## 1 Introduction  
Polygonum cuspidatum Siebold and [PERSON]. (syn. _Reynoutria japonica_ Houtt, _Fallopia japonica_ (Houtt.) Ronse Decr.) has two faces--it is listed by the World Conservation Union as one of the world's worst invasive species [1] and at the same time is a highly valued traditional medicinal plant [2]. Since 1977, its dried rhizome (called _hu zhang_ in Chinese), has been listed in the Pharmacopeia of the People's Republic of China [3]. The use of this raw material for various ailments has a long tradition in East Asia. The first written record of the use of this species as a medicinal plant can be found in Mingyi Bielu, a famous monograph on traditional Chinese medicine written during the Han Dynasty, approximately 1800 years ago [4]. Over the years, this herb has been used for various indications: for normalizing gallbladders and to cure jaundice, to treat abdominal masses, stranguria, urethritis and postpartum blood stasis as well as for treatment of suppuration, sore throat, toothache, ulcer, hemorrhoids, chronic bronchitis, and other ailments [4]. Modern scientific research confirms the wide spectrum of biological activity of _Polygoni cuspidati thrizona et radix_, having antimicrobial, antiviral, anti-inflammatory, osteogenic, neuroprotective, cardioprotective, and chemopre roles [5]. The inclusion of _Polygoni cuspidati thrizona et radix_ in the European Pharmacopoeia in 2017 [2] among herbal drugs created new possibilities for using the raw material, which is so abundant in Europe. One of the potential uses of this raw material is for oral hygiene and disease. From sources describing the traditional use of _Polygoni cuspidati thrizona et radix_, we learn that it has long been used as a traditional medicine for burns and wounds [4,6]. In Korean folk medicine it is used to support oral hygiene [7]. Moreover, its wound-healing properties have been confirmed in animal studies [8].  
The results of our previous studies also indicate its potential for healing wounds in the oral cavity. Extracts and decoctions obtained from European wildly growing plant stimulated human gingival fibroblast to proliferate, migrate, and increase collagen III synthesis [9,10]. The results of these studies encourage the use of this raw material in medicine, e.g., in regenerative dentistry. However, before we start using this raw material in formulations, it is worth finding out whether it is chemically and biologically equivalent to that considered a pharmacopejeal raw material.  
The aim of this study is to investigate the polyphenol composition in traditional decoctions of _Polygoni cuspidati thizoma et radix_ of different origins and their effect on human gingival fibroblasts. Decoctions were obtained from _Polygoni cuspidati rhizome et radix_ collected from a European wildly growing plant (self-collected decoction; SC decoction) and one from the _Polygoni cuspidati thizoma et radix_ purchased from a pharmacy in Europe as a pharmacopejeal-quality raw material (PH decoction). We performed a qualitative and quantitative UHPLC-DAD-qTOF-MS analysis to compare the phytochemistry of the decoctions and UPLC/QqQ-MS/MS analysis for quantification of selected flavan-3-ols and procyanidins. So far, the biological activity of _Polygoni cuspidati rhizoma et radix_ has been associated primarily with the presence of stilbenes and anthraquinones [11]. Our previous studies, however, indicate a significant content of flavan-3-ols and procyanidins in the extracts, which affect their antioxidant potential [12,13]. There is more and more evidence for the wide spectrum of activity of this class of compounds, especially useful in periodontal diseases or wounds [14, 15, 16]. Taking the above into account, in the research on gingival fibroblasts, we also included compounds found in significant amounts in the decoction, belonging to flavan-3-ols, procyanidins, and stilbenes.