Intracellular anti-leishmanial effect of Spergulin-A, a triterpenoid saponin of Glinus oppositifolius

Abstract

Present chemotherapeutics are inadequate against visceral leishmaniasis (VL) an immunosuppressive ailment caused by Leishmania donovani. Despite the interest in plant-based drug development, an antileishmanial drug from plant source is unavailable. Glinus oppositifolius had been reported in favor of being immunomodulators along with other traditional uses. Novel anti-VL therapies can rely on host immune-modulation with associated leishmanicidal action. With this rationale, an n-BuOH fraction of the methanolic extract of the plant and isolated triterpenoid saponin Spergulin-A were evaluated against acellular and intracellular L. donovani. Immunostimulatory activity of them was confirmed by elevated TNF-a and extracellular NO production from treated M{Phi}s and was found nontoxic to the host cells. Identification and structure confirmation for isolated Spergulin-A was performed by ESI-MS,13C, and 1H NMR. Spergulin-A was found ineffective against the acellular forms while, against the intracellular parasites at 30g/ml, the reduction was 92.6% after 72h. Spergulin-A enhanced ROS and nitric oxide (NO) release and changes in Gp91-phox, i-NOS, and pro and anti-inflammatory cytokines elaborated its intracellular anti-leishmanial activity. The results supported that G. oppositifolius and Spergulin-A can potentiate new lead molecules for the development of alternative drugs against VL.\n\nAuthor summaryVisceral Leishmaniasis (VL) is prevalent in tropical and temperate regions and is endemic in 88 countries with an estimated yearly incidence of 1-1.5 million cases of cutaneous leishmaniasis and 500,000 cases of VL, of which 70,000 people die every year. More than 90% of cases occur in India, Bangladesh, Nepal, Sudan, Ethiopia, and Brazil with an estimated incidence of at least 500,000 new cases and 50,000 deaths each year.\n\nThis work highlights the anti-leishmanial effect of a triterpenoid saponin that was extracted from a tropical plant, Glinus oppositifolius, commonly found in Asian and parts of African countries. The drug showed potent Leishmanicidal activity against Leishmania donovani at very low concentration. As the application of the conventional drugs (pentavalent antimoniates, amphotericin B, and pentamidine) is limited due to low efficacy, life-threatening side effects, high toxicity, induction of parasite resistance, length of treatment and high cost and anti-leishmanial vaccines may not become available in the near future, so plant extracts or plant compounds, represent a valuable source of new medicinal agents and alternative, effective and less toxic treatments, leading to a search for natural products with a potential leishmanicidal action. Being an immunosuppressive disease efficacy against VL can be demonstrated against intracellular parasites in the lights of emphasizing host M{Phi} immunostimulation as elaborated precisely in the present study.\n\n\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=139 SRC=\"FIGDIR/small/458653_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (30K):\norg.highwire.dtl.DTLVardef@f93fa1org.highwire.dtl.DTLVardef@1c073f0org.highwire.dtl.DTLVardef@1fbb86aorg.highwire.dtl.DTLVardef@1085c11_HPS_FORMAT_FIGEXP M_FIG C_FIG