No abstract

SummaryBioactive compounds from Brazilian hop (Humulus lupulus L.) cultivars were extracted by ultrasound and their phenolic profile compared with commercial hop from the USA. The most effective extraction conditions (solution of ethanol 49%, at 52 °C and a solid/liquid ratio of 1 g per 34 mL) for the total phenolic compounds (TPC) were determined using a Central Composite Rotatable Design. The Brazilian hop showed higher content of TPC (33.93 ± 0.67 mg GAE g−1), total flavonoids (54.47 ± 0.10 mg QE g−1) and higher antioxidant activity (ABTS: EC50 21.29 ± 1.36 μL mL−1; DPPH: EC50 3.91 ± 0.17 μL mL−1) when compared with the USA hop. The main phenolic compounds present in the extracts were the flavonoids isoquercitrin and quercetin. The antioxidant properties of the Brazilian hop extract had not been reported yet in the literature for this raw material, thus showing potential to be incorporated in polymeric films used as active packaging.

Considering the importance of biosynthesized silver nanoparticles (AgNPs) using plant phytochemicals, the aim of this work was to evaluate the effect of pH in the formulation of AgNPs, bioreduced with thyme essential oil. Biosynthesized AgNPs were prepared under different pH (7, 8, 9 and 10), and the physicochemical stability was evaluated during 90 days at 6°C and 25°C. Using GC/MS technique, 17 different compounds were observed in the thyme essential oil; however, borneol and αterpineol were the majoritarian compounds, probably responsible to the formation of AgNPs. UV-vis spectroscopy with absorbance between 415 and 440 nm and Transmission Electron Microscopy (TEM) confirmed the synthesis of nanoparticles, with diameters of 40 nm and spherical shapes to pH 7, 8 and 9. Through DLS approach, was observed that the average particle diameter was around 90 nm for all pH tested. AgNPs presented homogeneous size distribution, and zeta potential values very close to the theoretical stability range. Moreover, biosynthesized AgNPs presented high antibacterial activity against Escherichia coli and Staphylococcus aureus. Through x-ray Photoelectron Spectroscopic (XPS) analysis was possible confirm the presence of crystalline silver nanoparticles. Thus, silver nanoparticles eco-friendly prepared using thyme essential oil can be considered as an alternative way to produce this nanomaterial with great stability and high antibacterial activity.

Brazil is the biggest coffee producer in the world and different plantation management systems have been applied to improve sustainability and soil quality. Little is known about the environmental effects of these different management systems, therefore, the goal of this study was to use soil biological parameters as indicators of changes. Soils from plantations in Southeastern Brazil with conventional (CC), organic (OC) and integrated management systems containing intercropping of Brachiaria decumbens (IB) or Arachis pintoi (IA) were sampled. Total organic carbon (TOC), microbial biomass carbon (MBC) and nitrogen (MBN), microbial activity (C-CO 2 ), metabolic quotient (qCO 2 ), the enzymes dehydrogenase, urease, acid phosphatase and arylsulphatase, arbuscular mycorrhizal fungi (AMF) colonization and number of spores and soil fauna were evaluated. The greatest difference between the management systems was seen in soil organic matter content. The largest quantity of TOC was found in the OC, and the smallest was found in IA. TOC content influenced soil biological parameters. The use of all combined attributes was necessary to distinguish the four systems. Each management presented distinct faunal structure, and the data obtained with the trap method was more reliable than the TSBF (Tropical Soils) method. A canonic correlation analysis showed that Isopoda was correlated with TOC and the most abundant order with OC. Isoptera was the most abundant faunal order in IA and correlated with MBC. Overall, OC had higher values for most of the biological measurements and higher populations of Oligochaeta and Isopoda, corroborating with the concept that the OC is a more sustainable system. Keywords