Artigos
URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/11800
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Item Synthetic analogues of the natural compound cryphonectric acid interfere with photosynthetic machinery through two different mechanisms(Journal of Agricultural and Food Chemistry, 2013-05-17) Teixeira, Róbson Ricardo; Pereira, Wagner Luiz; Tomaz, Deborah Campos; Oliveira, Fabrício Marques de; Giberti, Samuele; Forlani, GiuseppeA 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.Item Synthesis, theoretical studies, and effect on the photosynthetic electron transport of trifluoromethyl arylamides(Pest Management Science, 2017-05-25) Teixeira, Róbson Ricardo; Barros, Marcus Vinícius de Andrade; Bressan, Gustavo Costa; Siqueira, Raoni Pais; Santos, Fabíola Suelen dos; Bertazzini, Michele; Kiralj, Rudolf; Ferreira, Márcia Miguel Castro; Forlani, GiuseppeThe photosynthetic apparatus is targeted by various herbicides, including several amides such as diuron and linuron. Considering the need for the discovery of new active ingredients to cope with weed resistance, the synthesis of a series of trifluoromethyl aryl amides is herein described whose inhibitory properties were assessed in vitro on the photosynthetic electron transport chain, and in vivo on the growth of a model cyanobacterial strain. Theoretical studies were also carried out. Starting with 1‐fluoro‐2‐nitro‐4‐(trifluoromethyl) benzene, the preparation of the amides was achieved via a three‐step sequence, namely nucleophilic aromatic substitution, reduction with SnCl2/HCl, and acylation reactions. The measurement of ferricyanide reduction by functionally intact spinach chloroplasts showed that several derivatives are capable of inhibiting the photosynthetic apparatus. The most active amides presented IC50 values close to 1 μmol L−1, and showed the presence of a 4‐bromophenyl group as a common structural feature. The addition of these brominated amides to the culture medium of a model cyanobacterial strain, Synechococcus elongatus PCC 6301, caused various degrees of growth inhibition. Theoretical studies (molecular modeling and quantitative structure–activity relationship) of all amides and their comparison with some known herbicides confirmed these experimental findings and provided more in‐depth information about the possible molecular target of these compounds. Trifluoromethyl amides herein described, which were shown to act at the PSII level, may represent a novel scaffold to be exploited aiming at the development of new active ingredients for weed control.Item Tailoring natural abenquines to inhibit the photosynthetic electron transport through interaction with the D1 protein in photosystem II(Journal of Agricultural and Food Chemistry, 2017-12-01) Nain-Perez, Amalyn; Barbosa, Luiz C. A.; Maltha, Celia R. A.; Giberti, Samuele; Forlani, GiuseppeAbenquines are natural N-acetylaminobenzoquinones bearing amino acid residues, which act as weak inhibitors of the photosynthetic electron transport chain. Aiming to exploit the abenquine scaffold as a model for the synthesis of new herbicides targeting photosynthesis, 14 new analogues were prepared by replacing the amino acid residue with benzylamines and the acetyl with different acyl groups. The synthesis was accomplished in three steps with a 68−95% overall yield from readily available 2,5-dimethoxyaniline, acyl chlorides, and benzyl amines. Key steps include (i) acylation of the aniline, (ii) oxidation, and (iii) oxidative addition of the benzylamino moiety. The compounds were assayed for their activity as Hill inhibitors, under basal, uncoupled, or phosphorylating conditions, or excluding photosystem I. Four analogues showed high effectiveness (IC 50 = 0.1− 0.4 μM), comparable with the commercial herbicide diuron (IC 50 = 0.3 μM). The data suggest that this class of compounds interfere at the reducing side of photosystem II, having protein D1 as the most probable target. Molecular docking studies with the plastoquinone binding site of Spinacia oleracea further strengthened this proposal.