Synthesis, antimalarial evaluation and structure-activity relationship in a series of dibenzlmethylamine (Dibemethin) derivatives of 4-amino-7-chloroquinoline

Includes abstract.Includes bibliographical references (leaves 138-154).A series of twelve 4-amino-7-chloroquinolines containing (N, N-dibenzylmethylamine) dibemethin side chains attached to the amino group of the quinoline were synthesized by reaction of aminomethyl dibemethins with 4,7-dichloroquinoline to give “dibemethinoquines”. The attachment between the quinoline ring and the side chain was varied from ortho, to meta to para. The aminomethyl dibemethin side chains were synthesized using the Staudinger reduction of azides or the reductive amination via oxime of an aldehyde. Derivatives in which the para substituent on the terminal phenyl ring were altered from the parent compound (X = H) by replacement with Cl, OCH₃ orNMe₂ group were also synthesized. The choice of substituents was based on the Topliss scheme

Potentising and application of a Combretum woodii leaf extract with high antibacterial and antioxidant activity

Given the drawbacks associated with the use of antibiotics as feed additives and the imminent banning of its use in the European Union, the aim of this project was to develop an extract that could be used as an alternative feed additive in poultry production. The desired extract preferably had to be rich in antibacterial activity to control proliferation of undesired microorganisms, and antioxidant activity to boost the immune system of the poultry. A number of trial extraction procedures were employed on dried leaf material samples to identify the best extraction method. In preliminary extraction studies, direct extraction was performed on leaf samples from the Lowveld National Botanical Gardens (LNBG) and from University of Pretoria Botanical Garden (UP). The principle aim of preliminary studies was to identify the solvents that extracted high antibacterial and antioxidant activity while also extracting large quantities of material. The secondary objective was to test for differences in activities between samples collected from LNBG and UP. Five extractants of varying polarities; acetone, ethanol, ethylacetate, dichloromethane and hexane were used. Antibacterial activity of all extracts was quantified by a serial dilution microplate technique while bioautography was used in qualitative analysis of the antibacterial active compounds. ATCC strains of Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Enterococcus faecalis were used as test organisms. Qualitative antioxidant activity was determined by using a DPPH assay on TLC plates. Results from preliminary extraction studies showed larger quantities of material were present in extracts from the LNBG sample than in the UP sample. Two major antioxidant compounds (Rf values of 0.85 and 0.35 in EMW solvent system) were seen on DPPH sprayed TLC plates, while bioautography showed the presence of a number antibacterial active compounds in the acetone, ethanol and ethylacetate extracts with Rr values ranging between 0.85 and 0.56 on TLC plates developed in the EMW solvent system. MIC values of the extracts tallied with the results from bioautography. The acetone, ethanol and ethyl acetate extracts had the highest antibacterial activity while the hexane extracts had the lowest activity with average MIC value of 0.55 mg/ml for both the LNBG and UP samples. MIC values as low as 0.04 mg/ml were measured in the acetone and ethylacetate extracts of the LNBG sample against S. aureus and E. faecalis. Based on results from preliminary extraction studies, hexane was identified as a possible pretreatment solvent for application in enrichment procedures, acetone and ethanol were chosen as the main extractants and only the LNBG sample was used for future work. Enrichment procedures were employed along two pathways; the first pathway involved the use of hexane "wash" as a pretreatment procedure prior to extraction with acetone or ethanol. The second pathway involved the use of various mixtures of acetone in water and ethanol in water as extractants. The rationale of using these various ratios was an attempt to identify solvent mixtures that would selectively extract the bioactive components or otherwise selectively remove inactive material. A serial dilution microplate method was used to determine Minimum Inhibitory Concentrations (MICs) and the Trolox Equivalent Antioxidant Capacity (TEAC) assay was used to quantify antioxidant activity of all extracts. The optimal extract was the one developed by pretreatment with a single direct extraction with hexane prior to extraction with acetone. It had a TEAC value of 2.3, an increase in TEAC value of 283% compared to that of the crude acetone extract. The average MIC of the crude acetone extract against ATCC stains of S. aureus, Ps. aeruginosa, E. coli and E. faecalis had dropped from 0.15 mg/ml to 0.08 mg/ml in the optimal extract (an improvement in antibacterial activity of 87.5%). Since the optimal extract is intended for commercial application in poultry production, its antibacterial activity was tested against Campylobacter jejuni, Clostridium perfringens, Salmonella enteritidis, E. coli and multi drug resistant E. coli isolated from chickens. Its in vitro toxicity was ascertained using the brine shrimp assay and the MTT cytotoxicity assay on monkey kidney cells. The optimal extract was effective against Campylobacter jejuni and Clostridium perfringens with MIC values ranging from 40 µ/ml to 80 µ/ml. It was also active against multi-resistant strains of E. coli and Salmonella enteritidis (MIC values of 125 µ/ml for both strains). LC50 results from the brine shrimp assay and the MTT cytotoxicity assay on monkey kidney cells gave values of 863 µ/ml and 226 µ/ml respectively indicating low toxicity. These results meant that though in some cases the MICs of the optimal extract were higher than befitting of typical antibiotics, due to its relatively low toxicity, large quantities of the extract may possibly be feed to achieve the desired activity without causing any toxicity in the poultry. The major antioxidant compound was isolated by silica gel column chromatography. The isolated compound was identified by nuclear magnetic resonance and mass spectroscopy as combretastatin BS (2', 3', 4-trihydroxyl, 3, S, 4'-trimethoxybibenzyl), previously isolated from the seeds of C. kraussii and also from C. woodii leaves. Famakin (2002) showed this compound to be the major antibacterial compound in C. woodii leaves. Combretastatin BS (CBS) demonstrated in vitro cytotoxicity in the MTT assay on monkey kidney cells with an LC50 value of 1 0 µ/ml. In vitro cytotoxicity of CBS could be due to its antimitotic activity. The TEAC value of 7.9 found in this study means that combretastatin BS has about 8 times the antioxidant capacity of vitamin E. This is the first report of the antioxidant activity of any of the combretastatins. Tolerance of broiler chickens to the optimal extract was assessed at clinically inferred doses of 2 mg/kg, Smg/kg and 10 mg/kg . After 21 days of infeed-dosing with the optimal extract, none of the chickens died or showed any behavioral signs of toxicity. There were no statistically significant differences in weight gain between broilers fed the optimal extract and the positive and negative control. There was also no positive correlation between weight gain and amount of the optimal extract incorporated in feed. Although the optimal extract did not result in significant growth promotion relative to the positive and negative control, 2 mg/kg dose regimens showed the best Feed Conversion Ratio (FCR), with a 6.2% improvement compared to the negative control. The positive control was the only other feed regimen to provide a positive FCR with an improvement of 1.73% compared to the negative control. Because purchase of feed could represent up to 80% of costs of broiler production, this is an important finding. If these results can be confirmed, the product may therefore have commercial value. Repetition of the experiment with lower doses of the optimal extract on poultry challenged with bacterial infections is required to confirm the commercial applicability of this product. CopyrightDissertation (MSc (Paraclinical Science))--University of Pretoria, 2004.Paraclinical Sciencesunrestricte

Southern African HIV Clinicians Society guidelines for harm reduction

We support public-health-focused interventions, as opposed to recovery-focused interventions. We support the decriminalisation of drug use as much as we oppose the criminalisation of sex work, mandatory HIV disclosure and policing of sexual preferences.Additional inputs received from Lize Weich, Tanya Venter, Johannes Hugo, Urvisha Bhoora, Magriet Spies, Rafaela Rigoni, Cara O’Conner, Julia Samuelson, Viriginia Macdonald, Michelle Rodolph, Shona Dalal, Nurain Tisaker and Shaheema Allie. Regional harm reduction case studies developed by Kunal Naik (PILS, Mauritius) and Bernice Apondi (VOCAL, Kenya). Inputs from the guideline development workshop held in August 2019 are also included. Participants of the workshop included: Leora Casey, Andrew Gray, Harry Hausler, Signe Rotberga, Muhangwi Mulaudzi, Lauren Jankelowitz, Annette Verster, Busisiwe Msimanga-Radebe, Nontsikelelo Mpulo, Zukiswa Ngobo, Mpho Maraisane, Rogerio Phili, Kgalabi Ngako, Maria Sibanyoni, Yolanda Ndimande, Valencia Malaza, Johannes Hugo, Urvisha Bhoora and Cara O’Conner. We extend our thanks to the external reviewers, including Julie Bruneau, Annette Verster, Kunal Naik, Nkereuwem William Ebiti and Ali Feizzadeh.http://www.sajhivmed.org.za/am2021Family MedicineImmunolog

Interference with Hemozoin Formation Represents an Important Mechanism of Schistosomicidal Action of Antimalarial Quinoline Methanols

Heme is an essential molecule to most living organisms, but once in a free state it exerts toxic effects. Blood-feeding organisms evolved efficient ways to detoxify free heme derived from hemoglobin digestion. A key mechanism present in some hematophagous organisms consists of the crystallization of heme into a pigment named hemozoin. Schistosoma mansoni is one of the etiologic agents of human schistosomiasis, a parasitic disease that affects over 200 million people in tropical and subtropical areas. Hemozoin formation represents the main heme detoxification pathway in S. mansoni. Here, we report that the antimalarial quinoline methanols quinine and quinidine exert schistosomicidal effects notably due to their capacity to interfere with hemozoin formation. When quinine or quinidine were administered intraperitoneally during seven days to S. mansoni-infected mice (75 mg/kg/day), both worm and eggs burden were significantly reduced. Interestingly, hemozoin content in female worms was drastically affected after treatment with either compound. We also found that quinine caused important changes in the cellular organization of worm gastrodermis and increased expression of genes related to musculature, protein synthesis and repair mechanisms. Together, our results indicate that interference with hemozoin formation is a valid chemotherapeutic target for development of new schistosomicidal agents

The cost and intermediary cost-effectiveness of oral HIV self-test kit distribution across 11 distribution models in South Africa.

BACKGROUND: Countries around the world seek innovative ways of closing their remaining gaps towards the target of 95% of people living with HIV (PLHIV) knowing their status by 2030. Offering kits allowing HIV self-testing (HIVST) in private might help close these gaps. METHODS: We analysed the cost, use and linkage to onward care of 11 HIVST kit distribution models alongside the Self-Testing AfRica Initiative's distribution of 2.2 million HIVST kits in South Africa in 2018/2019. Outcomes were based on telephonic surveys of 4% of recipients; costs on a combination of micro-costing, time-and-motion and expenditure analysis. Costs were calculated from the provider perspective in 2019 US$, as incremental costs in integrated and full costs in standalone models. RESULTS: HIV positivity among kit recipients was 4$4.87 (sex worker model) and $18.07 (mobile integration model), with differences largely driven by kit volumes. HIVST kit costs (at$2.88 per kit) and personnel costs were the largest cost items throughout. Average costs per outcome increased along the care cascade, with the sex worker network model being the most cost-effective model across metrics used (cost per kit distributed/recipient screening positive/confirmed positive/initiating ART). Cost per person confirmed positive for HIVST was higher than standard HIV testing. CONCLUSION: HIV self-test distribution models in South Africa varied widely along four characteristics: distribution volume, HIV positivity, linkage to care and cost. Volume was highest in models that targeted public spaces with high footfall (flexible community, fixed point and transport hub distribution), followed by workplace models. Transport hub, workplace and sex worker models distributed kits in the least costly way. Distribution via index cases at facility as well as sex worker network distribution identified the highest number of PLHIV at lowest cost

HIV prevalence and the cascade of care in five South African correctional facilities.

BACKGROUND:South Africa is home to the world's largest HIV epidemic. Throughout the world, incarcerated individuals have a higher prevalence of HIV than the general public, and South Africa has one of the highest rates of incarceration in sub-Saharan Africa. In spite of this, little has been published about the burden of HIV and how care is delivered in South African correctional facilities. OBJECTIVE:To estimate the prevalence of people living with HIV and identify initiation and retention in the HIV cascade of care across five correctional facilities. METHODS:Cross-sectional retrospective analysis of 30,571 adult inmates who participated in a tuberculosis screening and HIV counseling and testing campaign in South African correctional facilities (January 1, 2014-January 31, 2015). Descriptive statistics were used to estimate the proportion and 95% confidence intervals of HIV. Proportions of persons retained and lost at each step in the HIV cascade of care under this intervention were calculated. Poisson regression with robust variance estimates were used, and clustering by facility was accounted for in all analyses. RESULTS:Results of the screening campaign found previously undiagnosed HIV among 13.0% of those consenting to screening, with a total estimated HIV prevalence of 17.7% (n = 3,184, 95% CI: 17.2-18.3%) in the sample. When examining the overall cascade of care, 48.3% of those with HIV initiated care, and overall 45.6% of persons who entered care qualified for ART initiated treatment. A Poisson regression accounting for clustering by facility found HIV high risk groups within the population such as women (aRR = 1.72, 95% CI: 1.57, 1.89), those over 35 years of age (aRR = 2.43, 95% CI: 1.53, 3.85), and people incarcerated less than one year (aRR = 1.41, 95% CI: 1.19, 1.67). CONCLUSION:In this setting, routine screening is recommended, and measures are needed to ensure that persons diagnosed are adequately linked to and retained in care

A series of structurally simple chloroquine chemosensitizing dibemethin derivatives that inhibit chloroquine transport by PfCRT

A series of 12 new dibemethin (N-benzyl-N-methyl-1-phenylmethanamine) derivatives bearing an N-aminomethyl group attached to the one phenyl ring and an H, Cl, OCH3 or N(CH3)2 group on the other have been synthesized. These compounds all showed strong chloroquine chemosensitizing activity, comparable to verapamil, when present at 1 μM in an in vitro culture of the chloroquine-resistant W2 strain of the human malaria parasite, Plasmodium falciparum. Their N-formylated derivatives also exhibited resistance-reversing activity, but only at substantially higher IC10 concentrations. A number of the dibemethin derivatives were shown to inhibit chloroquine transport via the parasite's 'chloroquine resistance transporter' (PfCRT) in a Xenopus laevis oocyte expression system. The reduced resistance-reversing activity of the formylated compounds relative to their free amine counterparts can probably be ascribed to two factors: decreased accumulation of the formylated dibemethins within the parasite's internal digestive vacuole (believed to be the site of action of chloroquine), and a reduced ability to inhibit PfCRT. The resistance-reversing activity of the compounds described here demonstrates that the amino group need not be attached to the two aromatic rings via a three or four carbon chain as has been suggested by previous QSAR studies. These compounds may be useful as potential side chains for attaching to a 4,7-dichloroquinoline group in order to generate new resistance-reversing chloroquine analogues with inherent antimalarial activity

Quinoline Antimalarials Containing a Dibemethin Group are Active against Chloroquinone-Resistant Plasmodium falciparum and Inhibit Chloroquine Transport via the P. falciparum Chloroquine- Resistance Transporter (PfCRT)

A series of 4-amino-7-chloroquinolines with dibenzylmethylamine (dibemethin) side chains were shown to inhibit synthetic hemozoin formation. These compounds were equally active against cultures of chloroquine-sensitive (D10) and chloroquine-resistant (K1) Plasmodium falciparum. The most active compound had an IC50 value comparable to that of chloroquine, and its potency was undiminished when tested in three additional chloroquine-resistant strains. The three most active compounds exhibited little or no cytotoxicity in a mammalian cell line. When tested in vivo against mouse malaria via oral administration, two of the dibemethin derivatives reduced parasitemia by over 99%, with mice treated at 100 mg/kg surviving the full length of the experiment. Three of the compounds were also shown to inhibit chloroquine transport via the parasite's chloroquine-resistance transporter (PfCRT) in a Xenopus oocyte expression system. This constitutes the first example of a dual-function antimalarial for which the ability to inhibit both hemozoin formation and PfCRT has been demonstrated directly

Implementation of different HIV self-testing models with implications for HIV testing services during the COVID-19 pandemic: study protocol for secondary data analysis of the STAR Initiative in South Africa.

Introduction HIV self-testing (HIVST) presents a convenient, private approach that removes barriers to providing HIV testing services. The Self-Testing Africa (STAR) Initiative aims to scale up HIVST among priority and undertested populations. HIVST has the potential to help maintain testing services during the social distancing restrictions implemented to prevent the spread of COVID-19. This project evaluates linkage to confirmatory testing and treatment for HIV-positive clients for the STAR South Africa site.Methods and analysis This secondary data analysis protocol aims to evaluate different HIVST distribution models from a prospective study implemented during November 2017 and December 2020 by Ezintsha, a subdivision of Wits Reproductive Health and HIV Institute. Routinely collected distribution and self-reported HIVST outcomes data will be deidentified and analysed. The main outcomes of interest are linkage to care and treatment among HIVST users who report a reactive HIVST result. Additionally, we plan to determine sociodemographic factors associated with linkage to care and treatment among HIVST users. Descriptive statistics will be used to describe the variables of interest, and modified Poisson regression with robust variance estimation will be performed to identify factors associated with linkage to care and treatment among HIVST users who report a reactive HIVST result. Risk ratios and 95% CIs for the risk ratios will be reported.Ethics and dissemination The study protocol has been approved by the University of Witwatersrand Human Research Ethics Committee. The dissemination plan for the study findings will include presentations to local and international health authorities, international conferences and publications in open access journals