Phomentrioloxin: A Phytotoxic Pentasubstituted Geranylcyclohexentriol Produced by Phomopsis sp., a Potential Mycoherbicide for Carthamus lanatus Biocontrol

Abstract

A new phytotoxic geranylcyclohexenetriol, named phomentrioloxin, was isolated from the liquid culture of Phomopsis sp., a fungal pathogen proposed for the biological control of Carthamus lanatus, a widespread and troublesome thistle weed belonging to the Asteraceae family causing severe crop and pastures losses in Australia. The structure of phomentrioloxin was established by spectroscopic, X-ray, and chemical methods as (1S,2S,3S,4S)-3-methoxy-6-(7-methyl-3-methylene-oct-6-en-1-ynyl)cyclohex-5-ene-1,2,4-triol. At a concentration of 6.85 mM, the toxin causes the appearance of necrotic spots when applied to leaves of both host and nonhost plants. It also causes growth and chlorophyll content reduction of fronds of Lemna minor and inhibition of tomato rootlet elongation. Finally, in preliminary bioassays, phomentrioloxin did not show any antibacterial, fungicidal, or zootoxic activities.

Fungal phytotoxins with potential herbicidal activity: chemical and biological characterization

“…84 Assayed on leaves of several weedy plants, i.e. 8, Table S1 ESI †), 86 was puried from the liquid culture of a Phomopsis sp. None of these compounds showed antibiotic, fungicidal or zootoxic activity.…”

“…93 Poor results of mechanical 93 and chemical control have made this weed a suitable target for biological control. 86 A more virulent strain of D. gulyae was shown to produce different new and known metabolites when grown in a static liquid culture or in a bioreactor. 94 Tested at different concentrations against the host plants of C. lanatus L. and some other weeds (M. annua L., C. album L., C. arvense L., Sonchus oleraceus L. and S. viridis L.), phomentrioloxin (75) caused the appearance of necrotic spots when applied to the leaves of both the host and non host plants at 6.85 mM.…”

“…18) showing the saturation of the geranyl side chain. 86,167 The structural features important for the activity are drawn in red in Fig. The hydroxy groups at C-2 and C-4 appeared to be important features for the phytotoxicity, as well as an unchanged cyclohexentriol ring.…”

Structure and Absolute Configuration of Kongiidiazadione, a New Phytotoxic 3‐Substituted‐5‐Diazenylcyclopentendione Produced by Diaporthe Kongii

“…The strain of D . kongii used in this study was grown on a mineral defined liquid media, M1‐D as previously reported . The culture filtrates (7 L, pH 4.3), having high phytotoxic activity on leaves were lyophilized, dissolved in distilled water (1/10 of its original volume), and then extracted by EtOAc (4 x 700 mL).…”

“…gulyae was shown to produce phytotoxic metabolites when grown in vitro. The main metabolite, named phomentrioloxin, was characterized as (1 R , 2 R , 3 R , 4 R )‐3‐methoxy‐6‐(7‐methyl‐3‐methylene‐oct‐en‐1‐ynil)cyclohex‐5‐ene‐1,2,4‐triol …”