Sea buckthorn (
Hippophae Rhamnoides L
.) is an important source of bioactive compounds such as: antioxidants, vitamins, fatty acids, amino acids, and minerals. Sea buckthorn leaves extracts have been proved to have anti-microbial, antioxidant, anti-inflammatory, and anti-viral properties. In this paper, the extraction of polyphenols from sea buckthorn leaves using a semi-continuous small-scale reactor is described. The extraction conditions must not affect the composition and structure of polyphenols. For this reason, the influence of different parameters (residence time, solvent flow rate, stirring rate, reactor type, and solvent pre-heating) on the extraction process were studied. The polyphenolic extracts were analyzed in order to determine the total phenolic content (TPC), the antioxidant capacity and the concentration of the main phenolic compounds. The TPC increases with the stirring rate. Pre-heating the solvent leads to a better yield and reduced residence time. The antioxidant capacity is in concordance with the TPC results. HPLC analysis confirms that the semi-continuous microwave assisted extraction (MAE) does not affect the composition of the extracts. The energy consumption was significantly lower for MAE compared with conventional extraction (CE).
In this study, microwave assisted a hydrodistillation process (MWHD) of essential oils from lavender (Lavandula angustifolia Miller) was investigated. In order to examine any potential differences in essential oil extraction, the lavender flowers underwent enzymatic pretreatment.A 23 factorial design of experiments, combined with statistical methods of data analysis were used to optimize enzymatic pretreatment and to evaluate the influence of major variables (enzyme concentration, temperature and pH) on the performance of the microwave assisted extraction.Under optimal conditions, an extraction yield of 24 mg oil g−1 substrate was achieved (an increase by approximately 25% in comparison with the classic extraction conditions of conventional hydrodistillation).The main compounds of the essential oils obtained were analyzed and identified by gas chromatography coupled to mass spectrometry (GC-MS). Analyzing the data obtained indicated that the content of main compounds (linalool and linalyl acetate − 73%) was greater than that obtained by conventional extraction (67%).
Electron beam (EB) irradiation is a useful method to generate stable silver nanoparticles without the interference of inherent impurities generated from chemical reactions. Our experiments were carried out using linear electron beam accelerators with two different EB absorbed dose rates: 2 kGy min−1 and 7–8 kGy s−1, and with different absorbed dose levels. The optimum conditions for silver nanoparticles (AgNPs) generation by radiolysis, or by radiolysis combined with chemical reduction, were established. In order to obtain a good yield for AgNPs synthesized by radiolysis, a high dose rate is required, resulting in a rapid production process. At low absorbed dose rates, the utilization of a stabilization agent is advisable. By modifying the experimental conditions, the ratio between the chemical and radiolytic reduction process can be adjusted, thus it is possible to obtain nanoparticles with tailored characteristics, depending on the desired application.
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