Traditional medicine, that ancient medicine based on the culture of health practices, different from scientific medicine, is considered indigenous, alternative, or popular. The knowledge belonging to different cultures are usually transmitted orally (El Hachlafi et al., 2022). Genus Thymus is one of the popular herbs widely used in traditional medicine due to its many medicinal properties and used as a spice. The decoction and infusion of the aerial parts of this plant are used in folk medicine to treat various diseases such as inflammation, hypertension, digestive disorders, cough, bronchitis, whooping cough and rheumatism (Kabbaoui et al., 2016). Likewise, Myrtus communis having great medicinal, cultural values, is used as a flavoring and stomachic agent and in the treatment of various ailments, it is rarely used for blood purification and in constipation. The leaves are useful in cerebral diseases especially epilepsy, stomach diseases (Ullah et al., 2022). Regarding Artemisia herba alba, it is used as an antidiabetic; it is indeed a very popular remedy for the treatment of diabetes mellitus (Bouzid et al., 2023). Infusions of A. herba alba have also been used as analgesic, antibacterial, and hemostatic agents. A. herba alba's essential oil has been used as a disinfectant, anthelmintic, and antispasmodic agent (Benkhaira et al., 2021a). According to Brahmi et al. (2022), A. herba alba was among the most used aromatic plants to counter the threat of the Corona virus.

Essential oils (EOs) are plants' secondary metabolites, having a strong odor, and containing quite complex volatile compounds acting as chemical signals which control plant's environment (Bathily et al., 2021; Benkhaira et al., 2021b). Among many constituents of an essential oil, one generally dominates; it is called major compound and defines oil chemotype. Chemotype's knowledge is capital to target the EOs uses fields. Consequently, the EOs chemical composition determination constitutes a key step to their proper valorization. Their use as alternatives against resistant pathogenic microorganisms and to avoid synthetic additives toxicity is a global obligation (Moeini et al., 2021). In fact, antimicrobial resistance constitutes one of the top ten global health threats, according to the world health organization (WHO) (WHO, 2019), and affects an increasing number of people. On another side, most widely used food preservatives contain synthetic chemicals which represent a danger to consumers' populations, due to health problems and toxicity manifestations (Gupta and Yadav, 2021).

Essential oils have been well-documented for their antimicrobial effects against a range of bacterial (Dai et al., 2022), fungal (Singh et al., 2022) and viral pathogens (Reichling, 2021). Other reports have highlighted their safe uses as natural food preservatives (Pandey et al., 2021; Zahedi et al., 2021). In this sense, high concentrations were required to obtain an antibacterial and preservative effect similar to that obtained at laboratory scale tests (Burt, 2004), which resulted in an overdose and subsequently a change in food organoleptic quality (Bassolé and Juliani, 2012). Consequently, research has focused on synergistic and additive effect of many EOs associations to potentiate their effectiveness by reducing their concentration and subsequently keep good quality of food.

Several studies have been investigated to evaluate antimicrobial activity of EOs by combination using some limited methods like time-kill and checkerboard test which optimize only the EOs mixture (Foudah et al., 2021; Rosato et al., 2021). However, few research have used mixture design methodology enabling to develop better or innovative formulations offering optimal combinations. To the best of our knowledge, the present study aims to evaluate, for the first time, the combined antimicrobial effect of three EOs extracted from Moroccan aromatic and medicinal plants: T. saturoides, M. communis and A. herba alba against E. coli, S. aureus and C. tropicalis, based on MICs determination of formulas established by an augmented centered mixing plan.