## 1 Introduction
Kickxia elatine (L.) Dumort (sharpleaf cancerwort), a member of the Plantaginaceae family, contains a variety of metabolites, including phenylethanolamine glycosyl (such as acteoside, isoatecoside, echinacoside, and lavandulfioloside), phenolic acids (caffeic acid, _trans_-4-couamic acid), fatty acids (azelaic acid, linoleic acid), and peptides [19; 20; 21; 22; 23; 24]. Recent research highlights its cytotoxic potential, particularly against melanoma cells [23]. _K. elatine_ was used for internal bleeding, menstruation, and nosebleeds. In the Balkans and India, it aids wound healing, while in Serbia, it treats bedwetting. In Italy, its leaves help with foot hyperhidrosis [25; 26]. _Acanthamoeba_ is a genus of free-living amoebae that are widely distributed in the environment, inhabiting soil, air, and various water sources, including freshwater, seawater, swimming pools, and even contact lens solutions. These protozoa can exist in two distinct life stages: an active, feeding trophozoite stage and a dormant, resistant cyst stage. This ability to form cysts makes _Acanthamoeba_ highly resilient to adverse environmental conditions and contributes to its persistence in both natural and artificial habitats. Although _Acanthamoeba_ species are typically non-pathogenic, certain strains can act as opportunistic pathogens, causing serious human diseases such as _Acanthamoeba_ keratitis (AK) and granulomatous amoebic encephalitis (GAE). _Acanthamoeba_ keratitis is a severe and potentially sight-threatening corneal infection that primarily affects contact lens users, often resulting from improper lens hygiene or exposure to contaminated water. On the other hand, granulomatous amoebic encephalitis is a rare but fatal central nervous system infection that predominantly occurs in immunocompromised individuals. Additionally, _Acanthamoeba_ has been implicated in skin infections, sinusitis, and pulmonary complications, further emphasizing its medical significance. The treatment of _Acanthamoeba_-related infections remains challenging due to their ability to encryst, which makes them highly resistant to conventional therapies. Current pharmacological treatments often involve a combination of diamidines, biguanides, and antifungal agents, but their efficacy is limited, and prolonged treatment durations are required. Given these challenges, there is a growing interest in exploring alternative therapeutic agents, particularly those derived from natural sources, which may offer new avenues for effective _Acanthamoeba_ control [27; 28; 29]. In this context, previous studies have reported strong amoebicidal activity of _E. planum_ and _L. flos-cuculi_ from in vitro organ culture extracts, supporting their potential as promising and alternative sources for anti-_Acanthamoeba_ therapy [8; 30]. To the best of our knowledge, there have been no studies on the effect of _K. elatine_ extract for _Acanthamoeba_ treatment. This study aims to investigate the anti-amoeba potential of compounds from plant cell culture extracts of _E. planum_, _L. flos-cuculi_, and _K. elatine_, focusing on their effectiveness against _Acanthamoeba_ trophozoites. Antimicrobial activity is further assessed using in vitro and in silico approaches. By evaluating plant-derived extracts and secondary metabolites, this research seeks to contribute to the development of novel therapeutic strategies for combating _Acanthamoeba_ and other microbial infections.