## 1 Introduction  
Biotechnology tools such as in vitro cultures are useful for obtaining unified plant material with a guaranteed aroma quality, since the physical and chemical cultivation conditions, including temperature, photoperiod basal medium, the addition of plant growth regulators, and other factors such as CO\({}_{2}\), may be strictly controlled [1; 2; 3]. In vitro cultures also allow for the cultivation of plants that do not contain undesirable chemical compounds [4]. This is especially important currently, when the use of chemical compounds naturally occurring in plants is becoming increasingly appreciated. The usable raw material of peppermint consists of herbs and leaves (fresh or dried), oil, or herb extract. In order to obtain the raw material, the plant is cut before flowering, because it contains the most active substances when harvested in this way. Peppermint (_Mempha piperita_ L.), is widely used in the cosmetics, pharmaceutical, and food industries [5; 6; 7; 8]. One of its most valuable products is its essential oil (EO) [9]. The plant may contain about 300 different volatile constituents, mainly esters, ketones, and terpene oxides [10], but the most important is menthol [11], which belongs to the cyclic monoterpenic alcohols. It has three chiral centers in its structure, which allows it to exist in the form of eight stereoisomers. The naturally occurring isomer of menthol in peppermint is (\(-\))-menthol, with a 1\(R\), 2\(S\), 5\(R\) configuration [12; 13]. The levorotatory (\(-\))-menthol isomer is responsible for the characteristic taste, aroma, and properties of menthol [14]. Furthermore, characteristic peppermint EO volatile organic compounds (VOCs), such as 1,8-cineole, limonene, _trans_-menthyl acetate, and _trans_-sabinene hydrate, are appreciated in the cosmetics and pharmaceutical industries for their refreshing aroma and bioactive features [15; 16]. In addition, peppermint has been proven to have pharmacologically beneficial properties, such as being antioxidant, anti-allergic, antiviral, and antibacterial, preventing the development of microorganisms, and even inhibiting the development of cancer cells [17; 18; 19; 5; 13]. When used on small wounds, peppermint EO supports healing, making it an alternative to much more expensive lavernder or tea tree EOs [15; 20]. The food industry uses dried peppermint leaves in the form of mint teas or as blends for infusions. In this case, not only the EO composition is significant, but also the plant aromatic profile created by released volatile organic compounds (VOCs). As some previous studies have shown [21; 22], both factors-EO and VOC composition-can have a significant impact on the plant's material value regarding its product purpose. The EO is used for flavor and aroma purposes for chewing gums, hard candy, chocolate, liqueurs, or spirits. The tobacco industry also uses it to make menthol cigarettes [1]. Studies indicate that the aqueous extract of peppermint supports the defense mechanisms of radish (_Raphanus sativus_ L.) and tomato (_Solanum locyoresucum_ L.) against oxidative stress, and at the same time inhibits seed germination and weed seedling growth [13; 23]. A similar inhibiting effect was observed on the germination of Mediterranean weeds after application of cinnamon, lavernder, and peppermint EOs [24]. These observations might be the basis for developing a natural herbicide. In vitro plant cultures offer the possibility of obtaining homogeneous biological material on a large scale. Knowledge of this topic might also enable better adaptation of technological lines, including in bioreactors. This information may be of special value today, when the world is once again seeking natural chemicals in which peppermint is abundant.