Chlorophyll is the most abundant green pigment on the planet, it is unstable and decomposes naturally. Mate-herb is a traditional native plant in the southern region of South America, and its tea is part of the local culture and extractive agriculture. The mate-herb industry generates as a by-product a resinous material rich in chlorophyll whose use is proposed to be a natural pigment. The chlorophyll extraction method uses ethanol as a solvent; its structural modification leads to the obtainment of derivatives like pheophytin, Co-pheophytin, Ni-pheophytin, and Zn-pheophytin. The samples were analyzed by electronic (VISIBLE) and vibrational (FTIR) spectroscopy, and energy-dispersive X-ray fluorescence spectrometry (EDXRF). Color analysis (CIE L*a*b*) was performed by decomposition in grayscale and the classification of the samples by the supervised machine learning (ML) algorithm Random Forest (RF), showing adequate accuracy for this type of matrix. The pigments were dispersed in synthetic enamel paint to study color stability when exposed to lighting. It was verified that Co-pheophytin and Ni-pheophytin are the most stable. The chlorophyll extracted from the resin presents an economically viable use for residues from mate-herb industries, whose family farmers benefit, with the bias of environmental and social sustainability, within the circular economy.

Abstract Eragrostis plana (Nees) (Tough Lovegrass) shows ability to interfere with other plants, a phenomenon known as allelopathy. This chemical interaction between plants occurs due to the release of compounds into the environment. Thus, a phytotoxicity study was carried out with E. plana roots collected during each season throughout the year, and the compounds were extracted with solvents of increasing polarity. The data from the bioassays were analyzed by GLM and PCA. In addition, a fingerprint of these extracts was obtained by HPLC-DAD. The extracts in petroleum ether from roots collected in the winter and summer showed greater phytotoxicity on Ipomoea grandifolia germination and growth. The PCA obtained from the chromatogram of the crude extract showed that the extracts in petroleum ether were chemically different from the extracts in ethyl acetate and methanol. Thus, continuing this study in order to develop a new generation of bio-herbicides is essential.

The extraction process of bioactive compounds from propolis produced by selected bees was optimized using a 2³ factorial design planning to evaluate the effect of ethanol concentration, time and temperature on the extraction of total phenolic compounds and antioxidant activity. Analysis of total flavonoids, antioxidant activity and chemical characterization performed by high-performance liquid chromatography with photodiode array (HPLC-PDA) detection were carried out in optimal conditions of extraction. Optimizing results suggest that the best condition for extraction of bioactive compounds was obtained in higher levels: time (45 min), temperature (70 °C) and concentration of ethanol (80%). The extract evaluated in optimal conditions presented good antioxidant activity by the radical scavenging 2,2’-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and ferric reducing antioxidant power (FRAP) methods and chromatographic analysis identified phenolic acids: para-coumaric, ferulic and caffeic, indicating that this material is a potential source of bioactive compounds.

The investigation of the chemical properties of soil organic matter (OM), by the use of some spectroscopic techniques, requires the removal of the mineral impurities of the samples. Therefore, the objective of this study was to evaluate the influence of the pretreatment of samples and, also, the influence of instrumental conditions on the qualitative and quantitative results obtained by Fourier transform infrared (FTIR) spectroscopy to soil and humic acid (HA) samples. The obtained results showed that: the mass of potassium bromide (KBr) used on the background pellet influenced the characteristics of samples spectra; the baseline correction changes the intensity of the absorptions; both the extraction of HA as the hydrofluoric acid (HF) treatment were not efficient in removing the mineral impurities of the samples. The scanning electron microscopy (SEM) analysis showed differences due to the extraction, but not due to the HF treatment. The present study shows the importance of the use of adequate treatments, before, during and after the spectroscopic study of soil OM, providing valuable information for future works.