ABSTRACT
Aims: This study investigates the activity of tetracyclic iridoid compounds against Leishmania spp. and the mechanism(s) of action. Study Design: An experimental study. Place and Duration: Department of Parasitology, Noguchi Memorial Institute for Medical Research, between September 2017 and July 2018. Methodology: The 50 % inhibitory concentration (IC50) of compounds against Leishmania donovani and L. major promastigotes were determined after 48 hours of incubation using the Alamar blue. Cytotoxicity of compounds was determined against cell lines using MTT assay. The anti-amastigote activity of compounds was further assessed by DAPI (4′,6-diamidino-2-phenylindole) staining. The mechanism of cell death induced by compounds was determined using nexin assay. Mitosis, cytokinesis and morphometry were monitored by DAPI and Kinetoplastid Membrane Protein (KMP) staining. Cell cycle arrest induced by compounds was analyzed by FACS. Results: Molucidin and ML-F52 inhibited the growth of promastigote in L. donovani (Molucidin; IC50 = 2.94±0.60 µM, ML-F52; IC50 = 0.91±0.50 µM) and L. major (Molucidin; IC50 = 1.85± 0.20 µM, ML-F52; IC50 = 1.77± 0.20 µM). ML-F52 had a 10-fold cytotoxic effect on parasites relative to normal cell lines. Against intracellular forms, Molucidin and ML-F52 inhibited intracellular amastigote replication and infectivity. Amphotericin B, Molucidin and ML-F52, induced a dose-dependent apoptotic effect on promastigotes. Although no change in KMP-11 expression was observed, iridoids inhibited cell division and morphological changes in promastigote cultures. Molucidin and ML-F52 induced apoptotic mechanism of cell death, inhibited cytokinesis and induced phenotypic changes in promastigotes. Molucidin further induced ‘’nectomonad-like’’ forms and loss of kDNA, ML-F52 induced ‘cell-rounding’ with loss of flagellum. Molucidin also induced cell growth arrest at G2-M phase (54.5 %). A significant induction of apoptosis (P = .05) was shown by an enhanced peak in the sub-G1 confirming the apoptotic inducing properties of iridoids. Conclusion: This study shows the anti-leishmania activity of tetracyclic iridoids which could be further investigated for the development of new chemotherapy against Leishmaniasis.
ABSTRACT
Background: Cancer is one of the many diseases of global concern due to its high mortality rate with drug resistance becoming a major challenge to chemotherapy and this have propelled many cancer patients to seek alternative and complementary methods of treatment. The objective for this study was, therefore, to determine the antiproliferative activity as well as phytochemical, total phenolic content (TPC), and antioxidant activity of the stem and leaf extracts (FPS and FPL) of Ficus pumila (L.) using standard methods. Methods: The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was used to evaluate anti-proliferative effect and spectrophotometric-based assays for antioxidant and TPC. Phytochemical constituents were accessed by standard methods. Results: The hydroethanolic extracts of the leaves and stems were rich in tannins, general glycosides, saponins, terpenoids, alkaloids, flavonoids (leaves only), and sterols (stem only). Strong total antioxidant activities were observed with FPL and FPS with EC50 values of 0.07 mg/ml and 0.089 mg/ml, respectively. All the crude extracts showed anti-proliferative effect towards the three human leukemic cell lines used (Jurkat, CEM, and HL-60). However, FPL gave the strongest inhibition concentration at 50% values of 130.97 μg/ml (Jurkat) and 56.31 μg/ml (HL-60). Conclusion: These findings suggest that crude extracts of FPS and FPL have antiproliferative effect on the leukemia cells. The antioxidant properties of the plant including phenolics may be partly responsible for the anti-proliferative activity. Further studies are required to isolate chemical components of the plant and establish their anti-proliferative activities and mechanism of action.