Recent developments in antimalarial drug discovery.

Although malaria remains a big burden to many countries that it threatens their socio-economic stability, particularly in the countries where malaria is endemic, there have been great efforts to eradicate this disease with both successes and failures. For example, there has been a great improvement in malaria prevention and treatment methods with a net reduction in infection and mortality rates. However, the disease remains a global threat in terms of the number of people affected because it is one of the infectious diseases that has the highest prevalence rate, especially in Africa where the deadly Plasmodium falciparum is still widely spread. Methods to fight malaria are being diversified, including the use of mosquito nets, the target candidate profiles (TCPs) and target product profiles (TPPs) of medicine for malarial venture (MMV) strategy, the search for newer and potent drugs that could reverse chloroquine resistance, and the use of adjuvants such as rosiglitazone and sevuparin. Although these adjuvants have no antiplasmodial activity, they can help to alleviate the effects which result from plasmodium invasion such as cytoadherence. The list of new antimalarial drugs under development is long, including the out of ordinary new drugs MMV048, CDRI-97/78 and INE963 from South Africa, India and Novartis, respectively.

Ethnomedicinal, Phytochemical and Pharmacological Investigations of Tetradenia riparia (Hochst.) Codd (Lamiaceae).

Tetradenia riparia Hochsteter codd. (Lamiaceae) in its native African continent, is considered one of the most popular aromatic medicinal plants. In folk medicine it may be used as an infusion to treat respiratory problems, cough, headache, stomach pain, diarrhea, fever, malaria, and dengue; and in the form of compresses it is applied for the relief of headaches and toothaches. The species T. riparia has been researched for decades to isolate and identify chemical constituents present in extracts or essential oil obtained from the leaves, floral buds, or stems of this plant. The present study reviews the scientific literature on ethnomedicinal, phytochemical, and pharmacological aspects of T. riparia. We discuss issues related to the botanical and geographical description of the species, ethnobotanical uses, phytochemical studies on its essential oil and extracts, and biological activities of T. riparia. Several compounds have already been isolated from leaves, such as ibozol, 7α-hydroxyroileanone, 1',2'-dideacetylboronolide, 8(14),15-sandaracopimaradiene-7α,18-diol; 5,6-dihydro-α-pyrone and α-pyrone. Terpenes predominated in the essential oil, comprising monoterpenes, sesquiterpenes, diterpenes, hydrocarbons, and oxygenates. Most phytocompounds were isolated from the leaves and flower buds, namely fenchone, 14-hydroxy-9-epi (E)-caryophyllene, 9ß, 13ß-epoxy-7-abietene, and 6,7-dehydroroileanone. These compounds provide the species a high pharmacological potential, with antimicrobial, antioxidant, antitumor, analgesic, anti-leishmania, anti-tuberculosis, and anti-parasitic activities. Therefore, this species is a promising herbal medicine.

In Vitro Antiplasmodial and Cytotoxic Activities of Compounds from the Roots of Eriosema montanum Baker f. (Fabaceae).

Malaria remains one of the leading causes of death in sub-Saharan Africa, ranked in the top three infectious diseases in the world. Plants of the Eriosema genus have been reported to be used for the treatment of this disease, but scientific evidence is still missing for some of them. In the present study, the in vitro antiplasmodial activity of the crude extract and compounds from Eriosema montanum Baker f. roots were tested against the 3D7 strain of Plasmodium falciparum and revealed using the SYBR Green, a DNA intercalating compound. The cytotoxicity effect of the compounds on a human cancer cell line (THP-1) was assessed to determine their selectivity index. It was found that the crude extract of the plant displayed a significant antiplasmodial activity with an IC50 (µg/mL) = 17.68 ± 4.030 and a cytotoxic activity with a CC50 (µg/mL) = 101.5 ± 12.6, corresponding to a selective antiplasmodial activity of 5.7. Bioactivity-guided isolation of the major compounds of the roots' crude extract afforded seven compounds, including genistein, genistin and eucomic acid. Under our experimental conditions, using Artemisinin as a positive control, eucomic acid showed the best inhibitory activity against the P. falciparum 3D7, a well-known chloroquine-sensitive strain. The present results provide a referential basis to support the traditional use of Eriosema species in the treatment of malaria.

Bioassay-guided isolation of antibacterial compounds from the leaves of Tetradenia riparia with potential bactericidal effects on food-borne pathogens.

ETHNOPHARMACOLOGICAL RELEVANCE: Tetradenia riparia (commonly known as ginger bush) is frequently used in traditional African medicine to treat foodborne infections including diarrhoea, gastroenteritis, and stomach ache. AIM OF THE STUDY: The present study aims to identify in Tetradenia riparia the compounds active against foodborne pathogens. MATERIALS AND METHODS: Dried Tetradenia riparia leaf powder was consecutively extracted with hexane, ethyl acetate, methanol and water. The hexane extract was counter-extracted with methanol:water (9:1), and after evaporation of the methanol, this phase was extracted with dichloromethane. The water extract was counter-extracted with butanol. All these fractions were tested against a panel of foodborne bacterial pathogens. A bioassay-guided purification was performed to isolate antimicrobial compounds using Staphylococcus aureus as a target organism. Further, antibiofilm activity was evaluated on S. aureus USA 300. RESULTS: The dichloromethane fraction and ethyl acetate extract were the most potent, and therefore subjected to silica gel chromatography. From the dichloromethane fraction, one active compound was crystalized and identified using NMR as 8(14),15-sandaracopimaradiene-7alpha, 18-diol (compound 1). Two active compounds were isolated from the ethyl acetate extract: deacetylumuravumbolide (compound 2) and umuravumbolide (compound 3). Using a microdilution method, their antimicrobial activity was tested against eight foodborne bacterial pathogens: Shigella sonnei, S. flexneri, Salmonella enterica subsp. enterica, Escherichia coli, Micrococcus luteus, S. aureus, Enterococcus faecalis, and Listeria innocua. Compound 1 had the strongest activity (IC50 ranging from 11.2 to 212.5 µg/mL), and compounds 2 and 3 showed moderate activity (IC50 from 212.9 to 637.7 µg/mL and from 176.1 to 521.4 µg/mL, respectively). Interestingly, 8(14),15-sandaracopimaradiene-7alpha, 18-diol is bactericidal, and also showed good antibiofilm activity with BIC50 (8.8 ± 1.5 µg/mL) slightly lower than for planktonic cells (11.4 ± 2.8 µg/mL). CONCLUSIONS: These results support the traditional use of this plant to conserve foodstuffs and to treat gastrointestinal ailments, and open perspectives for its use in the prevention and treatment of foodborne diseases.

A review of recent advances in anti-tubercular drug development.

Tuberculosis is a global threat but in particular affects people from developing countries. It is thought that nearly a third of the population of the world live with its causative bacteria in a dormant form. Although tuberculosis is a curable disease, the chances of cure become slim as the disease becomes multidrug-resistant and the situation gets even worse as the disease becomes extensively drug-resistant. After approximately 5 decades without any new TB drug in the pipeline, there has been some good news in the recent years with the discovery of new drugs such as bedaquiline and delamanid as well as the discovery of new classes of anti-tubercular drugs. Some old drugs such as clofazimine, linezolid and many others which were not previously indicated for tuberculosis have been also repurposed for tuberculosis and they are performing well.

An ethnobotanical survey and inhibitory effects on NLRP3 inflammasomes/Caspase-1 of herbal recipes' extracts traditionally used in Rwanda for asthma treatment.

ETHNOPHARMACOLOGICAL RELEVANCE: Respiratory diseases and asthma, in particular, are nowadays a global health problem. In Rwanda, some traditional healers claim to treat asthma with plant-based recipes, though there is no scientific proof so far. AIM OF THE STUDY: Our study aimed at evaluating the toxicity and the anti-inflammatory effect of plant recipes used in Rwanda against asthma in order to select potential candidates for further characterization of the active compounds. MATERIALS AND METHODS: Water (aqueous) and methanol-dichloromethane (organic) extracts from selected folkloric recipes were submitted for toxicity test on THP-1 derived macrophages using CellTiter-Glo Luminescent Cell Viability Assay. The evaluation of the anti-inflammatory effect of the plant extracts was carried out using the Caspase-Glo 1 Inflammasome assay on THP-1 -derived macrophages. RESULTS: Most of both organic and aqueous extract showed more than 95% of cell viability up to 200 µg/ml, except for R03Cn organic extract that inhibited 25% of the cell viability. Plant extracts inhibited caspase-1 activation in THP-1 derived macrophages in a dose-dependent manner. Four extracts (R03Cn and R07Kn aqueous extracts, R10MK and R19Sz organic extracts) strongly downregulated the activation of caspase-1 (more than 70% at 50 µg/ml). In general, organic extracts exhibited better caspase-1 inhibitory effects than their aqueous counterparts. CONCLUSIONS: The inhibition of inflammasome/caspase-1 is one of key mechanisms of action in asthma. Some traditional recipes are active on this mechanism and are thus strong candidates for the treatment of asthma and other inflammasome-mediated diseases. Further investigations are needed to characterize active molecules.

Active principles of Tetradenia riparia. IV. Anthelmintic activity of 8(14),15-sandaracopimaradiene-7α,18-diol.

ETHNOPHARMACOLOGICAL RELEVANCE: Tetradenia (T.) riparia (Hochst.) Codd (Lamiaceae), formerly known as Iboza riparia (Hochst.) N.E.Br., is one of the most frequently used medicinal plants in traditional Rwandese medicine. It was used as a remedy against a wide range of diseases including malaria, angina, yaws, dental abscesses, headache, worm infections and several kinds of fevers and aches. AIM OF THE STUDY: This study aims to identify the compounds active against helminths from Tetradenia riparia. METHODS: A bioassay-guided isolation of anthelmintic compounds from the leaves of Tetradenia riparia was performed using a Caenorhabditis elegans (C. elegans) testing model. RESULTS: The bioassay-guided isolation led to one active compound, i.e. 8(14),15-sandaracopimaradiene-7α,18-diol. Its IC50 value was 5.4 ± 0.9 µg/mL (17.8 ± 2.9 µM). CONCLUSIONS: We identified the bioactive compound from Tetradenia riparia responsible for its anthelmintic activity: 8(14),15-sandaracopimaradiene-7α,18-diol. Although the compound and several of its bioactivities have been described before, this is the first report of its anthelmintic effect.

Traditional phytotherapy remedies used in Southern Rwanda for the treatment of liver diseases.

ETHNOPHARMACOLOGICAL RELEVANCE: Liver diseases represent a major health problem due to their complications and limited treatment possibilities. In Rwanda, given low accessibility to modern treatments, most people still rely on traditional medicinal plants. The symptomatology of many hepatic troubles (icterus) is evident for traditional healers who have a high probability of selecting efficient herbal medicines. OBJECTIVES: To document medicines used in the treatment of "hepatitis" in Southern Rwanda with the knowledge, attitudes and practices related to liver disorder recognition, control and treatment. MATERIALS AND METHODS: 56 traditional health practitioners, each a legal representative of an official association, were interviewed and participated in plant collection for the preparation of botanically identified herbarium specimens. RESULTS: 68 multi-component and 65 single-component herbal recipes were identified for the treatment of liver diseases with a total of 86 different herbs from 34 families identified. The most represented were the Asteraceae and the Lamiaceae. Crassocephalum vitellinum, Hypoestes triflora and Erythrina abyssinica were the most widely used plants. The principle of polymedication for complex (i.e. multifactorial) diseases ("Ifumbi" in Rwanda), is a constant in every traditional practice. It is striking that the Rwandese therapy of liver diseases proposes so many single-herb preparations (49% of all herbal preparations). Some of the recorded plants or other species from the same genus have previously been documented for liver protection using various in vivo and in vitro models. CONCLUSION: Herbal remedies for hepatitis are widely used and highly diverse in Southern Rwanda; further chemical, pharmacological and toxicological studies are clearly required to rationally develop the most important remedies.

Essential oils of four Rwandese hepatoprotective herbs: Gas chromatography-mass spectrometry analysis and antioxidant activities.

Following an ethnobotanical survey in Southern Rwanda for hepatoprotective remedies, four food and medicinal plants, Crassocephalum vitellinum, Guizotia scabra, Microglossa pyrifolia and Ocimum lamiifolium, were selected for pharmacological and chemical investigations aiming to validate their reported properties. The chemical compositions of essential oils obtained from leaves were investigated by GC-MS; essential oils and methanolic extracts were evaluated for antioxidant activity by 1,1-diphenyl-2-picryhydrazyl (DPPH) and linoleic acid peroxidation assays. C. vitellinum [limonene (34.8%), (E)-ß-ocimene (21.8%), ß-pinene (8.5%), α-pinene (6.6%), myrcene (6.3%)], G. scabra [germacrene-d (25.5%), limonene (9.7%), (E)-ß-ocimene (6.6%)], M. pyrifolia [germacrene-d (58.3%)] and O. lamiifolium [sabinene (12.2%), alpha phellandrene (11.6%)] volatile oils scavenge DPPH (10%, 39%, 27%, and 11% quercetin equivalents) and inhibit linoleic acid peroxidation (13%, 23%, 20%, and 13% Trolox® equivalents). The four methanolic extracts were quite active on the lipid peroxidation model (93%, 93%, 70%, and 67% Trolox equivalents) with modest activity on DPPH (5%, 10%, 8%, and 11% quercetin equivalents). These properties most probably participate in the four plants hepatoprotective activities reported in ethnopharmacological and/or pharmacological studies.

Evaluation of the hepatotoxic and hepatoprotective effect of Rwandese herbal drugs on in vivo (guinea pigs barbiturate-induced sleeping time) and in vitro (rat precision-cut liver slices, PCLS) models.

Precision-cut liver slices (PCLS) preserve the tissular organization of the organ and represent an in vitro model closer to in vivo conditions than hepatocytes cultures. As this may be an interesting tool not only for the investigation of hepatotoxic and protective effects but also for bioguided fractionations schemes, the usefulness of PCLS was compared with an in vivo test of liver function. Crude extracts derived from five herbs used in Rwanda for hepatoprotective activity were tested on CCl(4)-treated guinea pigs by the method of barbiturate-induced sleep modification. Aqueous extracts of Ocimum lamiifolium, Crassocephalum vitellinum, Guizotia scabra and Vernonia lasiopus leaves allowed animals to recover barbiturate sleep duration in proportions of 88%, 78%, 61% and 34%, respectively and Microglossa pyrifolia was found inactive. Dried methanolic extracts of the 5 plants were then tested in vitro on rat PCLS for protection against acetaminophen-induced hepatotoxicity. In this model, G. scabra, M. pyrifolia and V. lasiopus were found hepatotoxic by themselves and unable to prevent acetaminophen toxicity. The most active extract, obtained from O. lamiifolium, was subjected to bioassay-guided fractionation by chromatography on Si-C(18) to yield two quite active fractions. From a single animal, at least 50 PCLS explants can be prepared, which allows testing large amounts of samples, strengthening ethnopharmacological data on hepatoprotective medicinal plants and investigating hepatotoxic effects.