Two New Xanthone Derivatives from the Algicolous Marine Fungus Wardomyces anomalus Ahmed Abdel-Lateff, Christine Klemke, Gabriele M. Ko ¨nig,* and Anthony D. Wright Institute for Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany Received October 31, 2002 A marine fungal isolate, identified as Wardomyces anomalus, was cultivated and found to produce two new xanthone derivatives, 2,3,6,8-tetrahydroxy-1-methylxanthone (1) and 2,3,4,6,8-pentahydroxy-1- methylxanthone (2), in addition to the known xanthone derivative 3,6,8-trihydroxy-1-methylxanthone (3) and the known fungal metabolite 5-(hydroxymethyl)-2-furanocarboxylic acid (4). The structures of all compounds were determined on the basis of extensive spectroscopic measurements (1D and 2D NMR, MS, UV, and IR). Compounds 1 and 4 showed significant antioxidant activities. The total extract and 1, 3, and 4 were shown to be inhibitors of p56 lck tyrosine kinase. Marine-derived fungi are a source of structurally diverse, biologically active natural compounds. 1-7 Xanthone deriva- tives are widespread in nature, commonly occurring in a number of higher plant families and fungi. 8,9 Some fungal species are well known as sources of xanthone derivatives, e.g., Penicillium raistrickii, 10 Phomopsis sp., 11 Actinoplanes sp., 12 Ascodesmis sphaerospora, 13 and Humicola sp. 14 Xan- thones are known to have a variety of biological activities, e.g., antimicrobial, antitubercular, antitumor, and antivi- ral. 8,9 In continuation of our projects aimed at finding new natural products with biological activity and/or novel chemical structures from marine-derived fungi, 15 Wardo- myces anomalus Brooks & Hansford (Microascaceae, As- comycetes), isolated from the green alga Enteromorpha sp. (Ulvaceae) collected around Fehmarn island in the Baltic Sea, 16 was investigated. The crude extract showed antimi- crobial effects toward Microbotryum violaceum and Euro- tium repens, inhibition of HIV-1 reverse transcriptase (HIV-1-RT) (65.4% at 66 µg/mL), and inhibition of p56 lck tyrosine kinase (TK) (98% at 200 µg/mL). Radical scaveng- ing activity was observed using R,R-diphenyl--picrylhy- drazyl (DPPH) as indicator (71.9% at 500 µg/mL). An extensive computer survey indicated there to be no prior investigation of W. anomalus. On this basis, the current secondary metabolite investigation was undertaken, which afforded the two new xanthone derivatives 1 and 2, in addition to the known xanthone derivative 3 17 and the known furan derivative 4. 18 The fungus was cultivated on a solid biomalt medium with added artificial sea salt. Successive fractionation of the EtOAc extract over a reversed-phase Sep Pack column, followed by reversed- phase HPLC, yielded compounds 1-4. Compound 1 has the molecular formula C 14 H 10 O 6 , as established by high-resolution mass measurement. The 13 C NMR spectrum of 1 contained 14 carbon resonances attributable to 10 × C, 3 × CH, and 1 × CH 3 groups (Table 1). It was also evident from these data that seven of the 10 elements of unsaturation within 1 were present as CdC double bonds and a carbonyl group (this deduction being supported by an IR absorption at ν max 1646 cm -1 ); the molecule was thus tricyclic. As the 13 C and 1 H NMR spectral data enabled all but four of the hydrogen atoms within 1 to be accounted for, it was evident that the remaining four must be present as OH groups, a deduction that was supported by IR data (ν max 3275 cm -1 ). UV maxima at 234, 258, 311, 358 nm suggested a xanthone nucleus. 9 The 1 H NMR spectral data revealed the presence of three aromatic protons, two of them (H-5 and H-7) with a meta coupling, the third (H-4) one a singlet, an aryl methyl group (11-CH 3 ), and a hydrogen-bonded phenolic OH (8-OH). After association of all protons with directly bonded carbons via a 2D NMR (HMQC) spectral measure- ment, it was possible to deduce the substitution pattern of the xanthone nucleus from HMBC correlations. Thus, HMBC correlations were seen between H-5 and C-6, C-7, C-9 (weak), C-9a, and C-10a, between H-7 and C-5, C-6, C-9 (weak), and C-9a, between H-4 and C-1 (weak), C-1a, C-2, C-3, C-4a, and C-9 (weak), and also between H 3 -11 and C-1, C-1a, C-2, C-4a (weak), and C-9 (weak). The HMBC correlations associated with CH 3 -11 clearly showed it to reside at C-1. As the 8-OH proton formed a strong hydrogen bond with oxygen, it was likely that this occurred with the oxygen of the C-9 carbonyl group. From HMBC correlations as described previously, it was evident that the C-6 resonated at δ 165.1 and thus was hydroxylated. The 13 C NMR chemical shifts of all of the A-ring carbons were then found to be most consistent with the remaining * To whom correspondence should be addressed. Tel: +49-228-733747. Fax: +49-228-733250. E-mail: g.koenig@uni-bonn.de. Internet: http:// www.uni-bonn.de/pharmbio/queen/GAWK.html. 706 J. Nat. Prod. 2003, 66, 706-708 10.1021/np020518b CCC: $25.00 © 2003 American Chemical Society and American Society of Pharmacognosy Published on Web 04/18/2003