The intensive application of agrochemicals in crops has negatively impacted the environment and other organisms. The use of naturally occurring compounds may be an alternative to mitigate these ...effects. Plants are secondary metabolite reservoirs and may present allelopathic activity, which is potentially interesting to be used in bioherbicide formulations. In this context, the present work aimed to evaluate the phytotoxic and cytotoxic effects of essential oils extracted from leaves of Sparattanthelium botocudorum and Sparattanthelium tupiniquinorum in bioassays with the plant models Lactuca sativa L. and Sorghum bicolor L. Moench. The essential oils were applied at concentrations of 3,000, 1,500, 750, 375 and 187.5 ppm. Chemical characterization of the oils was performed, and their impact on the percentage of germinated seeds, initial development of L. sativa and S. bicolor seedlings, and changes in the mitotic cycle of meristematic cells from L. sativa roots was evaluated. The major compound of the essential oils was germacrene D, followed by bicyclogermacrene, β-elemene and germacrene A. The phytotoxicity assay showed that the essential oils of both species reduced the root and shoot growth in L. sativa and decreased the germination and shoot growth in S. bicolor. Inhibition was dependent on the tested oil concentration. In the cytotoxicity assay, a decrease in mitotic index and chromosomal and nuclear alterations were observed, which resulted from aneugenic and clastogenic action.
The essential oil of Plectranthus amboinicus and its chemotypes, carvacrol and thymol, were evaluated on the germination and root and aerial growth of Lactuca sativa and Sorghum bicolor and in acting ...on the cell cycle of meristematic root cells of L. sativa. The main component found in the oil by analysis in gas chromatography–mass spectrometry and gas chromatography flame ionization detection was carvacrol (88.61% in area). At a concentration of 0.120% (w v–1), the oil and its chemotypes retarded or inhibited the germination and decreased root and aerial growth in monocot and dicot species used in the bioassays. In addition, all substances caused changes in the cell cycle of the meristematic cells of L. sativa, with chromosomal alterations occurring from the 0.015% (w v–1) concentration. The essential oil of P. amboinicus, carvacrol, and thymol have potential for use as bioherbicides.
•Thymoxyacetic and carvacroxyacetic acids are similar to 2,4-D, but chlorine-free.•Thymol and carvacrol showed toxicity in Lactuca sativa and Sorghum bicolor at 3 mmol L−1.•Carvacrol and ...carvacroxyacetic acid demonstrated genotoxicity in L. sativa and S. bicolor.•Thymoxyacetic acid exhibited selective effect, similar to 2,4-D.•Natural phenols and their respective phenoxyacetic acids showed herbicidal potential.
Natural and semisynthetic compounds may be useful to obtain novel herbicides. Thymol and carvacrol, which belong to the class of phenols, are examples of molecules found in the nature that present phytotoxic activity. Thus, we aimed to synthesize phenoxyacetic acids from thymol and carvacrol and to use them in plant bioassays. The thymoxyacetic and carvacroxyacetic acids were obtained from thymol and carvacrol, respectively, in the presence of sodium chloroacetate, under reflux, followed by acidification. These compounds were tested against Lactuca sativa and Sorghum bicolor initial seed development and their effects were tested on L. sativa and S. bicolor DNA. We also evaluated the performance of these compounds in the mitotic cycle of meristematic cells of L. sativa roots. The synthesized compounds were characterized by mass spectrometry and nuclear magnetic resonancespectroscopy (NMR) of 1H and 13C. The compounds were tested in different concentrations regarding the biological assays: 0.0, 0.375, 0.750, 1.50 and 3.0 mmol L−1. After the analysis of the comet assay, carvacrol and carvacroxyacetic acid showed the most damaging effects on L. sativa and S. bicolor DNA. To corroborate the results found for these two compounds, we carried out an analysis with ISSR to verify the molecular damages in the two tested plants. We concluded that carvacrol, thymol, carvacroxyacetic and thymoxyacetic acids presented phytotoxic and cytotoxic activities. Carvacrol and the carvacroxyacetic acid also showed genotoxic action at the concentration of 3.0 mmol L−1. The toxic effect of the thymoxyacetic acid was similar to that of the commercial herbicide 2,4-D, that is, more pronounced in L. sativa (eudicot) than in S. bicolor (monocot).
Herbicides are commonly used to control weed. However, some plants are resistant to such products. To identify less harmful herbicides, it is crucial to search for different mechanisms of action. ...Thymol is an easily acquired allelopathic compound, capable of producing its respective semisynthetic derivative, thymoxyacetic acid. The aim of this study was to determine the effects of thymol and thymoxyacetic acid molecules as bioherbicides in greenhouse at the concentration of 3 mmol L
−1
in pre- and postemergence applications in five species:
Amaranthus viridis
L.,
Cucumis sativus
L.,
Lactuca sativa
L.,
Eleusine indica
L., and
Sorghum bicolor
L. The initial seedling development and DNA changes were analyzed. These molecules were contrasting with the solvent, in the negative control, and with the glyphosate, in the positive control, promoting phytogenotoxic activities. The toxic effect of thymoxyacetic acid was more effective in preemergence and thymol’s in postemergence. We also observed a reduction in the germination speed index and root growth with a negative correlation to the increase in potassium leaching. Damage to the root and shoot of the seedlings was verified at the DNA level, and the phytotoxicity of the plants treated with the herbicide glyphosate was similar to the plants treated with the natural molecules tested. The bioherbicidal effect of thymol and thymoxyacetic acid exacerbates the reduction of the environmental impact caused by the disordered and increased use of residual pesticides.
The synthesis of a series of 1,2,3-triazoles using glycerol as starting material is described. The key step in the preparation of these triazolic derivatives is the copper(I)-catalyzed azide-alkyne ...cycloaddition (CuAAC), also known as click reaction, between 4-(azidomethyl)-2,2-dimethyl-1,3-dioxolane (
) and different terminal alkynes. The eight prepared derivatives were evaluated with regard to their fungicide, phytotoxic and cytotoxic activities. The fungicidal activity was assessed in vitro against
, the causative agent of papaya anthracnose. It was found that the compounds 1-(1-((2,2-dimethyl-1,3-dioxolan-4-yl)methyl)-1
-1,2,3-triazol-4-yl)-cyclo-hexanol (
) and 2-(1-((2,2-dimethyl-1,3-dioxolan-4-yl)methyl)-1
-1,2,3-triazol-4-yl)propan-2-ol (
) demonstrated high efficiency in controlling
when compared to the commercial fungicide tebuconazole. The triazoles did not present any phytotoxic effect when evaluated against
. However, five derivatives were mitodepressive, inducing cell death detected by the presence of condensed nuclei and acted as aneugenic agents in the cell cycle of
. It is believed that glycerol derivatives bearing 1,2,3-triazole functionalities may represent a promising scaffold to be explored for the development of new agents to control
.
Pesticide misuse has led to problems in agriculture, contamination of environment, and human health. However, research into alternative methods of controlling invasive plants is expanding. The ...allelopathic effect of secondary metabolites from plant parts suggests a potential and sustainable alternative to plant residues for use as bioherbicides. Given the above, the current study aimed to investigate the allelopathic potential of various concentrations of the aqueous extract of fruit peels of genotypes of 'Passiflora mucronata' in seed germination and seedling growth of 'Lactuca sativa' L. Fruit peels of genotypes of 'P. mucronata' were used to obtain an aqueous extract, which was then filtered and diluted at the following concentrations: T1=100; T2=50; T3=25; T4=12.5 mg mL-1; T5= negative control (distilled water) and T6= positive control (glyphosate). Germination was carried out in Petri plates and was conditioned in a biochemical oxygen demand germination chamber at 25 +- 2 degreesC. Macroscopic evaluation was performed at the germination stage and root and aboveground growth of the seedlings, and the germination velocity index were also evaluated. Cytogenetic analysis was performed, and mitotic index was obtained. The design was entirely randomized, with five repetitions of 25 seeds each. Allelopathic substances found in the bark of 'P. mucronata' fruits interfere with seed germination and vigor, as well as initial seedling growth. The germination of 'L. sativa' seeds was 100% inhibited by extract concentrations of 50 % and 100 %. The cell cycle of 'L. sativa' seeds is inhibited by allelopathic substances present in the bark of P. mucronata fruits. It is concluded that aqueous extracts of 'Passiflora mucronata' have an allelopathic inhibitory effect on germination and initial growth of 'L. sativa'.
ABSTRACT The search for bioherbicides has been encouraged, and plants used in food or with bioactivity have been studied. Therefore, this article aimed to investigate the bioherbicidal potential of ...essential oils from Psidium cauliflorum and P. acidum through a plant toxicity bioassay using Lactuca sativa and Sorghum bicolor. The seeds were treated with essential oils of both species, along with control groups treated with distilled water, dichloromethane, and glyphosate. Germination percentage (GP), germination speed index (GSI), root growth (RG), shoot length (SL), mitotic index (MI), chromosomal alterations (CA), and nuclear alterations (NA) were evaluated. The major compound of the essential oil of P. cauliflorum was α-pinene, and of P. acidum were trans-caryophyllene, β-elemene, germacrene A, and α-copaene. The essential oils from both species exhibited phytotoxic effects. P. acidum oil inhibited sorghum RG and lettuce SL, while P. cauliflorum oil reduced GP, GSI, RG, and SL in both plants, indicating higher phytotoxicity than P. acidum and non-selective behavior. Cytotoxic investigations showed that both oils inhibited the MI. CA analysis revealed that P. cauliflorum oil exhibited aneugenic and clastogenic action mechanisms. The results demonstrate the bioherbicidal potential of P. cauliflorum essential oil, in addition to being non-selective and displaying a similar inhibition rate to glyphosate.
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