Chenopodolin: A Phytotoxic Unrearranged ent-Pimaradiene Diterpene Produced by Phoma chenopodicola, a Fungal Pathogen for Chenopodium album Biocontrol

Abstract

A new phytotoxic unrearranged ent-pimaradiene diterpene, named chenopodolin, was isolated from the liquid culture of Phoma chenopodicola, a fungal pathogen proposed for the biological control of Chenopodium album, a common worldwide weed of arable crops such as sugar beet and maize. The structure of chenopodolin was established by spectroscopic, X-ray, and chemical methods as (1S,2S,3S,4S,5S,9R,10S,12S,13S)-1,12-acetoxy-2,3-hydroxy-6-oxopimara-7(8),15-dien-18-oic acid 2,18-lactone. At a concentration of 2 mg/mL, the toxin caused necrotic lesions on Mercurialis annua, Cirsium arvense, and Setaria viride. Five derivatives were prepared by chemical modification of chenopodolin functionalities, and some structure-activity relationships are discussed.

Phytotoxins produced by Phoma chenopodiicola, a fungal pathogen of Chenopodium album

“…Assayed at 4 Â 10 À3 M on punctured detached leaves, 3 proved to be active in particular on Sonchus arvensis, causing the fast appearance of wide necrosis (scored +++) and on Urtica dioica and Parietaria officinalis, with smaller but still evident necrosis (+). This result differed from the non-toxic activity observed previously when 3 was tested on different plants (Mercurialis annua, Cirsium arvense and Setaria viride) using the same bioassay (Cimmino et al, 2013a). The different behavior could be due to different plant sensitivity.…”

“…The preliminary investigation of its 1 H and 13 C NMR spectra (Table 4) showed that they are very similar to those of chenopodolin (Cimmino et al, 2013a). Indeed, 3 showed the signal systems typical of the tetracyclic ent-pimaradiene lactone and also those corresponding to the a,b-unstaturated ketone at C(6)-C(8), the vinyl and the tertiary methyl both bonded to C-13, as well as the acetoxy groups at C-1 and C-12.…”

“…The structure assigned to 3 was supported by the data obtained from its HR ESIMS spectrum, which showed the sodium dimer form [2M+Na] + and the sodium cluster [M+Na] + at m/z 999 and 511.1953, respectively. When compared to the chenopodolin 1-Oacetyl derivative prepared by acetylation with pyridine and acetic anhydride (Cimmino et al, 2013a), 3 showed the same chromatographic behavior by TLC analysis of a mixture of the two samples with solvent systems A and C, and the same 1 H NMR data as previously reported (Cimmino et al, 2013a). Thus, 3 was formulated as (1S,2S,3S,4S,5S,9R,10S,12S,13S)-1,3,12-triacetoxy-2-hydroxy-6-oxo-ent-pimara-7(8),15-dien-18-oic acid 2,18-lactone.…”

“…Aa and v. Kest has been extensively studied for both purposes and, more recently Phoma chenopodiicola. From this latter organism a new phytotoxic unrearranged ent-pimaradiene diterpene, named chenopodolin (Cimmino et al, 2013a), along with three novel tetrasubstituted furopyrans, named chenopodolans A-C (Cimmino et al, 2013b) were recently isolated from liquid culture. The relation between the structural features and the phytotoxic activity against some weeds was determined by biological assay of the natural toxins and some of their hemisynthetic derivatives (Cimmino et al, 2013a,b).…”

Effect of Fungal and Plant Metabolites on Broomrapes (Orobanche and Phelipanche spp.) Seed Germination and Radicle Growth

“…21 Cavoxin, 10, and cavoxone, 11, and chenopodolin, 12; chenopodolan C, 13; and 6-hydroxymellein, 14 ( Figure 2), were isolated, respectively, from the culture filtrates of Phoma cava 22 and Phoma chenopodiicola. 23,24 Cytochalasins A, 15, and B, 16, and deoxaphomin, 17 (Figure 2), were isolated from the solid culture of Pyrenophora seminiperda. 25 All the above cited fungal metabolites were freshly isolated from the fungal cultures according to the protocols reported in the literature and were identified by 1 H NMR and electrospray ionization mass spectrometry (ESI MS), comparing these data with those previously described.…”