Phenguignardic Acid and Guignardic Acid, Phytotoxic Secondary Metabolites from Guignardia bidwellii

Abstract

Bioactivity-guided isolation led to the identification of phenguignardic acid (2), a new phytotoxic secondary metabolite from submerged cultures of grape black rot fungus, Guignardia bidwellii. The compound is structurally related to guignardic acid (1), a dioxolanone moiety-containing metabolite isolated previously from Guignardia species. However, in contrast to guignardic acid, which is presumably synthesized from deamination products of valine and phenylalanine, the biochemical precursor for the biosynthesis of the new phytotoxin appears to be exclusively phenylalanine. Guignardic acid was also found in extracts of cultures from Guignardia bidwellii. The phytotoxic activities of both compounds were assessed in plant assays using either detached vine leaves or intact plants. Antimicrobial and cytotoxic activities of phenguignardic acid were determined.

Synthesis of α‐Dawson‐Type Silicotungstate [α‐Si2W18O62]8− and Protonation and Deprotonation Inside the Aperture through Intramolecular Hydrogen Bonds

“…The fungus Guignardia bidwellii is the causal agent of grape black rot, a devastating disease that threatens vineyards in, for example, the Moselle and Nahe region and the Middle Rhine valley in Germany. We have recently elucidated the structures of eight dioxolanone‐type secondary metabolites isolated from culture filtrates of G. bidwellii 10,11. These compounds have in common a core structure similar to that of the previously known metabolite12 guignardic acid ( 1 , Figure 1) and differ only in the substituents at C‐2 and the carboxylate function.…”

Total Synthesis of (+)‐Phenguignardic Acid, a Phytotoxic Metabolite of Guignardia bidwellii

“…It is noteworthy that the TES ether ( S )‐ 16 was transformed equally well into the carboxylic acid ( S )‐ 2 . Phenguignardic acid ( 2 ) exhibited optical rotations of [ α ] D 22 = +227 ( c = 0.57, CH 3 CN), +194 ( c = 0.24, CDCl 3 ), +200 ( c = 1.0, CH 2 Cl 2 ) in the case of the S enantiomer and [ α ] D 22 = –197 ( c = 0.25, CDCl 3 ), –224 ( c = 0.55, CH 3 CN) for its optical antipode, whereas the optical rotation of natural 2 obtained by fermentation amounted to [ α ] D 23 = +116 ( c = 0.18, CDCl 3 ) 5…”

“…Other Guignardia species are responsible for diseases in the horse chestnut, in citrus plants, or in tropical fruits such as papayas 3. The major phytotoxic metabolite of G. bidwellii is ( S )‐guignardic acid ( 1 , Figure 1),4 but its congener phenguignardic acid ( 2 )5 shows an even more pronounced effect. Alaguignardic acid ( 3 ),6 another metabolite of G. bidwellii , shows nearly the same phytotoxic activity as 1 .…”

Lignocellulolytic Capability of Endophytic Phyllosticta sp.

“…Phytotoxins, phyllosinol, brefeldin, and PMtoxin are known as fungal pathogenic derivatives from Phyllosticta [20]. Recently, the phytotoxins guignarenones A-F and alaguignardic acid have been isolated which could stimulate the development of herbicides of natural origin [21][22][23]. In addition, antimicrobial activity active on growth inhibitor of Escherichia coli, Bacillus cereus, and Pseudomonas aeruginosa [24][25].…”