## 1 Introduction  
Cancer is the second leading cause of death [1], accounting for nearly 10 million deaths in 2020 worldwide [2], despite advances in chemotherapy development and tumor biology research. Surgery, radiotherapy, and chemotherapy are still the main forms of treatment. New discoveries in signalling pathways involved in tumor development, proliferation, and metastasis and also the completion of the Human Genome Project partially ameliorated some therapeutic problems. Nevertheless, the fundamental problems remain associated with the heterogeneity of the tumor, drug resistance, and systemic toxicities, since it often contains a diverse mixture of cells, and only a part of them can bounce back after treatment. The multiple, interconnected pathways presented in these cells complicate the efforts for providing effective therapies [3]. Troubleshooting remains based on the development of such small molecules which inhibit selectively and the most complexly undesired biological processes in a tumor cell, being able to selectively kill only tumor cells but not their healthy counterparts [4].  
The cytotoxic-active compounds isolated from non-edible plant parts can also be used as health benefit agents, such plants as _Sarcomopterium spinosum_ (L). This plant (syn: _Poterium spinosum_ L) is a spiny roasceous dwarf shrub, and it is thought to have originated from the semi-arid transition zone between the Mediterranean and Irano-Turanian steppe vegetation zone, and then expanded westward [5]. Chemical constituents of _S. spinosum_ and their bioactivity have been described in several works. Five pentacyclic triterpenoids [6], such as tormentic and urosolic acid, further beta-sitosterol [7], catechins, epicatechins [8], and proanthocyanidins [9] and other substances were identified in the root and aerial part of the extract. Most of the bioactive components are located in the thorns and leaves. [PERSON] [10] reported a gas chromatography-mass spectrometry (GC-MS) chromatogram of thorns and leaves methanolic extract of _S. spinosum_ and showed seven major peaks for thorns and six major peaks for leaves, while three of major constituents (thymol, boric acid and dodecenedioic acid) were found in the extract of both the parts. The compounds of \(\beta\)-D-glucopyranoside, linoleic acid and cinnamic acid were found as major compounds only in thorns extract. Otherwise, benzoic acid, palmitic acid and malonic acid were found only in leaf extracts as major phytoconstituents. [PERSON] et al. [11] reported that tormentic acid from _S. spinosum_ is suggested to be the major constituent extract, and to mediate its anti-proliferative activity on several cancer cell lines. Tormentic acid plays an important role in the cytotoxicity exhibited by the extract [12]. _S. spinosum_ extracts have been used in medical practice for the treatment of several disorders. Among other applications, the therapeutic applications in ethnopharmacological surveys are mostly for diabetes [13; 14] and disorders of the digestive system [15], pain relief [16], poisoning [17], anti-inflammatory effects [18], for the prevention and treatment of hepatic steatosis [19], and cancer [12]. Moreover, the anti-cancer effect of _S. spinosum_ extract has also been reported. [PERSON] showed significant tumor inhibitory activity of a crude extract of _S. spinosum_ in experimental animals [20].  
The purpose of the present study was to investigate aerial parts of _S. spinosum_, perform an in vitro cell proliferation assay testing all extracted fractions and subfractions, perform the identification and subsequent synthesis of the molecule as a possible way to obtain the basic material for the synthesis of new anti-cancer compounds, and study three identified compounds in the most cytotoxic subfraction individually and in combination.