In vitro, in silico and in vivo studies of ursolic acid as an anti-filarial agent.

As part of our drug discovery program for anti-filarial agents from Indian medicinal plants, leaves of Eucalyptus tereticornis were chemically investigated, which resulted in the isolation and characterization of an anti-filarial agent, ursolic acid (UA) as a major constituent. Antifilarial activity of UA against the human lymphatic filarial parasite Brugia malayi using in vitro and in vivo assays, and in silico docking search on glutathione-s-transferase (GST) parasitic enzyme were carried out. The UA was lethal to microfilariae (mf; LC100: 50; IC50: 8.84 µM) and female adult worms (LC100: 100; IC50: 35.36 µM) as observed by motility assay; it exerted 86% inhibition in MTT reduction potential of the adult parasites. The selectivity index (SI) of UA for the parasites was found safe. This was supported by the molecular docking studies, which showed adequate docking (LibDock) scores for UA (-8.6) with respect to the standard antifilarial drugs, ivermectin (IVM -8.4) and diethylcarbamazine (DEC-C -4.6) on glutathione-s-transferase enzyme. Further, in silico pharmacokinetic and drug-likeness studies showed that UA possesses drug-like properties. Furthermore, UA was evaluated in vivo in B. malayi-M. coucha model (natural infection), which showed 54% macrofilaricidal activity, 56% female worm sterility and almost unchanged microfilaraemia maintained throughout observation period with no adverse effect on the host. Thus, in conclusion in vitro, in silico and in vivo results indicate that UA is a promising, inexpensive, widely available natural lead, which can be designed and developed into a macrofilaricidal drug. To the best of our knowledge this is the first ever report on the anti-filarial potential of UA from E. tereticornis, which is in full agreement with the Thomson Reuter's 'Metadrug' tool screening predictions.

Heat shock protein 60 of filarial parasite Brugia malayi: cDNA cloning, expression, purification and in silico modeling and analysis of its ATP binding site.

We report here cloning and expression of full length mitochondrial HSP60 gene of Brugia malayi adult worm (mtHSP60bm), purification of the gene product by affinity chromatography, its in silico 3D structure and the sequence homology of the protein with Escherichia coli GroEL/ES and human HSP60. The ATP binding pocket of human HSP60 and mtHSP60bm were analyzed and compared using in silico models. The distribution of HSP60 in different life-stages of the parasite was determined using antibodies raised against recombinant mtHSP60bm (rmtHSP60bm). mtHSP60bm was present in all life-stages of the parasite except third stage infective larvae, in which it could be induced by heat-shock, and showed high degree of homology with E. coli GroEL/ES. The ATP binding pocket of HSP60 in humans, E. coli and B. malayi were also found structurally conserved. This similarity between human and mtHSP60bm might be useful in understanding the host-parasite interactions. This is the first ever report on distribution, cloning, sequence homology and ATP binding site of mtHSP60bm.

Integrated dataset of screening hits against multiple neglected disease pathogens.

New chemical entities are desperately needed that overcome the limitations of existing drugs for neglected diseases. Screening a diverse library of 10,000 drug-like compounds against 7 neglected disease pathogens resulted in an integrated dataset of 744 hits. We discuss the prioritization of these hits for each pathogen and the strong correlation observed between compounds active against more than two pathogens and mammalian cell toxicity. Our work suggests that the efficiency of early drug discovery for neglected diseases can be enhanced through a collaborative, multi-pathogen approach.

Antifilarial activity of Caesalpinia bonducella against experimental filarial infections.

BACKGROUND & OBJECTIVE: Lymphatic filariasis is a disabling disease that continues to cripple population in tropical countries. Currently available antifilarial drugs are not able to control the disease. Therefore, a better antifilarial is urgently required for proper management of the disease. We undertook this study to assess the antifilarial activity of Caesalpinia bonducella-seed kernel against rodent filarial parasite in experimental model. METHODS: Microfilaraemic cotton rats and Mastomys coucha harbouring Litomosoides sigmodontis and Brugia malayi respectively, were treated with crude extract or fractions of the seed kernel C. bonducella through oral route for 5 consecutive days. Microfilaricidal, macrofilaricidal and female worm sterilizing efficacy was assessed. RESULTS: Crude extract showed gradual fall in microfilariae (mf) count in L. sigmodontis-cotton rat model from day 8 post-treatment attaining more than 95 per cent fall by the end of observation period. It also exhibited 96 per cent macrofilaricidal and 100 per cent female sterilizing efficacy. The butanol fraction F018 caused 73.7 per cent reduction in mf count and 82.5 per cent mortality in adult worms with 100 per cent female sterilization. The aqueous fraction F019 exerted more than 90 per cent microfilaricidal activity and 100 per cent worm sterilization. Two chromatographic fractions, F024 and F025 of hexane soluble fraction exhibited 64 and 95 per cent macrofilaricidal activity, respectively. Both the fractions caused gradual fall in microfilaraemia and 100 per cent worm sterilization. In B. malayi-M. coucha model F025 showed gradual reduction in microfilaraemia and caused 80 per cent sterilization of female parasites INTERPRETATION & CONCLUSION: In conclusion, C. bonducella- seed kernel extract and fractions showed microfilaricidal, macrofilaricidal and female-sterilizing efficacy against L. sigmodontis and microfilaricidal and female-sterilizing efficacy against B. malayi in animal models, indicating the potential of this plant in providing a lead for new antifilarial drug development.

Studies in potential filaricides. 18. Synthesis of 2,2'-disubstituted 5,5'-dibenzimidazolyl ketones and related compounds as potential anthelmintics.

A series of 2,2'-disubstituted 5,5'-dibenzimidazolyl ketones and related compounds have been synthesized of which 2,2'-bis(carbomethoxyamino)-5,5'-dibenzimidazolyl ketone exhibited a broad spectrum of anthelmintic activity in experimental animals. At doses of 10-50 mg/kg given intraperitoneally, 5 killed 100% of the adult worms of Litomosoides carinii, Dipetalonema viteae, and Brugia malayi. By the oral route the macrofilaricidal efficacy of 5 was 97-100% at 100-200 mg/kg X 5 days. The treated animals showed gradual disappearance of microfilariae and before autopsy they became amicrofilariaemic. Some of the compounds also showed 100% efficacy against the human hookworms and tapeworm, Ancylostoma ceylanicum in hamsters, and Hymenolepis nana in rats at a single oral dose of 50-250 mg/kg. Compound 5 was also effective against Syphacia obvelata in mice at a single oral dose of 100 mg/kg and was found to be well tolerated by mice up to an oral dose of 2500 mg/kg.