Abstract
Cynaroside, a flavonoid, has been shown to have antibacterial, antifungal and anticancer activities. Here, we evaluated its antileishmanial properties and its mechanism of action through different in silico and in vitro assays. Cynaroside exhibited antileishmanial activity in time- and dose-dependent manner with 50% of inhibitory concentration (IC50) value of 49.49 ± 3.515 µM in vitro. It inhibited the growth of parasite significantly at only 20 µM concentration when used in combination with miltefosine, a standard drug which has very high toxicity. It also inhibited the intra-macrophagic parasite significantly at low doses when used in combination with miltefosine. It showed less toxicity than the existing antileishmanial drug, miltefosine at similar doses. Propidium iodide staining showed that cynaroside inhibited the parasites in G0/G1 phase of cell cycle. 2,7-dichloro dihydro fluorescein diacetate (H2DCFDA) staining showed cynaroside induced antileishmanial activity through reactive oxygen species (ROS) generation in parasites. Molecular-docking studies with key drug targets of Leishmania donovani showed significant inhibition. Out of these targets, cynaroside showed strongest affinity with uridine diphosphate (UDP)-galactopyranose mutase with −10.4 kcal/mol which was further validated by molecular dynamics (MD) simulation. The bioactivity, ADMET (absorption, distribution, metabolism, excretion and toxicity) properties, Organisation for Economic Co-operation and Development (OECD) chemical classification and toxicity risk prediction showed cynaroside as an enzyme inhibitor having sufficient solubility and non-toxic properties. In conclusion, cynaroside may be used alone or in combination with existing drug, miltefosine to control leishmaniasis with less cytotoxicity.
Highlights
Leishmaniasis is a vector-borne disease caused by obligate intra-cellular protozoan parasite of genus Leishmania
The cynaroside treatment showed the dose-dependent inhibition of parasite growth with 50% of inhibitory concentration (IC50) of 49.49 +− 3.515 μM (Figure 1A)
Cynaroside inhibited only 20% of parasites at 20 μM concentration though it inhibited more than 50% of parasites when used in combination with non-toxic dose of miltefosine, 4 μM (Figure 1B)
Summary
Leishmaniasis is a vector-borne disease caused by obligate intra-cellular protozoan parasite of genus Leishmania. The disease is endemic in more than 89 different countries worldwide. There are 20 different species of Leishmania which can infect animals, humans and sand-flies to cause species-specific complications in the host. The majority of Leishmania species responsible for causing leishmaniasis are Leishmania major, L. infantum, L. chagasi and L. donovani. The reservoirs of the disease are animals like canines and rodents (zoonotic cycle) and human (anthroponotic cycle) [1,2]. There are several molecules which are reported to have anti-leishmanial activity yet, but only a few are classified as effective antileishmanial drugs that are used for the treatment of leishmaniasis [3].
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