Production of (10S,11S)-(—)-epi-Pyriculol and Its HPLC Quantification in Liquid Cultures of Pyricularia grisea, a Potential Mycoherbicide for the Control of Buffelgrass (Cenchrus ciliaris)

Abstract

(10S,11S)-(—)-epi-pyriculol is a phytotoxic metabolite produced by Pyricularia grisea, a fungus identified as a foliar pathogen on the invasive weed species buffelgrass (Cenchrus ciliaris) in North America. The effective control of buffelgrass has not yet been achieved, and there is a need to develop effective and green solutions. Herbicides based on natural products and the use of phytopathogenic organisms could provide the most suitable tools for the control of weeds such as buffelgrass. Thus, one of the most relevant points to study about potential suitable phytotoxins such as (10S,11S)-(—)-epi-pyriculol is its production on a large scale, either by isolation from fungal fermentations or by synthesis. For these purposes, rapid and sensitive methods for the quantification of (10S,11S)-(—)-epi-pyriculol in complex mixtures are required. In this study, a high-pressure liquid chromatography (HPLC) method for its quantification was developed and applied to organic extracts from twelve P. grisea isolates obtained from diseased buffelgrass leaves and grown in potato dextrose broth (PDB) liquid cultures. The analysis proved that the production of (10S,11S)-(—)-epi-pyriculol is fungal-isolate dependent and strongly correlated with phytotoxic activity, shown by the P. grisea organic extracts in a buffelgrass radicle elongation test. The HPLC method reported herein allowed us to select the best strain for the production of (10S,11S)-(—)-epi-pyriculol and could be useful for selecting the best cultural conditions for its mass production, providing a tool for the use of this promising metabolite as a new bioherbicide for the control of buffelgrass.

Bioprospection of Phytotoxic Plant-Derived Eudesmanolides and Guaianolides for the Control of Amaranthus viridis, Echinochloa crus-galli, and Lolium perenne Weeds

“…Nevertheless, based on the presented results, it is necessary to avoid conclusively designating them as definitive model systems for herbicide development. Further studies regarding their applicability must be carried out, and this would include achieving high-yield production, ecotoxicological evaluation, and studies on a larger scale. , …”

“…Further studies regarding their applicability must be carried out, and this would include achieving high-yield production, ecotoxicological evaluation, and studies on a larger scale. 56,57 ■ ASSOCIATED CONTENT * sı Supporting Information…”

Phytotoxic fungal secondary metabolites as herbicides

“…A sensitive method using HPLC was recently developed to select the best Pyricularia grisea strain for the production of (10S,11S)‐()‐epi‐pyriculol (EPYR), a metabolite phytotoxic to weed buffelgrass ( Cenchrus ciliaris ). This then made it possible to optimize the cultivation conditions on a case‐by‐case basis and ensure mass production of EPYR 111 . This review reports on the diversity of weed‐phytotoxic fungal secondary metabolites.…”

Insights into the Ecotoxicology of Radicinin and (10S,11S)-(—)-epi-Pyriculol, Fungal Metabolites with Potential Application for Buffelgrass (Cenchrus ciliaris) Biocontrol

“…All radicinin samples were dissolved in methanol and analyzed at 0.5 mg/mL. The analysis of EPYR was performed using a methanol/H 2 O (0.1% formic acid) gradient, starting from 50% methanol, increasing linearly to 70% in 30 min, and finally rebalanced to the initial rate for 10 min [24]. The detection was performed at 231 nm, corresponding to the maximum UV absorption reported for (10S,11S)-(-)-epi-pyriculol [21].…”

“…However, to continue all of these studies at the whole-plant level for the development of natural bioherbicides, larger quantities of both compounds are needed. Thus, high-performance liquid chromatography (HPLC) analyses were used to select the best source and culture conditions in order to optimize their large-scale production by fungal fermentation [23,24] and prompt research on their total stereoselective synthesis [19,20,25]. Even though these two compounds (1 and 2) had already shown promising results, their efficiency, degradation, and Radicinin was also suggested as a key active metabolite produced by other fungi with herbicidal and fungicidal properties [11].…”