Isolation of a phytotoxic isocoumarin from Diaporthe eres‐infected Hedera helix (English ivy) and synthesis of its phytotoxic analogs

Abstract

BACKGROUND: The fungus Diaporthe eres was isolated from a fungal pathogen-infected leaf of Hedera helix (English ivy) exhibiting necrosis. It is hypothesized that the causative fungus produces phytotoxins as evidenced by necrotic lesions on the leaves. RESULTS:The fungus was isolated and grown in Czapek Dox broth culture medium and potato dextrose broth culture medium and identified as Diaporthe eres. The ethyl acetate extracts of the culture broths were phytotoxic to lettuce (Lactuca sativa) and bentgrass (Agrostis stolonifera). 3,4-Dihydro-8-hydroxy-3,5-dimethylisocoumarin (1) and tyrosol (2) were isolated and identified as the phytotoxic constituents. Six analogs of 3,4-dihydro-isocoumarin were synthesized and shown to be phytotoxic. The synthesized 3,4-dihydro-8-hydroxy-3,7-dimethylisocoumarin and 3,4-dihydro-8-hydroxy-3,3,7-trimethylisocoumarin were two-to three-fold more phytotoxic than the naturally occurring 1 in a Lemna paucicostata growth bioassay.CONCLUSION: Synthesis and herbicidal activities of the several new analogs of 1 are reported for the first time. These promising molecules should be used as templates for synthesis and testing of more analogs.

Secondary metabolites produced by the citrus phytopathogen Phyllosticta citricarpa

“…For example, the isocoumarin NM-3 was in phase I of clinical tests due its antineoplastic effect [17]. Consistent with previous reports [11,12] protocatechuic acid (3) and tyrosol (4) did not show any biological activity in our assays.…”

“…Finally, based on the NMR and MS data analyses, compounds 3 and 4 were identified as protocatechuic acid and tyrosol, respectively (Fig. 1), which are common metabolites previously reported from plants and fungi [11,12].…”

Phytotoxic metabolites produced by Diaporthe eres involved in cane blight of grapevine in Italy

“…Fungi belonging to the genus Diaporthe are well known as plant pathogens and as producers of phytotoxins as D. foeniculi (Evidente et al 1994) and D. gulyae, (Andolfi et al 2015;Cimmino et al 2015). D. eres, recently isolated from infected leaves of Hedera helix, also produced 3,4-dihydro-8-hydroxy-3,5-dimethylisocoumarin and tyrosol which together with some isocoumarin analogs were proposed as potential herbicides (Meepagala et al 2018).…”

Novel self-assembling conjugates as vectors for agrochemical delivery

“…Water treated controls were set up; picloram and picloram oleyl (PO) were simultaneously made in water to match the concentrations of the conjugate and were similarly sprayed on to A. thaliana plants [ 12 , 17 ]. Blind assessment is a widely accepted and robust procedure for the assessment of phytotoxic effect induced by herbicidal spray applications [ 27 ]. For our work, three independent blind assessors separately ranked all the photographs collected for plants after day three and seven spray treatments on a scale of zero to five (n = 3 for each replicate).…”