It is known that some plant essential oils have pesticide activities. Among the 29 oils evaluated in this study, 14 showed nematicidal activities of 8 to 100% at the concentration of 1,000 μg/ml, compared with a control of 0.01 g/ml Tween 80®. At a lower concentration of 500 μg/ml, only Dysphania ambrosioides oil caused >90% mortality of second‐stage juveniles (J2) of Meloidogyne incognita. The LC50 and LC95 values for D. ambrosioides oil were 307 μg/ml and 580 μg/ml, respectively. M. incognita eggs placed in D. ambrosioides oil solutions had a significant reduction in J2 hatching compared with controls. Therefore, the oil had a toxic effect on both eggs and J2 of M. incognita. This was in contrast to nematicides on the market that act efficiently only on J2. When J2 were placed in D. ambrosioides oil at its LC50 concentration and inoculated onto tomato plants, the reduction in numbers of galls and eggs was 99.5% and 100%, respectively. Dysphania ambrosioides oil applied to the potting substrate of plants at a concentration of 1,100 μg/ml significantly reduced the number of galls and eggs of M. incognita, whereas a concentration of 800 μg/ml only reduced the number of eggs compared with the controls (Tween 80® and water). The main components of the D. ambrosioides oil detected by gas chromatography–mass spectrometry were (Z)‐ascaridole (87.28%), E‐ascaridole (8.45%) and p‐cymene (3.35%), representing 99.08% of the total oil composition. Given its nematicidal activity, D. ambrosioides oil represents an exciting raw material in the search for new bioactive molecules for the pesticide industry.
Essential oils are natural complex substances biosynthesized by plants, and many of them have antimicrobial properties. Dysphania ambrosioides is a medicinal plant traditionally used as an anthelmintic medicine. In this study, the antifungal activity of D. ambrosioides essential oil was tested against Botrytis cinerea, which is responsible for large economic losses in the post-harvest of roses. Inflorescences of D. ambrosioides yielded 1.3 mg.g -1 of essential oil in fresh material, corresponding to a content of 0.13%. Gas chromatography coupled with mass spectrometry (GC-MS) revealed 11 compounds in the essential oil with ascaridol and O-cymene corresponding to 80% of the total. The essential oil reduced B. cinerea mycelial growth by approximately 60% and spores germination by 51% at the concentration of 1000 ppm. However, no apparent morphological changes were observed in scanning electron microscopy analyzes. The essential oil was not able to reduce mycelial growth on rose petals and caused a color change in the petals 24 h after the treatment. Although the essential oil has little potential to control B. cinerea on roses due to the color change it causes, its activity on mycelial growth and spores germination could be exploited in other pathosystems.
The objective of this research was to evaluate the physicochemical characteristics of Amaranthus spp. commonly happening in Brazil, besides defining the efficiency of different extraction processes of the phenolic compounds and of the antioxidant activity. Five species of the genus Amaranthus (A. spinosus, A. viridis, A. retroflexus, A. hybridus var. paniculatus e A. deflexus) were evaluated in regard to their physicochemical characteristics such as vitamin C, soluble solids, pH, moisture, lipids and protein levels as well as the coloration of the leaves. Also, the phenolic compounds and the antioxidants were defined through four extraction processes (reflux; hydroalcoholic turbo-extraction; aqueous; and methanolic). The species A. spinosus has stood out for its vitamin C levels, pH and moisture, indicating the potential of the species when compared to the others. The leaf extracts of the five Amaranthus species present differences in the total phenol levels, flavonoids and hydro flavonoids when subject to different extraction methods. The antioxidant activities were favored by the reflux and hydroalcoholic turbo-extraction, with A. viridis standing out in the reflux methods and A. spinosus in the hydroalcoholic.
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