Gliocladic acid

A chemical investigation of the Australian termite nest-derived fungus Trichoderma virens CMB-TN16 yielded the known sesquiterpene gliocladic acid (1), together with two new acetylated analogues, 3-acetylgliocladic acid (2) and 14-acetylgliocladic acid (3), and seven new dimeric congeners, divirensols A-G (4-10). All metabolites were identified by detailed spectroscopic analysis, supported by biosynthetic considerations, and were assessed for antibacterial and cytotoxic properties. The divirensols are examples of an exceptionally rare class of dimeric sesquiterpene, likely linked via a highly convergent biosynthetic pathway. HPLC-DAD-MS analysis of the crude fungal extract detected ions attributed to putative monomeric biosynthetic precursors.

The presence of fungi and mycotoxins in silage (fermented maize) for cattle and other ruminants have been studied extensively compared to wrapped haylage (fermented grass) for horses and other monogastric animals. The purpose of this work was to examine the fungal diversity of wrapped haylage and conventional hay and to analyse the forage sample for fungal metabolites. Faeces samples were also analysed to study the fate of fungi and metabolites. Fungal diversity of the samples was determined by direct plating on DG18, V8 and MEA and chemical analyses were done using LC-MS/MS. The results show that Sordaria fimicola was common in both hay and haylage, while Penicillium spp. was prevalent in haylage and Aspergillus spp. in hay. Communiols were found in all types of samples together with gliocladic acid. Roquefortines and fumigaclavines were found in haylage with no visible fungal growth, but not in hay. In haylage hot spot samples, a series of Penicillium metabolites were detected: Andrastins, fumigaclavines, isofumigaclavines, marcfortines, mycophenolic acid, PR toxins, and roquefortines. Penicillium solitum was found repeatedly in haylage and haylage hot spot samples and viridicatols were detected in a hot spot sample, which has not been reported before. Even haylage with no visible fungal growth contained more metabolites than hay. Individually, the metabolites detected in haylage may, in high doses, be mutagenic, neurotoxic or immunosuppressive; but the synergistic effect of small doses may also have other or greater negative health effects on equines than on ruminants.

Macrophomina phaseolina (Tassi) Goid., the causal agent of charcoal rot disease of soybean, is capable of causing disease in more than 500 other commercially important plants. This fungus produces several secondary metabolites in culture, including (-)-botryodiplodin, phaseolinone and mellein. Given that independent fungal isolates may differ in mycotoxin and secondary metabolite production, we examined a collection of 89 independent M. phaseolina isolates from soybean plants with charcoal rot disease using LC-MS/MS analysis of culture filtrates. In addition to (-)-botryodiplodin and mellein, four previously unreported metabolites were observed in >19% of cultures, including kojic acid (84.3% of cultures at 0.57-79.9 µg/L), moniliformin (61.8% of cultures at 0.011-12.9 µg/L), orsellinic acid (49.4% of cultures at 5.71-1960 µg/L) and cyclo[L-proline-L-tyrosine] (19.1% of cultures at 0.012-0.082 µg/L). In addition, nine previously unreported metabolites were observed at a substantially lower frequency (<5% of cultures), including cordycepin, emodin, endocrocin, citrinin, gliocladic acid, infectopyron, methylorsellinic acid, monocerin and N-benzoyl-L-phenylalanine. Further studies are needed to investigate the possible effects of these mycotoxins and metabolites on pathogenesis by M. phaseolina and on food and feed safety, if any of them contaminate the seeds of infected soybean plants.