Abiy Yenesew
University of Nairobi, Kenya, Chemistry, Faculty Member
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Research Interests: Complementary and Alternative Medicine, Plant Biology, Biology, Medicine, Drug Resistance, and 10 moreQuinones, Rubiaceae, Plant Roots, Anthraquinones, Plant extracts, Plasmodium falciparum, Antimalarials, Dichloromethane, Minimum inhibitory concentration, and Pharmacology and pharmaceutical sciences
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Research Interests: Microbiology, Chemistry, Complementary and Alternative Medicine, Biotechnology, Biology, and 15 moreMedicine, Humans, Antioxidant, Candida albicans, Ficus, Antimicrobial, Gram Positive Bacteria, Antibiotics, Bignoniaceae, Microbial Sensitivity Tests, HeLa, Cell Proliferation, Metabolite, Aggregatibacter actinomycetemcomitans, and Candida dubliniensis
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Research Interests: Chemistry, Organic Chemistry, Traditional Medicine, Plant Biology, Fungi, and 15 moreMedicine, Cercopithecus aethiops, Animals, Bacteria, Stereochemistry, Staphylococcus aureus, Plant Roots, Antimicrobial, Antibacterial activity, Plasmodium falciparum, Antifungal Agents, Vero cells, Cytotoxins, Molecular Structure, and Leishmania donovani
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Zanthoxylum species are credited with various uses in ethnomedicine due to their rich metabolite composition. In Kenya, these include management of cancer and microbial related ailments. However, there are limited reports showing how the... more
Zanthoxylum species are credited with various uses in ethnomedicine due to their rich metabolite composition. In Kenya, these include management of cancer and microbial related ailments. However, there are limited reports showing how the bioactivity of Kenyan Zanthoxylum species is linked to their phytochemical profiles. This study therefore aimed at examining the chemical variation among five Zanthoxylum species found in Kenya (Z. chalybeum, Z. gilletii, Z. holtzianum, Z. paracanthum and Z. usambarense) using metabolomics approaches and the anti-oxidant and antimicrobial activities of these species. In a Folin–Ciocalteu test, the phenolic content of the stem bark extracts of these species were 73.083–145.272 mg TAE/g, while the alkaloids (in bromothymol blue chromogenic test) and flavonoids (in aluminium chloride test) were found to be 152.39–207.19 mg ME/g, and 109.416–186.413 mg CE/g, respectively. These extracts also exerted strong antioxidant activities in the 2,2-iphenyl-1-pic...
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NMR data (FIDs, NMReDATA) for the isolated compounds
The CH2Cl2/MeOH (1:1) extract of the stems of Tephrosia uniflora yielded the new β-hydroxydihydrochalcone (S)-elatadihydrochalcone-2'-methyl ether (1) along with the three known compounds elongatin (2), (S)-elatadihydrochalcone (3),... more
The CH2Cl2/MeOH (1:1) extract of the stems of Tephrosia uniflora yielded the new β-hydroxydihydrochalcone (S)-elatadihydrochalcone-2'-methyl ether (1) along with the three known compounds elongatin (2), (S)-elatadihydrochalcone (3), and tephrosin (4). The structures were elucidated by NMR spectroscopic and mass spectrometric data analyses. Elongatin (2) showed moderate antibacterial activity (EC50 of 25.3 μM and EC90 of 32.8 μM) against the Gram-positive bacterium Bacilus subtilis, and comparable toxicity against the MCF-7 human breast cancer cell line (EC50 of 41.3 μM). Based on the comparison of literature and predicted data with that obtained experimentally, we propose the revision of the structure of three β-hydroxydihydrochalcones to flavanones.
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From the dichloromethane-methanol (1:1) extract of the seed pods of <i>Derris trifoliata</i>, a new flavanone derivative (<i>S</i>)-lupinifolin 4´-methyl ether was isolated. In addition, the known flavonoids... more
From the dichloromethane-methanol (1:1) extract of the seed pods of <i>Derris trifoliata</i>, a new flavanone derivative (<i>S</i>)-lupinifolin 4´-methyl ether was isolated. In addition, the known flavonoids lupinifolin and rotenone were identified. The structures were determined on the basis of spectroscopic evidence. Lupinfolin showed moderate <i>in vitro</i> antiplasmodial activity against the D6 (chloroquine-sensitive) and W2 (chloroquine-resistant) strains of <i>Plasmodium falciparum</i>. The different parts of this plant showed larvicidal activities against <i>Aedes aegypti</i> and rotenoids were identified as the active principles.
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Original NMR data (FIDs).
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Introduction . ConventionallY, neglected diseases are considered as a group of 13 infectious diseases that are . endemic in the low income populations in the tropical developing world. They can be classified as those caused by... more
Introduction . ConventionallY, neglected diseases are considered as a group of 13 infectious diseases that are . endemic in the low income populations in the tropical developing world. They can be classified as those caused by trypanosomal parasites, helminthes, bacteria and viruses. They cause death to an estimated 0.51m people annually. Trypanosomal diseases are represented by Kala-azar or visceral leshmaniasis, African sleeping sickness (African trypanosomiasis) and Chaga's disease (American trypanosomiasis); the current drugs for these diseases are relatively toxic even though the disease is not that lethal. Helminth infections include schistosomiasis treated with the inexpensive praziquantel but which cannot stop re-infection; onchocerciasis (river blindness), on which anthelmintic treatment is being tried; dracunculiasis (guinea worm), which should have been eradicated in 2009; lymphatic filiriasis (elephantiasis), managed by anthelmintic treatments. The others are soil tr...
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Commiphora holtziana gum resins when solvent extracted followed by a combination of chromatographic separation techniques on hexane extract of the Wajir sample, led to the isolation and characterization of a new compound,... more
Commiphora holtziana gum resins when solvent extracted followed by a combination of chromatographic separation techniques on hexane extract of the Wajir sample, led to the isolation and characterization of a new compound, 11–hydroxy-γ-muurolene 1. In addition, two known compounds, (1E)-2-methoxy-8,12epoxygermacra-1(10),7,11-triene-6-one 2 and (1E)-3-methoxy-8,12-epoxygermacra-1,7(8),10(15),11-tetraen-6one 3 were also characterized. A total of 14 compounds were identified by the comparison of the mass spectra with data available in the GC – MS library. Both dichloromethane and hexane extracts from both Isiolo and Wajir populations showed antibacterial activity. In addition the hexane extract from Wajir population showed antifungal properties. The acetone extract from Wajir population showed antibacterial properties. Activities were observed against Fungi, Gram (+) bacteria and Gram (-) bacteria. Pure compounds did not show any activity.
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Background: Plants and plant products are by far the most utilized by humans as source of medicine. They are used by various cultures in various ways. Although the beginning of the usage was by trial and error, accessibility may have also... more
Background: Plants and plant products are by far the most utilized by humans as source of medicine. They are used by various cultures in various ways. Although the beginning of the usage was by trial and error, accessibility may have also contributed to some potentially medicinal plants not being accessed and utilized, hence lack of ethnomedicinal usage in history. Gladiolus watsonoides Baker (iridaceae) is one such plant with high antifungal and cytotoxic activities yet no previous reports have been recorded on its usage, biological activities and phytochemicals. The aim of this study was to investigate the antifungal activity, cytotoxicity and the phytochemical components in this plant. Method: Organic and aqueous extracts were tested for antifungal activity against Candida albicans, Aspergillus niger and Cryptococcus neoformans by disc diffusion method. Toxicity tests were done using brine shrimp larvae – nauplii and phytochemical screening for the presence of selected classes of...
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From the stem bark and root bark of Erythrina burttii twenty-three flavonoids and isoflavonoids, including some eight new compounds, have been isolated and characterised. The stem bark of this plant mainly produces isoflavanones while the... more
From the stem bark and root bark of Erythrina burttii twenty-three flavonoids and isoflavonoids, including some eight new compounds, have been isolated and characterised. The stem bark of this plant mainly produces isoflavanones while the root bark elaborate pterocarpans and the rare isoflav-3-enes.
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Chromatographic separation of the extract of the roots of Dorstenia kameruniana (family Moraceae) led to the isolation of three new benzylbenzofuran derivatives, 2-(p-hydroxybenzyl)benzofuran-6-ol (1),... more
Chromatographic separation of the extract of the roots of Dorstenia kameruniana (family Moraceae) led to the isolation of three new benzylbenzofuran derivatives, 2-(p-hydroxybenzyl)benzofuran-6-ol (1), 2-(p-hydroxybenzyl)-7-methoxybenzofuran-6-ol (2) and 2-(p-hydroxy)-3-(3-methylbut-2-en-1-yl)benzyl)benzofuran-6-ol(3) (named dorsmerunin A, B and C, respectively), along with the known furanocoumarin, bergapten (4). The twigs of Dorstenia kameruniana also produced compounds 1-4 as well as the known chalcone licoagrochalcone A (5). The structures were elucidated by NMR spectroscopy and mass spectrometry. The isolated compounds displayed cytotoxicity against the sensitive CCRF-CEM and multidrug-resistant CEM/ADR5000 leukemia cells, where compounds 4 and 5 had the highest activities (IC values of 7.17 μM and 5.16 μM, respectively) against CCRF-CEM leukemia cells. Compound 5 also showed cytotoxicity against 7 sensitive or drug-resistant solid tumor cell lines (breast carcinoma, colon carc...
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Dalbergia melanoxylon Guill. & Perr (Fabaceae) is widely utilized in the traditional medicine of East Africa, showing effects against a variety of ailments including microbial infections. Phytochemical investigation of the root bark led... more
Dalbergia melanoxylon Guill. & Perr (Fabaceae) is widely utilized in the traditional medicine of East Africa, showing effects against a variety of ailments including microbial infections. Phytochemical investigation of the root bark led to the isolation of six previously undescribed prenylated isoflavanones together with eight known secondary metabolites comprising isoflavanoids, neoflavones and an alkyl hydroxylcinnamate. Structures were elucidated based on HR-ESI-MS, 1- and 2-D NMR and ECD spectra. The crude extract and the isolated compounds of D. melanoxylon were tested for their antibacterial, antifungal, anthelmintic and cytotoxic properties, applying established model organisms non-pathogenic to humans. The crude extract exhibited significant antibacterial activity against Gram-positive Bacillus subtilis (97% inhibition at 50 μg/mL) and antifungal activity against the phytopathogens Phytophthora infestans, Botrytis cinerea and Septoria tritici (96, 89 and 73% at 125 μg/mL, re...
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Abstract The manuscript describes the phytochemical investigation of the roots, leaves and stem bark of Millettia lasiantha resulting in the isolation of twelve compounds including two new isomeric isoflavones lascoumestan and... more
Abstract The manuscript describes the phytochemical investigation of the roots, leaves and stem bark of Millettia lasiantha resulting in the isolation of twelve compounds including two new isomeric isoflavones lascoumestan and lascoumaronochromone. The structures of the new compounds were determined using different spectroscopic techniques.
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NMReDATA for compound 1-5, and FIDs for all compounds in the publication "Prenylated Flavonoids from the roots of <em>Tephroisa</em><em> rhodesica</em>". MS and X-ray data.
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Research Interests: Chemistry and Antioxidant
NMR FIDs for the isolated compounds
Abstract In this study, the antileishmanial and cytotoxic activities of secondary metabolites isolated from Tabernaemontana ventricosa Hochst. ex A. DC., Aloe tororoana Reynolds, and Aloe schweinfurthii var. labworana Reynolds were... more
Abstract In this study, the antileishmanial and cytotoxic activities of secondary metabolites isolated from Tabernaemontana ventricosa Hochst. ex A. DC., Aloe tororoana Reynolds, and Aloe schweinfurthii var. labworana Reynolds were investigated. Overall, nineteen known compounds were isolated from the three plant species. The compounds were characterized based on their spectroscopic data. Voacristine and aloenin were the most active compounds against promastigotes of antimony-sensitive Leishmania donovani (IC50 11 ± 5.2 μM and 26 ± 6.5 µM, respectively) with low toxicity against RAW264.7, murine monocyte/macrophage-like cells. The in silico docking evaluation and in vitro NO generation assay also substantially support the antileishmanial effects of these compounds. In a cytotoxicity assay against cancer and normal cell lines, ursolic acid highly inhibited proliferation of lung cancer cells, A549 (IC50 6.61 ± 0.7 μM) while voacristine was moderately active against human liver cancer cells, HepG2 (IC50 23.0 ± 0.0 μM). All other compounds were inactive against the test parasites and cell lines.
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*S Supporting Information ABSTRACT: The known flemingins A−C (1−3) and nine new chalcones, named flemingins G−O (4−12), along with deoxyhomoflemingin (13) and emodin (14) were isolated from a leaf extract of Flemingia grahamiana. The... more
*S Supporting Information ABSTRACT: The known flemingins A−C (1−3) and nine new chalcones, named flemingins G−O (4−12), along with deoxyhomoflemingin (13) and emodin (14) were isolated from a leaf extract of Flemingia grahamiana. The isolated chalcones were found to have a geranyl substituent modified into a chromene ring possessing a residual chain, as shown by spectroscopic methods. The leaf extract showed an IC50 value of 5.9 μg/mL in a DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging assay. The chalcones flemingins A, B, C, G, and H were active in the DPPH radical scavenging assay (ED50 4.4−8.9 μM), while flemingins A and C showed cytotoxicity against MCF-7 human breast cancer cells (IC50 8.9 and 7.6 μM, respectively). Flemingia grahamiana Wight &amp; Arn. (Leguminosae) is a shrub or semishrub reaching a height of up to 1.8 m. It is native to tropical Africa, occurring in open and wooded savannas,
Antiplasmodial and larvicidal flavonoids from
HIV self-testing practices among Health Care Workers: feasibility and options for accelerating HIV testing services in Ethiopia
Malaria is the most lethal parasitic disease in the world. The frequent emergence of resistance by malaria parasites to any drug is the hallmark of sustained malaria burden. Since the deployment of artemisinin-based combination therapies... more
Malaria is the most lethal parasitic disease in the world. The frequent emergence of resistance by malaria parasites to any drug is the hallmark of sustained malaria burden. Since the deployment of artemisinin-based combination therapies (ACTs) it is clear that for a sustained fight against malaria, drug combination is one of the strategies toward malaria elimination. In Sub-Saharan Africa where malaria prevalence is the highest, the identification of plants with a novel mechanism of action that is devoid of cross-resistance is a feasible strategy in drug combination therapy. Thus, artemether and lumefantrine were separately combined and tested with extracts of Securidaca longipedunculata, a plant widely used to treat malaria, at fixed extract–drug ratios of 4:1, 3:1, 1:1, 1:2, 1:3, and 1:4. These combinations were tested for antiplasmodial activity against three strains of Plasmodium falciparum (W2, D6, and DD2), and seven field isolates that were characterized for molecular and ex...
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Research Interests: Phytochemistry, Biology, Magnetic Resonance Spectroscopy, Flavonoids, Medicine, and 14 moreMacromolecular X-Ray Crystallography, Biological Sciences, X Rays, Animals, Drug Resistance, Nmr, CHEMICAL SCIENCES, Plasmodium falciparum, Antimalarials, Chloroquine, Minimum inhibitory concentration, Molecular Structure, Rotenone, and Medical and Health Sciences
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The ethyl acetate extract of the stem bark of Erythrina abyssinica showed anti-plasmodial activity against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum with IC(50) values of 7.9+/-1.1 and... more
The ethyl acetate extract of the stem bark of Erythrina abyssinica showed anti-plasmodial activity against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum with IC(50) values of 7.9+/-1.1 and 5.3+/-0.7 microg/ml, respectively. From this extract, a new chalcone, 2',3,4,4'-tetrahydroxy-5-prenylchalcone (trivial name 5-prenylbutein) and a new flavanone,…