Xanthones from a Microfungus of the Genus Xylaria.

Abstract

Chemical investigations of a microfungus Xylaria sp. isolated from the Australian rainforest tree Glochidion ferdinandi have afforded two new natural products, 2-hydroxy-6-methyl-8-methoxy-9-oxo-9H-xanthene-1-carboxylic acid (1) and 2-hydroxy-6-hydroxymethyl-8-methoxy-9-oxo-9H-xanthene-1-carboxylic acid (2). Compound 1 has previously been synthesised but only partially characterised. Methylation of 1 using diazomethane afforded the crystalline compound 2,8-dimethoxy-6-methyl-9-oxo-9H-xanthene-1-carboxylic acid methyl ester (3), whose structure was determined by single crystal X-ray analysis. This paper reports the full spectroscopic characterisation of compounds 1-3 by NMR, UV, IR and MS data. All compounds were inactive in a brine shrimp lethality assay and several antimicrobial screens.

Two New Cyclopeptides and One New Nonenolide from Xylaria sp. 101

“…Inspection of the 1 H-1 H COSY, HMQC and HMBC data readily revealed a nonenolide core for 3 [15,16]. The HMBC correlations from H-C(2) to C(1) and C(4), from H-C(9) to C(1) and C (11), and from Me (12) 12) established the structure of 3 (Figure 1). The configurations of C(2)/C(3) and C(4)/C(5) double bonds were identified to be cis and trans, respectively, according to the coupling constants of those corresponding protons.…”

“…Fungi of the genus Xylaria are a rich source of bioactive metabolites, including terpenoids [1][2][3][4][5], cyclopeptides [6,7], polyketides [8,9], cytochalasins [10], xanthones [11,12], and unique unclassified xyloketals [13]. We isolated a fungal strain named 101 from Gaoligong Mountain of southwestern China, and identified it as Xylaria sp.…”

Antibacterial and antifungal screening of natural products sourced from Australian fungi and characterisation of pestalactams D–F

“…Owing to the range of biological activities of Pestalotiopsis-derived metabolites we decided to add pestalactams A (4) and D ( 1), 4-O-methylpestalactam A (5), and tyrosol (8) to our developing fungi-based screening compound library, which consisted of the previously isolated and identified secondary metabolites pestalactams B (6) and C (7) (Davis et al, 2010), trichodermamide C (9) (Davis et al, 2008), 3-chloro-4-hydroxyphenylacetamide (10) (Davis et al, 2005b), 3-chloro-4-hydroxyphenylacetic acid (11) (Davis et al, 2005b), (-)-xylariamide A (12) (Davis, 2005), 2hydroxy-6-methyl-8-methoxy-9-oxo-9H-xanthene-1-carboxylic acid (13) (Healy et al, 2004), 2hydroxy-6-hydroxymethyl-8-methoxy-9-oxo-9H-xanthene-1-carboxylic acid ( 14) (Healy et al, 7 2004), 2,8-dimethoxy-6-methyl-9-oxo-9H-xanthene-1-carboxylic acid methyl ester (15) (Healy et al, 2004), pistillarin (16) (Capon et al, 2007;Choomuenwai et al, 2013;Holinsworth and Martin, 2009;Lee et al, 2011;Steglich et al, 1984), (1S,3R)-austrocortirubin (17) (Elsworth et al, 1999), (1S,3S)-austrocortirubin ( 18) (Gill et al, 1990;Gill and Steglich, 1987), 1-deoxyaustrocortirubin ( 19) (Gill et al, 1990;Gill and Steglich, 1987) and austrocortinin ( 20) (Archard et al, 1985).…”

“…Compound 15 is a synthetic derivative of the natural product xanthone 13, the synthesis of which has been previously reported (Healy et al, 2004). This 20 membered library was screened for antibacterial activity against a panel of Grampositive and Gram-negative bacterial isolates, and for antifungal activity against a panel of pathogenic yeasts (detailed in Table S23).…”

“…A recent analysis of bioactive natural products and drugs currently in the clinical pipeline suggest that 67-80% of therapeutically useful drugs have been derived from preexisting drug-productive biota families (Zhu et al, 2011). As part of our continuing research on the bioactive chemistry of endophytic fungi from Australian plants (Davis, 2005;Davis et al, 2005a;Davis et al, 2010;Davis et al, 2008;Davis et al, 2005b;Healy et al, 2004) we recently reported the isolation and structure elucidation of three novel caprolactam natural products that we named pestalactams A-C (4, 6, 7) from Pestalotiopsis sp. (BRIP 39872) (Davis et al, 2010).…”