Phytotoxic α-pyrones produced by Pestalotiopsis guepinii, the causal agent of hazelnut twig blight

Abstract

Pestalotiopsis guepinii (Desm.) is the fungal causal agent of the so-called 'twig blight' , one of the most serious diseases of hazelnut (Corylus avellana L.) in Turkey, and one of the main causes of yield losses. P. guepinii has been also isolated from walnut (Juglans spp.) and gum mastic tree (Pistacia lentiscus var. Chia). Recently, the main lipophilic phytotoxic metabolite produced by P. guepinii in vitro culture was isolated and identified by spectroscopic methods as pestalopyrone (7), 1 a pentaketide already known as a minor toxin produced by Pestalotiopsis oenotherae. 2 When the fungus was grown on a different culture medium, 3 some fractions obtained by the purification of the culture filtrate, not containing pestalopyrone, proved to be phytotoxic. Their further purification yielded other two amorphous phytotoxic metabolites (1 and 6, Figure 1) that by preliminary spectroscopic experiments (including 1 H and 13 C NMR, IR and UV) appeared to be closely related to a-pyrones.Indeed 1 was identified as 6-(1-hydroxypentyl)-4-methoxy-pyran-2-one and showed optical rotation, IR, UV, 1 H and 13 C NMR spectra very similar to those previously reported in literature for the metabolite named PC-2 isolated from a Penicillium sp. 4,5 The same a-pyrone (1) was successively isolated also from Galiella rufa together with (-)-gallielactone and its biogenetic precursor. 6 Penicillium nordicum, P. olsonii and P. verrucosum 7 and recently a marine-derived fungus Xylaria sp. PSU-F100 8 also showed to produce 1. The structure assigned to 1 was supported by the data observed in its COSY, HSQC and HMBC spectra (Table 1) as well as also by the data of the ESIMS. Beside both sodium clusters of the dimmer and the toxin itself, and the pseudomolecular ion observed at m/z 447 [2XM+Na]+, 235[M+Na] + , 213 [M+H] + , the ESIMS spectrum also showed the significant fragmentation peak [M+Na-CO 2 ] + at m/z 191 generated from the sodium cluster by loss of CO 2 , which is a fragmentation mechanism typical of a-pyrones. 9 The structure assigned to 1 was also supported by the data of its NOESY spectrum in which a significant coupling was observed between the two a-pyrone protons H-5 and H-3 and the methoxy group; furthermore, H-5 also coupled with the greater part (H 2 -1¢, H 2 -2¢ and H 2 -3¢) of the 1-hydroxypentyl side chain protons and these latter themselves coupled.Some key derivatives were prepared by converting 1 into the corresponding monoacetyl and oxidized derivatives (2 and 3, respectively, Figure 1), whose spectroscopic data were fully consistent with those previously reported in literature. Indeed, 2 showed optical rotation IR, UV and 1 H NMR spectra very similar to those previously reported when PC2 was acetylated by a similar procedure. 4 The ESIMS spectrum of 2 showed, beside the sodium cluster and the pseudomolecular ion at m/z 277 [M+Na]+, 255 [M+H]+, the significant fragmentation peak at m/z 195 [M+H-AcOH]+, which was generated by the pseudomolecular ion through the typical loss of the acetic acid residue. 9 The oxidized de...

Two new compounds from the plant endophytic fungus Pestalotiopsis versicolor

“…Compounds 3 -6 were identified as LL-P880g (3) [13], scirpyrone A (4) [15], scirpyrone B (5) [15], and 6-pentyl-4-methoxy-pyran-2-one (6) [16] by comparison of their NMR and MS data with those reported.…”

The Effect of Stereochemistry on the Biological Activity of Natural Phytotoxins, Fungicides, Insecticides and Herbicides

“…Guepyrone B ( 29 , Fig. ) was identified as 6‐pentyl‐4‐methoxy‐pyran‐2‐one . It was originally reported as a synthetic compound in a work aiming to prepare natural polyketides, and as a metabolite of Galiella rufa .…”

“…If a substituent is present in this side chain it could be a nucleophilic group as are the hydroxy or the double bond present in 26 and 22 . Instead, the presence of an electrophilic group, such as the carbonyl present in 28 , causes the loss of activity …”

Penapisan dan potensi bakteri endofit asal tanaman Arecaceae sebagai agens pengendali hayati cendawan Pestalotiopsis sp. penyebab penyakit bercak daun pada kelapa kopyor (Cocos nucifera) [Selection and potency of endophytic bacteria from Arecaceae as biocontrol agents of Pestalotiopsis sp. causing leaf spot diseae on kopyor coconut (Cocos nucifera)]

“…merupakan cendawan yang mampu memproduksi beragam senyawa metabolit. Metabolit tersebut diantaranya senyawa alkaloids, terpenoids, isocoumarin, coumarins, chromones, quinones, semiquinones, peptides, xanthones, xanthone derivatives, phenols, phenolic acids, dan lactones (Evidente et al, 2012). Metabolit berupa kelompok phenol yang bersifat fitotoksin adalah pestaloside.…”

“…Oxysporone, pestalopyrone, pestalotin A dan B, hydroxypestalotin dan hydroxypestalopyron merupakan metabolit yang bersifat toksik yang berasal dari kelompok lactone (Nagata et al, 1992;Xu et al, 2010;Evidente et al, 2012). Dalam pengujian antibiosis dengan teknik kultur ganda, metabolit sekunder Pestalotiopsis sp.…”