Search

Purpose Continuous efforts into the discovery and development of new antimalarials are required to face the emerging resistance of the parasite to available treatments. Thus, new effective drugs, ideally able to inhibit the Plasmodium life-cycle stages that cause the disease as well as those responsible for its transmission, are needed. Eight compounds from the Medicines for Malaria Venture (MMV) Malaria Box, potentially interfering with the parasite polyamine biosynthesis were selected and assessed in vitro for activity against malaria transmissible stages, namely mature gametocytes and early sporogonic stages. Methods Compound activity against asexual blood stages of chloroquine-sensitive 3D7 and chloroquine-resistant W2 strains of Plasmodium falciparum was tested measuring the parasite lactate dehydrogenase activity. The gametocytocidal effect was determined against the P. falciparum 3D7elo1-pfs16-CBG99 strain with a luminescent method. The murine P. berghei CTRP.GFP strain was employed to assess compounds activities against early sporogonic stage development in an in vitro assay simulating mosquito midgut conditions. Results Among the eight tested molecules, MMV000642, MMV000662 and MMV006429, containing a 1,2,3,4-tetrahydroisoquinoline-4-carboxamide chemical skeleton substituted at N-2, C-3 and C-4, displayed multi-stage activity. Activity against asexual blood stages of both strains was confirmed with values of IC50 (50% inhibitory concentration) in the range of 0.07-0.13 µM. They were also active against mature stage V gametocytes with IC50 values below 5 µM (range: 3.43-4.42 µM). These molecules exhibited moderate effects on early sporogonic stage development, displaying IC50 values between 20 and 40 µM. Conclusion Given the multi-stage, transmission-blocking profiles of MMV000642, MMV000662, MMV006429, and their chemical characteristics, these compounds can be considered worthy for further optimisation toward a TCP5 or TCP6 target product profile proposed by MMV for transmission-blocking antimalarials.

Phytochemical investigation of the aerial parts of the Tunisian plant Daucus virgatus led to the isolation of eight new germacranolides named daucovirgolides A-H (1-8). The stereostructures of these sesquiterpene lactones, decorated by either one or two angeloyl groups, have been determined by a combination of MS, NMR spectroscopy, chemical derivatization, and comparison of experimental electronic circular dichroism curves with TDDFT-predicted data. Daucovirgolide G (7) proved to be the single member of this family to possess a marked inhibitory activity (92% at 50 μg/mL) on the development of Plasmodium early sporogonic stages, the nonpathogenic transmissible stages of malaria parasites, devoid of general cytotoxicity. The selective activity of daucovirgolide G points to the existence of strict structural requirements for this transmission-blocking activity and therefore of a well-defined, although yet unidentified, biological target.

Targeting the transmissible stages of the Plasmodium parasite that develop in the human and mosquito host is a crucial strategy for malaria control and elimination. Medicinal plants offer a prolific source for the discovery of new antimalarial compounds. The recent identification of the gametocytocidal activity of lophirone E, obtained from the African plant Lophira lanceolata (Ochnaceae), inspired the evaluation of the plant also against early sporogonic stages of the parasite development. The bioassay-guided phytochemical study led to the isolation of two known lanceolins and of a new glycosylated bichalcone, named glucolophirone C. Its stereostructure, including absolute configuration of the bichalcone moiety, was elucidated by means of NMR, HRMS, ECD and computational calculations. Lanceolin B proved to be a potent inhibitor of the development of Plasmodium early sporogonic stages indicating that the plant produces two different stage-specific antimalarial agents acting on transmissible stages in the human and mosquito host.

Bioassay-guided fractionation of the organic extract obtained from stem barks of the African plant Lophira lanceolata has led to the isolation of seven biflavonoids, including the new α′-chlorolophirone E (5) and 5′-chlorolophirone D (6). Among the isolated compounds, the bichalcone lophirone E was identified as a potent gametocytocidal agent with an IC50 value in the nanomolar range and negligible cytotoxicity (selectivity index = 570). Lophirone E proved to be about 100 times more active against P. falciparum stage V gametocytes than on asexual blood stages, thus exhibiting a unique stage-specific activity profile. The isolation of structural analogues allowed to draw preliminary structure-activity relationships, identifying the critical positions on the chemical scaffold of lophirone E.

Background Medicinal plant research may contribute to develop new pharmacological control tools for vector borne diseases, such as malaria. Methods The effects of methanol extracts (ME) obtained from seed kernel of ripe and unripe Azadirachta indica fruits were studied on erythrocytic proliferation of the rodent malaria parasite Plasmodium berghei strain ANKA and on mice pro-inflammatory response, as evaluated by measuring the matrix-metalloproteinase-9 (MMP-9) and tumour necrosis factor (TNF) plasma levels, in two mouse strains (C57BL/6 and BALB/c) which are considered as prototypical of Th1 and Th2 immune response, respectively. Results ME obtained from seed kernel of unripe Azadirachta indica fruits decreased by about 30% the proportion of erythrocytes infected with the malaria parasite in C57BL/6 mice in the 4 days suppressive test. In this treatment group, MMP-9 and TNF levels were notably higher than those measured in the same mouse strain treated with the anti-malarial drug artesunate, Azadirachta indica kernel extracts from ripe fruits or solvent. In BALB/c mice, treatment with kernel extracts did not influence parasitaemia. MMP-9 and TNF levels measured in this mouse strain were notably lower than those recorded in C57BL/6 mice and did not vary among treatment groups. Conclusions The effects of the ME on the parasite-host interactions appeared to be mouse strain-dependent, but also related to the ripening stage of the neem fruits, as only the unripe fruit seed kernel extracts displayed appreciable bioactivity. Electronic supplementary material The online version of this article (10.1186/s12936-019-2671-8) contains supplementary material, which is available to authorized users.

This paper investigates the socioeconomic impact of two large earthquakes (1997 and 2016) that occurred in Central Italy on the agricultural sector, and in particular on animal husbandry. Through a questionnaire-based field survey, involving 55 farm holdings located in Umbria (Assisano district), this work points out: i) the farmers' perception of the damage suffered with regard to residential buildings, agricultural facilities and animal husbandry activities; ii) the interventions carried out in the emergency phases; and iii) the reconstruction phases, as experienced by the farming households. Major vulnerabilities of these agricultural holdings have emerged: small-scale family-based farming, increased householders average age, little on-farm and off-farm diversification, persisting economic marginalisation. Recall and perception of the impact of the earthquakes in the Assisano district - direct damage and reconstruction interventions - are compared with the perception in the nearby mountainous area of the Marche Region, largely affected by the 2016 earthquake. In both areas, the experienced earthquakes have not acted as triggers for agents' mobilisation and change. Rather, the situation calls for a drastic, farsighted change of development policies by national and regional governments and for a convinced prompting for holistic local “building back better” initiatives.

Due to the surge in resistance to common therapies, malaria remains a significant concern to human health worldwide. In chloroquine (CQ)-resistant (CQ-R) strains of Plasmodium falciparum, CQ and related drugs are effluxed from the parasite’s digestive vacuole (DV). This process is mediated by mutant isoforms of a protein called CQ resistance transporter (PfCRT). CQ-R strains can be partially re-sensitized to CQ by verapamil (VP), primaquine (PQ) and other compounds, and this has been shown to be due to the ability of these molecules to inhibit drug transport via PfCRT. We have previously developed a series of clotrimazole (CLT)-based antimalarial agents that possess inhibitory activity against PfCRT (4a,b). In our endeavor to develop novel PfCRT inhibitors, and to perform a structure-activity relationship analysis, we synthesized a new library of analogues. When the benzhydryl system was linked to a 4-aminoquinoline group (5a-f) the resulting compounds exhibited good cytotoxicity against both CQ-R and CQ-S strains of P. falciparum. The most potent inhibitory activity against the PfCRT-mediated transport of CQ was obtained with compound 5k. When compared to the reference compound, benzhydryl analogues of PQ (5i,j) showed a similar activity against blood-stage parasites, and a stronger in vitro potency against liver-stage parasites. Unfortunately, in the in vivo transmission blocking assays, 5i,j were inactive against gametocytes.

Background Current efforts towards malaria elimination include the discovery of new transmission blocking (TB) drugs and identification of compounds suitable to replace primaquine, recommended as transmission blocking post treatment after artemisinin combination therapy (ACT). High through put screening of compound libraries has allowed to identify numerous compounds active in vitro against gametocytes and insect early sporogonic stages, but few studies have been performed to characterize TB compounds in vivo. Here we propose a double TB drug Direct Feeding Assay (2TB-DFA), suitable to assess the combined effects of TB compounds. Materials and methods Plasmodium berghei GFPcon (PbGFPcon), BALB/c mice and Anopheles stephensi mosquitoes were used. Artemisinin (ART) and artesunate (AS) served as examples of artemisinins, NeemAzal® (NA), as a known TB-product with sporontocidal activity. DFA experiments were performed to assess the appropriate time point of administration before mosquito feeding and estimate suitable sub-optimal doses of the three compounds that allow combination effects to be appreciated. Results Suboptimal dosages, that reduce about 50% of oocyst development, were recorded with ART in the range of 16-30 mg/ kg, AS 14-28 mg/kg and NA 31-38mg/kg. Ten hours before mosquito feeding (corresponding to 3.5 days after mouse infection) was determined as a suitable time point for mouse treatment with ART and AS and 1 hour for post-treatment with NA. ART given at 35 mg/kg in combination with NA at 40 mg/kg reduced oocyst density by 94% and prevalence of infection by 59%. Similarly, the combination of ART at 25 mg/kg plus NA at 35 mg/kg decreased oocyst density by 95% and prevalence of infection by 34%. In the 2TB-DFA, conducted with AS (20 mg/kg) and NA (35 mg/kg) the combination treatment reduced oocyst density by 71% and did not affect prevalence of infection. Applying ‘Highest Single Agent’ analysis and considering as readout oocyst density and prevalence of infection, cooperative effects of the combination treatments, compared with the single compound treatments emerged. Conclusion This study suggests the 2TB-DFA to be suitable for the profiling of new TB candidates that could substitute primaquine as a post-treatment to ACT courses.

Repeated chromatographic purifications of aerial parts of the Tunisian plant Daucus virgatus led to the isolation of four new germacranolides, named daucovirgolides I-L (2-5), along with the Plasmodium transmission-blocking agent daucovirgolide G. The chemical structures of the new compounds were defined as mono- or di-angeloylated germacrane-type sesquiterpenoids by spectroscopic (mainly 1D and 2D NMR) and spectrometric methods (ESIMS). The low potency exhibited by daucovirgolides I-L further supports the observation that strict structural requirements do exist for the Plasmodium transmission blocking activity in the daucovirgolide series. In particular, the endocyclic double bond system seems to be crucial for bioactivity.

Hamisi M Malebo,1 Sarah D’Alessandro,2,3 Yehenew A Ebstie,4 Harouna Sorè,5 Alain R Tenoh Guedoung,4 Shaaban J Katani,1 Silvia Parapini,2,3 Donatella Taramelli,3,6 Annette Habluetzel3,4 1Department of Traditional Medicine Research, National Institute for Medical Research, Dar es Salaam, Tanzania; 2Dipartimento di Scienze Biomediche per la Salute , University of Milan, Milan, Italy; 3Centro Interuniversitario di Ricerca Sulla Malaria/Italian Malaria Network, University of Milan, Milan, Italy; 4School of Pharmacy, University of Camerino, Camerino, Italy; 5Centre National de Recherche et de Formation sur le Paludisme (CNRFP), Ouagadougou, Burkina Faso; 6Dipartimento di Scienze Farmacologiche e Biomolecolari, University of Milan, Milan, ItalyCorrespondence: Hamisi M MaleboDepartment of Traditional Medicine Research, National Institute for Medical Research, Postal Box 9653, Dar es Salaam, TanzaniaTel +255 22 2121400Fax +255 22 2121360Email hmalebo@gmail.comSilvia ParapiniDipartimento di Scienze Biomediche per la Salute, University of Milan, Via Pascal 36, 20133, Milan, ItalyTel +39 02 3031 5082Fax +39 02 5031 5093Email silvia.parapini@unimi.itPurpose: Continuous efforts into the discovery and development of new antimalarials are required to face the emerging resistance of the parasite to available treatments. Thus, new effective drugs, ideally able to inhibit the Plasmodium life-cycle stages that cause the disease as well as those responsible for its transmission, are needed. Eight compounds from the Medicines for Malaria Venture (MMV) Malaria Box, potentially interfering with the parasite polyamine biosynthesis were selected and assessed in vitro for activity against malaria transmissible stages, namely mature gametocytes and early sporogonic stages.Methods: Compound activity against asexual blood stages of chloroquine-sensitive 3D7 and chloroquine-resistant W2 strains of Plasmodium falciparum was tested measuring the parasite lactate dehydrogenase activity. The gametocytocidal effect was determined against the P. falciparum 3D7elo1-pfs16-CBG99 strain with a luminescent method. The murine P. berghei CTRP.GFP strain was employed to assess compounds activities against early sporogonic stage development in an in vitro assay simulating mosquito midgut conditions.Results: Among the eight tested molecules, MMV000642, MMV000662 and MMV006429, containing a 1,2,3,4-tetrahydroisoquinoline-4-carboxamide chemical skeleton substituted at N-2, C-3 and C-4, displayed multi-stage activity. Activity against asexual blood stages of both strains was confirmed with values of IC50 (50% inhibitory concentration) in the range of 0.07– 0.13 μM. They were also active against mature stage V gametocytes with IC50 values below 5 μM (range: 3.43– 4.42 μM). These molecules exhibited moderate effects on early sporogonic stage development, displaying IC50 values between 20 and 40 μM.Conclusion: Given the multi-stage, transmission-blocking profiles of MMV000642, MMV000662, MMV006429, and their chemical characteristics, these compounds can be considered worthyfor further optimisation toward a TCP5 or TCP6 target product profile proposed by MMV for transmission-blocking antimalarials.Keywords: Plasmodium, multi-stage antimalarials, transmission blocking drugs, malaria elimination

Detoxifying pathways of mosquitoes against the neem (

Additional file 1. Chromatogram of methanol extract from neem fruit kernel.