Metabolites from the Endophytic Fungus Hypoxylon monticulosum
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METABOLITES FROM THE ENDOPHYTIC FUNGUS Hypoxylon monticulosum
Ming-Jen Cheng,1* Ming-Der Wu,1 Thanda Aung,2 Hsiang-Ruei Liao,3 Nanthaphong Khamthong,4* and Sung Yuan Hsieh1
Plant endophytes are a group of microorganisms, including fungi and bacteria, which not only live within the internal tissues or organs of plants without causing any apparent symptoms of disease in the host plants [1–3], but also serve as important sources of bioactive compounds, presumably owing to the symbiotic relationship with their hosts [1–3]. Research on endophytes from different plant sources has yielded many structurally diverse and pharmacologically active natural products [4–10]. Fungi are one of the main sources of antimicrobial drugs because of their ability to produce diverse bioactive secondary metabolites [1–3], which have made a significant contribution to new drug discovery and treatments for diseases [3]. During a program of investigation on potentially bioactive secondary metabolites from Formosan endemic plant endophytes, an endophytic fungal strain, Hypoxylon monticulosum (Xylaraceae), was isolated from the stems of Litsea akoensis var. chitouchiaoensis (Lauraceae). This fungus is an ascomycete fungus belonging to the order Xylariales. So far, more than 200 metabolites with various bioactivities have been identified from the Hypoxylon species [4]. Hence, isolation and identification of new natural products from this species have been a focus for us. Our previous investigations of secondary metabolites from the genus Hypoxylon have led to the isolation of three new compounds, hypoxyloamide, 8-methoxynaphthalene-1,7-diol, and hypoxylonol, together with seven compounds isolated from nature for the first time, along with 19 known compounds isolated from the culture broth of Hypoxylon investiens BCRC 10F0115. However, to our knowledge, secondary metabolites from H. monticulosum are not very well known. To further understand the chemotaxonomy of the Hypoxylon species, H. monticulosum was chosen for phytochemical investigation. The compounds derived from the above fungus include 3,4,5-trimethoxybenzaldehyde (1) [11], stigmastane-3β,6α-diol (2) [12], eudesm-4(15)-ene-1β,6 α-diol (3) [13], ursolic acid (4) [14], p-hydroxybenzaldehyde (5) [15], methylparaben (6) [16], vanillin (7) [17], N-trans-feruloylmethoxytyramine (8) [18], and N-trans-feruloyltyramine (9) [19]. All of these known compounds were obtained for the first time from this fungus and were identified by direct comparison with authentic sample and literature. General Experimental Procedures. TLC: silica gel 60 F254 precoated plates (Merck). Column chromatography (CC): silica gel 60 (70–230 or 230–400 mesh, Merck) and spherical C18 100A reversed phase silica gel (RP-18) (particle size: 20–40 μm) (Silicycle). UV spectra: Jasco UV-240 spectrophotometer. IR Spectra: Perkin-Elmer-2000 FT-IR spectrophotometer. 1H, 13C, and 2D NMR spectra: Varian-VNMRS-600 and Varian-Mercury-400 spectrometers. EI-MS: VG-Biotech Quatro-5022 mass spectrometer. HR-EI-MS spectra were recorded on a
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