190 Spectral Assignments and Reference Data Received: 6 June 2008 Revised: 15 October 2008 Accepted: 20 October 2008 Published online in Wiley Interscience: 24 November 2008 (www.interscience.com) DOI 10.1002/mrc.2373 1 H and 13 C NMR assignments for two new cordiaquinones from roots of Cordia leucocephala Ja´ ecio Carlos Diniz, a Francisco Arnaldo Viana, a* Odaci Fernandes Oliveira, b Maria Aparecida M. Maciel, c Maria da Conceic ¸˜ ao de Menezes Torres, d Raimundo Braz-Filho, d Edilberto R. Silveira d and Otília Deusd ˆ enia L. Pessoa d From the roots of Cordia leucocephala (Boraginaceae), two new meroterpenoid naphthoquinones, 6-[10-(12,12-dimethyl- 13α-hydroxy-16-methenyl-cyclohexyl)ethyl]-1,4-naphthalenedione (cordiaquinone L) and 5-methyl-6-[10-(12,12-dimethyl- 13β -hydroxy-16-methenyl-cyclohexyl)methyl-1,4-naphthalenedione (cordiaquinone M) were isolated. Their structures were elucidated after detailed 1D and 2D NMR (COSY, HSQC, HMBC and NOESY) data analyses and comparison with literature data for analogous compounds. Copyright c  2008 John Wiley & Sons, Ltd. Keywords: 1 H NMR; 13 C NMR; 2D NMR; Cordia leucocephala; Boraginaceae; naphthoquinones Introduction Innumerous plants of the genus Cordia, one of the major and most important of the Boraginaceae family, are used in folk medicine for their antiulcerogenic, antimicrobial, anti-inflammatory and analgesic properties, [1] as well as for the treatment of diverse pathologies, including pneumonia, cough, [2] rheumatism and dyspepsia. [3] The genus Cordia is known as a prolific source of struc- turally diverse secondary metabolites such as sesquiterpenes, [4] diterpenes, [5] triterpenes, [6] flavonoids, [7] saponins [8] and, spe- cially for their ability to biosynthesize benzoquinones and naphthoquinones, including their respective reduced forms (hydroquinones). [2,3,9,10] The occurrence of such compounds seems to be taxonomically important to this genus. As a part of our search for bioactive compounds from Cordia, we have investigated the chemical composition of some Cordia species native to Brazil’s flora. [3,4,8] In the present work, we describe the phytochemical investigation of the hexane extract from the roots of Cordia leucocephala Moric (syn.: C. leucocalyx Fresen), a flowering woody shrub native to the northeastern Brazil. Results and Discussion The new meroterpenoid naphthoquinones (1 and 2) were isolated, through chromatographic fractionation techniques (open silica gel column and HPLC), from the hexane extract of C. leucocephala roots. The two naphthoquinones are being reported for the first time and, due to their structural similarity with a series of naphthoquinones previously isolated from other Cordia species, were named cordiaquinones L (1) and M (2). Their structures were unequivocally elucidated by spectroscopic analysis including high- resolution electron spray ionization mass spectra (HRESIMS) and, particularly, NMR methods after comparison with published data. Compound 1,[α] 20 D + 35 ◦ (0.05, CHCl 3 ), was isolated as a yel- low resin, and its molecular formula was assigned as C 21 H 24 O 3 by HRESIMS (observed m/z 323.1642 [M − H] − ; calculated for C 21 H 23 O 3 : 323.1647) and NMR spectral data. The infrared (IR) spec- trum showed absorption bands to hydroxyl group (3466 cm −1 ), conjugated carbonyl (1665 cm −1 ) and carbon–carbon double bond (ν =CH 3073, 893 and 835; ν C=C 1599 and 1447 cm −1 ). The 1 H NMR spectrum showed a signal at δ 6.94 (s), integrating for two hydrogens (H-2 and H-3), three aromatic proton signals at δ 7.99 (d, J = 8.0 Hz, H-8), 7.87 (s, H-5) and 7.55 (br d, J = 8.0 Hz, H-7) of an AMX spin system and, two signals at δ 4.96 (s, H-17a) and 4.69 (s, H-17b), which were characteristic of an exocyclic carbon–carbon double bond. Additionally, the 1 H NMR spectrum displayed signals for an oxymethine proton (δ 3.41, dd, J = 9.0 and 4.0 Hz, H-13), two methyl groups (δ 0.99 and 0.75), beside a set of signal in the range of δ 2.88 to 1.54, corresponding to protons attached to nonfunctionalized sp 3 carbons. ∗ Correspondence to: Francisco Arnaldo Viana, Departamento de Química, Universidade do Estado do Rio Grande do Norte, 59610-210, Mossor´ o-RN, Brazil. E-mail: arnnaldo@yahoo.com.br a Departamento de Química, Universidade do Estado do Rio Grande do Norte, 59610-210, Mossor´ o-RN, Brazil b Universidade Federal Rural do Semi- ´ Arido, CP 117, 59600-970, Mossor´ o-RN, Brazil c Departamento de Química, Universidade Federal do Rio Grande do Norte, CP 1524, 59072-970, Natal-RN, Brazil d Departamento de Química Orgˆ anica e Inorgˆ anica, Centro de Ciˆ encias, Universidade Federal do Cear´ a, CP 12.200, 60021-970, Fortaleza-CE, Brazil Magn. Reson. Chem. 2009, 47, 190–193 www.soci.org Copyright c  2008 John Wiley & Sons, Ltd.