Optimization of Ultrasound-Assisted Extraction of Phenolics from Sideritis raeseri Using Response Surface Methodology

Abstract

In this study we define the optimal conditions for ultrasound-assisted extraction of bioactive polyphenols from S. raeseri aerial parts using response surface methodology. The influence of ethanol concentration (10–90%), extraction temperature (20–80 °C), extraction time (10–60 min), and solid-to-solvent ratio (1:10–1:50) on total phenolic content as well as on content of individual flavonoids, and hypolaetin and isoscutellarein derivatives was studied. For the experimental design, a central composite design was chosen. In the obtained extracts, the following ranges of targeted compounds were detected: total phenol from 19.32 to 47.23 mg GAE/g dw, HYP from 1.05 to 11.46 mg/g dw, ISC 1 from 0.68 to 10.68 mg/g dw, and ISC 2 from 0.74 to 15.56 mg/g dw. The optimal extraction conditions were set as: ethanol concentration of 65%, extraction time of 50 min, extraction temperature of 63 °C, and solid-to-solvent ratio of 1:40. Contents of TP, HYP, ISC 1, and ISC 2 in optimal extracts were 47.11 mg GAE/g dw, 11.73 mg/g dw, 9.54 mg/g dw, and 15.40 mg/g dw, respectively. Experimentally set values were in good agreement with those predicted by the response surface methodology model, indicating suitability of the used model, as well as the success of response surface methodology in optimizing the conditions of the extraction.

Bioassay-Guided Skin-Beneficial Effects of Fractionated Sideritis raeseri subsp. raeseri Extract

“…Concentrations of HYP1 (2.89–5.31 mg/g dw) and ISC2 (0.79–2.24 mg/g dw) were much lower than in our study. On the other hand, in the study carried out by Šavikin et al [ 32 ], the amounts of HYP1 (1.05–11.46 mg/g dw), ISC1 (0.68–10.68 mg/g dw) and ISC2 (0.74–15.56 mg/g dw), determined in hydroethanolic extract of the same species, were in agreement with our results. Although plant material in all studies was collected on the same mountain, diversity in the published results could be a consequence of genotypic and environmental variations, as well as the different solvents used for extraction, indicating that aqueous ethanol could be a preferable solvent system to methanol/water for the efficient extraction of bioactive compounds from S. raeseri .…”

Comparative Study on Assisted Solvent Extraction Techniques for the Extraction of Biologically Active Compounds from Sideritis raeseri and Sideritis scardica

“…The Mediterranean region, the Balkan Peninsula and the Middle East possess suitable climate conditions for house plant communities rich in herbs and shrubs from the Lamiaceae family, including the Sideritis genus [ 1 ]. In traditional medicine, infusions or decoctions prepared with the flowering aerial parts of the Sideritis species were widely used for the treatment of the common cold, cough, gastrointestinal disorders and for the healing of wounds [ 2 , 3 ].…”

“…Sideritis raeseri is another popular herb variety endemic to the Balkans and the Iberian Peninsula, also cultivated in Greece [ 8 , 9 ]. All these mentioned plants contain a variety of health-promoting phytochemical constituents, including phenolic acids, flavonoids, phenylethanoid glycosides and terpenoids [ 1 ]. Previous studies indicated miscellaneous biological properties of the Sideritis species: anti-inflammatory, gastroprotective, cytotoxic, antimicrobial and antioxidant [ 7 , 10 ].…”

Extraction, structural characterization, and antioxidant activity of polysaccharides derived from Arctium lappa L.

“…The significance of each coefficient was estimated by comparing the magnitude of the p -value. The smaller the p -value, the more significant the coefficient, and vice versa ( 43 ). The results of ANOVA analysis are presented in Table 3 .…”

“…If the interaction between the two factors was weak, the contour line was closer to a circle ( 31 , 44 ). There was strong interaction among the factors, and if the surface diagram was steeper, the influence was more significant ( 43 ). The surface diagram of ALPs extraction results between any two factors was analyzed systematically to determine the optimal factor level and evaluate the effect on the extraction rate of ALPs.…”