Fusaproliferin, Terpestacin and Their Derivatives Display Variable Allelopathic Activity Against Some Ascomycetous Fungi

Abstract

Herbivorous mammal dung supports a large variety of fimicolous fungi able to produce different bioactive secondary metabolites to compete with other organisms. Recently, the organic extracts of the Solid State Fermentation (SSF) cultures of Cleistothelebolus nipigonensis and Neogymnomyces virgineus, showing strong antifungal activity, were preliminarily investigated. This manuscript reports the isolation of the main metabolites identified, using spectroscopic and optical methods, as fusaproliferin (1) and terpestacin (2). Furthermore, some key hemisynthetic derivatives were prepared and their antifungal activity was tested against the same fungi previously reported to be affected by the organic extracts obtained from SSF. These metabolites and their derivatives resulted able to reduce the growth of Alternaria brassicicola, Botrytis cinerea and Fusarium graminearum in a variable extent strongly dependent from chemical modifications and test fungi. The hydroxy enolic group at C(17) appeared to be a structural feature important to impart activity. This study represents the first report of these secondary metabolites produced by C. nipigonensis and N. virgineus.

Phytotoxic Activity of Metabolites Isolated from Rutstroemia sp.n., the Causal Agent of Bleach Blonde Syndrome on Cheatgrass (Bromus tectorum)

“…Terpestacin ( 5 ): : –17.7 ( c = 0.4, CHCl 3 ); Its 1 H- and 13 C-NMR spectra were very similar to those already reported in literature [ 19 ]; HRESIMS (+) m / z : 425.2743 [M + Na] + (calcd. for C 25 H 38 NaO 4 , 425.2750).…”

“…No biological activities were reported and its AC was not determined. Thus, the AC of 3 was determined applying the advanced Mosher’s method [ 19 ] appropriately derivatizing the chiral secondary alcohol at C-1’. In particular, 5- O -methylnectriafurone ( 3 ) by reaction with R -(−)-α-methoxy-α-trifluoromethylphenylacetyl (MTPA) and S -(+)-MTPA chlorides, was converted into the corresponding diastereomeric esters at C-1’ ( 6 , 7 ).…”

Fungal Metabolites Antagonists towards Plant Pests and Human Pathogens: Structure-Activity Relationship Studies

“…A SAR study was conducted to understand the role of each functional group of these natural products to the imparted activity. In particular, four fusaproliferin derivatives ( 80 – 83 , Scheme 7 ) and four terpestacin derivatives ( 84 – 87 , Scheme 8 ) were prepared and tested (using a concentration of 10 −3 M) against A. brassicicola , B. cinerea , and F. graminearum [ 59 ]. These results showed that the three fungi have different sensitivities towards fusaproliferin and terpestacin.…”

“…These results showed that the three fungi have different sensitivities towards fusaproliferin and terpestacin. Furthermore, the hydroxy enolic group at C-17 and the conformational freedom of the macrocyclic ring, due to the presence/absence of the three double bonds, are structural features important to impart activity [ 59 ].…”

“…Thus, it seems very hard to hypothesize on its application as a biopesticide, although the SAR study performed was useful in order to speculate on the mechanisms of action of these natural products. The functions in nature of these two mycotoxins have not been clearly established, but they are believed to play a role in eliminating other microorganisms competing in the same environment [ 59 ].…”