Godfred Darko | Kwame Nkrumah University of Science and Technology (original) (raw)

Papers by Godfred Darko

Cogent Chemistry, 2018

Sulfadoxine and pyrimethamine are often formulated together and used in the treatment of malaria ... more Sulfadoxine and pyrimethamine are often formulated together and used in the treatment of malaria especially in pregnant women serving as a prophylaxis. A new simple, precise and accurate reverse-phase high-performance liquid chromatography (RP-HPLC) method has been developed for simultaneous identification and quantification of sulfadoxine and pyrimethamine in tablet dosage form. The analysis was carried out on Waters uBondapak C 18 Column (39 × 300 mm, 3.6 µm) with acetonitrile: phosphate buffer (75:25 v/v) as the mobile phase at pH of 2.5, and a flow rate of 1.0 mL/min and a detection wavelength of 230 nm. Sulfadoxine and pyrimethamine eluted at mean times of 2.86 and 3.60 min, respectively. The method was linear with r 2 values of 0.9976 and 0.9841 for sulfadoxine and pyrimethamine, respectively (range 31.25-500 µg/mL). The Akwasi Acheampong ABOUT THE AUTHORS Akwasi Acheampong is a senior lecturer in Chemistry with research interests covering analytical chemistry, pharmaceutical chemistry, organic chemistry and natural product chemistry. He is excited about developing cheap and robust HPLC methods for simultaneous estimation of active ingredients of multi-component drug formulations. He is also involved in the development of HPLC-MS methodologies for triacylglycerols profiling of vegetable oils, search for potent phytochemicals that may serve as lead compounds for anti-microbial, anti-malarial, anti-oxidant, or anthelminthic drugs. He is also into heavy metal pollution, water quality analysis and radioactivity exposure research. Albert Gyebi is a Master of Philosophy candidate. Godfred Darko is a senior lecturer in Chemistry with research interests covering environmental chemistry, analytical chemistry, nano-chemistry, and natural products. Joseph Apau is a senior lecturer in Chemistry with research interest covering analytical chemistry and environmental chemistry. Wilfred Owusu Gyasi is a Master of Philosophy candidate. Sylvester Addai Arhin is a lecturer in pharmaceutical science with research interests in analytical chemistry and pharmaceutical chemistry.

Chemosphere, Mar 1, 2008

Determination of six organochlorine pesticides, lindane, aldrin, dieldrin, endosulfan, dichlorodi... more Determination of six organochlorine pesticides, lindane, aldrin, dieldrin, endosulfan, dichlorodiphenyltrichloroethane (DDT), and dichlorodiphenyldichloroethylene (DDE), residues were carried out on three dairy products sampled from six communities in the Kumasi metropolis in Ghana. Cheese samples were collected from three communities, (Tafo, Asawasi, and Aboabo), yoghurt samples from K-Poly and Ayeduasi while yoghurt and milk samples were collected from KNUST. Concentrations of DDT and DDE were, respectively, 42.17+/-6.00 microg kg(-1) and 31.50+/-3.44 microg kg(-1) in cheese sampled from Asawasi. Cheese samples from Tafo had an average DDT concentration of 298.57+/-28.02 microg kg(-1) while DDE concentration was 140.15+/-56.77 microg kg(-1). The highest average concentration of DDT in all the samples was 149.07 microg kg(-1) detected in cheese samples from Aboabo. Levels of DDT and its metabolite, DDE, in cheese from all the three sampling sites (Aboabo, Asawasi and Tafo) were well below the levels recommended by World Health Organisation (WHO). Mean concentration of DDT in fresh milk samples from KNUST was 12.53+/-1.61 microg kg(-1). As bioaccumulation of these residues is likely to pose problems in higher organisms, like human beings, there is the need for effective monitoring of these residues in the environment. This work, thus, seeks to provide information on levels of pesticide residues in dairy products that will assist in a scientific assessment of the impact of pesticides on public health, agriculture and the environment in Ghana.

International journal of toxicology and risk assessment, Dec 31, 2018

The objective of this study was to determine health risks associated with consumption of cabbage ... more The objective of this study was to determine health risks associated with consumption of cabbage and lettuce sampled in an urban industrialized study area. Samples were initially digested in Teflon vessels using HNO 3 and H 2 O 2 , homogenized in Na 2 SO 4 , agitated in a mixture of hexane/acetone, cleaned-up and analyzed in ICP-MS in order to quantify toxic heavy metals. The PAH content was also quantified in GC-MS against reference PAH congeners. Food frequency questionnaire designed based on the US EPA format, was used to collect elements of chronic daily intake and information on consumption characteristics of the selected samples. The data was processed in Palisade@Risk-based Microsoft Excel, where distributions were fitted for the elements of chronic daily intake. Exposure quantifications of hazards based on the US EPA guidelines, presented hazard quotients and risks, relative to the respective reference doses and cancer slopes factors (CSF). Incremental lifetime cancer risks (ILTCR) were determined as the product of the CSF of the carcinogens and their chronic exposures. The modal and median mercury exposures were low but the exposures of total PAHs (expressed as benzo[a]pyrene-BaP) were extremely high. The hazard quotients revealed that cadmium and mercury had negligible risks (HQ ≤ 1). Though the median and modal ILTCR showed lead to have low health risk concerns (≤ 10-6), the uncertainty ranging from 0 to 3 out-10-thousand consumers revealed insidous risk unacceptability. Similarly, even though the modal and median values of ILTCR of arsenic appeared acceptable (≤ 10-6), the risk uncertainty ranging from 0 to 6 out-1-thousand consumers, still raise health concerns. The median and modal ILTCR values of BaP suggested both a cautiously acceptable risk (≥ 10-6 ≤ 10-4) and a barely negligible risk (≤ 10-6) levels respectively. Thus, every effort must be made to mitigate the seriously high risks lurking in the study area.

SpringerPlus, Jun 24, 2016

Residues of organochlorine pesticides were determined in soils and drinking water sources in coco... more Residues of organochlorine pesticides were determined in soils and drinking water sources in cocoa growing areas in Ghana. Soil samples analysed showed the presence of four organochlorine pesticide residues namely lindane (0.005-0.05 mg/kg), beta-HCH (<0.01-0.05 mg/kg), dieldrin (0.005-0.02 mg/kg), and p,p′-DDT (0.005-0.04 mg/kg), with dieldrin occurring most frequently. Similarly, organochlorine pesticide residues detected in the water samples were lindane (0.01-0.03 µg/l), alpha-endosulfan (0.01-0.03 µg/l), endosulfan-sulphate (0.01-0.04 µg/l), dieldrin (0.01-0.03 µg/l) and p,p′-DDT (0.01-0.04 µg/l), with heptachlor occurring most frequently. The concentrations of the detected organochlorine residues in the soil samples were below their respective US maximum residues limits (MRLs) for agricultural soils, except for lindane recorded at Kwakuanya (S4) and beta-HCH recorded at Krakrom (S3) and Kwakuanya (S4). Similarly, the organochlorine pesticide residues recorded in the water samples were below and within their respective WHO MRLs for drinking water except for alpha-endosulfan at Diabaa (S2) and Kwakuanya (S4) at distance 0-15 m and Kwakuanya (S4) at distance 16-30 m, endosulfan-sulfate at Nkrankwanta (S1) and Diabaa (S2) at distance 0-15 m and heptachlor at Krakrom (S3) at distance 16-30 m which were above their WHO MRLs. The presence of the banned organochlorine pesticide residues in soil and water samples from the study area indicates that these chemicals are still being used, illegally, on some cocoa farms. Routine monitoring of pesticide residues in the study area is necessary for the prevention, control and reduction of environmental pollution to minimize health risks.

International Journal of Urban Sustainable Development

The increase in human activities in urban areas resulting from the urbanisation process continues... more The increase in human activities in urban areas resulting from the urbanisation process continues to put immense pressure on urban ecological resources including water bodies. This study seeks to assess the relationship between the various categories of human activities within the 100 m buffer of the major water bodies in the Kumasi Metropolis and the chemical and biological composition of the pollutants that are emitted into the water bodies. The findings of this study showed that the Kumasi Metropolis is confronted with weak enforcement of regulations that protect water bodies. For example, along the Subin River, human activities such as commercial activities and the development of squatter settlements did not conform to the standard setback average distance of 100 feet in the Zoning Regulation and Planning Standards. There is a need for city authorities to strategically respond to the various human activities that threaten the sustainability of water resources in cities.

Journal of Chemistry

The study aimed to ascertain the levels of trace elements present in the face powders marketed in... more The study aimed to ascertain the levels of trace elements present in the face powders marketed in Ghana. Fifteen different brands of facial makeup powders were purchased from a local market in Ghana. The samples were analyzed using an X-ray fluorescence (XRF) analyzer to determine the concentrations of 16 elements (Pb, As, Hg, Zn, Fe, Mn, Cr, Ti, Cu, Ni, Co, Sb, Cd, Ag, Sn, and Au). The contents of the trace elements were ordered in the following descending order according to the maximum concentrations: Fe > Zn > Ti > Mn > Cr > Hg > As > Pb > Cu, Ni, Co, Sb, Cd, Ag, Sn, and Au. Pearson correlation statistics showed strong positive relationships between Pb and Zn (r = 0.71), Pb and Cr (r = 0.57), Hg and Zn (r = 0.63), Hg and Fe (r = 0.73), Hg and Cr (r = 0.61), Zn and Fe (r = 0.69), Zn and Cr (r = 0.88), Fe and Cr (r = 0.67), and Fe and Ti (r = 0.62). Except for Pb and Cr, all the other elements had their margin of safety (MOS) values less than 100. The hazard...

Chemistry Africa

Cocoa consumption, driven by the health benefits of mineral nutrients, is surging globally though... more Cocoa consumption, driven by the health benefits of mineral nutrients, is surging globally though, emerging evidence indicates anthropogenic contaminants. Thus, this study set out to conduct a health benefit-risk assessment of the trace elements in cocoa beans and derived products. Cocoa beans sampled from aggregation sites in four major cocoa-producing regions in the country were analyzed for trace elements. The clustering of these trace elements were explored using principal component analysis. The US EPA protocols were used to quantify the potential risks of adverse health outcomes through the oral route. Specifically the hazard quotient, hazard index, cancer risk and margin of exposure were determined. The adequacy of essential minerals intakes was estimated according to the British Nutrition Foundation guidelines. The results showed that the concentrations of mercury (13.99 mg/kg), lead (5.15 mg/kg) and molybdenum (11.18 mg/kg) exceeded some international regulatory thresholds. The principal component analysis showed that toxic elements in cocoa beans could be traced to soil uptake and atmospheric deposition pollution mechanisms from mining activities. Further, the results show for lead, the modal margin of exposure (0.06–0.78) and cancer risk (2 × 10–6–1 × 10–5) breached their respective risk thresholds (MoE < 1 and deminimis > 1 × 10–6) suggesting potential adverse health outcomes among chocolate consumers. The range (3.81–493.13) of hazard index for the toxic elements (mercury, molybdenum, selenium, strontium, vanadium, zirconium, and uranium) exceeded the threshold (HI > 1), signifying cumulative risk of adverse health outcomes. The results further showed that cocoa beans had a rich range (0.97–2563.93 mg/kg) of beneficial elements: potassium > sulfur > calcium > iron > titanium > zinc > molybdenum > chromium > vanadium > selenium > scandium. The range of nutritional adequacy assessments (0.01–57.70%) followed the order: iron > zinc > potassium > selenium > calcium among chocolate consumers. Finally, since the safety regulatory standpoint demands zero-tolerance of carcinogenic hazards, but there were significant risks associated with lead in cocoa beans, it outweighs the beneficial elements in cocoa beans.

Cogent Chemistry, Mar 22, 2016

The aquatic environment is a vital resource for bioprospecting pharmacologically important natura... more The aquatic environment is a vital resource for bioprospecting pharmacologically important natural products. Molluscs are known to harbour compounds with antimicrobial, antitumor and antioxidant activities. This study evaluated the antimicrobial and antioxidant properties of ethyl acetate and methanol tissue extracts of two molluscs, Littorina littorea (L. littorea) and Galatea paradoxa (G. paradoxa). Agar diffusion and broth dilution assays were used to test for antimicrobial activity against nine microbes. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) method was used to determine antioxidant activity of the extracts. Extracts of both molluscs showed significant activity against all the bacteria strains tested but were inactive towards the fungus. The best antibacterial activity was recorded by methanol extract of L. littorea towards Pseudomonas aeruginosa. In comparison to ethyl acetate extracts, methanol extracts were more efficient in scavenging the DPPH radical. Methanol extracts of L. littorea had an IC 50 of 0.37 mg/mL which was closer to that of the standard ascorbic acid drug (0.0048 mg/mL) than any of the other extracts. The findings of this work indicate that the tissue extracts of L. littorea and G. paradoxa are promising sources of antimicrobial and antioxidant agents that can be utilized for pharmaceutical and nutraceutical purposes.

Chemistry Africa, Jun 3, 2023

Journal of Chemistry, Mar 28, 2023

Vitex doniana (West African plum or black plum) is a plant with varying phytoconstituents and bio... more Vitex doniana (West African plum or black plum) is a plant with varying phytoconstituents and biological activities across diferent countries. In this study, essential oils extracted from the leaves and fruits of Vitex doniana cultivated in Ghana were investigated for their antimicrobial and antioxidant activities. Te antioxidant actions of the essential oils were determined using hydrogen peroxide (H 2 O 2), phosphomolybdenum, thiobarbituric acid reactive substances (TBARS), and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assays. For both essential oils, the total antioxidant capacities ranged from 44 to 68 µg/g AAE, the IC 50 values for H 2 O 2 scavenging activity were between 87 and 242 µg/mL, whereas that for DPPH assay were between 322 and 599 µg/mL. Te IC 50 for the TBARS assay for both essential oils also ranged from 247 to 414 µg/mL. Te antimicrobial activities of the essential oils were investigated using the broth dilution assay. Te minimum inhibition concentration for the essential oils ranged from 12.5 to 50 mg/mL. Bioflm inhibitory activity was also evaluated for both essential oils, and the fruit essential oil showed a half-maximal inhibition of bioflm formation (BIC 50) at 44.40 ± 0.6 mg/mL, whereas the BIC 50 value of the leaf essential oil was 109.1 ± 0.9 mg/mL. Te fruit essential oil was superior to the leaf essential oil in inhibiting the secretion of pyoverdine. Molecular docking analyses suggested that methyl cinnamate, ethyl cinnamate, p-menth-4-en-3-one, trans-α-ionone, benzyl benzoate, isobutyl cinnamate, and folic acid likely interacted with LasR and algC proteins, and hence, contributed to the inhibition of bioflm formation and pyoverdine secretion. Essential oils from Vitex doniana could, therefore, be exploited as a natural source of radical scavenging and antimicrobial agents and could be useful in the pharmaceutical, food, and cosmetic industries.

Environmental Geochemistry and Health, Feb 28, 2023

Agbogbloshie in Accra, Ghana, was a center for informal e-waste recycling until it was closed rec... more Agbogbloshie in Accra, Ghana, was a center for informal e-waste recycling until it was closed recently. This study investigated the potential health risks of toxic metals (including As, Cd, Cu, Ni, Pb, Sb, and Zn) found in the surface soils based on their concentrations and in vitro bioaccessibility. Mean concentrations at the burning sites

Evidence-based Complementary and Alternative Medicine, Aug 28, 2022

is work focused on characterizing the chemical constituents and evaluating the antioxidant and an... more is work focused on characterizing the chemical constituents and evaluating the antioxidant and antimicrobial activities of the essential oils obtained from the fruit and leaves of Spondias mombin-a owering plant of the Anacardiaceae family. Essential oils were extracted through steam distillation and characterized by gas chromatography-mass spectrometry. For the fruit essential oil, 35 compounds were obtained, and 25 compounds were identi ed in the leaf essential oil. e dominant compounds present in the fruit essential oil were (E)-ethyl cinnamate (14.06%) and benzyl benzoate (12.27%). Methyl salicylate (13.05%) and heptacosane (12.69%) were the abundant compounds in the leaf essential oil. e antioxidant activity of the essential oils was evaluated via phosphomolybdenum, hydrogen peroxide scavenging, 2, 2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging, and thiobarbituric acid reactive substances (TBARS) assays. e total antioxidant capacity of fruit and leaf essential oils was 48.5 ± 0.7 μg/gAAE and 48.5 ± 0.7 μg/g AAE, respectively. e half maximal scavenging concentrations of the essential oils in the hydrogen peroxide; DPPH and TBARS assays ranged from 252.2 μg/mL to 2288 μg/mL. e antimicrobial activity of the essential oils was tested using broth dilution and disc di usion assays against eight microorganisms. e essential oils exhibited broadspectrum antimicrobial activity against the microorganisms with minimum inhibitory concentrations of 9.75-50 mg/mL. Also, the zones of inhibition of the oils ranged from 12 mm to 25 mm. e bio lm inhibitory activities of the oils were dose-dependent with BIC 50 values of 42.49 ± 0.1 mg/mL and 97.34 ± 0.6 mg/mL for fruit and leaf essential oils, respectively. Molecular docking studies revealed that the antibio lm action of the fruit and leaf essential oils could be due to inhibition of the quorum sensing protein, LasR. e results suggest a possible application of the oils as antioxidant and antimicrobial agents.

Scientific African, Nov 1, 2020

This study investigated the heavy metal content and the extent of pollution in soils from abandon... more This study investigated the heavy metal content and the extent of pollution in soils from abandoned dump sites in Kumasi, Ghana. Concentrations of heavy metals in the 70 soil samples were determined using a Niton XL3t GOLD field portable X-ray fluorescence spectrometer and confirmed on an Agilent 7800 inductively coupled plasma-mass spectrometer. Mercury was determined with a Lumex mercury analyzer. Mean concentrations of metals in soils were in the order: Zn (166 mg/kg). Cr (67 mg/kg) > Cu (32 mg/kg), Ni (22 mg/kg) > Pb (11 mg/kg) Cd (8.9 mg/kg) > As (4.2 mg/kg) > Hg (0.04 mg/kg) for Kronum; and Zn (558 mg/kg), Cu (347 mg/kg), Pb (288 mg/kg) > Cr (77 mg/kg) > Ni (35 mg/kg) > As (11 mg/kg) > Cd (3.0 mg/kg) > Hg (0.19 mg/kg) for Amakom. Pollution indices (geo-accumulation, contamination factor, pollution load and potential ecological risk) indicated very high contamination for arsenic, cadmium and lead at Kronum and arsenic, cadmium, copper, lead and zinc at Amakom. Mercury recorded the least level of pollution for both dump sites. Regular monitoring of these abandoned dump sites is required. Remediation programs in these sites should also be instituted.

SpringerPlus, Sep 17, 2015

This study evaluated the antimicrobial and antioxidant activities of crude peptide extracted from... more This study evaluated the antimicrobial and antioxidant activities of crude peptide extracted from Galatea paradoxa (G. paradoxa) and Patella rustica (P. rustica). The extracts were tested against eight strains of bacteria (Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Salmonella typhi, Enterococcus feacalis, Klebseilla pneumoniae, Streptococcus pneumoniae, Pseudomonas aeruginosa) and one strain of fungi (Candida albicans) using agar well diffusion and broth dilution assays. The extracts from G. paradoxa demonstrated a high degree of activity against the bacteria strains but were inactive towards the fungus. P. rustica, however, showed a markedly higher antifungal activity but little antibacterial effect. The minimum inhibitory concentrations (MIC) of the extracts determined by the broth tube dilution assay were 17 mg/mL of G. paradoxa against the entire spectrum of microorganisms tested except for C. albicans which was 20 mg/mL. The MIC of the extracts of P. rustica was 13 mg/mL against all the strains of microorganisms tested except for E. feacalis (17 mg/mL), K. pneumoniae (17 mg/mL) and C. albicans (13 mg/mL). Antioxidant activity using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay showed scavenging ability on the DPPH radical was 56.77 % at 0.39 mg/ mL for G. paradoxa and 79.77 % at 0.39 mg/mL for P. rustica. The study indicates that the crude peptide extracts from the two molluscs have promising antimicrobial and antioxidant activities that can be harnessed as leads for potential bioactive compounds.

Chemistry Africa, Feb 1, 2021

The use of veterinary drugs on farm animals has the potential of generating drug residues in edib... more The use of veterinary drugs on farm animals has the potential of generating drug residues in edible animal products that may affect public health. Veterinary drug residues in 144 samples including beef, chicken, and egg were measured using ultra-high-performance liquid chromatography in tandem with a triple quadrupole mass spectrometer. Sixty-three percent of the samples had quantifiable multiple detections of veterinary drug residues. The mean amounts of the tetracyclines (tetracycline, oxytetracycline, and chlortetracycline) residues in the samples were 81.35 μg/kg, 76.94 μg/kg, and 234.43 μg/kg, respectively. The mean β-lactam (amoxicillin, cefazolin, and penicillin G) residues were 35.76 μg/kg, 47.02 μg/kg, and 41.02 μg/kg respectively. The mean residues of the sulphonamides (sulfamethoxazole, sulfadoxine, and sulfathiazole) were 103.98 μg/kg, 46.05 μg/kg, and 68.63 μg/kg respectively. The mean fluoroquinolone (enrofloxacin) concentration was 30.19 μg/kg. The mean residue concentrations of salbutamol, erythromycin, prednisone, ketoprofen, and haloperidol were 6.32, 77.18, 23.66, 14.94, and 9.62 μg/kg respectively. The exposure estimations conducted on residues whose concentrations exceeded their maximum residue limits shows that consumers are at risk of acute exposure to tetracycline in egg, and cefazolin, penicillin G, sulphamethoxazole, salbutamol, prednisone, and haloperidol which may be injurious to the health and wellbeing.

Cogent food & agriculture, 2017

Spices are generally consumed because of the taste and flavor they add to food. Some are also con... more Spices are generally consumed because of the taste and flavor they add to food. Some are also consumed because of their medicinal properties. We herein report on the nutrient and antinutrient compositions of five Ghanaian spices namely Xylopia aethiopica, Piper guineense, Monodora myristica, Aframomum melegueta and Parkia biglobosa. Nutritional composition was assessed by proximate analysis, minerals by atomic absorption spectrophotometry while titrimetric methods were utilized in vitamin C and antinutrients analysis. P. biglobosa was rich in proteins (38.60%) and had highest moisture content (32.79%). The highest levels of ash, fiber, fat and carbohydrates were observed P. guineense (11.90%), A. melegueta (31.12%), M. myristica (31.01%) and X. aethiopica (50.1%) respectively. Calorific values for all spices were between 243 and 402 kcal. Calcium, magnesium, potassium and iron were the most abundant minerals with levels ranging from 2.67 to 5,381.88 mg/kg. Zinc, copper and manganese were present in trace amounts. Vitamin C levels ranged from 3.3 to 18.4 mg/100 g. Phytates were present at generally higher levels than oxalates. P. biglobosa and X. aethiopica contained the highest