Extraction of polyphenols from sea buckthorn leaves using microwave-assisted extraction (MAE) is described. The influence of different parameters on the extraction process (reactor type, stirring rate, extraction time, temperature, ethanol/water ratio) was studied. The polyphenolic extracts were analyzed in order to determine the total phenolic content (TPC) either by the Folin–Ciocalteu method or by differential pulse voltammetry (DPV), and the concentration of the main polyphenolic compounds by high-performance liquid chromatography (HPLC). The specific microwave energy was also determined. MAE resulted in a shorter extraction time (7.5 versus 30 min for the conventional method). The best results for MAE were obtained at a temperature of 90°C, using a solvent/plant ratio of 20/1 and 50% ethanol in the extraction solvent. The highest values of antioxidant capacity were obtained for polyphenolic extracts resulted from microwave extraction.

The extraction of essential oils (EOs) and polyphenols from rosemary and thyme has been done using an integrated process: microwave hydro-diffusion and gravity (MHG) for EOs and microwave-assisted extraction (MAE) for polyphenols. The innovative installation based on the MHG principle allows uniform microwave irradiation field due to a mechanical stirring and experiments done at low pressure. The results of quantitative analysis of the EOs extracted by MHG after 10 min were similar with those obtained by traditional methods (conventional hydro-distillation (CHD) and microwave-assisted hydro-distillation (MHD)) after 150 and 105 min, respectively. The specific energy for MHG was 5–15 times lower compared with these classical methods. The MHG extraction of EOs is also an effective method for plant material pretreatment before polyphenol extraction. Total phenolic content increased from 35 to 55 mg GAE/g DM for rosemary and from 23 to 38 mg GAE/g DM for thyme.

The aim of this study was to establish the best ultrasound assisted extraction (UAE) conditions of saponins from Hedera helix L. leaves and to evaluate the in vitro biocompatibility of the extracts richest in saponins. Different parameters, such as extraction time, temperature, ultrasound power, solvent to plant material ratio, and solvent concentration, were investigated. The most efficient extraction conditions were a temperature of 50 °C, an ultrasound amplitude of 40%, an extraction time of 60 min, a plant material to solvent ratio of 1:20 (w:v), and 80% ethanol as solvent. In vitro cytotoxicity of the extracts richest in saponins and their influence on the DNA content of L929 (NCTC) fibroblasts were tested. Until 200 µg/mL, the studied extracts were cytocompatible with L929 fibroblast cell lines at 48 h of treatment. These in vitro cell culture results provide useful information for further applications of Hedera helix extracts in a pharmaceutical field.

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 paper, the essential oil (EO) extraction from thyme by the consecutive use of ultrasound and microwave treatments is presented. The aim of this study was to apply an ultrasound pre-treatment of thyme leaves to enhance the thymol content and the extraction yield of the EO obtained by microwave-assisted hydro-distillation (MWHD). Compared with conventional hydro-distillation (CHD), the consecutive use of ultrasound pre-treatment and microwave extraction resulted in a 72% lower extraction time. When the ultrasound pre-treatment (using the ultrasonic processor with an amplitude of 70%) was applied, the EO content was 23% higher compared to the extraction without pre-treatment (2.67 ± 0.06 g EO/100 g DM for the MWHD with ultrasound pre-treatment compared with 2.18 ± 0.07 g EO/100 g DM for the MWHD without pre-treatment). The EO samples were analyzed by GC/MS. The results showed that the major component, thymol, varied from 43.54% (by CHD) to 65.94% (by the consecutive use of ultrasound and microwave treatments).