ABSTRACT
Olive leaves are residues from pruning and harvesting and are considered an environmental management problems. Interestingly, these residues contain high polyphenol concentrations, which can be used to treat chronic diseases. However, these compounds are a technological challenge due to their thermolability and reactivity during extraction. Thus, this study assessed the use of pressurized liquid extraction (PLE) with green solvents like water-ethanol and water-glycerol mixtures (0-15%) at 50 °C and 70 °C to yield polyphenol-rich antioxidant extracts with reduced glucose and fructose content. The use of 30% ethanol at 70°C presented the highest polyphenol content (15.29 mg gallic acid equivalent/g dry weight) and antioxidant capacity, which was expressed as IC50 (half maximal inhibitory concentration): 5.49 mg/mL and oxygen radical absorbance capacity (ORAC): 1259 µmol Trolox equivalent/g dry weight, as well as lower sugar content (glucose: 3.75 mg/g dry weight, fructose: 5.68 mg/g dry weight) compared to water-glycerol mixtures. Interestingly, ethanol exhibits a higher degree of effectiveness in recovering flavanols, stilbenes and secoiridoids, while glycerol improves the extraction of phenolic acids and flavonols. Therefore, to enhance the efficiency of polyphenol recovery during the PLE process, it is necessary to consider its solvent composition and chemical structure.
ABSTRACT
The use of water-ethanol mixtures in hot pressurized liquid extraction (HPLE) to recover phenolic compounds from agro-industrial waste has been successfully investigated. However, the unresolved challenge of reducing solvent costs associated with the process hinders the scaling of this eco-friendly technology. This study evaluated the use of isopropanol as an alternative, lower-cost solvent for recovering polyphenols from discarded blueberries through the HPLE process. HPLE was carried out using water-isopropanol mixtures (0, 15 and 30%) at 70, 100, and 130 °C. The total polyphenol content (TPC), antioxidant capacity (DPPH and ORAC), glucose and fructose contents, and polyphenol profile of the extracts were determined. HPLE extracts obtained using high isopropanol concentrations (30%) and high temperatures (130 °C) presented the highest TPC (13.57 mg GAE/gdw) and antioxidant capacity (IC50: 9.97 mg/mL, ORAC: 246.47 µmol ET/gdw). Moreover, the use of 30% water-isopropanol resulted in higher yields of polyphenols and removal of reducing sugars compared to atmospheric extraction with water-acetone (60%). The polyphenolic profiles of the extracts showed that flavanols and phenolic acids were more soluble at high concentrations of isopropanol (30%). Contrarily, flavonols and stilbenes were better recovered with 15% isopropanol and pure water. Therefore, isopropanol could be a promising solvent for the selective recovery of different bioactive compounds from discarded blueberries and other agro-industrial residues.
ABSTRACT
The presence of antibiotic residues in drinking water may be a source of contamination, which could affect the diffusion of polyphenols into the wine must during the traditional fermentation process. Antibiotic residues such as ivermectin, hydroxychloroquine, ciprofloxacin, and azithromycin on the diffusion of polyphenols and anthocyanins during wine fermentation were studied. Different samples were taken at different periods (0, 48, 96, and 168 h) to analyse the total polyphenols, anthocyanin content, and antioxidant capacity, which were correlated with Peleg's equation to establish the diffusion kinetics of these compounds. The results indicated that the presence of antibiotics reduced between 40 and 50% the diffusion of the total polyphenols and monomeric anthocyanins in red wine. The use of ivermectin showed the highest kinetic parameter k1 compared with the use of other antibiotics. This suggested that the chemical structure and molecular weight of the antibiotics could play an important role in inhibiting the metabolism of yeasts affecting the ethanol and CO2 production. Consequently, cell membranes would be impermeable and would not allow the release of polyphenols and anthocyanins. Therefore, it is necessary to establish strategies that allow future water quality control in wine production companies.
