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.
The excessive use of herbicides has caused a series of problems related to human health, environmental pollution, and an increase in the resistance of plants to commercial herbicides. As an ...alternative, natural compounds and their semisynthetic derivatives have been widely studied to obtain environmentally friendly and more effective herbicides than the usual ones. In view of these factors, the aim of this work was to synthesize new molecules with herbicidal potential using thymol as a starting material, a natural phenol that has a pronounced phytotoxic effect. Novel N-phenyl-2-thymoxyacetamides were synthesized and characterized by MS and by 1H and 13C NMR. All prepared molecules were subjected to phytotoxic and cytotoxic activity assays using Lactuca sativa L. and Sorghum bicolor L. as model plants. Molecules containing chlorine in the para position of the thymoxy group exhibited phytotoxic and cytogenotoxic effects superior to those of the commercial herbicides 2,4-D and glyphosate.
The use of allelopathic compounds is an alternative for weeds control, since they present low toxicity when compared with the synthetic herbicides, that may cause several damages, as the ...contamination of the environment. Our objective was to determine the chemical composition and allelopathic properties of the essential oils of
Psidium cattleianum
,
P. myrtoides
,
P. friedrichsthalianum
, and
P. gaudichaudianum
on the germination and root growth of
Lactuca sativa
and
Sorghum bicolor
, and to evaluate their action on the cell cycle of root meristematic cells of
L. sativa.
The main compound found in all the studied species was (E)-caryophyllene (
P. cattleianum
—23.4 %;
P. myrtoides
—19.3%;
P. friedrichsthalianum
—24.6% and
P. gaudichaudianum
—17.0%). The different essential oils were tested at different concentrations on
L. sativa
and
S. bicolor
, reducing germination, germination speed index, and root and shoot growth of lettuce and sorghum seedlings. The cytotoxicity and aneugenic potential of these oils were evidenced by the reduction of the mitotic index and increase of the frequency of chromosomal alterations in
L. sativa
. The essential oils of the species of
Psidium
studied have potential to be used in weeds control.
•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).
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 control of fungal species in agriculture is mainly conducted with the use of contact or systemic fungicides. However, environmental and human health concerns and increased resistance of fungal ...species to existing fungicides have increased the pressure on researchers to find new active ingredients for fungal control which present low toxicity to non-target organisms, are environmentally safe, and can be applied at very low concentrations. It is herein described the synthesis of eleven glycerol triazole containing compounds (ten of them fluorinated derivatives) and evaluation of their fungicidal activity. Eight out of eleven synthesized compounds are novel and all of the glycerol derivatives were characterized using infrared (IR), nuclear magnetic ressonance (NMR), and mass spectrometry (MS) techniques. Theoretical calculations were also carried out and the results are discussed. Starting from glycerol, the triazole derivatives were prepared in four steps. Evaluation of them against Colletrotricum gloesporioides showed that compound 1-((2,2-dimethyl-1,3-dioxolan-4-yl)methyl)-4-(2-fluorophenyl)-1H-1,2,3-triazole (4d) (ED50 = 59.14 µg mL-1) was slightly more active than commercial fungicide tebuconazole (61.35 µg mL-1). Compound 4d presented attractive physicochemical features for agrochemical purposes as revealed by the calculated physicochemical parameters. It is believed that glycerol-fluorinated triazole derivatives can be explored towards the development of new chemicals for the control of fungal species.
Some forest trees have been polyploidized to improve their traits and to supply new germplasms for breeding programs. As trees have a long juvenile stage, the early characterization of the chromosome ...set doubling effects is crucial for previous selection. Thus, we aimed to characterize the chemical variability of essential oils from diploid and autotetraploid germplasms (autotetraploid A and B) of Eucalyptus benthamii, as well as to evaluate their larvicidal and allelopathic effects. Autotetraploid A showed a higher essential oil yield than diploid and autotetraploid B, which did not differ quantitatively. Aromadendrene, viridiflorol and α-pinene were the major compounds in the diploid essential oil. In contrast, compounds were present in autotetraploids, such as 1,8-cineole, limonene, α-terpineol, and α-terpinyl-acetate. Essential oils from the diploid at 50-200 ppm were twice as larvicidal than those from autotetraploids against Aedes aegypti larvae. Considering the phytotoxicity bioassays using Lactuca sativa, essential oils from both ploidy levels affected root growth. Moreover, the essential oils inhibited shoot growth at all concentrations tested (187.5; 375; 750; 1500; and 3000 ppm). Autotetraploid A and B had the same effect on shoot growth as glyphosate. The essential oils had no cytogenotoxic effect on root meristematic cells of L. sativa, whereas phytotoxic potential was identified mainly in shoot growth. This work demonstrated a dramatic change in secondary metabolism (terpene composition) related to an increase in the ploidy level in Eucalyptus germplasms. In addition, we report the novelty of the chemical composition of essential oils among germplasms and their potential use as larvicidal and post-emergence weed control agents.
The present investigation aimed to develop inclusion complexes (ICs) from
(GAU) essential oil (EO) and its major compound
-caryophyllene (
-CAR), and to evaluate their herbicidal (against
and
) and ...cytogenotoxic (on
) activities. The ICs were obtained using 2-hydroxypropyl-
-cyclodextrin (HP
CD) and they were prepared to avoid or reduce the volatility and degradation of GAU EO and
-CAR. The ICs obtained showed a complexation efficiency of 91.5 and 83.9% for GAU EO and
-CAR, respectively. The IC of GAU EO at a concentration of 3000 µg mL
displayed a significant effect against weed species
and
. However, the
-CAR IC at a concentration of 3000 µg mL
was effective only on
. In addition, the cytogenotoxic activity evaluation revealed that there was a reduction in the mitotic index and an increase in chromosomal abnormalities. The produced ICs were able to protect the EO and
-CAR from volatility and degradation, with a high thermal stability, and they also enabled the solubilization of the EO and
-CAR in water without the addition of an organic solvent. Therefore, it is possible to indicate the obtained products as potential candidates for commercial exploration since the ICs allow the complexed EO to exhibit a more stable chemical constitution than pure EO under storage conditions.
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 genus Passiflora has gaps in delimitations and relationships between species.•The chromosome number of 19 species was revised and defined for further nine.•Chromosome classification was ...re-evaluated for nine species and established for 19.•The karyogram was assembled for first time for 24 species.•The nuclear DNA content was revisited for 22 species and expanded for 19.
The Passiflora genus, which is recognized for its economic and ecological potential, has been studied in botanical, systematic and evolutionary aspects. Currently, Passiflora is represented by five subgenera subdivided into 16 supersections, 31 sections and 13 series. However, their delimitations and relationships are still conflicting. We applied classical cytogenetics to revise the chromosome number of 19 species and to define it for further nine. The classification of chromosome pairs was re-evaluated for nine species and established for further 19. For 24 species, the karyogram was assembled for the first time, and for the other four it was updated. Using flow cytometry, the nuclear DNA content was revisited for 22 species and expanded for 19. Chromosome number 2n = 12 was found for the subgenus Decaloba, as well as 2n = 18 and 2n = 20 for Passiflora, 2n = 24 for Astrophea and Deidamioides, and the unpublished 2n = 48 for P. contracta (subgenus Deidamioides). Metacentric and submetacentric chromosomes predominated in all karyotypes, except in P. lindeniana and P. arborea (subgenus Astrophea), which some acrocentric pairs occur. The nuclear 2C value ranged from 0.59 pg (P. capsularis) to 5.46 pg (P. quadrangularis), with differences exceeding 925 %. The karyotypes and nuclear genome size of the genus Passiflora supported the current subgeneric division. The evaluated characters also corroborate with the hypothesis of x = 6 as the ancestral chromosome number and the diversification by polyploidy and ascendant dysploidy. Furthermore, the cytogenetic and genome size data were complementary to systematic of the genus.
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