Chemistry Department

Permanent URI for this collection

Browse

Recent Submissions

Now showing 1 - 20 of 251
  • Item
    Modified Corn Starch as an Environmentally Friendly Rheology Enhancer and Fluid Loss Reducer for Water-Based Drilling Mud
    (Society of Petroleum Engineers, 2022-01-07) Emanuel Xwaymay Ricky; Musa Mpelwa; Chao Wang; Bahati Adnan Hamad; Xingguang Xu
    Drilling fluid rheology and fluid loss property are fundamental parameters that dictate the effectiveness and easiness of a drilling operation. Maintaining these parameters under high temperatures is technically challenging and has been an exciting research area for the drilling industry. Nonetheless, the use of drilling mud additives, particularly synthetic polymers threatening the ecological environments. Herein, modified corn starch (MCS) was synthesized, characterized, and investigated as an environmentally friendly rheology enhancer and filtration loss controlling agent for water-based mud (WBM) at high temperatures. The experimental results indicated that MCS exhibits better performance in improving rheological properties and fluid loss controlling ability for WBM than the commonly used mud additives. With the addition of an optimal concentration (0.3 wt%), MCS improved the rheology and fluid loss behaviour of WBM formulation at harsh ageing temperature (220 °C) practically 4 times and 1.7 times, respectively. The MCS was revealed to perform superbly over polyanionic cellulose (PAC) addition at all investigated temperatures. The better performance of the MCS was ascribed to the improved entanglements in the mud system due to the additional hydroxyl (OH) groups. Besides, the Herschel–Bulkley model was found to be a constitutive model that described the rheological properties of the investigated muds satisfactorily. Moreover, the MCS was found to exhibit acceptable biodegradability properties.
  • Item
    Systematic and Facile Analysis of Deposits Composition: Implication on Effective Treatment of Oilfield Solid Deposits
    (American Society of Mechanical Engineers, 2021-07-27) Ricky, Emanuel X; Xu, Xingguang
    Oilfield solid deposits present the major flow assurance problems in the oil and gas industry. In general, the deposits need to be accurately identified and quantified for appropriate design and successful implementation of any treatments. However, few works have been reported on the establishment of a systematic analytical procedure. This work, for the first time, presents a systematic approach that may be used to identify and quantify the composition of oilfield solid deposits, with different analytical methods been jointly used. The X-ray Diffraction and Fourier Transform Infrared Spectroscopy techniques were found very helpful in identifying the composition of the investigated oilfield solid deposit, whereas Thermogravimetric Analysis and Microwave Induced Plasma-Atomic Emission Spectroscopy were the most appropriate quantification techniques. The collected sample was found to contain mainly CaCO3 and consequently, the acid treatment method that involves the use of hydrochloric acid (HCl) solution was proposed to be the most applicable and cost-effective treatment method for its remediation. The exact amount of CaCO3 scale in the oilfield system, the concentration and volume of HCl solution required for the acid treatment method need to be precisely determined to ensure the effective treatment. We believe this well-established analytical procedure will be helpful and enlightening for identification and quantification of oilfield solid deposits and thus may facilitate the effective and efficient treatments on the undesirable deposits
  • Item
    Corrosion Inhibition of Mild Steel in Seawater by 2,4,6-Triamino-3-Pentadecylphenyl Acetate Derived from Cashew Nut Shell Liquid
    (Tanzania Journal of Science, 2021-02-15) Ricky, Emanuel X; Lugwisha, Esther HJ; Philip, Joseph YN
    The corrosion inhibition performance of 2,4,6-triamino-3-pentadecylphenyl acetate on mild steel in seawater at stationary condition, 30 °C and pH 8 was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy. The maximum inhibition efficiency of 93% was found in the presence of 300 ppm of 2,4,6-triamino-3-pentadecylphenyl acetate for both potentiodynamic polarization and electrochemical impedance spectroscopy techniques. The potentiodynamic polarization curves show that 2,4,6-triamino-3-pentadecylphenyl acetate acts as a mixed type inhibitor which influences more the anodic processes. The Nyquist plots revealed that the polarization resistance (Rp) increases whereas the double-layer capacitance (Cdl) and corrosion current density (icorr) decrease as the concentrations of the inhibitors increase due to the formation of a protective layer of inhibitor over the mild steel surface. The results obtained from the two electrochemical techniques are in good agreement. The adsorption of 2,4,6-triamino-3-pentadecylphenyl acetate on the mild steel surface obeyed Langmuir adsorption isotherm.
  • Item
    The study of m-pentadecylphenol on the inhibition of mild steel corrosion in 1 M HCl solution
    (Journal of Industrial and Engineering Chemistry, Published by Elsevier B.V., 2021-06-07) Ricky, Emanuel X; Mpelwa, Musa; Xu, Xingguang
    The acidic fluids used in the acidification of oil wells provoke corrosion of metallic materials unenviably. As a consequence, corrosion inhibitors are needed to mitigate or retard the corrosion process. Herein, we report m-pentadecylphenol as an eco-friendly corrosion inhibitor in acidic media developed from cashew nut shell liquid (CNSL), which is a low-cost and sustainable source. The inhibitor was evaluated as corrosion inhibitor for mild in 1 M HCl corrosive solution by potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), weight loss, Fourier transform infrared (FT-IR) spectroscopy, atomic force microscopy (AFM), and energy-dispersive x-ray fluorescence (EDX-RF) spectrometry methods. The results showed that the inhibition efficiency of m-pentadecylphenol was at least 95% at an optimal concentration (300 ppm). The inhibition efficiency was found to increase as the inhibitor concentration increments from 100 to 300 ppm. Further studies revealed the inhibition performance of m-pentadecylphenol to be marginally reliant on temperature as the temperature rises from 303 to 333 K. At 333 K, the inhibition performance of the inhibitor was still promising (about 85%) when the concentration was 300 ppm. The adsorption studies revealed the spontaneous aptitude of m-pentadecylphenol to inhibit corrosion by forming a non-conductive inhibitive layer on the mild steel surface mainly through the chemisorption mechanism. The chemisorption adsorption was satisfactorily described by the Langmuir adsorption isotherm model. Besides, the potentiodynamic polarization measurements revealed m-pentadecylphenol to act as an anodic inhibitor. The overall findings revealed that m-pentadecylphenol to be an effective corrosion inhibitor in harsh corrosive vicinities with the added advantages of being eco-friendly and relatively cheaper. Thus, it can replace the use of non-green and expensive corrosion inhibitors in the industry.
  • Item
    Draft Genome Sequence of Limnospira sp. Strain BM01, Isolated from a Hypersaline Lake of the Momela Ecosystem in Tanzania
    (American Society for Microbiology, 2021-04) Reuben Maghembe, Angelina Michael, Ajith Harish, Stephen S. Nyandoro, Sylvester L. Lyantagaye, Rajni Hati-Kaul
    The genus Limnospira includes cyanobacterial species used for industrial production of dietary supplements and nutraceutical agents. The metagenome assembled genome of Limnospira sp. strain BM01 from Big Momela Lake, Tanzania, was 6,228,312 bp long with a GC content of 44.8% and carried 4,921 proteins and 52 RNA genes, including 6 rRNA genes
  • Item
    Tanning capacity of Tessmannia burttii extracts: the potential eco-friendly tanning agents for the leather industry
    (Journal of Leather Science and Engineering, 2021-05-15) Cecilia R. China, Stephen S. Nyandoro, Joan J. E. Munissi, Mihayo M. Maguta, Michael Meyer and Michaela Schroepfer
    In the present study, the tannins from stem and root barks of Tessmannia burttii Harms (Caesalpiniaceae), a plant species abundantly growing in Tanzania and other parts of Africa, were investigated for their suitability in hides tanning. Tannin powder was extracted at selected temperatures (30, 50 and 80 °C) and the influence of each temperature on the crosslinking capacity was evaluated. The interaction mechanism between hide powder collagen and the tannins was studied by Differential Scanning Calorimetry (DSC), trinitrobenzensulfonic (TNBS) acid assay and amino acid hydrolysis methods. Extraction temperatures showed low influence on crosslinking capacity of the tannins. However, extract obtained at 50 °C exhibited best performance in terms of gap size between Tonset and Tpeak. The stem bark extract yield was higher than that from the root bark, but both were within the recommended ranges. The tannin content (61%) of T. burttii stem bark extract was above recommended value (10%), whereas its total phenolic content and total flavonoic content were found to be above that of commercial Acacia mearnsii tannin. The study of cross-linking parameters as a function of pH showed cross-linking to occur via a covalent mechanism at the basic amino groups. However, the bonds were not resistant to acid hydrolysis. The observed interaction mechanism indicated that tannins from stem and root barks of T. burttii belong to the condensed tannin, similar to A. mearnsii (black wattle), a commercial tannin source that was used in this study as a reference. Findings from this study depict that T. burttii extracts are auspicious eco-friendly alternative source of vegetable tannins to overcome the use of chromium salts in the leather industry.
  • Item
    A zooprophylaxis strategy using l-lactic acid (Abate) to divert host-seeking malaria vectors from human host to treated non-host animals
    (BioMed Central (BMC), 2020-01) Kemibala, Elison, E; Mafra‑Neto, Agenor; Dekker, Teun; Saroli, Jesse; Silva, Rodrigo; Philbert, Anitha; Nghabi, Kija; Mboera, Leonard, E.G
    Background: Zooprophylaxis is a technique in which blood‑seeking vectors are diverted to non‑host animals in order to lower blood‑feeding rates on human hosts. The success of this technique depends on the host preference of the vector being targeted. The objective of this study was to evaluate the efect of l‑lactic acid (Abate) to divert malaria mosquito, Anopheles gambiae from feeding on human host. Methods: A 14‑month‑old female goat was treated with Abate, a formulation incorporating l‑lactic acid into a slow‑ release matrix. This formulation was applied on the fur of the goat’s back and neck. The treated animal was then pre‑ sented to Anopheles gambiae sensu stricto (s.s.) as a prospective host in a semi‑feld environment (‘mosquito sphere’) together with either an untreated animal or a human. The number of mosquitoes caught to each host choice ofered were compared. Results: Goat treated with the l‑lactic acid formulation successfully attracted An. gambiae at higher rates (70.2%) than the untreated ones (29.8%). Furthermore, An. gambiae s.s. were attracted to a treated goat at an equivalent degree (47.3%) as to their preferred human host (52.7%), even when the preferred host was present in the same environment. Conclusions: The fndings indicate that human host‑seeking mosquitoes can be diverted into feeding on non‑ preferred hosts despite the close proximity of their favoured host, hence reducing chances for the transmission of blood‑borne parasites
  • Item
    Dynamics and monitoring of insecticide resistance in malaria vectors across mainland Tanzania from 1997 to 2017: a systematic review
    (BioMed Central (BMC), 2019-03) Matiya, Deokary, J; Philbert, Anitha, B; Kidima, Winfrida; Matowo, Johnson, J
    Background: Malaria still claims substantial lives of individuals in Tanzania. Insecticide-treated nets (ITNs) and indoor residual spray (IRS) are used as major malaria vector control tools. These tools are facing great challenges from the rapid escalating insecticide resistance in malaria vector populations. This review presents the information on the dynamics and monitoring of insecticide resistance in malaria vectors in mainland Tanzania since 1997. The information is important to policy-makers and other vector control stakeholders to refect and formulate new resistance management plans in the country. Methods: Reviewed articles on susceptibility and mechanisms of resistance in malaria vectors to insecticides across mainland Tanzania were systematically searched from the following databases: PubMed, Google scholar, HINARI and AGORA. The inclusion criteria were articles published between 2000 and 2017, reporting susceptibility of malaria vectors to insecticides, mechanisms of resistance in the mainland Tanzania, involving feld collected adult mosquitoes, and mosquitoes raised from the feld collected larvae. Exclusion criteria were articles reporting insecticide resistance in larval bio-assays, laboratory strains, and unpublished data. Reviewed information include year of study, malaria vectors, insecticides, and study sites. This information was entered in the excel sheet and analysed. Results: A total of 30 articles met the selection criteria. The rapid increase of insecticide resistance in the malaria vectors across the country was reported since year 2006 onwards. Insecticide resistance in Anopheles gambiae sensu lato (s.l.) was detected in at least one compound in each class of all recommended insecticide classes. However, the Anopheles funestus s.l. is highly resistant to pyrethroids and DDT. Knockdown resistance (kdr) mechanism in An. gambiae s.l. is widely studied in the country. Biochemical resistance by detoxifcation enzymes (P450s, NSE and GSTs) in An. gambiae s.l. was also recorded. Numerous P450s genes associated with metabolic resistance were over transcribed in An. gambiae s.l. collected from agricultural areas. However, no study has reported mechanisms of insecticide resistance in the An. funestus s.l. in the country. Conclusion: This review has shown the dynamics and monitoring of insecticide resistance in malaria vector populations across mainland Tanzanian. This highlights the need for devising improved control approaches of the malaria vectors in the country.
  • Item
    Habitat productivity and pyrethroid susceptibility status of Aedes aegypti mosquitoes in Dar es Salaam, Tanzania
    (BioMed Central (BMC), 2017-05) Mathias, Leah; Baraka, Vito; Philbert, Anitha; Innocent, Ester; Francis, Filbert; Nkwengulila, Gamba; Kweka, Eliningaya, J
    Background: Aedes aegypti (Diptera: Culicidae) is the main vector of the dengue virus globally. Dengue vector control is mainly based on reducing the vector population through interventions, which target potential breeding sites. However, in Tanzania, little is known about this vector’s habitat productivity and insecticide susceptibility status to support evidence-based implementation of control measures. The present study aimed at assessing the productivity and susceptibility status of A. aegypti mosquitoes to pyrethroid-based insecticides in Dar es Salaam, Tanzania. Methods: An entomological assessment was conducted between January and July 2015 in six randomly selected wards in Dar es Salaam, Tanzania. Habitat productivity was determined by the number of female adult A. aegypti mosquitoes emerged per square metre. The susceptibility status of adult A. aegypti females after exposure to 0.05% deltamethrin, 0.75% permethrin and 0.05% lambda-cyhalothrin was evaluated using the standard WHO protocols. Mortality rates were recorded after 24 h exposure and the knockdown effect was recorded at the time points of 10, 15, 20, 30, 40, 50 and 60 min to calculate the median knockdown times (KDT50 and KDT95). Results: The results suggest that disposed tyres had the highest productivity, while water storage tanks had the lowest productivity among the breeding habitats Of A. aegypti mosquitoes. All sites demonstrated reduced susceptibility to deltamethrin (0.05%) within 24 h post exposure, with mortalities ranging from 86.3 ± 1.9 (mean ± SD) to 96.8 ± 0.9 (mean ± SD). The lowest and highest susceptibilities were recorded in Mikocheni and Sinza wards, respectively. Similarly, all sites demonstrated reduced susceptibility permethrin (0.75%) ranging from 83.1 ± 2.1% (mean ± SD) to 96.2 ± 0.9% (mean ± SD), in Kipawa and Sinza, respectively. Relatively low mortality rates were observed in relation to lambda-cyhalothrin (0.05%) at all sites, ranging from 83.1 ± 0.7 (mean ± SD) to 86.3 ± 1.4 (mean ± SD). The median KDT50 for deltamethrin, permethrin and lambda-cyhalothrin were 24.9–30. 3 min, 24.3–34.4 min and 26.7–32.8 min, respectively. The KDT95 were 55.2–90.9 min for deltamethrin, 54.3–94. 6 min for permethrin and 64.5–69.2 min for lambda-cyhalothrin. Conclusions: The productive habitats for A. aegypti mosquitoes found in Dar es Salaam were water storage containers, discarded tins and tyres. There was a reduced susceptibility of A. aegypti to and emergence of resistance against pyrethroid-based insecticides. The documented differences in the resistance profiles of A. aegypti mosquitoes warrants regular monitoring the pattern concerning resistance against pyrethroid-based insecticides and define dengue vector control strategies
  • Item
    Farmers’ pesticide usage practices in the malaria endemic region of North-Western Tanzania: implications to the control of malaria vectors
    (BioMed Central (BMC), 2019-11) Philbert, Anitha; Lyantagaye, Slyvester, L; Nkwengulila, Gamba
    Background: Pesticides remain the mainstay for the control of agricultural pests and disease vectors. However, their indiscriminate use in agriculture has led to development of resistance to both crop pests and disease vectors. This threatens to undermine the success gained through the implementation of chemical based vector control programs. We investigated the practices of farmers with regard to pesticide usage in the vegetable growing areas and their impact on susceptibility status of An. gambiae s.l. Methods: A stratified multistage sampling technique using the administrative structure of the Tanzanian districts as sampling frame was used. Wards, villages and then participants with farms where pesticides are applied were purposively recruited at different stages of the process, 100 participants were enrolled in the study. The same villages were used for mosquito larvae sampling from the farms and the surveys were complimented by the entomological study. Larvae were reared in the insectary and the emerging 2–3 days old female adults of Anopheles gambiae s.l were subjected to susceptibility test. Results: Forty eight pesticides of different formulations were used for control of crop and Livestock pests. Pyrethroids were the mostly used class of pesticides (50%) while organophosphates and carbamates were of secondary importance. Over 80% of all farmers applied pesticides in mixed form. Susceptibility test results confirmed high phenotypic resistance among An. gambiae populations against DDT and the pyrethroids (Permethrin-0.75%, Cyfluthrin-0.15%, Deltametrin-0.05% and Lambdacyhalothrin-0.05%) with mortality rates 54, 61, 76 and 71%, respectively. Molecular analysis showed An. arabiensis as a dominant species (86%) while An. gambiae s.s constituted only 6%. The kdr genes were not detected in all of the specimens that survived insecticide exposures. Conclusion: The study found out that there is a common use of pyrethroids in farms, Livestocks as well as in public health. The study also reports high phenotypic resistance among An. gambiae s.l against most of the pyrethroids tested. The preponderance of pyrethroids in agriculture is of public health concern because this is the class of insecticides widely used in vector control programs and this calls for combined integrated pest and vector management (IPVM).
  • Item
    Pyrethroids and DDT tolerance of Anopheles gambiae s.l. from Sengerema District, an area of intensive pesticide usage in north-western Tanzania
    (Willey online Library, 2017-04) Philbert, Anitha; Lyantagaye, Slyvester, L; Pradel, Gabriela; Ngwa, Julious, C; Nkwengulila, Gamba
    objective To assess the susceptibility status of malaria vectors to pyrethroids and dichlorodiphenyltrichloroethane (DDT), characterise the mechanisms underlying resistance and evaluate the role of agro-chemical use in resistance selection among malaria vectors in Sengerema agro-ecosystem zone, Tanzania. methods Mosquito larvae were collected from farms and reared to obtain adults. The susceptibility status of An. gambiae s.l. was assessed using WHO bioassay tests to permethrin, deltamethrin, lambdacyhalothrin, etofenprox, cyfluthrin and DDT. Resistant specimens were screened for knockdown resistance gene (kdr), followed by sequencing both Western and Eastern African variants. A gas chromatography–mass spectrophotometer (GC-MS) was used to determine pesticide residues in soil and sediments from mosquitoes’ breeding habitats. results Anopheles gambiae s.l. was resistant to all the insecticides tested. The population of Anopheles gambiae s.l was composed of Anopheles arabiensis by 91%. The East African kdr (L1014S) allele was found in 13 of 305 specimens that survived insecticide exposure, with an allele frequency from 0.9% to 50%. DDTs residues were found in soils at a concentration up to 9.90 ng/g (dry weight). conclusion The observed high resistance levels of An. gambiae s.l., the detection of kdr mutations and pesticide residues in mosquito breeding habitats demonstrate vector resistance mediated by pesticide usage. An integrated intervention through collaboration of agricultural, livestock and vector control units is vital
  • Item
    Concentrations of polar pesticide residues in the surface waters of selected areas of Coast region, Tanzania
    (Makerere University, Kampala-Uganda, 2005-01-20) Mahugija, John A.M.; Kishimba, Michael A.
    The concentrations of 60 polar pesticide residues were investigated in surface waters from eleven sites in two rivers, a pond and four drinking water wells in Coast region, Tanzania. The extracts were analyzed by Gas Chromatography-Nitrogen Phosphorus Detection (GC-NPD) and confirmed by high-performance liquid chromatography-tandem mass spectrometry (HPLC/MS/MS). Quantification of analytes was done by using the peak heights with two different m/z for each analyte. The compounds detected were atrazine, isoproturon and diuron. The highest concentrations of atrazine were 13 ng/l in drinking water, 16 ng/l in pond water and 172 ng/l in river water. The highest concentrations of isoproturon and diuron in river water were 18 ng/l and 12 ng/l, respectively. Atrazine was the most predominant pollutant in water. The results indicate that the source of contamination is due to the agricultural use of these pesticides in the nearby areas. The concentrations of atrazine, isoproturon and diuron in drinking water were far below the WHO guidelines for drinking-water quality.
  • Item
    Levels of heavy metals in urine samples of school children from selected industrial and non-industrial areas in Dar es Salaam, Tanzania
    (Makerere University Medical School, 2018-12) Mahugija, John A.M.; Kasenya, Zainab S.; Kilulya, Kessy F.
    Objectives: The levels of lead, zinc, iron, copper and cadmium metals in the urine samples of selected school children in industrial and non-industrial areas in Dar es Salaam were investigated. Methods: Urine samples were collected from 120 children in industrial areas and 120 children in non-industrial areas then digested in concentrated acids and analysed using atomic absorption spectrophotometry (AAS). Results: The concentrations of the heavy metals in the urine samples ranged from below detection limit/non-detectable (ND) to 1.92 mg/L for lead, ND to 2.55 mg/L for zinc, ND to 8.98 mg/L for iron and ND to 0.05 mg/L for copper. Cadmium was not detected. Significant differences were found between the concentrations of heavy metals in urine of pupils from the industrial areas and those from non-industrial areas. The mean concentrations of lead and copper in samples from industrial areas were significantly higher than those found in non-industrial areas (p < 0.002), while the mean concentrations of zinc and iron found in samples from non-industrial areas were significantly higher than those found in industrial areas (p < 0.0001). Conclusion: The contamination levels were generally high in samples from both areas indicating exposure from various sources. The findings indicate public health risks.
  • Item
    Aromatic Bio-Based Solvents
    (John Wiley & Sons, 2017-06-30) Mubofu, Egid B.; Mgaya, James; Munissi, Joan J.E
    This chapter focuses on alkylresorcinols (AR) and cashew nut shell liquid (CNSL) as bio‐based solvents from agricultural produce and waste. It highlights the possible biological sources for bio‐based aromatics, such as cereals and CNS wastes, and the techniques for their extraction. The chapter also introduces the possible potential applications of these extracts as solvents or reagents in the production of functional or platform chemicals. The competitive advantage of utilizing agricultural by‐products or wastes, such as cereal bran and CNSs, as renewable bio‐resources for the production of aromatic bio‐based solvents is manifested in non‐interference with food supply and their contributions towards waste minimization. Thus, this chapter centres its discussion onaromatic bio‐based solvents from agricultural by‐products and waste materials, and emphases on resorcinolic lipids and CNSL. Basically, there are three methods used to extract CNSL from the shells: solvent extraction, thermal extraction and mechanical extraction
  • Item
    Polyoxygenated Cyclohexenes and Other Constituents of Cleistochlamys kirkii Leaves
    (American Chemical Society, 2016-12-21) Nyandoro, Stephen S.; Munissi, Joan J.E; Gruhonjic, Amra; Duffy, Sandra; Pan, FangFang; Puttreddy, Rakesh; Holleran, John P.; Fitzpatrick, Paul A.; Pelletier, Jerry; Avery, Vicky M.; Rissanen, Kari; Erdelyi, Mate
    Thirteen new metabolites, including the polyoxygenated cyclohexene derivatives cleistodiendiol (1), cleistodienol B (3), cleistenechlorohydrins A (4) and B (5), cleistenediols A–F (6–11), cleistenonal (12), and the butenolide cleistanolate (13), 2,5-dihydroxybenzyl benzoate (cleistophenolide, 14), and eight known compounds (2, 15–21) were isolated from a MeOH extract of the leaves of Cleistochlamys kirkii. The purified metabolites were identified by NMR spectroscopic and mass spectrometric analyses, whereas the absolute configurations of compounds 1, 17, and 19 were established by single-crystal X-ray diffraction. The configuration of the exocyclic double bond of compound 2 was revised based on comparison of its NMR spectroscopic features and optical rotation to those of 1, for which the configuration was determined by X-ray diffraction. Observation of the co-occurrence of cyclohexenoids and heptenolides in C. kirkii is of biogenetic and chemotaxonomic significance. Some of the isolated compounds showed activity against Plasmodium falciparum (3D7, Dd2), with IC50 values of 0.2–40 μM, and against HEK293 mammalian cells (IC50 2.7–3.6 μM). While the crude extract was inactive at 100 μg/mL against the MDA-MB-231 triple-negative breast cancer cell line, some of its isolated constituents demonstrated cytotoxic activity with IC50 values ranging from 0.03–8.2 μM. Compound 1 showed the most potent antiplasmodial (IC50 0.2 μM) and cytotoxic (IC50 0.03 μM, MDA-MB-231 cell line) activities. None of the compounds investigated exhibited translational inhibitory activity in vitro at 20 μM.
  • Item
    Flavonoids from Erythrina Schliebenii
    (American Chemical Society, 2017-01-23) Nyandoro, Stephen S.; Munissi, Joan J.E; Kombo, Msim; Mgina, Clarence A; Pan, FangFang; Gruhonjic, Amra; Fitzpatrick, Paul A.; Lu, Yu; Wang, Bin; Rissanen, Kari; Erdelyi, Mate
    Prenylated and O-methylflavonoids including one new pterocarpan (1), three new isoflavones (2–4), and nineteen known natural products (5–23) were isolated and identified from the root, stem bark, and leaf extracts of Erythrina schliebenii. The crude extracts and their constituents were evaluated for antitubercular activity against Mycobacterium tuberculosis (H37Rv strain), showing MICs of 32–64 μg mL–1 and 36.9–101.8 μM, respectively. Evaluation of their toxicity against the aggressive human breast cancer cell line MDA-MB-231 indicated EC50 values of 13.0–290.6 μM (pure compounds) and 38.3 to >100 μg mL–1 (crude extracts).
  • Item
    Antimycobacterial and Cytotoxic Activities of Extracts from Fungal Isolates of Lake Magadi
    (International Formulae Group, 2017) Kowanga, Keno D; Munissi, Joan J.E; Masalu, Rose; Nyandoro, Stephen S.; Masimba, Pax; Gatebe, E.
    Antimycobacterial and cytotoxic activities of extracts from fungal isolates of Lake Magadi Keno David Kowanga, Joan John Eliona Munissi, Rose Masalu, Stephen Samwel Nyandoro, Pax Masimba, Erastus Gatebe Abstract In this study, antimycobacterial and cytotoxic activities of ethyl acetate extracts of fungal isolates from Lake Magadi were evaluated. The extracts were tested against Mycobacterium madagascariense (MM) and M. indicus pranii (MIP), and cytotoxicity against brine shrimp (Artemia salina) larvae. Fungal strains were identified using sequence comparison of the Internal Transcribed Spacer (ITS) region. Potent antimycobacterial activities against MM were exhibited by extracts from Volutella colletotrichoides, Helicoon richonis, Penicillium limosum, P. sacculum, Aspergillus parasiticus and A. nomius strains that exhibited minimum inhibition concentration (MIC) in the range of 0.19 – 12.5 mg/mL. On the other hand, significant antimycobacterial effects against MIP was shown by extracts from V. colletotrichoides, H. richonis, A. parasiticus, Fusarium merismoides, A. silvaticus and A. fumigatus strains in the same MIC range. Notable cytotoxic activities of the extracts were from A. versicolor, A. nomius, P. janthinellum and H. richonis strains with LC50 values ranging from 46.60 – 98.12 μg/mL. These results indicate that fungi inhabiting Lake Magadi have the ability to produce bioactive metabolites that could be further explored for potential medicinal agents
  • Item
    Evaluation of Antimycobacterial Activity of Higenamine Using Galleria mellonella as an In Vivo Infection Model
    (Springer, 2018-02) Erasto, Paul; Omolo, Justin; Sunguruma, Richard; Munissi, Joan J.E; Wiketye, Victor; Konig, de Charles; Ahmed, Atallah F.
    The Phytochemical investigation on MeOH extract on the bark of Aristolochia brasiliensis Mart. & Zucc (Aristolochiaceae) led to the isolation of major compound (1) as light brown grainy crystals. The compound was identified as 1-(4-hydroxybenzyl)-1,2,3,4-tetrahydroisoquinoline-6,7-diol (higenamine) on the basis of spectroscopic analysis, including 1D and 2D NMR spectroscopy. The compound was evaluated for its antimycobacterial activity against Mycobacterium indicus pranii (MIP), using Galleria mellonella larva as an in vivo infection model. The survival of MIP infected larvae after a single dose treatment of 100 mg/kg body weight of higenamine was 80% after 24 h. Quantitatively the compound exhibited a dose dependent activity, as evidenced by the reduction of colony density from 105 to 103 CFU for test concentrations of 50, 100, 150 and 200 mg/kg body weight respectively. The IC50 value for higenamine was 161.6 mg/kg body weight as calculated from a calibration curve. Further analysis showed that, a complete inhibition of MIP in the G. mellonella could be achieved at 334 mg/kg body weight. Despite the fact that MIP has been found to be highly resistant against isoniazid (INH) in an in vitro assay model, in this study the microbe was highly susceptible to this standard anti-TB drug. The isolation of higenamine from the genus Aristolochia and the method used to evaluate its in vivo antimycobacterial activity in G. mellonella are herein reported for the first time.
  • Item
    Aflatoxin Levels in Sunflower Seeds and Unrefined Sunflower Oils from Singida, Tanzania
    (Taylor & Francis, 2018-03-16) Mohammed, Salum; Munissi, Joan J.E; Nyandoro, Stephen S.
    A total of 61 samples comprising sunflower seeds (40) and unrefined sunflower oils (21) samples collected randomly from Singida, Tanzania were analysed by Reverse Phase-high performance liquid chromatography (RP-HPLC). 15% (6/40) of the seed samples were contaminated with aflatoxin B1 ranging from limit of detection (LOD) to 218 ng g−1 with three of them exceeding the European Commission/European Union (EC/EU) and Tanzania Bureau of Standards (TBS)/Tanzania Food and Drug Authority (TFDA) maximum limits of 2 ng g−1 for AFB1 in oilseeds. The levels of total aflatoxins (AFT) in seeds ranged from LOD to 243 ng g−1. Other aflatoxins, except AFG2, were also detected. For the unrefined sunflower oils, the levels of AFB1 ranged from LOD to 2.56 ng mL−1. About 80.9% (17/21) of the analysed oil samples contained AFB1 of which 17.65% (3/17) exceeded the EC/EU and TBS/TFDA maximum limits of 2 ng mL−1. Other aflatoxins were also detected in the oils. The measured levels indicate there is a need for food quality education among food processors.
  • Item
    In silico pharmacokinetic, molecular docking and molecular dynamics simulation studies of n-cinnamoyltetraketide derivatives as inhibitors of cyclooxygenase-2 enzyme
    (Dar es Salaam University Press, 2018-06) Nyandoro, Stephen S.; Shadrack, Daniel M; Munissi, Joan J.E; Mubofu, Egid B.
    Recent phytochemical analysis of Toussaintia orientalis leaves yielded series of novel bioactive N-cinnamoyltetraketide derivatives namely toussaintines A-G (t_1 - t_8) some portraying cytotoxicity against the triple negative aggressive human breast cancer cell line (MDA-MB-231) among other potencies. Despite having broad bioactivity spectrum, their general drug-likeness profiles and mode of action (simulated or actual) targeting any enzyme remains uninvestigated. In silico pharmacokinetic, drug-likeness descriptors and molecular docking of the compounds t_1-t_8 targeting inhibition of cyclooxygenase-2 (COX-2) enzyme were evaluated. The Lipinski Rule of Five heralded the pharmacokinetic properties of the studied metabolites. The studied compounds were docked with COX-2 following already established protocol. ADMET descriptors fell within the recommended range, except for compound t_3 that was predicted to potentially have positive blood brain barrier (BBB+) penetration. Docking studies indicated N-cinnamoyltetraketide derivatives as potential inhibitors of COX-2 enzyme. Compounds t_3 and t_5 showed lower binding energy of -13 and -12.3 kcal/mol, respectively, being closely comparable to celecoxib (-12.3 kcal/mol) indicating compatibility with the protein receptor. The findings provide baseline information on drug or lead-likeness and potential mode of action of the studied molecules towards inhibition of COX-2 enzyme