dschang, Cameroon 2Department of Organic Chemistry, University of Glasgow, Glasgow G12 8QQ, Scotland 3CNRS-UPRESA 6013, Laboratoire de Pharmacognosie CPCBAT-Bâtiment 18, Moulin de la Housse, B.P. 1039, 51097 Reims cedex 2, France  (Received October 10, 2002; revised April 17, 2003)  ABSTRACT. A novel indole alkaloid, nauclefolinine (1) and five known triterpenic compounds, rotundic acid (2), α-L-rhamnoquinovic acid (3), 3-O-β-D-glucopyranosyl-β-sitosterol (4), squalene (5) and sitosterol-3-O-6’-stearoyl-β-D-glucopyranoside (6) have been isolated from the roots of Nauclea latifolia.  KEY WORDS: Nauclea latifolia, Rubiaceae, Indole alkaloid, Triterpenic acids, Rotundic acid, Rhamnoquinovic acid  INTRODUCTION  Nauclea latifolia Smith is a large evergreen tree abundant in the rain forests of West and Central Africa. The bark finds some local use in the treatment of stomach pains, fever and sometimes diarrhoea [1]. Previous work on Nauclea latifolia has yielded a number of alkaloids [2, 3]. We here present the isolation and the structural elucidation of a new alkaloid (1), together with five previously known triterpene derivatives identified as rotundic acid (2) [4], α-L-Rhamnoquinovic acid (3) [5], 3-O-β-D-glucopyranosyl-β sitosterol (4) [6], squalene (5) [7] and sitosterol-3-O-6’-stearoyl-β-D-glucopyranoside (6) [8].  RESULTS AND DISCUSSION  Nauclefolinine 1 was isolated as a dark brown powder m.p. 115-116 °C, [α]25D +3 (CH2Cl2, c 0.6). Its UV spectrum showed two absorption maxima at 224 and 282 nm characteristic of indole alkaloids [9]. The study of its IR spectrum indicated the presence of a lactam group (1660 cm-1), monoalkylated external exocyclic carbon-carbon double bond (1736 cm-1) [10] and a secondary amine group (3298 cm-1).  The mass spectrum agreed with the C21H24N2O3 formula for compound 1. Observation in its mass spectrum of fragments ions at m/z 169 (52%), 156 (27%), 144 (40%) and 143 (72%) suggests the presence of tetrahydro β-carboline ring. The 13C NMR of 1 displayed signals for 21 carbon atoms: one vinyl methyl and one OMe ether, four methylenes (sp3), nine methines including five olefinic, three sp3 carbons and one sp3 bearing oxygen, six quaternary sp2 carbons including one carbonyl group and two carbon atoms bearing nitrogen. This was confirmed by the 1H NMR spectrum in which two methyls were observed as singlet and doublet. The signal which appears at δ 3.40 is attributed to the OMe group due to the downfield shift. The proton geminal to this group appears as a doublet at 5.30. This value of the chemical shift indicated D. Ngnokam et al.  Bull. Chem. Soc. Ethiop. 2003, 17(2) 174that, this methine group bears two oxygen atoms. RCH2OR’ protons appear at 3.75 and 4.20, the aromatic protons together appear between 7.34 and 7.50, and the exchangeable amine proton (RNHR’) at 8.21 ppm. The comparison of the 13C NMR spectrum data (see Table 1) of 1 and those of strictosamide (7) [5] allowed to suggest that, those compounds would have the same carbon skeleton. The carbon-carbon double bond C16-C17 of strictosamide has been hydrogenated, and the terminal double bond C18-C19 does not exist in compound 1. This terminal double bond C18-C19 would have migrated inside between the carbons C19 and C20. This suggestion has been confirmed by the Cosy spectrum which showed correlations between H18 and H19, H16 and H15, H19 and H21 on the one hand H16 and the RCH2OR’protons on the other. Coupling between H3 and H14, H14 and H15 were also observed and the coupling constant value (11.4 Hz) between H15 and H16 allowed to suggest that, the latter proton is fixed in α position of carbon C16.                                                                                           HOCOOHHCH2OHHO2   5  NNOOCH3CH3OHHHH1235678910111213141516171819202122OOHHOHOROH2C4 R = H6 R = CO(CH2)16CH3COOHHROCOOH3 R = RhamnoseNNOOGluOHHHH7Nauclefolinine, a new alkaloid from the roots of Nauclea latifolia  Bull. Chem. Soc. Ethiop. 2003, 17(2) 175Table 1. 1H and 13C NMR data of 1 and 7, and HMBC correlations of 1.  C 1 7 H 1 HMBC Correlations of 1: Hi correlates with Ci 1   1 8.20, s   2 132.7 134.3     3 53.6 52.6 3 H3 5.10 broad doublet J3-14b = 6.7 Hz  J3-14a = 2 Hz H3 with C14, C2, C15 5 42.8 42.7 5 H5a 4.95, m H5b 2.95, m H5 with C6, C3, C7, C=O 6 20.7 20.5 6 H6a 3.05, m H6b 2.70, m H6 with C5, C7 7 111.1 107.5     8 127.3 126.9     9 118.1 117.4 9 H9, 7.50, d J9-10 = 7.7 Hz H9 with C7, C11, C13 10 119.8 118.6 10 H10, 7.15, m  H10 with C12, C8 11 122.2 120.8 11 H11, 7.21, m  H11 with C9, C13 12 111.1 111.1 12 H12, 7.34, d J12-11 = 8.0 Hz H12 with C8, C10 13 135.7 135.7         H14b, 2.15, m J14b-3 = 6.7 Hz  14 27.6 25.6 14 H14a, 2.48  broad doublet J14a-14b = 13.6 Hz J14a-15 = 11.4Hz H14 with C15, C16, C3      J14a-3 = 2 Hz  15 32.7 23.4 15 H15, 2.55, m J15-14a = 11.4 Hz J15-16 = 11.4 Hz       J15-14b = 0.5 Hz  16 46.2 108.7 16 H16, 2.38, m J16-17a = 5.8 Hz H16 with C14, C15, C17, C=O      J16-17b = 11.4 Hz  17 59.7 146.5 17 H17a, 4.20 dd J17a-16 = 5.8 Hz      H17b, 3.75 t J17a-17b = 11.4 Hz = J17b-16 H17 with C15, C16, C18 18 12.7 119.7 18 H18, 1.5, d J18-19 = 6.9 Hz H18 with C20, C19 19 118.4 133.1 19 H19, 5.42, m J19-21 = 1.8 Hz H19 with C18, C15      J18-19 = 6.9 Hz  20 135.6 42.2     21 94.9 95.9 21 H21, 5.30, d J21-19 = 1.8 Hz H21 with C17, OCH3 22 168.7      OCH3 54.4   3.40, s  CH3 with C21   HMBC correlations (see Table 1) between the methyl of the methoxyl group and C21, vinyl methyl and neighbouring carbon atoms, the other protons and neighbouring carbon atoms allowed to establish connectivities among fragments of the molecule and confirm the structure 1. More ever the presence of an OMe in C21 induced a characteristics 13C and 1H NMR signals around δ 94.9 and δ 5.30, respectively.  Structures (2-6) were determined by means of spectroscopic data and by comparative analysis of physical and spectral data with those in the literature.   EXPERIMENTAL  General. M.p. uncorr. IR: NaCl. NMR spectra were recorded at 125 MHz for 13C and 500 MHz for 1H. Chemical shifts are given in δ value (ppm) with TMS as internal standard. EI-MS was measured at 70 eV. TLC was carried out on silica gel. The alkaloid was detected by their intense D. Ngnokam et al.  Bull. Chem. Soc. Ethiop. 2003, 17(2) 176yellow-white fluorescence in UV light (365 nm), by the yellow colour obtained on spraying with Dragendorff’s reagent. The triterpenoid compounds were detected by spraying with 50% solution of H2SO4 in H2O following by heating. UV spectra were determined as methanol solutions.  Plant material. The roots of Nauclea latifolia SM were collected on February 1998 in Foumban (Western Province of Cameroon). A voucher specimen has been deposited at the National Herbarium, Yaounde.   Extraction and isolation. The air dried powdered material (3 kg) was extracted in the mixture of methanol and methylene chloride (1:1) (10 L) and the extract was divided in to chloroform and methanol portions. The chloroform soluble fraction (40 g) was subjected to a silica gel dry flash chromatography, elution performed with a mixture of hexane and ethyl acetate of increasing polarity followed by the mixture of ethyl acetate and methanol. Fractions eluted with a mixture of hexane and ethyl acetate (60:40) were rechromatographed over silica gel to yield compound 1 (15 mg).  Fractions obtained with a mixture of hexane and ethyl acetate (20:80) were purified over silica gel to yield 2 (35 mg), 3 (25 mg), 4 (60 mg) and 6 (20 mg) while 5 (22 mg) was obtained from fractions eluted with a mixture of hexane and ethyl acetate (9.5:0.5). TLC data indicated the following polarity from the less to the more polar compound: 5, 1, 6, 2, 3 and 4 with the retention factor 1, 0.86, 0.63, 0.51, 0.43 and 0.2, respectively in the mixture CH2Cl2/MeOH (95:5).   Nauclefolinine (1). Dark brown powder. M.p. 115-116 °C. [α]25D +3 (CH2Cl2. c 0.6). UV: λmax (MeOH) nm: 224, 282. IR νmax (NaCl) cm-1: 3298, 1736, 1660, 1614. 1H and 13C NMR (CDCl3): see Table 1. EI-MS m/z (rel. int.): 352 (100), 320 (60), 307 (25), 169 (52), 156 (27), 144 (40), 143 (72).  ACKNOWLEDGMENTS  We gratefully acknowledge Financial support from the AUPELF-UREF (Agence Universitaire de la Francophonie).  REFERENCES  1. Kerharo, J.; Adam, J.G. La Pharmacopée Sénégalaise Traditionnelle, Vigot: Paris; 1974. 2. Hotellier, F.; Delaveau, P.; Pousset, J.L. J. Med. Plant Res. 1979, 35, 242.  3. Hotellier, F.; Delaveau, P.; Pousset, J.L. C.R.. Acad. Sci. Paris 1981, Serie II, 293, 577.  4. Nakatani, M.; Miyazaki, Y.; Iwashitaa, T.; Naokia, H.; Hase, T. Phytochemistry 1989, 28, 1479. 5. Zeches, M.; Richard, B.; Gueye-M’Bahia, L.; Le Men, L.O. J. Nat. Prod. 1985, 48, 42.  6. Ngnokam, D.; Massiot, G.; Nuzillard, J.M.; Tsamo, E. Bull. Chem. Soc. Ethiop. 1994, 8, 15. 7. Ngnokam, D.; Massiot, G.; Nuzillard, J.M.; Connolly, J.D.; Tsamo, E.; Morin, C. Phytochemistry 1993, 34, 1603. 8. Pei-Wu, G.; Fukuyama, Y.; Rei, W.; Jinxian, B.; Nakagawa, K. Phytochemistry 1988, 27, 1895. 9. Hotellier, F.; Delaveau, P.; Pousset, J.L. Phytochemistry 1980, 19, 1884.  10. Silverstein, R.M.; Webster, F.X. Spectrometric Identification of Organic Compounds, 6th ed., John Wiley: New York; 1998.  

Nauclefolinine: A new alkaloid from the roots of Nauclea latifolia

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Nauclefolinine: A new alkaloid from the roots of Nauclea latifolia

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