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

Katarina Šavikin,Teodora Janković,Nebojša Menković,Zorica Drinić,Jelena Živković,Gordana Zdunić,Nada Ćujić-Nikolić

doi:10.3390/molecules26133949

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.

Highlights

The genus Sideritis (Lamiaceae) comprises over 150 species, which are distributed throughout the Mediterranean region, the Balkan Peninsula, and the Middle East
In order to estimate the optimization of the UAE process of Sideritis raeseri, we use the response surface methodology (RSM) as a compilation of mathematical and statistical analyses established on the fit of polynomial equations to the experimental data [14]; this describes well the behaviour of the dataset, aiming to make statistical previsions; since it reduces time, space, and raw material usage, it is more favourable than the traditionally used single parameter optimization [15]
The content of total phenolics in S. raeseri extracts obtained using UAE varied between 19.32 and 47.23 mg GAE/g dw. These results were similar or higher compared with our results previously reported for wild-growing S. raeseri and S. scardica collected on the mountain Galicica, North Macedonia (18.25–20.28 mg GAE/g dw) [2]

Summary

Introduction

The genus Sideritis (Lamiaceae) comprises over 150 species, which are distributed throughout the Mediterranean region, the Balkan Peninsula, and the Middle East. Diverse chemical composition of Sideritis species’ aerial parts has been reported, and includes phenolic acids, flavonoids, phenylpropanoids, iridoid glycosides, diterpenes, and essential oils [2,4,5,6]. Due to such diverse chemical composition, many biological activities are reported for Sideritis species, such as anti-inflammatory, spasmolytic, gastroprotective, antimicrobial, hypotensive, vasorelaxant, analgesic, antioxidant etc. Antioxidant, anti-inflammatory, and antimicrobial activities of the extracts are mainly connected with phenylpropanoids and flavonoids, while diterpenoids contribute to the antibacterial, cytotoxic, neuroprotective, and antitumor activities [3,7]

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Conclusion