Studies of the phytotoxic effects between plants can be a crucial tool in the discovery of innovative compounds with herbicide potential. In this sense, we can highlight ruzigrass (Urochloa ruziziensis), which is traditionally used in the crop rotation system in order to reduce weed emergence. The aim of this work was to characterize the secondary metabolites of ruzigrass and to evaluate its phytotoxic effects. In total, eight compounds were isolated: friedelin, oleanolic acid, α‐amyrin, 1‐dehydrodiosgenone, sitosterol and stigmasterol glycosides, tricin and p‐coumaric acid. Phytotoxic effects of the crude methanolic extract and fractions of ruzigrass were assessed using germination rate, initial seedling growth, and biomass of Bidens pilosa, Euphorbia heterophylla and Ipomoea grandifolia. Chemometric analysis discriminated the weed species into three groups, and B. pilosa was the most affected by fractions of ruzigrass. The phytotoxic activities of 1‐dehydrodiosgenone, tricin, and p‐coumaric acid are also reported, and p‐coumaric acid and 1‐dehydrodiosgenone were active against B. pilosa.

Os lodos de indústria de gelatina apresentam potencial de utilização como biofertilizante, entretanto possuem elevado teor de umidade (98%). Este trabalho objetivou analisar a influência de três diferentes vazões mássicas do ar de secagem (0,3, 0,4 e 0,5 kg.min-1) para uma temperatura fixa de 110ºC na secagem deste lodo em um secador convectivo. Foram utilizados os modelos de Lewis, Page, Henderson e Pabis e Logarítmico para ajuste aos modelos. Os resultados mostraram que, para a menor vazão, o tempo de secagem foi maior. Já para as duas maiores vazões o tempo de secagem foi o mesmo, mostrando que a velocidade de secagem não apresentou tanta influência. Os modelos apresentaram bons ajustes para as vazões de 0,3 e 0,5 kg.min-1, destacando-se os modelos de Page e Logarítmico, com coeficientes de correlação de aproximadamente 99,85%. Entretanto, para a vazão de 0,4 kg.min-1 os modelos não apresentaram bons ajustes, com coeficientes de correlação de aproximadamente 86,94%.

No abstract

An increase in crop competitiveness relative to weed interference has the potential to reduce crop yield losses. In this study, the effects of phytoalexin resveratrol were examined in Zea mays L. (corn) and in the weed species Ipomoea grandifolia (Dammer) O’Donell (morning glory). At a concentration range from 220 to 2200 μM resveratrol exerted a stimulus on Z. mays seedling growth that was more pronounced at low concentrations; in the weed species I. grandifolia, resveratrol exerted inhibitory action on seedling growth in all of the assayed concentration range. In I. grandifolia, resveratrol also inhibited the respiratory activity of the primary roots. In mitochondria isolated from Z. mays roots, resveratrol at concentrations above 440 μM inhibited the respiration coupled to ADP phosphorylation and the activities of NADH-oxidase, succinate-oxidase, and ATPsynthase. These effects were not reproduced in Z. mays grown in the presence of resveratrol as the respiratory activities of the roots were not affected. The finding that the resveratrol exerts beneficial effects on growth of Z. mays seedlings and inhibits the growth of I. grandifolia heightens the potential of resveratrol application for crop protection.

Pfaffia glomerata, known as ginseng-brasileiro, is a root widely used in folk medicine, being effective against inflammation, rheumatism, and fatigue, in addition to present aphrodisiacs and antidiabetics properties. Among the classes of substances reported for the specie, the phenolic acids, in special gallic acid, has shown positive activity to learning and memory, having a considerable effect against neurotoxic and pro-oxidant substances. Therefore, the article’s objective was to quantify gallic acid in the chloroform and ethyl acetate fractions from P. glomerata. Thus, the aerial parts of ginseng were collected, dried and subjected to extraction with ethanol followed by fractionation with organic solvents in different polarities, obtaining the hexanic, dichloromethane (CHCl3) and ethyl acetate (AcOEt) fractions. Then, gallic acid was identified by TLC and quantified by HPLC in the ethyl acetate fraction. The total phenolic content was determined in the chloroform and ethyl acetate fractions, presenting values of 70,3 mg/g and 118,6 mg/g, respectively. The gallic acid content determined by HPLC in the AcOEt fraction was 904,15 µg/g, while in the CHCl3 fraction it was not possible to quantify. So, the species can be a source of phenolic compounds for possible applications in the pharmaceutical area.

Owing to an increasing demand for food, a constant agricultural production flow must be maintained. Further, for doing so, the use of pesticides is necessary. An alternative that results in less damage to the ecosystem and people themselves may be identified by studies on the allelopathic effect of weeds. Therefore, this work aimed to evaluate the allelopathic action of hexane, dichloromethane, butanol, and ethyl acetate fractions of sorghum (Sorghum bicolor [L.] Moench) on the initial growth of morning glory (Ipomoea grandifolia [Dammer] O’Donell) and slim amaranth (Amaranthus hybridus L.), which was verified by the percentage of germination, speed of germination, seedling length, and fresh and dry biomass weight. The experiments were conducted in an incubation chamber at 25 °C for 7 and 14 days for morning glory and slim amaranth, respectively. The experimental design was completely randomized, with five replicates in Petri dishes. The data were evaluated by analysis of variance, and the averages between each treatment were compared using the Scott Knott test at a 5% significance level. The results indicated that the dichloromethane and ethyl acetate fractions decreased the initial growth of morning glory and slim amaranth more, when compared with the effects of hexane and butanol.

Brazil has a diversity of plant species and many of them are medicinal plants used in the production of herbal medicines. Passiflora incarnata is popularly known as passion fruit, its fruits and aerial parts have anxiolytic and sedative properties. Recent studies have shown that P. incarnata has several bioactive compounds such as indole alkaloids, cyanogenic glycosides, maltol and flavonoids. Among the substances identified in the species, vitexin has action on the Central Nervous System, interfering with the functioning of gamma-aminobutyric acid. Thus, the objective of the study was to identify and quantify the vitexin present in the ethyl acetate fraction of the aerial parts of the passion fruit. For this, the aerial parts of P. incarnata were submitted to extraction with ethanol, followed by fractionation in organic solvents, obtaining the hexane, dichloromethane and ethyl acetate fractions. The presence of vitexin in the ethyl acetate fraction was verified by Thin Layer Chromatography (TLC) and the total flavonoid content by colorimetric reaction in a spectrophotometer. The quantification of vitexin was performed by High Performance Liquid Chromatography (HPLC). The total flavonoid content was 5.34 mg/g and 960 µg/g of vitexin in the ethyl acetate fraction. Studies like this contribute to the development of new pharmaceutical formulations from the substance vitexin.

Psidium guajava is popularly known as guava. It is a very common species in South America, found most often in tropical climate. It is a plant known for its anti-inflammatory property, used in folk medicine for combating intestinal discomfort, colic, colitis, among others. The leaves of P. guajava present flavonoids in their composition, with emphasis on quercetin. The flavonoid class has antioxidant properties and acts on the central nervous system through oxidative inhibition of the endoplasmic reticulum. Thus, the objective of this study was to quantify the quercetin of the aerial parts of guava. Therefore, ethanol extraction was performed, followed by fractionation with solvents of different polarities, obtaining the hexanic, dichloromethane and ethyl acetate fractions. Then, quercetin was identified in the ethyl acetate fraction by Thin Layer Chromatography (CCD), the total flavonoid content was quantified by spectrophotometry and quercetin by High Efficiency Liquid Chromatography (HPLC). The qualitative analysis in CCD of the ethyl acetate fraction revealed the presence of flavonoids. Quantitative spectrophotometry analysis showed 46.2 mg of total flavonoids per g of the ethyl acetate fraction, being 816 μg g-1 of quercetin revealed by HPLC. With this study, it was possible to identify the presence of flavonoids, and about 2% correspond to the substance quercetin, present in the ethyl acetate fraction of P. guajava. Therefore, further studies can be carried out aiming at the isolation of quercetin for application in a pharmaceutical form acting on the central nervous system.