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Dr. Richard Mampa
University of Limpopo Turfloop Campus

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Research Keywords & Expertise

0 Medicinal Chemistry
0 water pollution and bioremediation
0 ICP-MS analytical methods
0 Sequential extraction
0 Spectroscopy (NMR, UV-VIS, LC-MS, FT-IR)

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Journal article
Published: 12 August 2021 in Minerals
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In this study, the sequential extraction method was applied to extract selected potentially toxic elements (PTEs) (Cd, Cr, Cu, Fe, Ni, Pb and Zn) in river sediments collected from the Blood River situated in Seshego area, Limpopo Province, South Africa. The study aimed to assess a possible trend of mobilisation of these elements from sediment to water. The accuracy of the sequential extraction method was confirmed by analysing sediment-certified reference material, and quantitative percentage recoveries ranging from 86 to 119%, 81 to 111% and 77 to 119% were achieved for exchangeable, reducible and oxidisable fractions, respectively. The potential risk of the PTEs in sediments was evaluated. The calculated values of contamination factor (CF) as well as risk assessment code (RAC) for Cd, Cu, Ni and Pb revealed the mobility of these elements. The PTEs in river sediments are at a high toxicity-risk level and could therefore cause a threat to organisms dwelling in sediments and humans via consumption of crops irrigated with the polluted river water.

ACS Style

Dithobolong L. Matabane; Taddese W. Godeto; Richard M. Mampa; Abayneh A. Ambushe. Sequential Extraction and Risk Assessment of Potentially Toxic Elements in River Sediments. Minerals 2021, 11, 874 .

AMA Style

Dithobolong L. Matabane, Taddese W. Godeto, Richard M. Mampa, Abayneh A. Ambushe. Sequential Extraction and Risk Assessment of Potentially Toxic Elements in River Sediments. Minerals. 2021; 11 (8):874.

Chicago/Turabian Style

Dithobolong L. Matabane; Taddese W. Godeto; Richard M. Mampa; Abayneh A. Ambushe. 2021. "Sequential Extraction and Risk Assessment of Potentially Toxic Elements in River Sediments." Minerals 11, no. 8: 874.

Journal article
Published: 04 June 2021 in Journal of Molecular Structure
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A series of 4-(pyridylamino)- and 4-(ethynylpyridine)quinazolines were successfully prepared via Sonogashira cross-coupling and dechloroamination reactions on the C(4)-Cl position of the requisite 2-(p-phenyl)-4-chloroquinazolines. The prepared compounds were characterized by means of 1H- and 13C-NMR, FT-IR and mass spectrometry techniques. The structure of 2-(4-chlorophenyl)-4-(2-(pyridin-4-yl)ethynyl)quinazoline from the 4-(ethynylpyridine) series was confirmed by single crystal X-Ray analysis which indicates monoclinic crystal system and P21/c space group. Compounds from the 4-chloro-, 4-(pyridylamino)- and 4-(ethynylpyridine)-quinazoline series were evaluated for anti-Mycobacterium tuberculosis (Mtb) properties in vitro employing rifampicin as a reference drug. The results from the Alamar Blue assay (Mtb H37Rv strain) revealed promising MIC90 ranging from 125 µM. The cytotoxicity of the synthesised compounds was tested against the Raw 264.7 microphage cell line at a maximum concentration of 50 µM. The possible mode of interaction against the Mtb was theoretically explained through molecular 3ZXR protein and the more prominent hydrogen bond is observed between the nitrogen of the pyridine ring moiety of the 5 and 6 series with OH group of SER280. Also, a metal coordination between the methoxy benzene moiety of compound 6e and Mg2+ is also observed, explaining the SAR of these compounds to MtGS.

ACS Style

Kabelo B. Dilebo; Njabulo J. Gumede; Winston Nxumalo; Thabe M. Matsebatlela; Dikgale Mangokoana; Ngaoko R. Moraone; Bernard Omondi; Richard M. Mampa. Synthesis, in vitro cytotoxic, anti-Mycobacterium tuberculosis and molecular docking studies of 4-pyridylamino- and 4-(ethynylpyridine)quinazolines. Journal of Molecular Structure 2021, 1243, 130824 .

AMA Style

Kabelo B. Dilebo, Njabulo J. Gumede, Winston Nxumalo, Thabe M. Matsebatlela, Dikgale Mangokoana, Ngaoko R. Moraone, Bernard Omondi, Richard M. Mampa. Synthesis, in vitro cytotoxic, anti-Mycobacterium tuberculosis and molecular docking studies of 4-pyridylamino- and 4-(ethynylpyridine)quinazolines. Journal of Molecular Structure. 2021; 1243 ():130824.

Chicago/Turabian Style

Kabelo B. Dilebo; Njabulo J. Gumede; Winston Nxumalo; Thabe M. Matsebatlela; Dikgale Mangokoana; Ngaoko R. Moraone; Bernard Omondi; Richard M. Mampa. 2021. "Synthesis, in vitro cytotoxic, anti-Mycobacterium tuberculosis and molecular docking studies of 4-pyridylamino- and 4-(ethynylpyridine)quinazolines." Journal of Molecular Structure 1243, no. : 130824.

Journal article
Published: 28 May 2019 in Crystals
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The conformation of the title compounds was determined in solution by 1H-NMR spectroscopy and in solid state by single-crystal X-ray diffraction (XRD) complemented with density functional theory. The compounds were found to exist exclusively in solution and solid state as trans-2-aminochalcone epoxides with strong intramolecular hydrogen bonding interaction between the amino and carbonyl groups. These 2-aminochalcone epoxides experienced a solvent effect in DMSO-d6, which resulted in an anomalous chemical shift for the α-hydrogen signal, presumably due to complexation of solute molecules with DMSO. The solute–solvent interaction would probably fix the trans conformation of epoxyketone such that α-H is more accessible to both aryl rings, and in turn, experience their combined anisotropic effect. Intermolecular interactions in the crystal structures were confirmed and quantified using the Hirshfeld surface analysis. Moreover, the trans stereochemistry of the α-epoxyketones facilitated direct one-pot sequential sulfuric acid-mediated ring opening and aryl migration to afford the corresponding 3-arylquinolin-4(1H)-ones (azaisoflavones).

ACS Style

Malose J. Mphahlele; Marole M. Maluleka; Richard M. Mampa. Elucidation of the Structure of the 2-amino-3,5-Dibromochalcone Epoxides in Solution and Solid State. Crystals 2019, 9, 277 .

AMA Style

Malose J. Mphahlele, Marole M. Maluleka, Richard M. Mampa. Elucidation of the Structure of the 2-amino-3,5-Dibromochalcone Epoxides in Solution and Solid State. Crystals. 2019; 9 (6):277.

Chicago/Turabian Style

Malose J. Mphahlele; Marole M. Maluleka; Richard M. Mampa. 2019. "Elucidation of the Structure of the 2-amino-3,5-Dibromochalcone Epoxides in Solution and Solid State." Crystals 9, no. 6: 277.

Journal article
Published: 04 January 2017 in Molecules
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The structures of the mono- and the dihalogenated N-unsubstituted 2-aminobenzamides were characterized by means of the spectroscopic (1H-NMR, UV-Vis, FT-IR, and FT-Raman) and X-ray crystallographic techniques complemented with a density functional theory (DFT) method. The hindered rotation of the C(O)–NH2 single bond resulted in non-equivalence of the amide protons and therefore two distinct resonances of different chemical shift values in the 1H-NMR spectra of these compounds were observed. 2-Amino-5-bromobenzamide (ABB) as a model confirmed the presence of strong intramolecular hydrogen bonds between oxygen and the amine hydrogen. However, intramolecular hydrogen bonding between the carbonyl oxygen and the amine protons was not observed in the solution phase due to a rapid exchange of these two protons with the solvent and fast rotation of the Ar–NH2 single bond. XRD also revealed the ability of the amide unit of these compounds to function as a hydrogen bond donor and acceptor simultaneously to form strong intermolecular hydrogen bonding between oxygen of one molecule and the NH moiety of the amine or amide group of the other molecule and between the amine nitrogen and the amide hydrogen of different molecules. DFT calculations using the B3LYP/6-311++G(d,p) basis set revealed that the conformer (A) with oxygen and 2-amine on the same side predominates possibly due to the formation of a six-membered intramolecular ring, which is assisted by hydrogen bonding as observed in the single crystal XRD structure.

ACS Style

Malose Jack Mphahlele; Marole Maria Maluleka; Lydia Rhyman; Ponnadurai Ramasami; Richard Mokome Mampa. Spectroscopic, DFT, and XRD Studies of Hydrogen Bonds in N-Unsubstituted 2-Aminobenzamides. Molecules 2017, 22, 83 .

AMA Style

Malose Jack Mphahlele, Marole Maria Maluleka, Lydia Rhyman, Ponnadurai Ramasami, Richard Mokome Mampa. Spectroscopic, DFT, and XRD Studies of Hydrogen Bonds in N-Unsubstituted 2-Aminobenzamides. Molecules. 2017; 22 (1):83.

Chicago/Turabian Style

Malose Jack Mphahlele; Marole Maria Maluleka; Lydia Rhyman; Ponnadurai Ramasami; Richard Mokome Mampa. 2017. "Spectroscopic, DFT, and XRD Studies of Hydrogen Bonds in N-Unsubstituted 2-Aminobenzamides." Molecules 22, no. 1: 83.

Journals
Published: 01 January 1999 in Journal of Chemical Research
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2-Aryl-1,2,3,4-tetrahydro-4-quinolones are converted in high yields to the corresponding 2-aryl-4-methoxyquinolines using molecular iodine in refluxing methanol; the structures of the quinoline derivatives are determined using 1H and 13C NMR spectroscopic techniques.

ACS Style

Malose J. Mphahlele; Fidelia K. Mogamisi; Mutshutshu Tsanwani; Sebayitseng M. Hlatshwayo; Richard M. Mampa. Iodine–Methanol-promoted Oxidation of 2-Aryl-1,2,3,4-tetrahydro-4-quinolones to 2-Aryl-4-methoxyquinolines. Journal of Chemical Research 1999, 706 -707.

AMA Style

Malose J. Mphahlele, Fidelia K. Mogamisi, Mutshutshu Tsanwani, Sebayitseng M. Hlatshwayo, Richard M. Mampa. Iodine–Methanol-promoted Oxidation of 2-Aryl-1,2,3,4-tetrahydro-4-quinolones to 2-Aryl-4-methoxyquinolines. Journal of Chemical Research. 1999; (12):706-707.

Chicago/Turabian Style

Malose J. Mphahlele; Fidelia K. Mogamisi; Mutshutshu Tsanwani; Sebayitseng M. Hlatshwayo; Richard M. Mampa. 1999. "Iodine–Methanol-promoted Oxidation of 2-Aryl-1,2,3,4-tetrahydro-4-quinolones to 2-Aryl-4-methoxyquinolines." Journal of Chemical Research , no. 12: 706-707.