Sesquiterpene aryl ester natural products in North American Armillaria species

Abstract

In the first comprehensive study on the secondary metabolism of all ten North American Armillaria species, we analyzed their capacity to produce sesquiterpene aryl ester natural products. All species were identified as producers. Species-specific trends were observed for some species, e.g., for Armillaria ostoyae and A. gemina (low diversity of aryl esters) or A. tabescens (very low number of chlorinated aryl esters). The crude extracts were assayed for antibiotic activity against wood-rotting basidiomycetes and ubiquitous soil fungi. Inhibitory effects were strongly dependent on the target organism, with basidiomycetes being more susceptible than other fungi. Tapinella panuoides and Omphalotus illudens were inhibited by extracts of all Armillaria species whereas the same extracts were completely inactive against Trichoderma harzianum, widely inactive against Mucor racemosus, and only moderately active against Aspergillus flavus and Penicillium oxalicum. Activity tests with seven purified aryl esters suggest that lipophilicity and the position of the double bond in the tricyclic sesquiterpene moiety impact upon bioactivity while the substitution pattern of the aromatic ring does not. Arnamial was the most active compound and showed a minimum inhibitory concentration of <5 μg/ml for all four basidiomycetes and Penicillium oxalicum, but did not inhibit Trichoderma harzianum and Mucor racemosus.

Secrets of the subterranean pathosystem of Armillaria

“…A combination of biosynthetic processes (e.g. hydroxylation, methylation, chlorination, oxidation/reduction) generates in excess of 50 sesquiterpene aryl ester derivatives (Misiek and Hoffmeister, 2011), which makes them one of the most diverse groups of natural products known among fungi. Given this immense structural diversity, Armillaria exemplifies the ‘screening hypothesis’ (Firn and Jones, 2003).…”

“…Tapinella panuoides (Basidiomycota, Tapinellaceae), Omphalotus illudens (Basidiomycota, Marasmiaceae)] than on nonwood‐rotting fungi [e.g. Aspergillus (Ascomycota, Trichocomaceae); Misiek and Hoffmeister, 2011]. In this way, aryl esters may have an important role in the persistence of Armillaria mycelium within residual roots by preventing colonization by rhizomorphs of other saprophytic fungi.…”

“…In this way, aryl esters may have an important role in the persistence of Armillaria mycelium within residual roots by preventing colonization by rhizomorphs of other saprophytic fungi. As the mycoparasite Trichoderma (Ascomycota, Hypocreaceae) is completely resistant to inhibition by Armillaria aryl esters (Misiek and Hoffmeister, 2011), screening for resistance to these natural products may be an efficient means of identifying antagonistic strains for biological control.…”

Recent Advances in Homogeneous Metal-Catalyzed Aerobic C–H Oxidation of Benzylic Compounds

“…Aryl ketones, benzoate esters, and benzamides are ubiquitous structures found in natural and biologically active compounds (e.g., hypericin [1-3], acetosyringone [4,5], oxcarbazepine [6,7], daidzein [8,9], sitaxentan [10,11], radicicol [12,13], arnamial [14][15][16], epicatechingallate [17], Rucaparib [18][19][20][21], and Leucine-rich repeat kinase-2 (LRRK2) [22,23], Figure 1). In addition, such carbonyl compounds are also extensively used in advanced materials [24][25][26][27][28] and as key intermediates for the synthesis of fine chemicals, including structurally complex compounds.…”

Reagent-Enabled ortho -Alkoxycarbonylation of Aryl Iodides via Palladium/Norbornene Catalysis

“…Here, we describe a unique method for direct preparation of multifunctionalized aromatic carboxylic esters from simple readily available aryl iodides via palladium/norbornene cooperative catalysis. building blocks 42 and ubiquitously found in various biologically important molecules, including natural products, 43 pharmaceuticals, 44 and agrochemicals. 45 In addition, the carboxylate group can serve as a versatile C1 unit and be conveniently converted to other functional groups, such as formyl (CHO), hydroxylmethyl (CH 2 OH), and cyano (CN) groups, etc.…”