## 1 Introduction  
_Articum lappa_ L., commonly known as burdock, is a member of the Asteraceae family. It is a widely distributed plant native to Asia, particularly China, but also commonly found across Europe and North America [1]. It thrives in disturbed, nutrient-rich environments, growing at altitudes up to 3300 m above sea level, and even higher in Central Asia [2]. Although burdock favors moist soils and temperate climates, it is highly adaptable, flourishing in sunny, fertile, and clay-rich soils, a trait that has led to its classification as an invasive species in several regions [3]. For centuries, burdock leaves, roots, flowers, and stalks have been valued in traditional medicine and as food ingredients due to their notable bioactive properties [4]. These health benefits, including hepatoprotective, antioxidant, and anti-inflammatory effects, are primarily attributed to a rich composition of secondary metabolites such as tannins, lignans, caffeic acid derivatives, inulin, and diarctigenin [5; 6; 7; 8]. Among plant secondary metabolites, phenolic compounds play a crucial role in protecting against environmental stressors like insects, pathogens, and harsh climatic conditions [9; 10]. It is well established that, under adverse environmental factors, plants increase their phenolic production as a defensive strategy [11; 12; 13]. However, to date, there are limited studies that specifically address how the phenolic profile of burdock roots is influenced by the growing site. This is particularly relevant because altitude-related factors, such as elevated UV radiation, temperature variability, oxygen availability, and soil composition, significantly influence the secondary metabolism of plants. Increased UV exposure at higher altitudes stimulates phenolic synthesis, while cooler temperatures (generally ranging from 5 to 15 \({}^{\circ}\)C) and oxidative stress further enhance the production of these protective compounds. Soil nutrient variability along altitudinal gradients also affects phenolic concentrations and profiles. Understanding these relationships is essential for optimizing the bioactive potential of burdock and harnessing its health benefits [14; 15; 16; 17; 18; 19; 20; 21]. Notably, burdock roots are the most extensively studied plant part, although the seeds and leaves have also demonstrated medicinal value [5; 22; 23; 24; 25; 26; 27; 28]. In traditional Chinese medicine, burdock roots were revered as a \"blood detoxifier,\" promoting the elimination of toxins, supporting circulation, and improving skin conditions such as eczema [22]. Modern pharmacological studies confirm that burdock roots possess antimutagenic, antimutogenic, anti-inflammatory, antioxidant, antibacterial, and antiviral activities [22]. These effects are largely attributed to phenolic acids, mainly caffeoylquinic acid derivatives, and other bioactive phenolics such as caffeic acid, arctigenin, and arcitin [23; 24; 25; 26; 27; 28]. Traditionally, phenolic compounds from _Arctium lappa_ L. have been extracted using conventional solid-liquid extraction (SLE) methods with aqueous-organic solvents [3]. However, in recent years, these conventional techniques have increasingly been replaced by advanced, eco-friendly alternatives such as ultrasound-assisted extraction (UAE) and pressurized liquid extraction (PLE), which offer improved efficiency and selectivity. UAE has been applied in the isolation of phenolic compounds from both burdock leaves and roots [26; 29; 30; 31]. Nonetheless, studies have demonstrated that PLE, particularly at elevated temperatures and pressures, significantly enhances the extraction of bioactive phenolics from burdock roots compared to UAE and maceration, as it improves solvent penetration and mass transfer within the plant matrix [32; 33]. Despite its potential, the application of PLE to burdock has been limited.