BC-Department of Chemistry

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    Bioassay-Guided Isolation of Active Phytochemicals Against Tuta absoluta (Meyrick) from Turraea floribunda and Caesalpinia welwitschiana
    (Springer, 2020) Ehawa, Flaure Rosette Essoung; Mohamed, Samira Abuelgasim; Hassanali, Ahmed; Chhabra, Sumesh Chander
    Tuta absoluta Meyrick is now one of the most harmful insect pests of Solanaceae in various parts of the world. Synthetic pesticides are the most used, current control method, but are associated with several problems including the development of resistance and negative ecological effects. These led to the search for more eco-friendly methods of controlling the pest, such as a search for phytochemicals that show subtle anti-pest properties. In the present study, the effects of the constituents of methanolic extracts associated with Turraea floribunda and T. nilotica leaves (Meliaceae) and those of Caesalpinia welwitschiana and C. bonduc roots (Fabaceae-Caesalpiniaceae) were evaluated on second instar larvae of T. absoluta. The extract from T. floribunda leaves was the most active (LD50 = 587.0 ng/μl), followed by C. welwitschiana (LD50 = 779.1 ng/μl). Bioassay-guided isolation of active compounds from these active extracts, using column chromatographic and preparative HPLC, led to the identification of twenty-two compounds. Their structures were established using spectroscopic techniques, including MS, 1 and 2D-NMR, and also by comparison with reported data. The methanolic leaf extract of T. floribunda yielded ten compounds (β-sistosterol, stigmasterol, ursolic acid, betulinic acid, a mixture of β-sistosterol-3-O-β-D-glucopyranoside and stigmastreol-3-O-β-D-gluco pyranoside, fridelin, lupeol, 11-epi-21-hydroxytoonacilide and 11β, 12α-diacetoxycedrelone). The methanolic roots extract of C. welwitschiana afforded twelve constituents, including apigenin, luteolin, afzelin, quercitrin, epiafzelechin-3-O-gallate, Kaempferol 3-O-α-L-rhamnopyranosyl-(1→2)-β-D-glucopyranoside, Kaempferol, dipteryxic acid, neocaesalpin L, rutin, methyl gallate, and galic acid. Some of the isolates were tested on T. absoluta eggs. They showed varying levels of ovicidal effect, with quercitrin being the most active constituent at 81%. The results of the study showed potential of the phytochemicals of these plants in the management of T. absoluta.
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    A Comparative Study of Modified and Unmodified Algae (Pediastrum boryanum) for Removal of Lead, Cadmium and Copper in Contaminated Water
    (INTECH, 2017) Joseph, John Okapes; Mwangi, Isaac W.; Swaleh, Sauda; Wanjau, Ruth N.; Ram, Manohar; Ngila, Jane Catherine
    The presence of heavy metals in water is of concern due to the risk toxicity. Thus there is need for their removal for the safety of consumers. Methods applied for removal of heavy metals include adsorption, membrane filtration and co-precipitation. However, studies have revealed adsorption is highly effective technique. Most adsorbents are expensive or require extensive processing before use and hence need to explore for possible sources of inexpensive adsorbents. This research work investigated the use an algal biomass (pediastrum boryanum) as an adsorbent for removal of Lead, Cadmium and Copper in waste water in its raw and modified forms. The samples were characterized with FTIR and was confirmed a successful modification with tetramethylethlynediamine (TMEDA). Sorption parameters were optimized and the material was finally applied on real water samples. It was found that the sorption was best at lower pH values (4.2-6.8). Sorption kinetics was very high as more that 90% of the metals were removed from the solution within 30 minutes. The adsorption of copper fitted into the Langmuir adsorption isotherm indicating a monolayer binding mechanism. Cadmium and lead fiĴed best the Freundlich adsorption mechanism. Sorption of lead and cadmium was of pseudo-second order kinetics, confirming a multisite interaction whereas copper was pseudoȬfirst order indicating a single site adsorption. The adsorption capacity did not improve upon modification but the stability of the material was improved and secondary pollution of leaching colour was alleviated. This implies that the modified material is suitable for application on the removal of metals from water.
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    Innovative but Not Feasible: Green Water Saving Schemes at the Crossroad in Semi-Arid Lands
    (Organisation for Social Science Research in Eastern and Southern Africa (OSSREA), 2014) Obando, Joy Apiyo; Shisanya, C.A.; Cush, Ngonzo Luwesi
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    Essential Elements in Watermelons Grown in Kenya
    (LAP Lambert Academic Publishing, 2013-01-01) Wanjau, R. N.; Wanjau, R.; Murungi, J.
    To be healthy and active, one requires food in adequate quantity, quality and variety to meet energy needs and nutrients. Watermelon has high content of water of about 93%. It is a rich source of essential minerals such as calcium, magnesium, phosphorous, potassium, sodium and smaller amounts of copper, iron, zinc and selenium. Watermelons have substantial amounts of boron, iodine, chromium, silicon and molybdenum. The levels of nutrients in different parts of the watermelons may be different. Different people consume different parts and varieties of watermelon and thus depending on the part/variety of watermelon consumed these people may get different nutrients and levels of the same. However, levels of nutrients in various parts/varieties of watermelon have not been documented.This study therefore determined the levels of Si, Ca, B, Mo, Cr and V in the four parts of Charleston grey, Crimson sweet and Sugar baby watermelons.
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    Analysis of Essential Trace Elements in Selected Medicinal Plants Used In Kenya
    (Kenyatta University) Njenga, Isaac Kariuki
    Kenya is endowed with nature where hundreds of medicinal plants are available. During photosynthesis and respiration process in plants, animals and other organisms, ions of metal elements play a major role with a few of the elements being essential to the body as nutrients. Trace elements Zn, Cr, V and Se with known immunological response and healing properties were analysed from selected medicinal plants available in Kenya. These plants were; Prunus africana, Urtica massaica, Maytenus obscura, Maytenus putterlickiodes, Azadiracta indica (Neem), Mondia whytei, Zanthoxylum usambarense, Maerua edulis, Trigonella foenum-graecum (fenugreek) and Glycyrrhiza glabra. The concentrations of elements were determined using Energy Dispersive X-ray Fluorescence Spectrometer (EDXRF). The levels of zinc varied from 25.94±1.89 to 70.58±4.70 mg/kg (mean 45.94± 12.42 mg/kg). Vanadium from 1.69±0.18 to 9.99±0.86 mg/kg with an average level of 5.89± 2.09 mg/kg. Chromium from 1.44±0.30 to 6.94±0.59 mg/kg with a mean of 3.49±1.32 mg/kg. For selenium the levels varied from 53.21±5.45 to 124.01±4.41 μg/kg with a mean of 90 ±19.17 μg/kg. The levels of the trace elements were compared with recommended dietary intake (RDI) and were found to provide these essential elements as part of therapeutic utility. The levels in different plant parts were found not to be statistically significantly different (P>0.05) except for vanadium levels in urtica massaica (P=0.05). The results of this study will be used to sensitize the public on the presence of essential trace elements in the studied medicinal plants and to contribute to the advancement of knowledge.