A conformational study of proline derivatives

From the study of the structures and molecular conformations of a number of proline derivatives, some conclusions were drawn. The widening effect of angle C-C'-N' is caused by steric repulsion between a hydrogen atom at C of the preceding prolyl residue with any other at either C or C of the pyrrolidine ring cis to it. This effect is influenced by the distance between the said hydrogen atoms: the nearer this distance is, the greater is the steric repulsion and the wider is the angle of steric repulsion. The ratio of the angle of steric repulsion to the distance between C and the following C (or C) cis to it is approximately 40 and 41 for peptides with trans and cis configurations, respectively. The torsion angle ranges for 1, 3, 4, and in these derivatives are widened more than usual. The highest vibration, which more often takes place at either the C or C of the pyrrolidine ring, does so not necessarily at the one that is puckered. A -relationship is established, for the determination of -helixity or collageneity, also in small peptides and amino acids that contain proline. The -relationship is versatile and gives about +180o and 180o for the two categories, respectively. The distance between the carbonyl and hydroxyl (or otherwise) terminal end atoms is minimal (2.2 ) and constant, for all peptides. The ratios of the angles at the carbonyl carbons (O'-C'-N') or (O'-C'-O') to this distance is also constant: 56 and 57 for the cis and trans confirgurations, respectively; i.e. a proline O'-C'-N'- (or O'-C'-O')-test, hereinafter called the CT-test, has been established for the determination of cis and trans configurations. It is also established in these proline derivatives, that whereas puckering takes place at C for the CS form, it does so at C for the C2 form. (Received December 10, 2001; revised June 13, 2002) (Bulletin of The Chemical Society of Ethiopia: 2002 16 (2): 199-206

Use of weak ion association in the separation of inorganic anions by capillary electrophoresis with specific application to simultaneous-trace determination of bromate and iodate in drinking water

In this work weak ion association was used to effect selectivity and detection of inorganic anions with environmental or health significance by capillary electropheresis, CE. Tetrabutylammonium ion was used as a pairing anion to separate mixtures containing closely or co-migrating inorganic anions at pHs 3.8 and pH 7. Despite taking a longer analysis time, better resolution is achieved at pH 7 than 3.8. Trace level of bromate and iodate present in drinking water were determined after online pre-concentration by field enhanced sample injection (FESI) technique. Consequently an internal standard (SCN-) was employed, which entailed the use of tetrabutylammonium ion as a pairing cation to resolve the internal standard from a co-migrating broad peak. The LODs (S/N = 3) were 7.8 x 10-10 M (10 ppb) and 1.2 x 10-9 M (0.21 ppb) for bromate and iodate, respectively. The method was subsequently used to determine bromate and iodate levels in drinking water.  KEY WORDS: Weak ion association, Selectivity, Capillary electrophoresis, Tetrabutylammonium ion, Bromate, Iodate, Drinking water  Bull. Chem. Soc. Ethiop. 2008, 22(1), 1-9

Urban Dietary Heavy Metal Intake from Protein Foods and Vegetables in Dar Es Salaam

Contamination of food and food products by heavy metals has made dietary intake as one of the major routes of these harmful elements to human beings. The human dietary intake of heavy metals cadmium, copper, lead and zinc from protein-foods (beans, meat, fish, milk) and green vegetables consumed daily from restaurants and street food-vendor kiosks in Dar es Salaam were determined using the Total Diet Study (TDS) method. The cooked food was bought from the restaurants and street food-vendors at several city locations (i.e. Buguruni, Manzese, Mwenge, Temeke and Ubungo) over several months and analyzed. Heavy metal concentrations were determined by Atomic Absorption Spectrophotometry (AAS) after wet digestion of the edible portions of pooled samples of the foodstuff. The results showed significant variation in heavy metal concentration among the foodstuff and at the different locations. The results were compared to the FAO/WHO levels for Acceptable Daily Intake (ADI) and Provisional Tolerable Weekly Intake (PTWI) to estimate risk of toxicity and to the US Recommended Dietary Allowance (RDA) and/or Estimated Safe and Adequate Daily Dietary Intake (ESADDI) for a deficiency in intake. The average weekly dietary intake of cadmium and lead from protein-foods and vegetables ranged from 0.20 - 0.42 µg/kg-bw/week (i.e. 2.82 - 6.00% of PTWI) and 4.77 - 9.83 µg/kg-bw/week (i.e. 68.1 – 140.4% of PTWI) respectively. These dietary intakes were below the ADI values of 0.5 µg/kg-bw/day and 3.6 µg/kg-bw/day of the WHO for cadmium and lead respectively. The daily dietary intake of zinc and copper at all the locations were also below the ADI for these elements, the average being 21.5% for copper and 19.8% for zinc. The results show clearly that the daily urban dietary intake of copper and zinc, from protein foods and vegetables along main streets at the above locations, was acceptable.Keywords: Heavy metal, dietary intake, protein foods, vegetables, Dar es SalaamTanz. J. Sci. Vol 36 2010, 85-9

Cytotoxic activity of some Tanzanian medicinal plants

Thirty-three aqueous methanolic extracts obtained from thirty plant species, belonging to seventeen families were screened for cytotoxic activity against HeLa (Human cervical carcinoma) cells. The ability of the extracts (10 g/ml and 1 g/ml) to inhibit proliferation of HeLa cells was determined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) dye reduction assay. Extracts from roots of Agathisanthemum bojeri, Synaptolepis kirkii and Zanha africana and the leaf extract of Physalis peruviana at a concentration of 10 µg/ml inhibited cell proliferation by 58.3 %, 68.1 %, 75.7 % and 91.8 %, respectively. The remaining 29 extracts exhibited no pronounced cytotoxic activity at the tested concentrations. It is worth investigating the four extracts, which showed pronounced cytotoxic activity so as to isolate and identify the compounds responsible for cytotoxic activity. Keywords: cytotoxic plants, Tanzanian medicinal plants, Agathisanthemum bojeri, Synaptolepis kirkii, Zanha africana, Physalis peruviana The East and Central African Journal of Pharmaceutical Sciences Vol. 8(2) 2005: 35-3

Speciation of lead, chromium, cadmium, copper and zinc in sediments and plants along Msimbazi river in Dar es Salaam, Tanzania

The speciation of lead, chromium, cadmium, copper and zinc in sediments and plants (pumpkin) along Msimbazi River in Dar es Salaam were determined using Atomic Absorption Spectrophotometry.  Results in sediments indicated that the heavy metal contents (mg/kg) in the form of total trace metals ranged from 50.34 to 161.63 for Pb, 68.38 to 501.85 for Zn, 18.43 to 66.61 for Cu, 20.93 to 76.46 for Cr and BDL to 0.23 for Cd. The contents (mg/kg) in the form of metals bound to organic matter ranged from 18.24 to 46.58 for Pb, 27.64 to 228.62 for Zn, 3.55 to 16.76 for Cu, 1.37 to 4.10 for Cr whereas Cd was not detected. In plant samples results in  forms of total labile heavy metals ranged from 0.86 to 1.46 for Pb, 2.68 to 4.59 for Zn, BDL to 0.41 for Cu and from not detected to 0.21 mg/kg for Cr. In the form of total heavy metals, the ranges were from 19.62 to 36.68 for Pb, 33.56 to 68.80 for Zn, 3.33 to 13.06 for Cu while Cr and Cd were not detected. It was generally found that the levels of lead in plant samples along Msimbazi River were above the permissible levels recommended by WHO and TBS.Key words:    Atomic Absorption Spectrophotometry, Metal speciation, heavy metals, trace metals and pollutant

1-D Transport Behaviour of Emerging Contaminants in the Unidirectional Flowing Surface Waters of the Msimbazi River

The primary objectives of this investigation of environmental pollution were to assess spatio-temporal concentrations and predictions of transport behaviour of pollutants in aqueous media. In order to attain these goals for the Msimbazi river, the analytical and numerical solutions to the 1-D advection-dispersion equation (ADE) implemented the first-type inlet condition. The MATLAB software was used to solve the analytical equation resulting from the ADE equation. The solution to the ADE model enabled effective prediction of contaminants’spatial distribution within a distance of 200 m from a point source in the direction of flowing water. Among the first and third-types inlet conditions, the first-type had the best exponential concentration prediction with descending concentration gradients between –100 ng/L.m and –0.4 ng/L.m, while beyond it the concentration gradient was merely constant. These findings are the first of this type in our region to the best of our knowledge, and hence a milestone for understanding the transport behaviour of emerging contaminants, and enable estimation of probable pollution-free zones. This study gave results that can form a basis for analytical and public interventions. Keywords: Modelling emerging contaminants; Advection-Dispersion Equation; Contaminants transport; First-type inlet condition; Concentration gradien

Biological Activities of Essential Oils from Plants Growing in Tanzania

Essential oils from eleven plant species belonging to the Asteraceae, Lamiaceae, Lauraceae and Myrothamnaceae families growing in Tanzania were screened for mosquito larvicidal and anti-candida activities, and were subjected to the brine shrimp lethality test. In the larvicidal and brine shrimp tests, the organisms were exposed to varying oil concentrations for 24 h, after which mortality was assessed. The anticandida activity was determined using the bioautography agar overlay method. All oils showed larvicidal activity with two Ocimum suave oil samples being the most active with LC50 values of 169.8 and 151.3 ppm. The same Ocimum suave oils also exhibited the highest brine shrimp mortality (LC50 4.0 and 12.6 ppm). Most of the oils showed anti-candida activity, with oils from Ocimum species being the most active compared to the others. Thus, Ocimum suave oils merit further investigation towards the development of safe and biodegradable larvicides. Furthermore, oils from Ocimum basilicum and Ocimum kilimandscharicum could offer useful alternatives for combating candidiasis, a common opportunistic infection in HIV/AIDS patients.Keywords: Ocimum species, larvicides, brine shrimp, Candida albicansEast and Central African Journal of Pharmaceutical Sciences Vol. 13 (2010) 85-9

Chemical Composition and Antimicrobial Activity of Geniosporum rotundifolium Briq and Haumaniastrum villosum (Bene) AJ Paton (Lamiaceae) Essential Oils from Tanzania

Purpose: To determine the chemical composition and antimicrobial potential of essential oils from two aromatic plants of Tanzania, Geniosporum rotundifolium Briq. and Haumaniastrum villosum (Benè) A.J. Paton (Lamiaceae).Method: Essential oils from the aerial parts of the plants were extracted by hydro-distillation for 3 h using a Clevenger type of apparatus. The constituents were analyzed by gas chromatography – mass spectrometry (GC/MS).The minimum inhibitory concentrations of the essential oils were determined for eight bacterial strains and three pathogenic fungi using agar dilution method.Results: The constituents of G. rotundifolium oil were mainly oxygenated derivatives of mono- and sesquiterpenes; spathulenol (12.46 %), α-terpineol (4.65 %) and germacrene-D (3.71 %) were the most abundant. Those of H. villosum oil were predominantly sesquiterpenes (72.61 %) with caryophyllene oxide (19.01 %), humulene epoxide II (11.95 %), β-bourbonene (5.7 %), α-humulene (5.63 %) and β- caryophyllene (5.39 %) being more abundant. The oil of G. rotundifolium exhibited weak to moderate activity against the bacterial species but showed no activity against the test fungi. However, H. villosum oil showed very promising activity against all the test microorganisms (MIC 0.08 – 10.34 mg/mL).Conclusion: The major components of G. rotundifolium essential oil were oxygenated derivatives of mono- and sesquiterpenes whereas those of H. villosum were sesquiterpenes. All tested microorganisms were susceptible to H. villosum oil.Keywords: Geniosporum rotundifolium, Haumaniastrum villosum, Essential oils, Chemical composition, Antimicrobial activit

Biopiracy <i>versus </i>one-world medicine – from colonial relicts to global collaborative concepts

Background: Practices of biopiracy to use genetic resources and indigenous knowledge by Western companies without benefit-sharing of those, who generated the traditional knowledge, can be understood as form of neocolonialism.Hypothesis: : The One-World Medicine concept attempts to merge the best of traditional medicine from developing countries and conventional Western medicine for the sake of patients around the globe.Study design: Based on literature searches in several databases, a concept paper has been written. Legislative initiatives of the United Nations culminated in the Nagoya protocol aim to protect traditional knowledge and regulate benefit-sharing with indigenous communities. The European community adopted the Nagoya protocol, and the corresponding regulations will be implemented into national legislation among the member states. Despite pleasing progress, infrastructural problems of the health care systems in developing countries still remain. Current approaches to secure primary health care offer only fragmentary solutions at best. Conventional medicine from industrialized countries cannot be afforded by the impoverished population in the Third World. Confronted with exploding costs, even health systems in Western countries are endangered to burst. Complementary and alternative medicine (CAM) is popular among the general public in industrialized countries, although the efficacy is not sufficiently proven according to the standards of evidence-based medicine. CAM is often available without prescription as over-the-counter products with non-calculated risks concerning erroneous self-medication and safety/toxicity issues. The concept of integrative medicine attempts to combine holistic CAM approaches with evidence-based principles of conventional medicine.Conclusion: To realize the concept of One-World Medicine, a number of standards have to be set to assure safety, efficacy and applicability of traditional medicine, e.g. sustainable production and quality control of herbal products, performance of placebo-controlled, double-blind, randomized clinical trials, phytovigilance, as well as education of health professionals and patients