Browsing by Author "Osei-Fosu, P."
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Item The cocoa mirid (Hemiptera: Miridae) problem: Evidence to support new recommendations on the timing of insecticide application on cocoa in Ghana(International Journal of Tropical Insect Science, 2014) Adu-Acheampong, R.; Jiggins, J.; Van Huis, A.; Cudjoe, A.R.; Johnson, V.; Sakyi-Dawson, O.; Ofori-Frimpong, K.; Osei-Fosu, P.; Tei-Quartey, E.; Jonfia-Essien, W.; Owusu-Manu, M.; Nana Karikari Addo, M.S.; Afari-Mintah, C.; Amuzu, M.; Nyarko Eku-X, N.; Quarshie, E.T.N.The government's cocoa spraying gangs in Ghana treat about two million hectares of the crop against black pod disease and mirids, the key insect pests of cocoa in West Africa, each August through to December, based on recommendations issued in the 1950s. A few cocoa farmers use additional pesticides. We studied the temporal distribution of two important mirid species, Distantiella theobroma (Dist.) and Sahlbergella singularis Hagl., in 1991, 1999, 2003 and 2012 to determine the appropriate timing for the application of control measures in current farming systems. There was a significant correlation between mirid abundance and pod availability on trees, as well as the number of basal shoots and the cocoa variety grown. Mirid populations peaked between January and April and from September to October. Surveys (interviews and focus group discussions involving over 300 farmers in 33 cocoa-growing districts) on pesticide use, sources of recommendations, and perceived successes and failures of current cocoa pest treatments suggested that the 1950 recommendations on the timing of insecticide application need revising. Copyright © ICIPE 2014.Item The crystal structures of O,O-Dimethylalpinumisoflavone and 5-O-Methyl-4′-O-(3-methyl-but-2-en-1-yl)alpinumisoflavone(Crystal Research and Technology, 2001-01) Kingsford-Adaboh, R.; Osei-Fosu, P.; Asomaning, W.A.; Weber, M.; Luger, P.The petrol extract of the rootbark of Milletia Thonningii obtained by column chromatography afforded sixteen different crystalline samples to be isolated. The crystal structures of two of these compounds, O,O-Dimethylalpinumisoflavone (I) and 5-O-Methyl-4′-O-(3-methyl-but-2-en-1-yl)alpinumisoflavone (II) are being reported here. (II) has two independent molecules in the asymmetric unit and differs from (I) in a longer side chain attached to C(15) of the phenyl ring. The structural features of the three molecules in the title compounds are reported and compared. The derivatives, being subject of this article are the first reported crystal structures where the isoflavone fragment is fused to a further six membered ring that results in a tricyclic ring system. The benzopyrone fragments are planar. The dihedral angles between the benzopyrone fragment and the phenyl ring being 55.38(6)° for (I) and 44.75(15)°/44.64(15)° for the respective independent molecules of (II) are within the range of values observed for similar structures.Item A preliminary assessment of consumer's exposure to organochlorine pesticides in fruits and vegetables and the potential health risk in Accra Metropolis, Ghana(Food Chemistry, 2011-10) Bempah, C.K.; Donkor, A.; Yeboah, P.O.; Dubey, B.; Osei-Fosu, P.Accra Metropolis is the major recipient of agricultural produce in Ghana, with almost the entire population depending on rural agricultural activities for subsistence. To increase agricultural produce, various forms of pesticides are normally used in fruits and vegetable farming. The consequence is that several cases of pesticide poisoning have been observed. In this preliminary study, a field survey was carried out to assess the knowledge, attitudes, and peoples' perception concerning the use of pesticides by farmers in fruit production. The residual concentrations of selected pesticides in pawpaw, imported apples and tomato samples and the potential health risks associated with the exposure to these pesticides were also assessed. The field survey data indicated that more than 70% of the participants reported one or more poisoning upon fruits consumption resulting in pesticide-related illnesses. Pesticide residues in the various environmental samples were determined by gas chromatography with electron capture detector (GC-ECD). The results showed that, the levels of pesticide residues varied from <0.01 μg/g to as high as 0.11 μg/g depending on the pesticide monitored. The analysis of health risk estimates revealed heptachlor, heptachlor epoxide, endrin aldehyde, and endrin ketone levels exceeded the reference dose, suggesting a great potential for systemic toxicity in children considered the most vulnerable population subgroup. Lastly, the public is in the know of pesticide residues in fruits and calls for the curtailing of pesticide use on fruits and vegetable production via educational programmes for farmers on control and safer use of pesticides. © 2011 Elsevier Ltd. All rights reserved.Item Respiratory and non-respiratory symptoms associated with pesticide management practices among farmers in Ghana's most important vegetable hub.(Environmental Monitoring and Assessment, 2019-11-04) Quansah, R.; Bend, J.R.; Armah, F.A.; Bonney, F.; Aseidu, J.; Yawson, D.O.; Adu, M.O.; Luginaah, I.; Essumang, D.K.; Abdul-Rahaman, A.; Cobbina, S.; Iddi, S.; Tersigni, M.; Afful, S.; Osei-Fosu, P.; Nketiah-Amponsah, E.The data presented here are from the Offinso North District Farm Health Study (ONFAHS), a population-based cross-sectional study among vegetable farmers in Ghana. The paper addresses knowledge, pesticide handling practices, and protective measures related to pesticide use by self-reported symptoms for 310 adult farmers who completed a comprehensive questionnaire on pesticide management practices and health. In addition, an inventory was prepared using information supplied by pesticide sellers/dealers in this district. We report that cough and wheezing (but not breathlessness) are positively associated with stirring pesticide preparations with bare hands/drinking water while mixing/applying pesticides, and stirring pesticide preparations with bare hands/drinking water/smoking cigarettes while mixing/applying pesticides. There is a significant exposure-response association between the number of precautionary measures practiced while handling pesticides and cough and wheezing but not with breathlessness. We also found unsafe practices to be associated with sexual dysfunction, nervousness, and lack of concentration. The results also suggest a negative association between practice of any precautionary measure when mixing/applying pesticides and sexual dysfunction, nervousness, and lack of concentration. We found that in spite of the fact that farmers have adequate knowledge about the environment and health effects of pesticides, several unhygienic practices are in widespread use, indicating that knowledge is not necessarily always translated in action. Further action is necessary to promote the safe use of pesticides and to replace existing poor management practices among these and other farmers in Ghana.Item Structural Elucidation and Antiplasmodial Activities of Some Compounds Isolated from The Rhizome of Cochlospermum Tinctorium(University of Ghana, 2001-10) Osei-Fosu, P.; Sittie, A.; Akanmori, B.D.; Oppong, I.V.; Akuamoah, R.K.; Asomaning, W.A.; University of Ghana, College of Basic and Applied Sciences, School of Physical and Mathematical Sciences, Department of ChemistryCochlospernum tinctorium A. Rich was investigated for its chemical constituents and its antiplasmodial activities. The chemical constituents of petroleum ether, dichloromethane and ethyl acetate extracts of the rhizome of the plant were successively studied. The in vitro antiplasmodial activities for petroleum ether, dichloromethane, ethyl acetate, ethanol and water extracts as well as the isolated compounds were determined. Three compounds isolated from the dichloromethane extract have been identified by spectroscopic methods to be triacontanol, triacontanyl p-coumarate and triacontanyl ferulate. This is the first report of the isolation of the two esters and the long chain saturated alcohol from the plant. Another compound was obtained from the dichloromethane extract and coded D9. The petroleum ether extract of the rhizome yielded stigmasterol and two compounds which were coded PE6 and PE11. The ethyl acetate extract of the rhizome yielded two compounds which were coded E13 and E166 Using an in vitro technique, the inhibition of growth of Plasmodium falciparum (chloroquine sensitive, 3D7 and chloroquine resistance DD2, strains,) were investigated based on the principle of uptake of 3H-hypoxanthine by viable parasites on various extracts of Cochlospermum tinctorium and also on the isolated compounds with chloroquine as standard. The percentage inhibition for all the extracts and isolated compounds were found to be dose-dependant, with the aqueous and dichloromethane extracts being more active with IC50 values 32.27 (ig/ml and 24.34 |J.g/ml for the chloroqiune sensitive and 30.90 jig/ml and 23.45 |j.g/m! for the chloroquine resistant strains respectively.Item Validation of QuEChERS method for the determination of 36 pesticide residues in fruits and vegetables from Ghana, using gas chromatography with electron capture and pulsed flame photometric detectors(Journal of Environmental Science and Health - Part B Pesticides, Food Contaminants, and Agricultural Wastes, 2015-06) Donkor, A.; Osei-Fosu, P.; Nyarko, S.; Kingsford-Adaboh, R.; Dubey, B.; Asante, I.In this study, “Quick, Easy, Cheap, Effective, Rugged and Safe” ‘QuEChERS’ method was modified for the determination of 36 pesticides fortified at (0.01–1.0) mg kg−1 in three vegetables and a fruit (lettuce, carrot, tomatoes and pineapples respectively) from Ghana. The method involved extraction with acetonitrile, phase separation with primary secondary amine and magnesium sulfate; the final injection solution was reconstituted in ethyl acetate. Organochlorine and synthetic pyrethroids residues were detected with electron capture detector whereas organophosphorus, pulsed flame photometric detector was used. The recoveries at different concentration levels (0.01, 0.1 and 1.0 mg kg−1) were in the range of 83% and 93% with relative standard deviation ranging from 2% to 10% (n = 5) and the coefficient of determination (R2) was greater than 0.99 for all the 36 pesticides. The method was successfully tested on 120 real samples from Accra markets and this proved to be useful for monitoring purposes particularly in laboratories that have no gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry. © 2015, Copyright © Taylor & Francis Group, LLC.