Synthetic Analogues of the Natural Compound Cryphonectric Acid Interfere with Photosynthetic Machinery through Two Different Mechanisms

Abstract

A series of isobenzofuran-1(3H)-ones (phthalides), analogues of the naturally occurring phytotoxin cryphonectric acid, were designed, synthesized, and fully characterized by NMR, IR, and MS analyses. Their synthesis was achieved via condensation, aromatization, and acetylation reactions. The measurement of the electron transport chain in spinach chloroplasts showed that several derivatives are capable of interfering with the photosynthetic apparatus. Few of them were found to inhibit the basal rate, but a significant inhibition was brought about only at concentrations exceeding 50 μM. Some other analogues acted as uncouplers or energy transfer inhibitors, with a remarkably higher effectiveness. Isobenzofuranone addition to the culture medium inhibited the growth of the cyanobacterium Synechococcus elongatus , with patterns consistent with the effects measured in vitro upon isolated chloroplasts. The most active derivatives, being able to completely suppress algal growth at 20 μM, may represent structures to be exploited for the design of new active ingredients for weed control.

Amino‐substituted para‐Benzoquinones as Potential Herbicides

“…Contrary to what expected, no inhibition was observed. Conversely, in compounds 6 and 8 – 13 , a slight stimulation was found, similar to that due to a partial dissipation of the proton gradient across the membrane, which may be caused by the presence of uncouplers . Interestingly, the compounds exerting this effect contain aromatic substituents, as well as amino acids fragments.…”

Synthesis, theoretical studies, and effect on the photosynthetic electron transport of trifluoromethyl arylamides

“…Synechococcus elongatus , strain PCC 6301, was grown at 24 ± 1 °C under 14‐h days (150 μmol m −2 s −1 PAR) and 10‐h nights as previously described . Late log‐grown cells were sedimented by centrifugation 5 min at 4000 × g and used to inoculate 96‐well plates, 0.2 mL per well, to an initial density of about 1.0 mg L −1 chlorophyll.…”

“…Synechococcus elongatus, strain PCC 6301, was grown at 24 ± 1 ∘ C under 14-h days (150 mol m −2 s −1 PAR) and 10-h nights as previously described. 12 Late log-grown cells were sedimented by centrifugation 5 min at 4000 × g and used to inoculate 96-well plates, 0.2 mL per well, to an initial density of about 1.0 mg L −1 chlorophyll. Aliquots (2 L) of suitable dilutions of a given compound in DMSO were added so as to obtain final concentrations ranging from 0.5 to 200 mol L −1 .…”

Mechanisms and metabolomics of the host–pathogen interactions between Chestnut (Castaneaspecies) and Chestnut blight (Cryphonectria parasitica)

“…The mode of action for cryphonectric acid growth suppression has not been identified. However, one recent study examined the effects of a series of isobenzofuran‐1 (3H)‐ones; synthetic analogues of cryphonectric acid (Teixeira et al, ). In this study, the analogues caused interference with the photosynthetic apparatus of spinach ( Spinacia oleracea ).…”

“…However, some analogues also depressed the growth of the cyanobacterium Synechococcus elongatus in culture. The Teixeira et al () study was conducted with synthetic analogues of cryphonectric acid and therefore cannot be used to directly infer the mode of action cryphonectric acid may take in a Castanea host. To date, no study has examined the effect of this secondary metabolite on Castanea tissues, or its potential role during the infection process or disease cycle.…”