# _Thuja occidentalis_ L. (Cupressaceae): Ethnobotany, Phytochemistry and Biological Activity  
[PERSON]  
1 Faculty of Pharmacy, [PERSON] Western University of Arad, Rebreanu 86, 310414 Arad, Romania; [EMAIL_ADDRESS] (S.C.); [EMAIL_ADDRESS] (N.K.O.) [PERSON]  
2 [PERSON]\" Institute of Life Sciences, [PERSON] Western University of Arad, Rebreanu 86, 310414 Arad, Romania; [EMAIL_ADDRESS] (N.K.O.) [PERSON]  
1 Faculty of Pharmacy, [PERSON] Western University of Arad, Rebreanu 86, 310414 Arad, Romania; [EMAIL_ADDRESS] (S.C.); [EMAIL_ADDRESS] (N.K.O.) [PERSON]  
3 [PERSON]\" University Botanical Garden from Macea, [PERSON] Western University of Arad, Rebreanu 86, 310414 Arad, Romania; [EMAIL_ADDRESS] (N.K.O.) [PERSON]  
dietary, and cosmetic fields [8; 9]. The use of medicinal plants has increased significantly in Western countries due to the adverse effects of chemical drugs and significant financial benefits. Although it is difficult to estimate the exact amount earned from the trade in plants and plant extracts, it is certain that the pharmaceutical industry based on folk medicine grows annually by over 4% [10; 11]. Medicinal plants are a source of bioactive natural compounds with high therapeutic potential. Today, biologically active compounds in plants and their derivatives are found in a high percentage in drugs on the pharmaceutical market. It is estimated that about 25% of current drugs are composed of natural compounds [12]. Moreover, more and more food supplements and cosmetics contain various plant extracts and biologically active compounds as main active ingredients [13]. The importance of medicinal plants is due to the great diversity of bioactive molecules with beneficial effect, as well as phenolic compounds, carotenoids, tocopherols, and vitamins. Due to their antioxidant properties, bioactive compounds are increasingly being studied for their beneficial effects against many chronic conditions, such as obesity, diabetes, and cancer [14; 15; 16; 17]. Some bioactive compounds react slowly and need a long time to exert their antioxidant action. Moreover, the synergism between biomolecules in a mixture makes the target effect not only dependent on concentration, but also on the interaction between antioxidants [18; 19]. In recent years, there has been an increase in the number of preclinical and clinical studies aimed at testing the use of plant extracts and biologically active compounds with beneficial effects on human health [20]. Thuja trees belongs to the order Pineales, in the _Cupressaceae_ family [21]. The Thuja genus contains five species: _Thuja koriaensis_, Nakai-Korean thuja; _Thuja occidentalis_ L., eastern arborvitae, northern white cedar; _Thuja plicata_ Donn ex D. Don, Western red cedar; _Thuja standishii_ ([PERSON]), Carriere-Japanese thuja; and _Thuja suchuenensis_, Franch-Sichuan thuja. They are evergrerens trees growing from 3 to 60 m tall with flattened branchlets, distributed in North America and East Asia. The leaves of _T. koriaensis_ have a high content of vitamin C, being used by the American natives and the first European explorers as a treatment for scurvy. The leaves of this tree have also been used as a treatment for rheumatism [22]. _T. koriaensis_ oil is a known remedy with topical application in the treatment of the human papilloma virus (HPV), as well as for genital or common warts treatment [23], as an antioxidant [24], and for antibacterial properties [22]. Due to its antimicrobial and insecticidal properties, _T. plicata_ essential oil has traditionally been used for wood preservation and insect repellent [25; 26; 27]. _T. plicata_ leaf oil has traditionally been used by Aborigines in the Pacific Northwest, to treat a number of upper respiratory tract diseases [25]. Moreover, its essential oil has antibacterial and antifungal activity [26]. Its antimicrobial effect is thought to be due to the high concentration of \(\alpha\)- and \(\beta\)-thujone, the main biologically active compounds in various essential oils that possess similar antimicrobial properties [28; 29]. _T.