Javier Chao-Pellicer

Free-living amoebae (FLA) are protozoa ubiquitous in nature, isolated from a variety of environments worldwide. In addition to their natural distribution, some species have been found to be pathogenic to humans. In the present study, FLA presence was evaluated and characterized at the molecular level from different water and soil samples in Fuerteventura Island, Canary Islands, Spain. A total of 31 samples were analyzed by culture and molecular assays (q-PCR and PCR). Moreover, the microbiological quality of the water samples was examined as required by current legislation and international standards. The obtained data revealed that the genus Acanthamoeba was the most prevalent genus of FLA in soil samples and the species Vermamoeba vermiformis was the most isolated in water samples collected from Fuerteventura by culture and molecular assays, q-PCR, and conventional PCR/Sanger sequencing. On the other hand, a microbiological analysis revealed heterogeneous contamination patterns. Escherichia coli was detected in several samples, with some exhibiting high counts while others showed no presence. Salmonella spp. appeared in multiple samples, particularly FTVW1, FTVW9, and FTVW13, whereas Shigella spp. was only found in one sample (FTVW1). Moreover, q-PCR detection offers advantages such as reduced detection time and cost. In addition, culture was proven to be more effective for confirming FLA viability and isolating a greater variety of FLA. Overall, the occurrence of potentially pathogenic free-living amoebae in habitats related to the human population, as reported in the present study, supports the relevance of FLA as a potential health threat to humans.

Phytochemical investigation of Radula voluta, a liverwort species collected in the Ecuadorian Amazon, led to the isolation of four known bibenzyl derivatives: 2-prenyl-3,5-dihydroxy-bibenzyl (1), 2-geranyl-3,5-dihydroxybibenzyl (2), 2,2-dimethyl-5-phenethyl-2H-chromen-7-ol (3), and radulanin L (4). Structural elucidation was achieved through extensive NMR and MS analyses, supported by comparison with previously reported data. Compounds 1 and 4 are reported for the first time in R. voluta. The crude extract and isolated compounds were evaluated for their in vitro antiprotozoal activity against Trypanosoma cruzi, Leishmania amazonensis, Leishmania donovani, Naegleria fowleri, and Acanthamoeba castellanii Neff. Among the isolated compounds, bibenzyls 2 and 4 exhibited the most potent activity across multiple protozoan strains. Cytotoxicity was assessed against murine macrophages (J774A.1), obtaining moderate–low toxicities against compounds 1 and 3. These findings highlight the pharmacological value of liverwort-derived bibenzyls and support further research on R. voluta as a promising source of antiparasitic leads.

Current therapies for Primary Amoebic Meningoencephalitis (PAM) present several limitations; consequently, there is an urgent need to develop new therapeutic agents. In this regard, we undertook bioassay-guided isolation of Mentha rotundifolia leaves which allowed the identification of ursolic acid (1) as the main bioactive metabolite against two ATCC strains of Naegleria fowleri (ATCC^® 30808^TM and ATCC^® 30215^TM). Moreover, ten ursolic acid derivatives (2–11) were synthesized through esterification and nucleophilic substitution to obtain halo or amino ester derivatives. Among these derivatives, compound 7 exhibited the highest activity against the N. fowleri ATCC^® 30808^TM strain with an IC₅₀ value of 28.66 µM, whereas compound 10 showed the top activity against the N. fowleri ATCC^® 30215^TM strain with an IC₅₀ of 7.61 µM, surpassing the efficacy of the reference drug, miltefosine. Both compounds, 7 and 10, showed a good selectivity index and hence low toxicity in vitro. Structure–activity relationship studies revealed that the type of acylating agent played a crucial role in the activity. Furthermore, both compounds induced autophagy and apoptosis-like processes in both treated N. fowleri strains. These results highlight the potential of ursolic acid-related triterpenoids as drug scaffolds and identify M. rotundifolia as a promising natural source of amoebicidal agents against PAM.

Primary amoebic meningoencephalitis (PAM) is a rapidly progressive and fulminant disease that affects the central nervous system caused by the free-living amoeba Naegleria fowleri. The adhesion to extracellular matrix (ECM) proteins is considered as one of the key steps in the success of the infection and could represent an interesting target to be explored in the prevention and treatment of the disease. In this work, the effect of two sesquiterpenes with proven anti-Naegleria activity on the adhesion of the parasite was evaluated using an in vitro ECM-based model, compared with the reference drugs amphotericin B and staurosporine. Both laurinterol and (+)-elatol inhibited the adhesion of the N. fowleri trophozoites to the main proteins of the ECM when treating them at different concentrations and exposure times. This work not only reinforces the therapeutic potential of laurinterol and (+)-elatol against N. fowleri infection but also introduces the application of ECM-based adhesion assays as a novel and valuable tool for screening candidate compounds that disrupt host–pathogen interactions critical to PAM pathogenesis.