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- ItemOpen AccessNitrate-nitrite, Vitamin C and in-vitro methemoglobin formation from some vegetables(Nutrition Reports International, 1979) Okiei, W.O.; Adamson, IThe content of nitrate, nitrite and Vitamin C in eleven samples of fresh vegetables were determined. The levels of nitrate were beyond 300 ppm recommended in six of the vegetables, namely, Celisia sp, Lactuca saliva, Amaranthus hybrids, Brassica oleracea variety acephala, Talinum sp, Spinacia oleracea. Minute quantities of nitrite were detected in Celosia so and Daucus carrots. With a accompanying high concentration of Vitamin C (a reducing agebt) present in Celodia so, this vegetable may be a potential source of nitrite in foods. Effects of cooking caused less than 25% reduction in nutrate-nitrite content of the vegetables. When in vitro testing methemoglobin formation was carried out with extract from the samples, modified haemoglobin formed paralleled content of nitrate in the vegetables. It is suggested that caution must be exercised in the use of some of these vegetables in infant foods as they may contribute to the induction of methemoglobin.
- ItemOpen AccessPolycyclic nitrogen compounds. Part I. Synthesis of new heterotricyclic quinoxalinones with bridgehead nitrogen atoms(Journal of Heterocyclic Chemistry, 1982-10) Adegoke, E.A.; Alo, B.I.; Ogunsulire, F.O.New tricyclic quinoxalinone skeletons with a fully‐reduced ring ‘C’ ‐1,2,3,3a‐tetrahydropyrrolo[1,2‐α]quin‐oxalin‐4‐one (I‐II) and 7,8,9,10‐tetrahydropyrido[1,2‐α]quinoxalin‐6‐one (III‐IV) derivatives were obtained by selective hydrogen transfer reductive cyclisation of N‐(2‐nitrophenyl)pyrrolidine‐2‐carboxylic acid esters and N‐(2‐nitrophenyl)piperidine‐2‐carboxylic acid esters (VIa,b and VIIIa,b), respectively.
- ItemOpen AccessPolycyclic nitrogen compounds. Part II. Tricyclic quinoxalinones and their 4‐ or 6‐aza analogues(Journal of Heterocyclic Chemistry, 1983-11) Adegoke, E.A.; Alo, B.I.1,2,3,3a‐Tetrahydro‐9‐nitropyrrolo[1,2‐α]quinoxalin‐4‐one and 7,8,9,10‐tetrahydro‐3‐nitropyrido[1,2‐α]quin‐oxalin‐6‐one (V‐VI) were reduced and deaminated to give new parent tricyclic quinoxalinone skeletons I‐II. The latter compounds were identical with the tricycles obtained by an unambiguous independent synthesis. New 6‐aza‐1,2,3,3a‐tetrahydropyrrolo[1,2‐α]quinoxalin‐4‐one (III) and 4‐aza‐7,8,9,10‐tetrahydropyrido[1,2‐α]‐quinoxalin‐6‐one (IV) were prepared by selective hydrogen transfer reductive cyclisation of esters of N‐(2‐nitro‐3‐pyridyl)pyrrolidine‐2‐carboxylic acid and N‐(2‐nitro‐3‐pyridyl)piperidine‐2‐carboxylic acid (Xb and XIb) respectively.
- ItemOpen AccessPolycyclic nitrogen compounds. Part iii. Synthesis of 3,3a‐dihydrothiazolo[3,4‐α]quinoxalin‐4‐ones(Journal of Heterocyclic Chemistry, 1983-11) Adegoke, E.A.; Alo, B.I.New tricyclic quinoxalinone skeletons with bridge‐head nitrogen atoms and containing sulphur in a fully‐reduced five‐membered ring C were obtained. 3,3a‐Dihydrothiazolo[3,4‐α]quinoxalin‐4‐ones I‐III were prepared by metal‐acid reductive cyclisation of N‐(nitrophenyl)‐ and N‐(dinitrophenyl)thiazolidine‐4‐carboxylic acids IVa,b,c. Attempts to obtain the skeleton by selective hydrogen transfer reductive cyclisation of the corresponding esters Va,b,c were unsuccessful.
- ItemOpen AccessPolycyclic nitrogen compounds. Part II. Tricyclic quinoxalinones and their 4‐ or 6‐aza analogues(Journal of Heterocyclic Chemistry, 1983-11) Adegoke, E.A.; Alo, B.I.1,2,3,3a‐Tetrahydro‐9‐nitropyrrolo[1,2‐α]quinoxalin‐4‐one and 7,8,9,10‐tetrahydro‐3‐nitropyrido[1,2‐α]quin‐oxalin‐6‐one (V‐VI) were reduced and deaminated to give new parent tricyclic quinoxalinone skeletons I‐II. The latter compounds were identical with the tricycles obtained by an unambiguous independent synthesis. New 6‐aza‐1,2,3,3a‐tetrahydropyrrolo[1,2‐α]quinoxalin‐4‐one (III) and 4‐aza‐7,8,9,10‐tetrahydropyrido[1,2‐α]‐quinoxalin‐6‐one (IV) were prepared by selective hydrogen transfer reductive cyclisation of esters of N‐(2‐nitro‐3‐pyridyl)pyrrolidine‐2‐carboxylic acid and N‐(2‐nitro‐3‐pyridyl)piperidine‐2‐carboxylic acid (Xb and XIb) respectively.
- ItemOpen AccessPolycyclic nitrogen compounds. Part iii. Synthesis of 3,3a‐dihydrothiazolo[3,4‐α]quinoxalin‐4‐ones(Journal of Heterocyclic Chemistry, 1983-11) Adegoke, E.A.; Alo, B.I.New tricyclic quinoxalinone skeletons with bridge‐head nitrogen atoms and containing sulphur in a fully‐reduced five‐membered ring C were obtained. 3,3a‐Dihydrothiazolo[3,4‐α]quinoxalin‐4‐ones I‐III were prepared by metal‐acid reductive cyclisation of N‐(nitrophenyl)‐ and N‐(dinitrophenyl)thiazolidine‐4‐carboxylic acids IVa,b,c. Attempts to obtain the skeleton by selective hydrogen transfer reductive cyclisation of the corresponding esters Va,b,c were unsuccessful.
- ItemOpen AccessSynthesis of 1,2,4-benzothiadiazines via readily generated iminium ions(Journal of the Chemical Society, 1986) Alo, B.I.; Adegoke, E.A.; Ligali-Ali, M.; Adesogan, E.K.A general method for the regiospecific synthesis of 1,2,4-benzothiadiazines, which are powerful diuretics and antihypertensive agents, has been developed. The N-arysulphonylprolyl chlorides (5)–(7) reacted instantaneously with silver trifluoromethanesulphonate at room temperature to give the iminium salts (9)–(11) which provided the nitroamines (13)–(15) in quantitative yield. Reductive cyclisation of the nitroamines led to the tetrahydro-1H-pyrrolo[1,2-b][1,2,4]benzothiadiazine 5,5-dioxides (17)–(20) in very good yields. No optimisation of yields was attempted. Efficient methods for the synthesis of some new substituted N-(nitrobenzenesulphonyl)-pyrrolidinecarboxylic acids (1)–(4), which were not readily available, are also described.
- ItemOpen AccessInhibition of the hydrolytic activity of thrombin by chitin heparinoids(Elsevier Science, 1986) Nishimura, S.; Nishi, N.; Tokura, S.; Okiei, W.O.; Somorin, O.Heparin, an anticoagulant polysaccharide, inhibits the thrombin activity that plays the most important role in blood clotting. Inhibition of thrombin activity is accelerated in the presence of antithrombin III (AT-III). The heparin-AT-III complex also inhibits Factor Xa, which transforms prothrombin into thrombin. As Chitin has a similar skeletal structure to heparin, the biomedical properties of chitin have received considerable attention. Chitosan (N-deacetylated chitin) has been used to prepare heparin-like derivatives, because it can be chemically modified under homogeneous conditions in few reaction steps. Although there have been many attempts prepare chitosan heparinoids, the role of each functional group has not been clarified satisfactorily. Use of chitin as a precursor for heparinoids allowa the role of ether-linked functional groups to be demonstrated independently of influence by N-sulfate groups. Carboxymethylation of chitin was employed, as carboxymethyl groups have been reported to augment the anticoagulant activity of sulfated dextran. Carboxymethylation of chitin to d. s. 0.8 under mild conditions causes mainly 6-o-substitution O-(Carboxymethyl)-chitin (CM-chitin) has been reported to adsorb bovine blood proteins, with a positive contribution by Ca2+, and the extent of adsorption is regulated by the degree of substitution. The present report describes the preparation the preparation of various chitin derivatives by the sulfation of chitin and CM-chitin under mild conditions, and studies of inhibition of thrombin activity, using bovine fibrinogen. Inhibition was observed to be increased upon introduction of carboxymethyl groups in the sulfated chitin =, as also observed for sulfated dextran. The sulfated CM-chitin showed activity comparable to that of heparin.
- ItemOpen AccessInhibitory Action of Sulphated Chitin Derivatives on the Hydrolytic Activity of Thrombin(1986-05) Okiei, W.O.; Nishimura, S.; Somorin, O.; Nishi, N.; Tokura, S.Heparin, an anticoagulant polysaccharide, inhibits thrombin activity which plays the most important role in the blood clotting process. It is known to accelerate neutralization of thrombin activity instantaneously in the presence of antithrombin III (AT-III) (l). The thrombin-AT-III complex also inhibits Factor Xa moiety in the blood clotting system (2). In order to understand the exact mechanism of heparin action, the stepwise preparation of heparin-like materials should be investigated from the point of view of inhibition mechanism.
- ItemOpen AccessNew lysine chromogenic substrates for trypsin(1986-05-29) Somorin, O.; Okiei, W.O.; Emokpae, T.; Ogunlesi, M.Eight new direct chromogenic lysine substrates, namely N~-benzyloxycarbonyl-L-lysine 3,5-dinitroanilide hydrochloride (L-ZLDA'HCI), N~-benzyloxycarbonyl-L-lysine 3-nitroanilide hydrochloride (L-ZLNA'HCI), N~benzyloxycarbonyl-L-lysine 3-nitro-5-bromoanilide hydrochloride (L-ZLNBA'HCI), N ~- benzyloxycarbonyl-L-lysine 3-nitro-5-chloroanilide hydrochloride (L-ZLNCA" HCI), N~-benzyloxycarbonyl-L - lysine 3-nitro-5-fluoroanilide hydrochloride (L-Z LN F A" H C I), N~-benzylo xycarbonyl-L-lysine 3-nitro-5- iodoanilide hydrochloride (L-Z LN I A " H C I), N~-benzylo xycarbonyl-L-lysine 3-nitro-5-(methylsulphonyl) anilide hydrochloride (L-ZLNMA'HCI) and N~-benzyloxycarbonyl-L-lysine 3-nitro-5-(trifluoromethyl) anilide hydrochloride (L-Z LN T A'HCI) were synthesized by the direct condensation of N~-benzyloxycarbonyl, N~-t butyloxycarbonyl-L-lysine and 3-nitro-5X-substituted aniline, where (X=F, Cl, Br, I, H, NO2, CF3 or S02CHa), using dicyclohexylcarbodiimide (DCC) as a coupling reagent. The resulting product, N ~- benzyloxycarbonyl-N~-t-butyloxycarbonyl-L-lysine-3-nitro-5X-substituted anilide was treated with 2 M HCI in dioxane at room temperature to give N~-benzyloxycarbonyl-L-lysine 3-nitro-5X-substituted were found to be stable to relatively wide variations of temperature and pH. Trypsin-catalysed hydrolysis of these substrates at 37°C proceeded at significantly different rates in the following order: L-ZLNIA'HCI> L-ZLNBA'HCI> LZLNCA'HCI> L-ZLNA'HCI> L-ZLNTA'HCI> L-ZLNFA.HCl> L-ZLNMA'HCI> L-ZLDA'HCI. Kinetic and thermodynamic parameters such as K,,, V,,,,=, k,~, E,, AH and AS were determined for the trypsincatalysed hydrolysis of each substrate. A Hammett plot of the catalytic rate constants gave a straight line with a p value of - 1.79 at 37°C thus indicating that electron withdrawing substituents inhibit the trypsin-catalysed hydrolysis of the new lysine substrates.
- ItemOpen AccessDevelopment of a slurry technique for the determination of cadmium in dried foods by electrothermal atomisation atomic absorption spectrometry(pubs.rsc.org, 1986-08) Olayinka, K. O.; Haswell, S. J.; Greszkowiak, R.A method is described for the the determination of cadmium in foods by atomic absorption spectrometry with direct slurry introduction into an electrothermal atomiser. Oxygen infusion facilitates in situ ashing of samples and avoids the build up of carbonaceous residue in the tube. The optimised conditions obtained for instrumental and slurry formation are detailed. Statistical evaluation of results from certified material indicate that the slurry method is both accurate and comparable in precision to traditional wet- and dry-ashing procedures. Calibration is achieved by a simple standard additions technique.
- ItemOpen AccessNew lysine chromogenic substrates for trypsin(Elsevier Science, 1987) Somorin, O.; Okiei, W.O.; Emokpae, T.; Ogunlesi, M.Eight new direct chromogenic lysine substrates, namely N α-benzyloxycarbonyl-l-lysine 3, 5-dinitroanilide hydrochloride (l-ZLDA· Hcl), N α-benzyloxycarbonyl-l-lysine 3-nitroanilide hydrochloride (l-ZLNA· HCl), N α-benzyloxycarbonyl-l-lysine 3-nitro-5-bromoanilide hydrochloride (l-ZLNBA· HCl), N α-benzyloxycarbonyl-l-lysine 3-nitro-5-chloroanilide hydrochloride (l-ZLNCA· HCl), N α-benzyloxycarbonyl-l-lysine 3-nitro-5-fluoroanilide hyrochloride (l-ZLNFA· HCl), N α-benzyloxycarbonyl-l-lysine 3-nitro-5-iodoanilide hydrochloride (l-ZLNIA· HCl), N α-benzyloxycarbonyl-l-lysine 3-nitro-5-(methylsulphonyl) anilide hydrochloride (l-ZLNMA· HCl) and N α-benzyloxycarbonyl-l-lysine 3-nitro-5-(trifluoromethyl) anilide hydrochloride (l-ZLNTA· HCl) were synthesized by the direct condensation of N α-benzyloxycarbonyl, N ϵ-t-butyloxycarbonyl-l-lysine and 3-nitro-5X-substituted aniline,(X= F, Cl, Br, I, H, NO 2, CF 3 or SO 2 CH 3
- ItemOpen AccessSynthesis of 4H‐3,3a‐dihydrothiazolo[4,3‐b]quinazolines(Wiley Online Library, 1987-01) Adegoke, E.A.; Alo, B.I.; Familoni, O.B.Regiospecific synthesis of 4H‐3,3a‐dihydrothiazolo[4,3‐b]quinazolines and 7‐methyl‐4H‐3,3a‐dihydrothiazolo[4,3‐b]quinazolines IVa and IVb is described. The N‐substituted thiazolidinecarboxylic acids Ia and Ib were converted to the corresponding acid chlorides, IIa and IIb but neither reacted with silver trifluoromethanesulphonate. The carboxylic acids Ic and Id were however, decarboxylated to the corresponding iminium ions using phosphorus oxychloride and these afforded the nitroamines IIIa and IIIb. Reductive cyclisation led to the quinazolines IVa and IVb.
- ItemOpen AccessSynthesis of 4H‐3,3a‐dihydrothiazolo[4,3‐b]quinazolines(Journal of Heterocyclic Chemistry, 1987-01) Adegoke, E.A.; Alo, B.I.; Familoni, O.B.Regiospecific synthesis of 4H‐3,3a‐dihydrothiazolo[4,3‐b]quinazolines and 7‐methyl‐4H‐3,3a‐dihydrothiazolo[4,3‐b]quinazolines IVa and IVb is described. The N‐substituted thiazolidinecarboxylic acids Ia and Ib were converted to the corresponding acid chlorides, IIa and IIb but neither reacted with silver trifluoromethanesulphonate. The carboxylic acids Ic and Id were however, decarboxylated to the corresponding iminium ions using phosphorus oxychloride and these afforded the nitroamines IIIa and IIIb. Reductive cyclisation led to the quinazolines IVa and IVb.
- ItemOpen AccessStudies on carboxymethyl derivative and cellulose obtained from cassava residue(1988) Ogunlesi, M.Cassava residue, the material obtained after aqueous extraction of starch from pulverized cassava tubers, was converted to the carboxymethyl derivative of various acid capacities. The acid capacity in 1M KCl was in the range of 0.1 to 0.73 meq/g of dry material while the corresponding value for the underivatized material was 0.03meq/g. The haemoglobin capacity was 214mg/g for the highest substituted derivative , 114mg/g for the least substituted and 60mg/g for the underivatized material. The cellulose contained in the cassava residue had been extracted by a process consisting of enzyme hydrolysis, dissolution in phosphoric acid and regeneration in sodium hydroxide. The acid capacity and protein capacity of the regenerated cellulose show that it compares well with chromatographic – grade cellulose. The cassava residue was derivatized to give the acetate. Copy to clipboard
- ItemOpen AccessPreparation and chromatographic application of hydrophobic supports from cassava cellulose(1988) Ogunlesi, M.; Rao, M.Hydrophobic groups have been incorporated into cassava cellulose to obtain benzyl, phenyl and octyl derivatives. These have been shown to bind serum proteins reversibly. The benzyl and octyl derivatives were used to fractionate serum proteins. The results of electrophoresis confirm the successful application of these supports in the fractionation of serum proteins.
- ItemOpen AccessSpeciation of cadmium in crab meat by reversed-phase high-performance liquid chromatography with electrothermal atomisation atomic absorption spectrometric(pubs.rsc.org, 1989-03) Olayinka, K. O.; Haswell, S. J.; Greszkowiak, R.The development of a model gut system has enabled the study of cadmium bioavailability to be carried out. The use of a biological membrane indicates that although soluble forms of cadmium may exist in the gut, only protein-complexed forms will pass through such a membrane. Chromatographic separation by high- performance liquid chromatography (HPLC) indicates that although cadmium - metallothioneine type complexes are present at the pH values of both the stomach and the intestine, their solubility is significantly reduced in the intestine. Experimental details are given for both the gut model and the speciation methodology used.
- ItemOpen AccessStudies on the antigenic S-type lipopolysaccharides of Brucella abortus strains 7 and Mustapha(Elsevier, 1989-06) Adeyeye, A.; Eze, E.N.; Ogunlesi, M.Antigenic phenol phase S-type lipopolysaccharides (LPS) isolated from Brucella abortus (B. abortus) strains 7 and Mustapha were observed to have 13C n.m.r. spectra which were almost identical to the one reported for the Brucella abortus 1119-3. The glycosyl content of the lipid A obtained from the LPS of strain 7 was found to be 2-acetamido-2-deoxyglucose only while strain Mustapha was found to contain both 2-acetamido-2-deoxyglucose and 2-acetamido-2-deoxygalactose. The fatty acid present in the lipid A of both strains was mainly n-hexadecanoic acid. Octadecanoic acid, 3-hydroxytetradecanoic acid as well as small quantities of 3-hydroxydodecanoic acid were also identified. This contrasts with the earlier reports of the absence of 3-OH-14:0 in the LPS of Brucella abortus.
- ItemOpen AccessStudies on the chemical constitution of the cell-wall lipooligosaccharide from Campylobacter coli, Labet 227(Elsevier, 1989-06-03) Adeyeye, A.; Odugbemi, T.; Ogunlesi, M.The lipo-oligosaccharide (LOS) from Campylobacter coli Labet 227 was extracted by aqueous phenol. After delipidation and gel chromatography, two oligosaccharides were isolated. The higher molecular weight material OS (I) which was estimated to contain six to seven sugar units was found to contain glucose, galactose, 2-acetamido-2-deoxyglucose, 2-acetamido-2-deoxygalactose and heptose. Analysis of the partially methylated alditol acetates by g.c.-m.s. revealed the presence of terminal hexoses, a 1,3-linked hexose, a terminated heptose, a 1,2,3-linked heptose as well as smaller quantities of a 1,3,4-linked heptose. 1H-n.m.r. spectra showed signals corresponding to six anomeric protons. The signals which corresponded to the methyl protons of the acetamido side chain confirmed that the acetamido forms of both amino sugars were present in OS (I). The lower molecular weight material OS (II) which was estimated to contain four sugar units was found to contain glucose, 2-acetamido-2-deoxy-galactose and very small quantities of heptose. It thus appears that OS (I) and OS (II) are the core oligosaccharides elaborated by this micro-organism. The possibility of a heterogeneous core is thus presented. The fatty acids present in the LOS were mainly 3-hydroxytetradecanoic acid, n-hexadecanoic acid and trace amounts of n-tetradecanoic acid and n-octadecanoic acid.
- ItemOpen AccessN-(arylsulphonyl)tetrahydropyridinium salts: intermediates for multi-ring heterocycles. Part 1. Synthesis of hexahydropyrido[1,2-b][1,2,4]benzothiadiazine dioxides(pubs.rsc.org, 1990) Alo, B.I.; Familoni, O.B.N-(Arylsulphonyl)tetrahydropyridinium salts were obtained regiospecifically and in high yield by smooth triflate-assisted decarbonylation of the corresponding N-(arylsulphonyl)piperidine-2-carboxylic acid chlorides at room temperature. These synthons were converted into the nitroamines, which reductively cyclocondensed to give the new 9-substituted tricyclic azacycles, hexahydropyrido[1,2-b][1,2,4]benzothiadiazine 6,6-dioxides.