Developing synergistic drug combinations to restore antibiotic sensitivity in drug-resistant Mycobacterium tuberculosis.

Tuberculosis (TB) is a leading global cause of mortality owing to an infectious agent, accounting for almost one-third of antimicrobial resistance (AMR) deaths annually. We aimed to identify synergistic anti-TB drug combinations with the capacity to restore therapeutic efficacy against drug-resistant mutants of the causative agent, Mycobacterium tuberculosis We investigated combinations containing the known translational inhibitors, spectinomycin (SPT) and fusidic acid (FA), or the phenothiazine, chlorpromazine (CPZ), which disrupts mycobacterial energy metabolism. Potentiation of whole-cell drug efficacy was observed in SPT-CPZ combinations. This effect was lost against an M. tuberculosis mutant lacking the major facilitator superfamily (MFS) efflux pump, Rv1258c. Notably, the SPT-CPZ combination partially restored SPT efficacy against an SPT-resistant mutant carrying a g1379t point mutation in rrs, encoding the mycobacterial 16S ribosomal RNA. Combinations of SPT with FA, which targets the mycobacterial elongation factor G, exhibited potentiating activity against wild-type M. tuberculosis Moreover, this combination produced a modest potentiating effect against both FA-monoresistant and SPT-monoresistant mutants. Finally, combining SPT with the frontline anti-TB agents, rifampicin (RIF) and isoniazid, resulted in enhanced activity in vitro and ex vivo against both drug-susceptible M. tuberculosis and a RIF-monoresistant rpoB S531L mutant.These results support the utility of novel potentiating drug combinations in restoring antibiotic susceptibility of M. tuberculosis strains carrying genetic resistance to any one of the partner compounds.

Phytochemical, Cytotoxicity, and Antimycobacterial Activity Evaluation of Extracts and Compounds from the Stem Bark of Albizia coriaria Welw ex. Oliver.

BACKGROUND: Albizia coriaria Welw ex. Oliver (Fabaceae) is one of the plants used by herbalists in the East Africa community to prepare herbal remedies for the management of symptoms of TB. Despite its widespread use, the antimycobacterial activity of this plant was uninvestigated and there was contradicting information regarding its cytotoxicity. METHODS: Cytotoxicity (MTT), antimycobacterial activity (MABA), and phytochemical screening were conducted on crude extracts (hexane, chloroform, acetone, and methanol) of the stem bark of A. coriaria. Gas chromatography-mass spectrometry (GC-MS) followed by Fourier transform infrared (FTIR) spectroscopy was carried out on the acetone and methanol extracts. The binding affinities and descriptors of pharmacokinetics and toxicity of the identified compounds were predicted using computational modelling software. RESULTS: The cytotoxic concentrations of all extracts were greater than 1000 µg/mL. The minimum inhibitory concentration of both the acetone and methanol extracts was 1250.0 ± 0.0 µg/mL against M. smegmatis, whereas that against M. tuberculosis was 937.0 ± 442.0 µg/mL and 2500.0 ± 0.0 µg/mL, respectively. Hexane and chloroform extracts were not active against both strains. Alkaloids, triterpenes, flavonoids, tannins, and saponins were the predominant phytochemicals present. GC-MS analysis revealed twenty-eight and nineteen compounds in acetone and methanol extracts, respectively. Among these was hydroquinone, which was previously reported to possess antimycobacterial activity. Seven compounds identified through GC-MS analysis had better binding affinities for the mycobacterial ATPase and polyketide synthase-13 than isoniazid and rifampicin. These compounds also showed variable but promising pharmacokinetic properties with minimum toxicity. CONCLUSION: There are phytochemicals in A. coriaria stem bark with potential antimycobacterial activity and acceptable cytotoxicity, which can be further explored and optimized for the development of novel antitubercular drugs.

Sub-Acute Toxicity Effects of Methanolic Stem Bark Extract of Entada abyssinica on Biochemical, Haematological and Histopathological Parameters in Wistar Albino Rats.

Background: Whereas the efficacy of Entada abyssinica (fabaceae) extracts against various ailments has been scientifically validated, its safety has not been established. This study was undertaken to evaluate the toxicity effects of methanolic stem bark extract of E. abyssinica on biochemical, haematological and histological parameters of Wistar albino rats following repeated oral administration. Methods: Wistar albino rats of both sexes were randomized into groups and orally administered daily with determined doses (150, 300 and 600 mg/kg) of E. abyssinica methanolic extract using 1% tween 80 in distilled water as a control for 28 days. On the 29th day, all the animals were sacrificed and dissected to collect blood and selected organs. The serum and whole blood were assayed for biochemical and haematological parameters respectively while selected organs were examined for histopathological lesions. Numerical data was analyzed using graph pad prism and expressed as mean ± standard error of mean. The differences between the treatment and control groups were tested for statistical significance using one-way analysis of variance and/or Student's t-test. Results: In repeated daily oral doses (150, 300 and 600 mg/kg), the methanolic stem bark extract of E. abyssinica did not cause significant alteration in majority of the biochemical and hematological indices. However, the extract significantly elevated the level of uric acid (all doses), aspartate aminotransferase (300 and 600 mg/kg), low density lipoproteins (150 mg/kg) and mean corpuscular heamoglobin concentration (all doses). On the other hand, the extracts reduced high density lipoproteins (150 and 300 mg/kg), mean corpuscular volume (all doses), haematocrit (150 and 600 mg/kg), mean platelet volume (150 and 600 mg/kg) and procalcitonin (150 mg/kg). In the vital organs, there were no significant lesions observed except at the highest dose (600 mg/kg) where there was mild evidence of lymphocyte infiltration in the liver and focal interstitial nephritis. Conclusion: The methanolic stem bark extract of E. abyssinica is relatively safe in Wistar albino rats when repetitively administered orally in small doses for a prolonged period of time. We recommend more chronic toxicity studies and clinical trials on herbal remedies containing this plant to ensure that its use is free of potential toxicity to humans.

Integrity, use and care of long-lasting insecticidal nets in Kirinyaga County, Kenya.

BACKGROUND: Vector control is an essential component in prevention and control of malaria in malaria endemic areas. Insecticide treated nets is one of the standard tools recommended for malaria vector control. The objective of the study was to determine physical integrity and insecticidal potency of long-lasting insecticidal nets (LLINs) used in control of malaria vector in Kirinyaga County, Kenya. METHOD: The study targeted households in an area which had received LLINs during mass net distribution in 2016 from Ministry of Health. A total of 420 households were sampled using systematic sampling method, where the household heads consented to participate in the study. A semi-structured questionnaire was administered to assess care and use while physical examination was used to determine integrity. Chemical concentration was determined by gas chromatography mass spectroscopy (GC-MS). Data analysis was done using Statistical Package for Social Sciences (SPSS) version 19. RESULTS: After 18 months of use, 96.9% (95% CI: 95.2-98.6%) of the distributed nets were still available. Regarding net utilization, 94.1% of household heads reported sleeping under an LLIN the previous night. After physical examination, 49.9% (95% CI: 43-52.8%) of the bed nets had at least one hole. The median number of holes of any size was 2[interquartile range (IQR) 1-4], and most holes were located on the lower part of the nets, [median 3 (IQR 2-5)]. Only 15% of the nets with holes had been repaired. The median concentration for α-cypermethrin was 7.15 mg/m2 (IQR 4.25-15.31) and 0.00 mg/g (IQR 0.00-1.99) for permethrin. Based on pHI, Chi-square test varied significantly with the manufacturer (X (6, N = 389) = 29.14, p = 0.04). There was no significant difference between nets with different number of washes (X2(2) = 4.55, p = 0.103). CONCLUSION: More than three-quarters of the nets supplied had survived and insecticidal potency was adequate in vector control. Standard procedure for field evaluation of surface insecticidal content available to a mosquito after landing on a net to rest is recommended.

Traditional Medicinal Uses, Phytoconstituents, Bioactivities, and Toxicities of Erythrina abyssinica Lam. ex DC. (Fabaceae): A Systematic Review.

BACKGROUND: Many studies have been undertaken on the medicinal values of Erythrina abyssinica Lam. ex DC. (Fabaceae). The details, however, are highly fragmented in different journals, libraries, and other publication media. This study was therefore conducted to provide a comprehensive report on its ethnobotany, ethnomedicinal uses, phytochemicals, and the available pharmacological evidence supporting its efficacy and safety in traditional medicine. METHOD: We collected data using a PROSPERO registered systematic review protocol on the ethnobotany, phytochemistry, and ethnopharmacology of Erythrina abyssinica from 132 reports that were retrieved from electronic databases. Documented local names, morphology, growth habit and habitat, ethnomedicinal and nonmedicinal uses, diseases treated, parts used, method of preparation and administration, extraction and chemical identity of isolated compounds, and efficacy and toxicity of extracts and isolated compounds were captured. Numerical data were summarized into means, percentages, and frequencies and presented as graphs and tables. RESULTS: Erythrina abyssinica is harvested by traditional herbal medicine practitioners in East, Central, and South African communities to prepare herbal remedies for various human and livestock ailments. These include bacterial and fungal infections, tuberculosis, malaria, HIV/AIDS, diarrhea, cancer, meningitis, inflammatory diseases, urinary tract infections, wounds, diabetes mellitus, and skin and soft tissue injuries. Different extracts and phytochemicals from parts of E. abyssinica have been scientifically proven to possess anti-inflammatory, antibacterial, antioxidant, antiplasmodial, antiproliferative, antifungal, antimycobacterial, antidiarrheal, anti-HIV 1, antidiabetic, and antiobesity activities. This versatile pharmacological activity is due to the abundant flavonoids, alkaloids, and terpenoids present in its different parts. CONCLUSION: Erythrina abyssinica is an important ethnomedicinal plant in Africa harboring useful pharmacologically active phytochemicals against various diseases with significant efficacies and minimal toxicity to mammalian cells. Therefore, this plant should be conserved and its potential to provide novel molecules against diseases be explored further. Clinical trials that evaluate the efficacy and safety of extracts and isolated compounds from E. abyssinica are recommended.

Ethnobotany, ethnopharmacology, and phytochemistry of traditional medicinal plants used in the management of symptoms of tuberculosis in East Africa: a systematic review.

OBJECTIVE: Many studies on the treatment of tuberculosis (TB) using herbal medicines have been undertaken in recent decades in East Africa. The details, however, are highly fragmented. The purpose of this study was to provide a comprehensive overview of the reported medicinal plants used to manage TB symptoms, and to analyze scientific reports on their effectiveness and safety. METHOD: A comprehensive literature search was performed in the major electronic databases regarding medicinal plants used in the management of TB in East Africa. A total of 44 reports were retrieved, and data were collected on various aspects of the medicinal plants such as botanical name, family, local names, part(s) used, method of preparation, efficacy, toxicity, and phytochemistry. The data were summarized into percentages and frequencies which were presented as tables and graphs. RESULTS: A total of 195 species of plants belonging to 68 families and 144 genera were identified. Most encountered species were from Fabaceae (42.6%), Lamiaceae (19.1%), Asteraceae (16.2%), and Euphorbiaceae (14.7%) families. Only 36 medicinal plants (18.5%) have been screened for antimycobacterial activity. Out of these, 31 (86.1%) were reported to be bioactive with minimum inhibitory concentrations ranging from 47 to 12,500 µg/ml. Most tested plant extracts were found to have acceptable acute toxicity profiles with cytotoxic concentrations on normal mammalian cells greater than 200 µg/ml. The most commonly reported phytochemicals were flavonoids, terpenoids, alkaloids, saponins, cardiac glycosides, and phenols. Only Tetradenia riparia, Warburgia ugandensis, and Zanthoxylum leprieurii have further undergone isolation and characterization of the pure bioactive compounds. CONCLUSION: East Africa has a rich diversity of medicinal plants that have been reported to be effective in the management of symptoms of TB. More validation studies are required to promote the discovery of antimycobacterial drugs and to provide evidence for standardization of herbal medicine use.

Esterase phenotyping in human liver in vitro: specificity of carboxylesterase inhibitors.

1. Esterases may play a major role in the clearance of drugs with functional groups amenable to hydrolysis, particularly in the case of ester prodrugs. To understand the processes involved in the elimination of such drugs, it is necessary to determine the esterases involved. However, the tools currently available for this enzyme phenotyping are relatively scarce. 2. The work was aimed at summarizing the selectivity of esterase inhibitors for carboxylesterases 1 and 2 (CES1 and CES2) in the human liver to clarify their suitability for esterase phenotyping. Eserine, at around 10 µM, was found to be a highly specific CES2 inhibitor, whereas other esterase inhibitors turned out less selective. When used together with tacrine, which inhibits cholinesterases but not CES, and ethylenediaminetetraacetic acid (inhibitor of paraoxonases), the involvement of the hydrolyzing esterases in the hepatic clearance of a drug can be elucidated. 3. The second approach to esterase phenotyping is based on data from recombinant or isolated esterases, together with relative activity factors, which relate their activities to those of the same enzymes in subcellular fractions. 4. These two approaches will help to characterize the hydrolytic metabolism of drug candidates in a similar manner as practiced routinely for the oxidative metabolism by cytochrome P450 enzymes.

Pharmacologically active metabolites, combination screening and target identification-driven drug repositioning in antituberculosis drug discovery.

There has been renewed interest in alternative strategies to address bottlenecks in antibiotic development. These include the repurposing of approved drugs for use as novel anti-infective agents, or their exploitation as leads in drug repositioning. Such approaches are especially attractive for tuberculosis (TB), a disease which remains a leading cause of morbidity and mortality globally and, increasingly, is associated with the emergence of drug-resistance. In this review article, we introduce a refinement of traditional drug repositioning and repurposing strategies involving the development of drugs that are based on the active metabolite(s) of parental compounds with demonstrated efficacy. In addition, we describe an approach to repositioning the natural product antibiotic, fusidic acid, for use against Mycobacterium tuberculosis. Finally, we consider the potential to exploit the chemical matter arising from these activities in combination screens and permeation assays which are designed to confirm mechanism of action (MoA), elucidate potential synergies in polypharmacy, and to develop rules for drug permeability in an organism that poses a special challenge to new drug development.

Experimental chemotherapy with Allium sativum (Liliaceae) methanolic extract in rodents infected with Leishmania major and Leishmania donovani.

BACKGROUND & OBJECTIVES: Several plant products have been tested and found to possess antileishmanial activity. The present study was undertaken to establish whether methanolic extract of Allium sativum Linn has antileishmanial activity in comparison to standard drugs. METHODS: Methanolic extract of A. sativum bulbs was screened for in vitro and in vivo antileishmanial activity against Leishmania major strain (NLB 145) and L. donovani strain (NLB 065). Pentostam and Amphotericin B were used as standard drugs. BALB/c mice and golden hamsters (Mesocricetus auratus) were used in in vivo studies on L. major and L. donovani respectively. RESULTS: The extract exhibited very low cytotoxicity (IC50 >450 µg/ml) against Vero cells. The extract had significantly better (p <0.001) leishmanicidal activity against both species (IC50 34.22 µg/ml to L. major, 37.41 µg/ml to L. donovani) than Pentostam. However, the activity was significantly lower (p <0.001) than that of Amphotericin B against both the species. At a concentration of 250 µg/ml, the extract induced the production of 60 µM of nitric oxide, a ten-fold up-regulation in activated macrophages. The multiplication indices for L. major amastigotes treated in 100 µg/ml were significantly different (p <0.05). Treatment with the extract, daily for 28 days led to a significant reduction (p <0.05) in footpad swelling in BALB/c mice; similar activity noticed in the treatment with standard drugs. The Leishman-Donovan Units (LDU) for the extract treated animals were significantly higher (p <0.05) than those of standard drugs, but lower compared to the negative control. INTERPRETATION & CONCLUSION: Since the mechanism of action for the methanolic extract is apparently immunomodulatory, garlic compounds could be purified and tried as complementary medicine in the management of leishmaniases.

Anti-parasitic activity and cytotoxicity of selected medicinal plants from Kenya.

Indigenous rural communities in the tropics manage parasitic diseases, like malaria and leishmaniasis, using herbal drugs. The efficacy, dosage, safety and active principles of most of the herbal preparations are not known. Extracts from 6 selected plant species, used as medicinal plants by indigenous local communities in Kenya, were screened for in vitro anti-plasmodial and anti-leishmanial activity, against 2 laboratory-adapted Plasmodium falciparum isolates (D6, CQ-sensitive and W2, CQ-resistant) and Leishmania major (IDU/KE/83=NLB-144 strain), respectively. The methanol extract of Suregada zanzibariensis leaves exhibited good anti-plasmodial activity (IC(50) 4.66+/-0.22 and 1.82+/-0.07 microg/ml for D6 and W2, respectively). Similarly, the methanol extracts of Albizia coriaria (IC(50) 37.83+/-2.11 microg/ml for D6) and Aspergillus racemosus (32.63+/-2.68 and 33.95+/-2.05 microg/ml for D6 and W2, respectively) had moderate anti-plasmodial activity. Acacia tortilis (IC(50) 85.73+/-3.36 microg/ml for W2) and Albizia coriaria (IC(50) 71.17+/-3.58 microg/ml for W2) methanol extracts and Aloe nyeriensis var kedongensis (IC(50) 87.70+/-2.98 and 67.84+/-2.12 microg/ml for D6 and W2, respectively) water extract exhibited mild anti-plasmodial activity. The rest of the extracts did not exhibit any anti-plasmodial activity. Although the leishmanicidal activity of extracts were lower than for pentosam (80%), reasonable activity was observed for Aloe nyeriensis methanol (68.4+/-6.3%), Albizia coriara water (66.7+/-5.0%), Maytenus putterlickoides methanol (60.0+/-6.23%), Asparagus racemosus methanol and water (58.3+/-8.22 and 56.8+/-6.58%, respectively), Aloe nyeriensis water (53.3+/-5.1%) and Acacia tortilis water (52.9+/-6.55%) extracts at 1000 microg/ml. Leishmania major infected macrophages treated with methanol extracts of Suregada zanzibariensis and Aloe nyeriensis var kedongensis and pentostam had infection rates of 28+/-2.11, 30+/-1.22 and 40+/-3.69%, respectively at 1000 microg/ml, indicating better anti-leishmanial activity for the extracts. The methanol extract of Albizia coriara (44.0+/-3.69%) and aqueous extracts of Asparagus racemosus (42+/-3.84%) and Acacia tortilis (44+/-5.59%) had similar activity to pentosam. Multiplication indices for Leishmania major amastigotes treated with methanol extracts of Albizia coriaria, Suregada zanzibariensis and Aloe nyeriensis var kedongensis, aqueous extract of Acacia tortilis and pentosam were 28.5+/-1.43, 29.4+/-2.15, 31.1+/-2.22, 35.9+/-3.49 and 44.0+/-3.27%, respectively, at 1000 microg/ml, confirming better anti-leishmanial activity for the extracts. Aqueous extracts of Aloe nyeriensis (46.7+/-3.28%) and Albizia coriaria (47.5+/-3.21%) had similar activity level to pentosam. The plant extracts have better inhibitory activity while pentosam has better leishmanicidal activity. All extracts exhibited very low cytotoxicity (CC(50) > 500 microg/ml) against human embryonic lung fibroblast (HELF) cells. The investigations demonstrated the efficacy and safety of some extracts of plants that are used by rural indigenous communities for the treatment of parasitic diseases.