###### Abstract
The antioxidant effect of this plant is often emphasised, for which the phenolic compounds are mainly responsible [13; 14; 16; 17]. Antioxidants are one of the methods of protecting the body against the negative effects of oxidative stress. This phenomenon causes damage to key structures of the body, such as proteins, nucleic acids, and membrane lipids, which contributes to the development of many diseases and accelerates the ageing process [18]. [PERSON] et al. (2022) assessed the content of polyphenic compounds in flowers, leaves, roots, and stalks. They determined the content of hydrolysable tannins, sanguis, sanguisorbic acids, phenolic acids, anthocyanins, davonols, catechins, and proanthocyanins. The total content of the tested compounds decreased in the following order: flowers > leaves > roots > stalks (14,445, 9963, 8687, and 4606 mg/100 g d.w., respectively) [12]. [PERSON] et al. (2016) also confirmed the presence of polyphenic compounds in _S. officinalis_[14]. Numerous studies have confirmed the antioxidant activity of extracts from the aboveground and underground parts of _S. officinalis_. [PERSON] et al. (2024) confirmed the antioxidant potential and polyphenol content in ethanolic extracts of _Sanguisorbae herba_ prepared in 70% and 40% ethanol. Extracts in both ethanol concentrations showed similar antioxidant potential and total polyphenol content [4]. [PERSON] et al. (2021) indicated that ethanolic extracts from great burnet roots and leaves are a much more valuable source of antioxidants than flowers and stems [13]. [PERSON] et al. (2016) showed that the great burnet methanolic extract was characterised by a higher antioxidant potential, assessed using the DPPH technique and the content of flavonoids, while the aqueous extract was characterised by a higher content of total polyphenols and phenolic acids [14]. [PERSON] et al. (2005) confirmed the antioxidant activity of ethanolic extracts of _Sanguisorbae radix_. The radical scavenging activity (RSA%) of the obtained extracts, assessed using the DPPH technique, was 32.92%, while the polyphenol content was 368.25 mg/g [19]. In the cited studies, the authors used various solventsand extraction methods as well as _in vitro_ spectrophotometric techniques to assess the antioxidant potential. However, the extraction process was optimised in none of the presented publications. To our knowledge, there are no reports in the available literature on optimising the ultrasound-assisted extraction process of the great burnet herb in terms of antioxidant activity and total polyphenol content. The aim of the study was to optimise the extraction process of the _S. officialis_ herb using the response surface methodology. We used a third-degree (3\({}^{3}\)) Central Composite Design (CCD). The raw material content, alcohol concentration, and extraction time were the independent variables used. Their influence on the antioxidant activity, assessed by the DPPH and FRAP methods, and the total polyphenol content (TPC), estimated by the Folin-Ciocalteu technique, was determined. We found no publications in the available literature discussing the optimisation of the _S. officialis_ herb extraction process in terms of the studied properties. The analysis of the obtained results revealed that the optimal extraction parameters for the _S. officialis_ herb in the ultrasound-assisted process, in terms of the antioxidant activity and TPC, are a raw material content of 7.5 g/100 mL of solvent, an ethanol concentration of 47% \(v/v\), and an extraction time of 10 min. Lipophilicity tests showed that the optimised extract is highly hydrophilic (log P = \(-\)0.307 \(\pm\) 0.001). The obtained extract, characterised by high antioxidant activity and polyphenol content, can be used in various industrial sectors, such as the pharmaceutical and cosmetic industries. Due to a number of other biological activities of the _S.