Bioguided study of the ethanolic extract of Empetrum rubrum against parasites of Leishmania spp.

DIMMER JESICA; COLLOCA CRISTINA; BARRIONUEVO CAMILA NEREA; LO PRESTI SILVINA; RAVETTI SOLEDAD; RIVAROLA HECTOR WALTER

Rosario

Otro; 7ma edición de Ricifa 2023; 2023

Ricifa

Cutaneous leishmaniasis (CL) is a disease caused by protozoans of the genus Leishmania. This infection is associated with the species Leishmania guyanensis, Leishmania braziliensis, and Leishmania amazonensis. The north of Argentina is considered an endemic area of CL. Empetrum rubrum Vahl ex Willf is a native species found on Tierra del Fuego Island in Argentina. Previously, an ethanol extract derived from E. rubrum (Er-EtOH) demonstrated higher parasiticidal activity, as evidenced by an IC50 value of 0.4 μg/mL against L. amazonensis. This outcome prompted us to conduct a bioguided study. To accomplish this, Er-EtOH was subjected to column chromatography and eluted with a step gradient of dichlorometane-ethyl acetate to yield two fractions (FA and FB) and two compounds (CA and CB). CA was identified as quercetin, a known flavonoid, whereas CB is still being studied. The purpose of this study was to determine the susceptibility of L. amazonensis and L. braziliensis promastigotes to CB, FA, y FB.A suspension of 3x106 parasites/mL in RPMI medium was incubated with serial dilutions of each fraction or compound ranging from 200 to 6,25 g/mL for this study. The trypan blue exclusion method was used to determine the number of parasites after 72 h. Morphology alterations were detected by May Grunwald-Giemsa staining. Results demonstrated that FA and FB have no effect against L. amazonensis and L. braziliensis at the highest concentration tested (IC50>200 µg/mL), although many parasites treated with these fractions showed a small and rounded body, indicating a retraction in growth. CB was the most active compound, with an IC50 of 22 µg/mL against L. amazonensis and an IC50= 13 µg/mL against L. braziliensis.In Leishmania species, the enzyme dihydroorotate dehydrogenase (DHODH) is crucial for cell survival and proliferation. In the search for parasiticidal compounds, the interaction of flavonoids and DHODH is an intriguing research area. According to some investigations, flavonoids may interact with DHODH, interfering with pyrimidine synthesis in Leishmania. Then, we hypothesize that the ethanolic extract's high activity is due to the synergism between quercetin and CB. Further investigation of the combination of these two compounds is needed.