Evaluation of a diospyrin derivative as antileishmanial agent and potential modulator of ornithine decarboxylase of Leishmania donovani.

World health organization has called for academic research and development of new chemotherapeutic strategies to overcome the emerging resistance and side effects exhibited by the drugs currently used against leishmaniasis. Diospyrin, a bis-naphthoquinone isolated from Diospyros montana Roxb., and its semi-synthetic derivatives, were reported for inhibitory activity against protozoan parasites including Leishmania. Presently, we have investigated the antileishmanial effect of a di-epoxide derivative of diospyrin (D17), both in vitro and in vivo. Further, the safety profile of D17 was established by testing its toxicity against normal macrophage cells (IC50∼20.7 µM), and also against normal BALB/c mice in vivo. The compound showed enhanced activity (IC50∼7.2 µM) as compared to diospyrin (IC50∼12.6 µM) against Leishmania donovani promastigotes. Again, D17 was tested on L. donovani BHU1216 isolated from a sodium stibogluconate-unresponsive patient, and exhibited selective inhibition of the intracellular amastigotes (IC50∼0.18 µM). Also, treatment of infected BALB/c mice with D17 at 2mg/kg/day reduced the hepatic parasite load by about 38%. Subsequently, computational docking studies were undertaken on selected enzymes of trypanothione metabolism, viz. trypanothione reductase (TryR) and ornithine decarboxylase (ODC), followed by the enzyme kinetics, where D17 demonstrated non-competitive inhibition of the L. donovani ODC, but could not inhibit TryR.

Anti-inflammatory and anticancer compounds isolated from Ventilago madraspatana Gaertn., Rubia cordifolia Linn. and Lantana camara Linn.

OBJECTIVES: The aim was to search for anti-inflammatory and anticancer compounds from three medicinal plants, viz. Ventilago madraspatana Gaertn., Rubia cordifolia Linn. and Lantana camara Linn. METHODS: The NO* scavenging potential of selected plant extracts was determined on LPS/IFN-gamma activated murine peritoneal macrophage cultures, and iNOS and COX-2 expression was evaluated by Western blot analysis. Bio-assay guided fractionation yielded four compounds: physcion and emodin from V. madraspatana, 1-hydroxytectoquinone from R. cordifolia, and oleanonic acid from L. camara. The anti-inflammatory activity of these compounds was tested through the carrageenan-induced rat-paw oedema model. They were then tested against a murine tumour (Ehrlich ascites carcinoma), and three human cancer cell lines, namely A375 (malignant skin melanoma), Hep2 (epidermoid laryngeal carcinoma) and U937 (lymphoma). KEY FINDINGS: All four compounds dose dependently inhibited NO* through suppression of iNOS protein without affecting macrophage viability. Physcion and emodin caused 65-68% reduction of oedema volume at 40 mg/kg, which validated their in-vivo anti-inflammatory effect. 1-Hydroxytectoquinone and oleanonic acid exhibited promising cytotoxicity against A375 cells. CONCLUSIONS: Ethnomedical reports on these traditional medicinal plants have been rationalised through an insight into the anti-inflammatory as well as anticancer potential of four constituents, characterised to be prospective candidates for designing novel therapeutic agents.

Synthesis of novel aminoquinonoid analogues of diospyrin and evaluation of their inhibitory activity against murine and human cancer cells.

The synthesis and tumor-inhibitory activity of a series of aminonaphthoquinone derivatives of diospyrin, which was isolated from Diospyros montana Roxb., are presented here for the first time. An aminoacetate derivative showed the maximum (approximately 93%) increase in life span in vivo against murine Ehrlich ascites carcinoma (EAC) at a dose of 1 mg kg(-1)day(-1) (ip; five doses), and the lowest IC50 (0.06 microM) in vitro. Further, the same analogue also exhibited considerable enhancement in antiproliferative activity when evaluated against human cell lines, viz. malignant skin melanoma and epidermoid laryngeal carcinoma (IC50=0.06 and 0.92 microM, respectively) in comparison to the natural precursor, diospyrin (IC50=0.82 and 3.58 microM, respectively). Moreover, diospyrin and all its derivatives were found to show significantly greater (approximately 17- to 1441-fold) cytotoxicity against the tumor cells as compared to normal human lymphocytes. All these quinonoids generated substantial amounts of reactive oxygen species in EAC cells, more or less commensurate to their respective IC50 values.

Synthesis and antiproliferative activity of some novel derivatives of diospyrin, a plant-derived naphthoquinonoid.

Derivatisation of diospyrin, a bisnaphthoquinonoid isolated from Diospyros montana Roxb., led to the modification of its inhibitory activity, in vitro, towards a murine tumour model, Ehrlich ascites carcinoma (EAC), and two human cancer cell lines, viz., malignant skin melanoma (A375) and epidermoid laryngeal carcinoma (Hep2). Among the novel derivatives, an epoxide exhibited the maximum antiproliferative activity (IC(50) values in the range of 0.03-0.21 microM) and a comparatively lower toxicity (IC(50) approximately 98 microM) in normal human peripheral blood mononuclear cells (PBMC). This compound might provide a novel 'lead' for the development of clinically effective antiproliferative agents against cancer.

Development of a voltammetric sensor for diospyrin determination in nanomolar concentrations.

A sensor based on glassy carbon (GC) electrode modified with cobalt tetrasulfonated phthalocyanine (CoTSPc) and a poly-l-lysine (PLL) film is proposed for diospyrin determination in nanomolar concentrations with differential pulse voltammetry (DPV) technique. The modified electrode showed excellent catalytic activity presenting much higher peak currents than those measured on a bare GC electrode. Linear response range, sensitivity and limit of detection (LOD) were of 1-120nmoll(-1), 220.46nAlnmol(-1)cm(-2) and 0.3nmoll(-1), respectively. The repeatability of the proposed sensor, evaluated in term of relative standard deviation (R.S.D.), was measured as 4.4% for 10 experiments in 50mumoll(-1) diospyrin samples. The developed sensor was applied for the determination of diospyrin in the crude extracts of the stem-bark of Diospyros montana Roxb. and the average recovery for these samples was 101.9 (+/-3.1)%.

Separation methods of quinonoid constituents of plants used in Oriental traditional medicines.

Analysis of molecular constituents of traditional Oriental medicines has acquired a fresh perspective in view of a surge in interest in the consumption of herbal prescriptions all over the world. Several of them contain quinonoid compounds, and the long-standing therapeutic applications of these herbs have been vindicated, to some extent, through recent studies on the significant pharmacological properties of these compounds. In fact, the bioactive quinonoids and their analogues often serve as the 'marker' constituents of the respective plants of major commercial importance. Hence, shikonin, plumbagin, diospyrin, emodin analogues, sennosides, hypericin, tanshinone and related compounds have been discussed in this review which focuses on their extraction, separation and analysis from plant sources, cell cultures and biological fluids. As for the analysis of quinonoids, high-performance liquid chromatography connected with various detectors (ultraviolet, photodiode array, fluorescence, mass, nuclear magnetic resonance) has been the most useful technology succeeding the conventional methods such as thin layer and column chromatography. In some cases, high-performance thin layer chromatography and capillary electrophoresis are also used for this purpose.