Showing papers in "Bulletin of The Chemical Society of Ethiopia in 2004"

Bioactive metabolites from Trichoderma harzianum and Trichoderma longibrachiatum

Abstract: The tea plant, Camellia sinensis (L.) O. Kuntze is an important crop in the agriculturally based economy of Kenya. Many diseases affect the tea plant but the most prevalent is armillaria root rot caused by the fungus Armillaria mellea . Compounds from the fermentation of Trichoderma species in different media were bioassayed against some selected gram-positive and gram-negative bacteria, fungi including Armillaria mellea , a yeast and a Mucor. Compounds obtained from T. harzianum , and T . longibrachiatum when cultured in various media were investigated individually for in-vitro antifungal and antibacterial activities by agar diffusion technique. Some of the compounds produced definite antifungal and antibacterial activities. 2-Phenylethanol ( 1 ) and tyrosol ( 2 ) obtained from T. harzianum are reported for the first time from Trichoderma species. The most active metabolite isolated from these strains was 6-n-pentyl-α-pyrone ( 3 ), which showed the highest antifungal and antibacterial activity and completely inhibited the growth of Armillaria mellea fungus at a concentration of 200 ppm. Compound 4 (sorbicillin) exhibited moderate activity against the fungal test organisms. KEY WORDS: Trichoderma harzianum , Trichoderma longibrachiatum , 2-Phenylethanol, Tyrosol, 6-n-Pentyl-•-pyrone, Armillaria Mellea Bull. Chem. Soc. Ethiop. 2003 , 17(2), 185-190.

Distribution of trace elements in muscle and organs of Tilapia, oreochromis niloticus from lakes Awassa and Ziway, Ethiopia

Abstract: Samples of Tilapia, Oreochromis niloticus , were collected from Lakes Awassa and Ziway during December 2002–March 2003. The moisture content of freeze-dried organs (muscle, bone, gill and liver) collected from six sites ranged between 76.0 and 80.7% (m/m). An optimal procedure required 12 mL of tertiary mixture consisting of HNO 3 , HClO 4 , and H 2 O 2 to mineralize powdered samples in open refluxed digestion vessels: 1.0 g bone or muscle, 0.5 g gill or liver. The concentrations of 8 elements in muscle, bone, gill and liver determined by flame atomic absorption spectrophotometer varied, respectively, (mg element/kg dry mass): Cd 0.44–1.43, 4.58–4.93, 2.20–2.85, and 1.08–1.90; Co 2.47–3.59, 17.1–18.9, 8.28–10.1, and 10.2–13.0; Cu 1.68–4.95, 6.65–7.58, 7.08–8.58, and 602–797; Fe 18.7–53.0, 81.9–94.3, 120–196, and 635–7139; Mn 1.03–6.78, 23.1–146, 26.1–107, and 8.80–24.5; Ni 7.80–15.9, 64.1–71.0, 34.8–42.4, and 14.1–21.3; Pb 1.65–2.69, 39.5–42.3, 17.1–23.1, and 2.20–3.37; Zn 34.6–38.6, 61.9–78.8, 82.3–97.1, and 85.6–115.9. Results revealed organ specific distribution of trace metals in Tilapia , which has been discussed in terms of physiological role in fish and/or the likely influence of anthropogenic origin on lakes. Application of the statistical t -test on trace elements data further showed significant difference between the two lakes, which could be attributed to anthropogenic influences. KEY WORDS: Tilapia, Oreochromis niloticus , Distribution of trace elements in fish, Water pollution, Lake Awassa, Lake Ziway Bull. Chem. Soc. Ethiop. 2004 , 18(2), 119-130.

VIBRATIONAL SPECTRA OF t-BUTYL ALCOHOL, t-BUTYLAMINE AND t-BUTYL ALCOHOL + t-BUTYLAMINE BINARY LIQUID MIXTURES

Abstract: Raman and FT-IR absorption spectra of t -butyl alcohol and t -butylamine pure components have been recorded in the liquid state in the region of 400-4000 cm -1 . The data obtained have been used to propose complete vibrational assignments for each of the liquid component and the structural features are discussed. Additionally, the Raman and infrared spectra of the binary liquid mixtures for the t -butyl alcohol/ t -butylamine system have also been recorded. The variations in frequency shifts, intensities and line widths are discussed with a view to understanding the origin of such variations. KEY WORDS: Infrared and Raman spectra, Binary solution, t -Butanol, t -Butylamine Bull. Chem. Soc. Ethiop. 2003 , 17(2), 211-218.

Anti-inflammatory and analgesic activities: chemical constituents of essential oils of ocimum gratissimum, eucalyptus citriodora and cymbopogon giganteus inhibited lipoxygenase l-1 and cyclooxygenase of pghs

Abstract: The following studies report the inhibitory effect produced by chemical constituents of essential oils of three plants used in traditional medicine as anti-inflammatory and analgesic drugs, in vitro , on soybean lipoxygenase L-1 and cyclooxygenase function of prostaglandin H synthase (PGHS), the two enzymes involved in the production of mediators of inflammation. The essential oils were extracted from plants of three families: O. gratissimum (Labiatae), C. giganteus ( Poaceae), and E. citriodora (Myrtaceae). Their chemical composition was established by GC/MS analyses. Among the three essential oils, one showed evident inhibition of L-1 with IC 50 value of 72 µg/mL for Eucalyptus citriodora. Only one essential oil that of O. gratissimum inhibited the two enzymes, cyclooxygenase function of PGHS and lipoxygenase L-1, with an IC 50 values, respectively, of 125 µg/mL and 144 µg/mL, whereas that of C. giganteus and E. citriodora, two of them had no effect on cyclooxygenase. KEY WORDS: Essential oils, Soybean lipoxygenase (L-1), Cyclooxygenase function of prostaglandine H synthase-1, PGHS, O. gratissimum (Labiatae), C. giganteus ( Poaceae), E. citriodora (Myrtaceae), Enantia chlorantha , Inhibition Bull. Chem. Soc. Ethiop. 2003 , 17(2), 191-197.

Physico-chemical characteristics of mesua ferrea seed oil and nutritional composition of its seed and leaves

Abstract: Studies on the physico-chemical characteristics of seed oils of Mesua ferrea collected from different districts of Bangladesh revealed specific gravity (0.9287-09312), refractive index (1.4690-1.4739), solidification point [-4.0-(-4.3)], pour point [-1.0-(-1.3)], cloud point (5.5-6.0), flash point (90-98), fire point (110-116), smoke point (44-47), iodine value (89.17-93.01), saponification value (199.03-206.40), saponification equivalent (271.80-281.86), acid value (9.64-11.87), free fatty acid (4.85-5.96), ester value (188.95-1.95.44), unsaponifiable matter (1.44-1.50), acetyl value (2.70-2.84), peroxide value (3.58-3.64), Reichert-Meissl value (5.852-6.031) and polenske number (0.7891-0.8401). Glyceride classes were estimated to be monoglycerides (1.05-1.35 %), diglycerides (2.12-2.32 %) and triglycerides (87.65-89.50 %) whereas total lipid extracts were fractionated into neutral lipid (89.83-92.18 %), glycolipid (3.65-4.15 %) and phospholipid (1.98-2.68 %). Saturated and unsaturated fatty acids present in the oils were separated and amounted to be (27.40-29.11 %) and (65.85- 68.31 %), respectively, depending upon the areas from where the seeds were collected. GLC analysis of the oil indicated the presence of palmitic acid (10.87%), linoleic acid (13.68%), oleic acid (55.93%) and stearic acid (14.19%) as major fatty acids in the oil. In addition, myristic acid (2.13%) and arachidic acid (2.921%) were also present in minor amount. In biochemical analysis, Mesua ferrea seeds contained total lipid (66.91-70.23 g %), moisture (4.02-5.05 g %), ash (1.46-1.50 g %), total protein (6.99-7.19 g %), water soluble protein (2.98-3.11 g %), starch (5.51-5.85 g %), crude fiber (1.22-1.98 g %), carbohydrate (15.88-18.68 g %) and energy value (700.55-724.15 kcal/100 g), while its leaves contained total lipid (2.32-2.44 g %), moisture (65.12-72.19 g %), ash (2.60-2.71 g %), total protein (4.23-4.85 g %), water soluble protein (1.47-2.01 g %), starch (3.06-3.27 g %), crude fiber (3.12-3.29 g %), carbohydrate (14.82-22.30 g %) and energy value (100.24-128.40 kcal/100 g ). The present investigations demonstrate that the results vary to some extent but not significantly enough with the locations from where samples were collected. KEY WORDS: Mesua ferrea , Seed oil, Glyceride compositions, Fatty acid compositions, Nutritional composition Bull. Chem. Soc. Ethiop. 2004 , 18(2), 157-166.

Further flavonol glycosides of Embelia schimperi leaves

Abstract: Fractionation of the methanolic extract of Embelia schimperi leaves has led to the isolation of two novel flavonol glycosides. The compounds were characterized as isorhamnetin 3- O - b -galactoysyl (1 ® 4)- b -galactoside and quercetin 3- O -[ a -rhamnosyl (1 ® 2)] [ a -rhamnosyl (1 ® 4)]- a -rhamnoside. Also reported from the same extracts were known compounds quercetin, myricetin, quercetin 3- O - a -rhamnoside, quercetin 3- O - b -glucoside, quercetin 3- O -rutinoside, myricetin 3- O - b -xyloside, isorhamentin 3- O - b -glucoside and myricetin 3- O - b -glucoside. Their structural elucidation was accomplished using spectral measurements and chemical methods. KEY WORDS: Embelia schimperi , Flavonol glycosides, Isorhamnetin 3- O - b -galactoysyl (1 ® 4)- b galactoside, Quercetin 3- O -[ a -rhamnosyl (1 ® 2)] [ a -rhamnosyl (1 ® 4)]- a -rhamnoside Bull. Chem. Soc. Ethiop. 2004 , 18(1), 51-57.

Inhibition of the acid corrosion of aluminium by some derivatives of thiosemicarbazone

Abstract: The inhibition of corrosion of aluminium in HCl solution by some derivatives of thiosemicarbazones has been studied using weight loss and hydrogen evolution techniques. The thiosemicarbazone derivatives used are 2-acetyl pyridine-(4-phenylthiosemicarbazone) (PTSC), 2-acetyl pyridine-(4-phenyl-iso-methylthiosemicarbazone) (PIMTSC) and 2-acetyl pyridine-(4-phenyl-iso-ethylthiosemicarbazone) (PIETSC). The inhibition efficiency depended on the compounds concentration until at very low concentration studied where they reversed their functions and became accelerators. Kinetic treatment of the results gave a first order type of mechanism. The results reported in this paper elucidate the effects of inhibitor concentration, temperature and the molecular structure on the inhibition efficiency. KEY WORDS: C orrosion inhibition, Aluminium, 2-Acetyl pyridine-(4-phenylthiosemicarbazone) (PTSC), 2-Acetyl pyridine-(4-phenyl-iso-methylthiosemicarbazone) (PIMTSC), 2-Acetyl pyridine-(4-phenyl-iso-ethylthiosemicarbazone) (PIETSC), Kinetics Bull. Chem. Soc. Ethiop. 2004 , 18(2), 181-192.

Chemical and structural characterization of natural phosphate of Hahotoe (Togo)

Abstract: Chemical and structural characterizations of natural phosphates of Hahotoe (Togo) have been performed. From chemical analysis and FTIR study, it can be concluded that the material is carbonated fluoroapatite with poor substitution of calcium by cadmium and manganese. From these results, the molecular formula proposed is: Ca 9.925 Cd 0.004 Mn 0.013 [(PO 4 ) 5.886 (CO 3 ) 0.113 ]F 2 . Powder X-ray diffraction fitting results confirm that compound belongs to the apatite family crystallising in the hexagonal system, space group P6 3 /m. The cell parameters are: a = 9.3547(5) A; c = 6.8929(4) A. KEY WORDS: N atural phosphate, Fluoroapatite, Infrared, X-Ray diffraction, Rietveld structure refinement Bull. Chem. Soc. Ethiop. 2003 , 17(2), 139-146.

Coordination of cassava starch to metal ions and thermolysis of resulting complexes

Abstract: Cassava starch formed Werner-type complexes with ions of metals from the transition groups. This was proven by conductivity and electron paramagnetic resonance measurements. The coordination of starch to central metal ions influenced the thermal decomposition of starch. As a rule complexes started to decompose at lower temperature than did starch. On the other hand, the decomposition proceeded at a lower rate than the decomposition of non-coordinated starch.

Physicochemecal studies of some hexamethylenetetramine metal(II) complexes

Abstract: Divalent metal (Mn, Co, Ni) complexes of the ligand hexamethylenetetramine (HMTA, C 6 H 12 N 4 ) with sulfate, nitrate and fluoroborate as counter ions have been synthesized in ethanolic media. Whereas the complexes with BF 4 - and NO 3 - as counter ions have two molecules of hexamethylenetetramine, those with SO 4 2- as counter ion contain just one molecule of hexamethylenetetramine. The complexes have been characterized by elemental analyses, infrared and visible spectroscopy and room temperature magnetic susceptibility measurements. The results suggest octahedral coordination in which the central metal ion is bonded to hexamethylenetetramine and water molecules. KEY WORDS: Divalent metal (Mn, Co, Ni) complexes, Hexamethylenetetramine, Sulfate as counter ion, Nitrate as counter ion, Fluoroborate as counter ion Bull. Chem. Soc. Ethiop. 2004 , 18(2), 143-148.

Ceramic properties of Pugu kaolin clays. Part I: Porosity and modulus of rupture

Abstract: The utilisation of Pugu kaolin clay as a raw material in porcelain has been tested by laboratory scale experiments. Physical characteristics of the clay have shown it to be of satisfactory quality and comparable to commercial clays found elsewhere. The chemical analysis has indicated the presence of high levels of iron oxide (~ 1.43%) which could adversely affect the translucency of whitewares. The “as mined” material could be suitable for ceramics that do not require high brightness specifications, such as stoneware and sanitary ware. The level of this oxide can, however, be reduced by appropriate means to give a relatively cleaner product that could be excellent for other types of whiteware products. Porcelain materials prepared using Pugu kaolin clay have shown to have similar properties as those prepared using other standard kaolin clays. The bulk density and flexural strength of the fired masses increase with firing temperature to a maximum at the soak temperature of 1200 o C. Beyond this soak temperature the flexural strength decreases. The decrease in strength is attributable to bloating which takes place as gasses are expelled from the matrix. Strictly firing procedures should be enforced in order to obtain a porcelain material of required strength. KEY WORDS: Kaolin clay, Ceramic properties, Porcelain materials, Bulk density, Sintering, Modulus of rupture, Bloating Bull. Chem. Soc. Ethiop. 2003 , 17(2), 147-154.

Nauclefolinine: a new alkaloid from the roots of nauclea latifolia

Abstract: A novel indole alkaloid, nauclefolinine ( 1 ) and five known triterpenic compounds, rotundic acid ( 2 ), a -L-rhamnoquinovic acid ( 3 ), 3- O - b -D-glucopyranosyl- b -sitosterol ( 4 ), squalene ( 5 ) and sitosterol-3- O -6’-stearoyl- b -D-glucopyranoside ( 6 ) have been isolated from the roots of Nauclea latifolia . KEY WORDS: Nauclea latifolia , Rubiaceae, Indole alkaloid, Triterpenic acids, Rotundic acid, Rhamnoquinovic acid Bull. Chem. Soc. Ethiop. 2003 , 17(2), 173-176.

Gossweilone: a new podocarpane derivative from the stem bark of drypetes gossweileri (euphorbiaceae)

Abstract: A new podocarpane diterpenoid, named gossweilone ( 1 ), has been isolated from the stem bark of Drypetes gossweileri , along with two known friedelane triterpenoids. The structure of the new compound was elucidated using spectroscopic methods. KEY WORDS: Gossweilone, Podocarpane diterpenoid, Drypetes gossweileri , Euphorbiaceae Bull. Chem. Soc. Ethiop. 2003 , 17(2), 181-184.

Electrochemical decontamination of waters by advanced oxidation processes (AOPS): Case of the mineralization of 2,4,5-T on BDD electrode

Abstract: In the present work, herbicide 2,4,5-trichlorophenoxyacetic acid, more commonly known as 2,4,5-T herbicide, has been completely mineralized (i.e. transformed into CO 2 and H 2 O) in saturated aqueous solutions using a semi-industrial electrochemical cell that contains a boron doped diamond anode and a zirconium cathode. We have performed cyclic voltammetry, chronoamperometry and bulk electrolysis to give the optimization characteristics of the degradation of such a compound and its by-products. Bulk electrolysis in the potential region of electrolyte decomposition leads to the complete destruction of 2,4,5-T and its degradation intermediates by means of the electrogeneration of the highly reactive hydroxyl radicals. The evolution of the chemical oxygen demand (COD) and the instant current efficiency (ICE) during the degradation process is perfectly predicted by a theoretical mathematical model. HPLC and GC-MS have also been performed to highlight the evolution of the mother product and its degradation intermediates. Kinetic analysis of the obtained results has shown a fast destruction of the mother herbicide asserting a diffusion-controlled process. 2,4,5-trichlorophenol and quinone-based organic compounds have been depicted as aromatic intermediates, all of them transformed into short chains carboxylic acids before complete mineralization happens. KEY WORDS: Electrochemical decontamination, Cyclic voltammetry, 2,4,5-T herbicide, Mineralization, BDD electrodes Bull. Chem. Soc. Ethiop. 2004 , 18(2), 205-214.

Spectroscopic studies and thermal analysis of lead(II) and tin(II) solid complexes with bi- , tri- and tetradentate Schiff bases

Abstract: The Schiff base complexes of Pb(II) and Sn(II) with bidentate (NO), [M(sal-An) 2 ] (sal-An = aniline salicylideneiminato); tridentate (ONO), [M(sal-OAP)H 2 O)] (sal-OAP = ortho- aminophenol salicylideneiminato); and tetradentate (N 2 O 2 ), [M(sal- o -phdn)] (sal- o -phdn = N,N'- o -phenylene bis(salicylideneiminato) have been synthesized. The infrared spectra were recorded and full assignments of all observed bands have been made. Differential thermal analysis (DTA) and thermogravimetric (TG) for all complexes were also carried out. The data obtained indicate that the complexes of both bi- and tetra dentate ligands are decomposed in one stage, but the complexes of tridentate are decomposed in two steps. KEY WORDS: Lead, Tin, Schiff base, Infrared spectra, Thermal analysis Bull. Chem. Soc. Ethiop. 2004 , 18(2), 149-156.

Chemical constituents of the ethyl acetate extracts of the stem bark and fruits of Dichrostachys cinerea and the roots of Parkia bicolor

Abstract: The antibacterial activities of ethyl acetate, methanol and aqueous extracts of the stem bark of Dichrostachys cinerea and the roots of Parkia bicolor have been evaluated. Ethyl acetate extracts have been investigated, studies that led to a series of known compounds, amongst which many are reported here for the very first time from both the species. KEY WORDS: Dichrostachys cinerea, Parkia bicolor, Chemical constituents, Antibacterial activity Bull. Chem. Soc. Ethiop. 2004 , 18(1), 111-115.

Symphonin: a new prenylated pyranoxanthone with antimicrobial activity from the seeds of symphonia globulifera (Guttiferae)

Abstract: A new prenylated pyranoxanthone, symphonin ( 1 ), 2-(3,3-dimethylallyl)-1,5- dihydroxy-6,7-dimethoxy-2”,2”-dimethylpyrano (5”,6”:3,4) xanthone, the known compounds guttiferone A, oleanolic acid and sitosterol were isolated from the methanol extract of the seeds of Symphonia globulifera (Guttiferae). The structural elucidation of the new compound was based mainly on spectroscopic analyses. The new xanthone showed antimicrobial activity against Staphylococcus aureus , Streptococcus feacalis , Klebsiella pneumonia and Escherichia coli . KEY WORDS: Symphonia globulifera , Seeds, Xanthone, Antimicrobial activity Bull. Chem. Soc. Ethiop. 2004 , 18(2), 175-180.

Ceramic properties of pugu kaolin clays. Part 2: Effect of phase composition on flexural strength

Abstract: Whiteware compositions prepared using Pugu kaolin and industrial grade quartz and feldspar were studied with respect to varying sintering temperatures. The strength developed was correlated to mullite (3Al 2 O 3 .2SiO 2 ) content and the microstructure. It was observed that within the vitrification temperature range, the strength mainly depended on the mullite content and the bulk density. Above the vitrification temperature range the deterioration of the strength is due to the coarsening of mullite needles and bloating. KEY WORDS: Ceremic properties, Kaolin clay, Flexural strength, Mullitisation, Bulk density, Modulus of Rupture, Microstructure Bull. Chem. Soc. Ethiop. 2004 , 18(1), 7-16.

4,5-Epoxide-1,6-dimethyl-1-vinylhexyl p-coumarate: a novel monoterpene derivative from Cleistopholis patens.

Abstract: A novel monoterpene derivative ( 1 ) and four known partially and total acetylated tri- and tetrarhamonoside dodecanyl ether derivatives: cleistrioside-2 ( 2 ) and cleistrioside-3 ( 3 ), cleistetroside-6 ( 4 ) and cleistetroside peracetate ( 5 ) have been isolated from the fruits of Cleistopholis patens. KEY WORDS: Cleistopholis patens, Annonaceae, Oligosaccharide, Partially acetylated tri- and tetrarhamnoside dodecanyl ether derivatives, Cleistrioside, Cleistetroside, Monoterpene derivative Bull. Chem. Soc. Ethiop. 2003 , 17(2), 177-180.

Larvicidal benzoquinone from Embelia schimperi

Abstract: Chromatographic analysis of air-dried berries of Embelia schimperi led to the isolation of methyl vilangin ( 1 ), which was characterized on the basis of physical and spectroscopic data. The compound was found to be lethal against 2 nd instar larvae of Aedes aegypti (yellow fever vector) by first stopping the process of metamorphosis from the 2 nd instar stage to the other stages and finally causing mortality to the larvae. KEY WORDS: Embelia schimperi , Aedes aegypti , 2 nd instar larvae, Benzoquinones, Methyl vilangin Bull. Chem. Soc. Ethiop. 2004 , 18(1), 45-49.

Construction and optimisation of a cartridge filter for removing fluoride in drinking water

Abstract: An attempt has been made to construct a cartridge to be used for the defluoridation of drinking water. The cartridge packed with bone char material could be fixed onto a domestic faucet as a flow through defluoridizer. PVC cartridges of various sizes were made from a ¾ inch pipe. The efficiency of f luoride removal was determined for the following parameters: cartridge length, flow rate of water, compactness of bone char material and particle size with the aim of determining the optimum conditions for a good cartridge. It was found that the optimal conditions for the F - filter that gave the best results in removing of F - from water with minimum inconvenience were: p article size, 0.2 mm mean diameter; the flow rate, equal or less than 20 mL/min; cartridge length, 10 cm filled with 20 g of bone char material. KEY WORDS: Bone char, PVC cartridge, Batch defluoridation, Flow-through defluoridation, Defluoridation efficiency Bull. Chem. Soc. Ethiop. 2004 , 18(1), 1-6.

High field 13C NMR spectroscopic analysis of the triacylglycerols of Jatropha curcas oil

Abstract: Gated decoupled 13 C NMR has been employed to determine the acyl composition and acyl positional distribution on the glycerol backbone in the triacylglycerols of Jatropha curcas oil. Results revealed the presence of saturated, oleic and linoleic acids in the oil. Integrals obtained from the allylic carbons were used for semiquantitative analysis of the oil and gave the percentage of total saturated, oleic and linoleic acids in the oil as 27, 41 and 32, respectively. The results obtained by 13 C NMR compared favourably with those obtained by gas chromatographic analysis. Analysis of the spectra further revealed that the saturated acyl esters are randomly distributed in the a and b glyceridic positions, with oleic being approximately 60% distrbuted at a glyceridic carbons and linoleic approximately 52% distributed at b glyceridic carbon. KEY WORDS: Gated decoupled 13 C NMR, Acyl composition, Acyl positional distribution, Triacylglycerols, Jatropha curcas oil Bull. Chem. Soc. Ethiop. 2004 , 18(1), 59-65.

Variations of the fatty acid composition in the oil from the larval stages of the emperor moth caterpillar, imbrasia belina

Abstract: The mophane caterpillar, phane, the larval stage of the emperor moth, Imbrasia belina , is an important food source, with increasing popularity, in the southern African region. The protein and fat contents of phane have been estimated as 55% and 33% (w/w), respectively. Unsaturation content is about 60%, with α-linolenic acid being the dominant fatty acid in the lipid content of phane. An earlier investigation showed that the iodine values of two oil samples from two batches of phane at different ages, i.e., instars, varied significantly. The proximate fatty acid composition has now been determined by capillary GC for five oil samples from five batches of mophane caterpillar, ranging between early III and late V instars in order to investigate any differences in the nature of the lipid content due to age. The oil yield increased steadily from 19.8% (w/w) for early III instars to 38.3% for late V instars. The contents of palmitic and linoleic acids were 8.5% and 24%, respectively, for early III instars, and 31.1% and 10.7%, respectively, for late V instars. The composition of α-linolenic acid peaked at 39.1% for III/IV instars but decreased to 32.5% for late V instars. The lipid content of the leaves of the mophane tree, the principal food source of the mophane caterpillar, was found to be composed of 24% palmitic acid, 4.1% palmitoleic acid, 5.6% stearic acid, 14.85% oleic acid, 15. 6% linoleic acid and 32.9% linolenic acid, a fatty acid composition quite similar to that of mature phane, late V instars. Crude protein content varied irregularly with early III and late V instars being 59.3% and 62.0% (w/w), respectively. This study has demonstrated a dramatic variation in the composition of palmitic and linoleic acids in the lipid content from early III to late V instars of the larvae of Imbrasia belina . The study has also confirmed the larvae of Imbrasia belina as a rich source of protein and α-linolenic acid, the precursor of the w 3 essential fatty acids. KEY WORDS: Crude protein, Instars, Larval stages, Imbrasia belina , Emperor moth, Mophane caterpillar, •-Linolenic acid, Phane, Variations of fatty acid composition Bull. Chem. Soc. Ethiop. 2004 , 18(1), 67-72.

Drop amalgam voltammetric study of lead complexation by natural inorganic ligands in a salt lake

Abstract: A study of inorganic complexation of lead using drop amalgam voltammetry is described. The study has been carried out in simulated salt lake water and at ionic strength of 7.35 M, the predetermined ionic strength of Lake Katwe. The complexation of lead with the simple ligands (Cl - , CO 3 2- ) created anodic waves and the shifts of the peak potentials of lead with the introduction of varying concentrations of each ligand measured. The analysis of these shifts furnished information about the stability constants of the lead complexes which was employed in the calculation of lead species distribution. These mathematical treatments revealed the existence of two lead chloride complexes with corresponding stability constants log b 1 = 0.88, log b 2 = 2.95; and two carbonate complexes with log b 1 = 8.50 and log b 2 = 9.62. The results obtained indicate that in Lake Katwe water (25 o C, carbonate alkalinity = 0.11 M, pH 11) approximately 0.00% of total inorganic lead exists as the free ion, and at chloride concentration of 1.8 M only 1.3% of lead exists as the free ion. KEY WORDS: Drop amalgam, Lead speciation, Stability constants, Lake Katwe, Voltammetric complexation, Species distribution Bull. Chem. Soc. Ethiop. 2004 , 18(1), 91-100.

Polymerization of propene with t BuNSiMe 2 C 5 Me 4 TiMe 2 : Effects of trialkylaluminiums as additives

Abstract: Propene was polymerized at 0 o C with t BuNSiMe 2 C 5 Me 4 TiMe 2 /MAO. Kinetic features and other parameters indicated quasi-living polymerization. Effects of various trialkylaluminiums as additives have been investigated; it was found that compounds with more bulky groups like i Bu 3 Al, Oct 3 Al increased the activities significantly whereas Me 3 Al and Et 3 Al reduced the activities of the catalyst system. The triad sequence in the 13 C NMR spectrum confirmed a syndiotactic-enriched atactic polypropene. KEY WORDS: P olymerization of propene, t BuNSiMe 2 C 5 Me 4 TiMe 2 , Trialkylaluminiums, Syndiotactic-enriched atactic polypropene Bull. Chem. Soc. Ethiop. 2004 , 18(2), 131-141.

Determination of bromoxynil and ioxynil in the presence of carbamates by supported liquid membrane-liquid chromatography in river waters

Abstract: Sample pre-treatment and enrichment using the supported liquid membrane (SLM) technique for the determination of phenolic nitrile herbicides in presence of carbamates in river water samples was investigated. The uncharged herbicide molecules from the flowing aqueous solution diffuse through an immobilized water-immiscible organic solvent, supported by a porous polytetrafluoroethylene (PTFE) membrane, and trapped in a stagnant acidic acceptor phase in an ionic form. Using n-undecane as a membrane solvent, the SLM extraction methodology was successfully used for the enrichment and separation of phenolic nitrile herbicides in environmental waters with extraction efficiencies of 60% or better. A RDS (%) of 2.1 and 1.8 was obtained for the extraction of ioxynil and bromoxynil from river water, respectively. KEY WORDS: Bromoxynil, Ioxynil, Phenolic nitrile herbicides, Carbamates, Supported liquid membrane, Sample pre-treatment, Sample enrichment Bull. Chem. Soc. Ethiop. 2003 , 17(2), 119-128.

INFLUENCE OF DOPED-CHARGE TRANSPORT LAYERS ON THE PHOTOVOLTAIC PERFORMANCE OF DONOR-ACCEPTOR BLEND p-i-n TYPE ORGANIC SOLAR CELLS

Abstract: This report demonstrates external power conversion efficiencies of 2% under 100 mW/cm 2 simulated AM1.5 illumination for organic thin-film photovoltaic cells using a phthalocyanine-fullerene (ZnPc/C 60 ) bulk heterojunction as an active layer, embedded into a p-i-n type architecture with doped wide-gap charge transport layers. For an optically optimized device, we found internal quantum efficiency (IQE) of above 80% under short circuit conditions. Such optically thin cells with high internal quantum efficiency are an important step towards high efficiency tandem cells. The p-i-n architecture allows for the design of solar cells with high internal quantum efficiency where only the photoactive region absorbs visible light and recombination losses at contacts are avoided. The I-V characteristics, power conversion efficiencies, the dependence of short circuit current on incident white light intensity, incident photon to collected electron efficiency (IPCE) and absorption spectra of the active layer system are discussed. KEY WORDS: Doped-charge transport layers, Organic solar cells, Photovoltaic cells, Phthalocyanine-fullerene Bull. Chem. Soc. Ethiop. 2004 , 18(1), 101-109.

Energy requirement for firing porcelain

Abstract: Results from studies on the ternary system Ribaue kaolin–Carapira feldspar– Marracuene quartz sands were used to test a procedure that we developed for calculation of the energy requirement for firing porcelain. Results obtained vary between 1300 and 1800 kJ/kg porcelain. These results differ largely from the ones obtained using Hennicke’s procedure. KEY WORDS: Porcelain, Energy requirement for firing porcelain, Kaolin---feldspar---quartz sands Bull. Chem. Soc. Ethiop. 2004 , 18(1), 73-80.

CNDO/SCF molecular orbital structural studies and charge transfer complex formation between 4,4’-dimethoxydiquinone and uracil

Abstract: Through CNDO/SCF molecular orbital calculations, the structure of 4,4’-dimethoxy- diquinone (DQ) has been discussed and compared with some related compounds. The electron transfer between DQ and uracil was studied in ethanol as an interaction medium. The ionization potentials and the electron affinities of the studied molecules have been calculated in addition to their charge densities giving the columbic potential energy of the donor and acceptor. The experimental charge transfer band lies at 500 nm. The electronic transitions have been calculated for the singlet and triplet transitions in uracil and DQ molecules using the SCF eigenvectors of the two HOMO’s, y n-1 and y n , and the two LUMO’s, y n+1 and y n+2 , using CI theory. The calculated electronic transitions are compared with those of the experimental data to verify the non-planar structure of the DQ molecule. KEY WORDS: CNDO/SCF molecular orbital calculations, 4,4’-Dimethoxydiquinone, Uracil, Ionization potentials, Electron affinities Bull. Chem. Soc. Ethiop. 2004 , 18(2), 193-204.

Larvicidal activity of myricoidine from clerodendrum myricoides

Abstract: Chromatographic separation of a methanolic extract of Clerodendrum myricoides led to the isolation of myricoidine ( 1 ) whose structure was elucidated using IR, NMR and melting point. The crude fractions as well as 1 were subjected to larvicidal tests using the second instar larvae of Anopheles gambiae (malaria vector) at concentrations of 100, 75, 50, and 25 ppm. The crude extract and the compound were found to be active with LC 50 values of 14 and 9 ppm, respectively. KEY WORDS: Clerodendrum myricoides, Anopheles gambiae, S econd instar larvae, M yricoidine Bull. Chem. Soc. Ethiop. 2004 , 18(2), 225-227.