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A novel LTTM composed of glycerol and sodium acetate was used to assess the effect of 2-hydroxypropyl β-cyclodextrin (CD) on the effectiveness of polyphenol extraction from M. oleifera leaves (MoL). The extraction process was based on a 23-full factorial design and response surface methodology, to evaluate simultaneously the effect of CD concentration (CCD), liquid-to-solid ratio (RL/S) and temperature (T). By employing optimized conditions (CCD = 1%, RL/S = 40 mL g−1, T = 40 °C), the yield in total polyphenols (YTP) was 67.18 ± 5.04 mg gallic acid equivalents per g dry weight. This yield was significantly higher than that achieved with the extraction performed with LTTM alone or 80% aqueous ethanol. The extraction kinetics suggested that the extraction rate was slowed down in the presence of CD, without compromising the higher extraction capacity of the LTTM/CD. Extract characterization by means of liquid chromatography-mass spectrometry showed that there was no selective extraction of any particular polyphenol, indicating that CD acted only as an extraction booster.

Medicinal and aromatic plants (MAPs) have always been a source of a vast variety of secondary metabolites with high biological potency. There is to-date an enormous ongoing research on the development of sophisticated methodologies for the production of bioactive MAP extracts, which may be applied in a spectrum of products, such as foods, pharmaceuticals and cosmetics. A great concern in implementing an extraction protocol is the use of appropriate conditions to achieve maximum efficiency with minimum cost, energy, and environmental aggravation. Although several parameters may affect the effectiveness of an extraction process, time and temperature are of utmost importance, and largely define both operating cost and quality of the final extract. Thus, there is a need for a simple tool of assessing an extraction method and allow for sound comparisons. In such a frame, this study introduces for the first time the concept of “extraction efficiency factor” (FEE). The purpose was to combine time (t) and temperature (T) in a single factor for evaluating extraction processes in general, and to enable easy and sound comparison of results obtained by solid-liquid extractions of MAPs. Such an approach could facilitate process control and would permit trading time and temperature of a treatment such that equivalent final effects are obtained.

The aim of the present study was the encapsulation of Rosmarinus officinalis essential oil (REO) in β-cyclοdextrin (β-CD) and two chemically modified β-CD matrices and the evaluation of the antibacterial activity of the prepared inclusion complexes against Staphylococcus aureus. The inclusion complexes possessed nanoscale size ranging from 395.7 ± 13.7 to 594.9 ± 18.8 nm, good size dispersion (0.366 ± 0.009 to 0.482 ± 0.043) and satisfactory stability in suspension (ζ-potential, −24.3 ± 4.2 to −31.5 ± 4.9 mV), while the inclusion efficiency ranged from 65% to 78%. The in vitro release profiles of the inclusion complexes revealed an initial burst effect, with the release kinetics being better fitted on the Higuchi model following quasi-Fickian diffusion. The antibacterial activity of the inclusion complexes of REO in β-CD, HP-β-CD and Me-β-CD against S. aureus was evaluated for 3 days and it was observed that both β-CD and HP-β-CD exhibited prolonged activity in comparison to the pure REO.

The medicinal plant Satureja thymbra (pink savory) has been chosen to study the capacity of three newly designed glycerol-based, natural low-transition temperature mixtures (LTTMs) to extract polyphenolic antioxidants. First, it was assessed the effect of water concentration ( C W ) and the liquid-to-solid ratio (R L/S ), by deploying response surface methodology (Box-Behnken design). As a further step, kinetics was investigated to examine the effect of temperature. It was found that the optimum C W varied from 54.8 to 63.8% (v/v) and R L/S from 29.5 to 36.2 mL g −1 . Under optimised conditions, all three LTTMs displayed apparent anti-Arrhenius kinetics over a temperature ranging from 40 to 80 °C, evidencing peculiar extraction behaviour. The investigation of the polyphenolic composition of the extracts obtained by liquid chromatography-diode array-mass spectrometry showed that the major constituents were apigenin, luteolin, quercetin and rosmarinic acid derivatives, but none of the LTTMs exhibited notable selectivity. However, significant differences were seen with regard to the antiradical activity and reducing power of the extracts, as extract obtained with LTTM1 displayed consistently strong effects, whereas the extract obtained with LTTM3 had rather questionable efficiency.

A step-by-step optimisation of an extraction process was carried out, with the aim of establishing an eco-friendly methodology for polyphenol recovery from two endemic Cretan Artemisia species. The extraction medium composed of water and glycerol, and the optimisation included factors that were critical to the process, such as glycerol concentration (Cgl) and liquid-to-solid ratio (RL/S). Maximum polyphenol yield was 48.45 and 59.91 mg GAE g−1 dw, for Artemisia arborescens and Artemisia inculta Delile, respectively, and it was achieved with Cgl = 90% (w/v) glycerol and RL/S = 100 mL g−1 for both botanical species. These conditions were used to further examine the extraction behaviour of water/glycerol mixtures with regard to temperature, employing kinetics. The extractions of both species were shown to display similar kinetic attributes, with the activation energy (Ea) being 37.64 and 33.59 kJ mol−1, for A. arborescens and A. inculta, respectively. The outcome concerning the effect of temperature on the antioxidant properties of the extracts was in concurrence of those findings. The liquid chromatography–diode array–mass spectrometry analysis revealed that extracts from both plants were dominated by several chlorogenates, accompanied mainly by flavone C-glycosides.

Hypericum perforatum is a plant rich in biologically functional polyphenolic phytochemicals. The efficient recovery of polyphenols from this material has not been previously investigated in depth, in terms of establishing an environmentally benign and cost effective process that would aim at producing extracts enriched in polyphenolic compounds. The objective of the present study was the examination of the efficiency of water/glycerol mixtures in extracting polyphenols from dried aerial parts of H. perforatum and its critical comparison with water. Extraction temperature and time were optimised using response surface methodology, while comparative assessment of the extraction efficiency between water/glycerol and water was carried out using kinetics. The results showed that 10% (w/v) aqueous glycerol at 70 °C provided very satisfactory extraction yield in total polyphenols (89.9 mg GAE g −1 dw), which was significantly higher than that attained with water. Similar results were drawn for the reducing power, in concurrence with the polyphenolic concentration. Liquid chromatography–mass spectrometry analysis showed that the polyphenolic profile of water/glycerol extract was composed by polar substances, such as chlorogenic acids and quercetin glycosides.