## 1 Introduction  
_Leishmania_ species is the causative agent of leishmaniasis. This unicellular trypanosomatid induces a broad-spectrum disease, varying from localized, self-healing, and cutaneous lesions to disfiguring forms of mucocutaneous leishmaniasis, possibly even lethal visceral forms, when neglected [1; 2; 3]. Chemotherapy treatment is considered the most cost-effective intervention on parasitic diseases. Nevertheless, given the ineffectiveness of the current therapeutic approaches, the appearance of drug-resistant microorganisms, the rate of incidence of parasitic diseases, linked with the associated toxicity, bioavailability, and care costs, more intense studies are needed towards effective drugs discovery [4].  
Plant extracts, characterized by their rich diversity and complexity of secondary metabolites, involved on the expression of evolutionary strategies to overcome competitive disadvantages of plants, comprise valuable collections of compounds to screen bioactive effects [5; 6]. In some endemic foci of parasitism, plants and their corresponding extracts are the only readily available treatment forms, and therefore, this knowledge must be preserved and scientifically examined towards upcoming drugs formulation. Aqueous and alcoholic extractions are the most commonly selected extraction methods used to assess the antimicrobial activity of plant matrices; however, the use of purified essential oils (EO) of a plant may represent a plus. In fact, EO composes a pool of hydrophobic molecules that easily diffuse across cell membranes [7] and, consequently, gain advantage and interact with intracellular targets [8]. They can be conceived as a promisor approach on parasite infections control and even treatment.  
_Lavandula_ genus gives valuable EO for food, perfume, and cosmetic industries. Moreover, its EO has been reported to have prominent biological activities, namely sedative and antispasmodic, as well as, acaricidal, antibacterial, antifungal, and antioxidant effects [9]. Among _Lavandula_ genus, _Lavandula viridis_ L'He'r. and _Lavandula_ _luisieri_ Rivas-Martinez, both endemic aromatic shrubs from the Iberian Peninsula, have been widely used for medical purposes [10]. For example, it has been reported that _L.__luisieri_ EO possesses remarkable antifeedant, antimicrobial, and antioxidant effects, in addition of being a source of biologically active molecules against yeast, dermatophyte, and _Aspergillus_ strains, responsible for food contamination and human infections [11]. However, there are only few reports available investigating EO effects on _Leishmania_ species, and, specifically, no previous reports were stated on _L.__luisieri_ and _L.__viridis_.  
In recent years, our research group focused on EO antimicrobial effects evaluation; thus, based on previous promising results obtained to _Lavandula_ species EO and its main chemotypes (1,8-cineole, 1,8-cineole/borneol, and 1,8-cineole/linaly acetate/linalool) on different fungal strains [1; 2; 3; 4], we also started evaluating their anti-protozoa activity, mainly against _Giardia lamblia_ and _Leishmania_ spp. [5; 6; 7; 8; 9; 10].  
In this sense, this study aimed to access the _L.__luisieri_, _L.__viridis_, and its major compounds' (\(\alpha\)-pinene, 1,8-cineole,linal, and borneol) leishmaniasisicidal effects against three _Leishmania_ species, namely _L.__infuntum_, _L.__major_, and _L.__tropica_. Other assays were also undertaken to extend our knowledge on EO safety and to assess the effective modes of action underlining its biological potential.