Structures of new phenylphenalene-related compounds from Eichhornia crassipes (water hyacinth) Marina DellaGreca * , Lucio Previtera, Armando Zarrelli UdR Napoli 4 of Consortium INCA, Dipartimento di Chimica Organica e Biochimica, Universita ` Federico II, Complesso Universitario Monte Sant’Angelo, Via Cinthia 4, I-80126 Napoli, Italy article info Article history: Received 3 June 2009 Received in revised form 29 June 2009 Accepted 23 July 2009 Available online 29 July 2009 Keywords: Eichhornia crassipes Phenyl naphthalenedicarboxylic ester Phenylphenalene phenyl naphthalenecarboxylic ester Spectroscopic analysis abstract Two new compounds identified as methyl derivatives of phenyl naphthalenedicarboxylic acid and phenyl naphthalenecarboxylic acid linked to a phenylphenalene unit were isolated from the extract of Eichhornia crassipes (water hyacinth). The structures have been determined on the basis of spectroscopic analyses, mainly using 2D NMR techniques. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Eichhornia crassipes (water hyacinth) is invasive in much of the world where it often jams rivers and lakes with thousands of tons of floating plant matter. 1 In our search for compounds from aquatic plants, phenylphenalene metabolite derivatives were isolated from the ethyl acetate extract of E. crassipes and characterized as methyl ether derivatives obtained by treatment with methanolic CH 2 N 2 . 2 Recently, based on detailed spectroscopic analysis we revised the structures of some of them. 3 Further examination of the ethyl acetate extract has afforded two new compounds with a phenyl naphthalenedicarboxylic ester and a dimeric oxidized phenyl- phenalene skeletons. Phenylphenalenones represent a class of phenylpropanoid derived natural products that are of special interest because of their potential role as phytoalexins and phytoanticipins. 3–8 2. Results and discussion The ethyl acetate extract of E. crassipes was concentrated in vacuo and fractionated into acidic and neutral fractions. The crude acidic residue was treated with methanolic CH 2 N 2 and chromato- graphed on silica gel and Sephadex LH-20 columns and pure new compounds 1 and 2 were purified by HPLC. Compound 1 showed the molecular ion peak at m/z 350 [M] þ and significant fragments at m/z 319 [MCH 3 O] þ , 291 [MC 2 H 3 O 2 ] þ in the EIMS spectrum. Its molecular formula was deduced to be C 21 H 18 O 5 from a molecular ion peak at m/z 350.1150 in HREIMS spectrum and NMR spectral data. The 1 H and 13 C resonances of 1 were assigned by combination of COSY, DEPT, HSQC, and HMBC experiments (Table 1). The 1 H NMR spectrum showed two narrow doublets at d 8.26 and 8.13 (J¼1.5), two doublets at d 8.04 and 7.98 (J¼8.5), one triplet at d 7.56 (J¼8.5), two doublets at d 7.68 and 7.04 (J¼8.5), and two singlets at d 3.94 and 3.88. These signals were attributed to a 1,3,8 trisubstituted naphthalene and a 1,4 disubstituted benzene by a COSY experiment. * Corresponding author. Tel.: þ39 81 674162; fax: þ39 81 674393. E-mail address: dellagre@unina.it (M. DellaGreca). Contents lists available at ScienceDirect Tetrahedron journal homepage: www.elsevier.com/locate/tet 0040-4020/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.tet.2009.07.069 Tetrahedron 65 (2009) 8206–8208 Contents lists available at ScienceDirect Tetrahedron journal homepage: www.elsevier.com/locate/tet