Browsing Chemistry by Author "Abegaz, B."
Now showing items 1-13 of 13
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Mbaveng, A.; Ngameni, B.; Kuete, V.; Simo, I.K.; Ambassa, P.; Roy, R.; Bezabili, M.; Etoa, F.X.; Ngadjui, B.; Abegaz, B.; Meyer, J.J.M.; Lall, N.; Beng, V.P. (Elsevier Ireland Ltd. http://www.elsevier.com/wps/find/journaldescription.cws_home/506035/description#description, NaN, 2008)[more][less]
Abstract: The aim of this study was to evaluate the antimicrobial activity of the crude extract of the twigs of Dorstenia barteri (DBT) as well as that of four of the five flavonoids isolated from this extract. Gram-positive bacteria (six species), Gram-negative bacteria (12 species) and fungi (four species) were used. The agar disc diffusion test was used to determine the sensitivity of the tested samples while the well micro-dilution was used to determine the minimal inhibition concentrations (MIC) and the minimal microbicidal concentration (MMC) of the active samples. The results of the disc diffusion assay showed that DBT, isobavachalcone (1), and kanzonol C (4) prevented the growth of all the 22 tested microbial species. Other compounds showed selective activity. The inhibitory activity of the most active compounds namely compounds 1 and 4 was noted on 86.4% of the tested microorganisms and that of 4-hydroxylonchocarpin (3) was observed on 72.7%. This lowest MIC value of 19.06 g/ml was observed with the crude extract on seven microorganisms namely Citrobacter freundii, Enterobacter aerogens, Proteus mirabilis, Proteus vulgaris, Bacillus megaterium, Bacillus stearothermophilus and Candida albicans. For the tested compounds, the lowest MIC value of 0.3 g/ml (on six of the 22 organisms tested) was obtained only with compound 1, which appeared as the most active compound. This lowest MIC value (0.3 g/ml) is about 4-fold lower than that of the RA, indicating the powerful and very interesting antimicrobial potential of isobavachalcone (1). The antimicrobial activities of DBT, as well as that of compounds 1, 3, 4, amentoflavone (5) are being reported for the first time. The overall results provide promising baseline information for the potential use of the crude extracts from DBT as well as some of the isolated compounds in the treatment of bacterial and fungal infections. URI: http://hdl.handle.net/10311/234 Files in this item: 2
Antimicrobial activity of the crude.pdf (2.258Mb)license.txt (1.998Kb) -
Kuete, V.; Metuno, R.; Ngameni, B.; Ngandeu, F.; Bezabih, M.; Etoa, F-X.; Ngadjui, B.; Abegaz, B.; Beng, V. (Elsevier Ltd. www.elsevier.com/locate/sajb, NaN, 2007)[more][less]
Abstract: The crude methanolic extracts from Treculia africana and Treculia acuminata, three compounds isolated from T. africana and identified as, Phyllocoumarin (1), Catechin (2) and 6, 9-dihydroxy-megastigmane-3-one (3), four compounds namely 2, 3, 2,3-dihydroxypropyl-heptadecanoate (4), and Ferulic acid (5) isolated from T. acuminata were tested for their antimicrobial activity against Gram-positive bacteria (six species), Gramnegative bacteria (12 species) and three Candida species. The micro-dilution method for the determination of the minimal inhibition concentration (MIC) and the Minimal microbicidal concentration (MMC) was used. The MIC values obtained with the crude extracts varied from 78 to 156 à ¼g/ ml against 12 (57.14%) and 20 (95.24%) of the 21 tested microorganisms respectively for T. acuminata and T. africana. Apart from compound 2 that prevented the growth of all the tested microorganisms, other bioactive compounds showed selective activity. The obtained results provide promising baseline information for the potential use of these crude extracts as well as some of the isolated compounds in the treatment of bacterial and fungal infections. URI: http://hdl.handle.net/10311/245 Files in this item: 2
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Omisore, N.; Adewunmi, C.; Iwalewa, E.; Ngadjui, B.; Watchueng, J.; Abegaz, B.; Ojewole, J. (Elsevier Ltd. www.elsevier.com/locate/jethpharm, NaN, 2004)[more][less]
Abstract: The present studywas undertaken to investigate the antinociceptive and anti-inflammatory activities of the leaf and twig extracts of Dorstenia barteri (Moraceae) in mice. Both the leaf and twig extracts of Dorstenia barteri at 50, 100 and 200 mg/kg showed significant (P < 0.05-0.01) antinociceptive activities in chemical-, mechanical- and thermal-induced pain test models. Intraperitoneal administration of the plant extracts at 50, 100 and 200 mg/kg significantly (P < 0.05-0.01) inhibited carrageenin-induced acute inflammation in oedema paw weight, pulmonary oedema and number of pleural leucocytes in a dose-dependent way. The twig extract was found to be more active than the leaf extract in all the experimental models used. The inhibitory effects of the plant extracts were comparable to those of the reference drugs acetylsalicyclic acid (ASA) and phenylbutazone (PBZ) at 100 mg/kg i.p. The significant reduction in acetic acid-induced abdominal contractions, the decrease in oedema paw weight as well as in the number of leucocytes in the pleural cavity exudates, and the significant increase in the reaction time and pain threshold of mice observed in this study suggest that Dorstenia barteri extracts possess both anti-inflammatory and antinociceptive activities. The present study, therefore, lend pharmacological support to the folkloric uses of Dorstenia barteri extracts in the treatment, control and/or management of arthritis, rheumatism, gout, headache and other forms of body pains in some parts of Africa. URI: http://hdl.handle.net/10311/256 Files in this item: 2
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Antioxidant activity of prenylated flavonoids from the West African medicinal plant Dorstenia manniiDufall, K.; Ngadjui, B.; Simeon, K.; Abegaz, B.; Croft, K. (Elsevier Science Ireland Ltd. www.elsevier.com/locate/jethpharm, NaN, 2003)[more][less]
Abstract: The antioxidant activities of three prenylated flavonoids from Dorstenia mannii (6,8-diprenyleriodictyol, dorsmanin C and dorsmanin F) were compared to the common, non-prenylated flavonoid, quercetin. The prenylated flavonoids were found to be potent scavengers of the stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH), and are more potent than butylated hydroxy toluene (BHT), a common antioxidant used as a food additive. The prenylated flavonoids also inhibited Cu2+-mediated oxidation of human low density lipoprotein (LDL). Dose-response studies indicated that the prenylated flavonoids were effective inhibitors of lipoprotein oxidation with IC50 values <1 M and had similar inhibitory potency compared to quercetin, but was not directly related to Cu binding. Unlike quercetin, they did not show any pro-oxidant activity at high doses in the Cu2+-mediated lipoprotein oxidation system. The medicinal action of Dorstenia mannii may be related to the high concentration of potent antioxidant prenylated flavonoids in this species. URI: http://hdl.handle.net/10311/261 Files in this item: 2
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Ngadjui, B.; Dongo, E.; Abegaz, B.; Fotso, S.; Tamboue, H. (Elsevier Science Ltd. www.elsevier.com/locate/phytochem, NaN, 2002)[more][less]
Abstract: Three prenylated flavonoids, dinklagins A, B and C identified, respectively, as ( )-6-(3,3-dimethylallyl)-7-hydroxy-6000, 6000-dimethylchromeno-( 40,30,2000,3000)-flavanone, (+)-5,40,500x-trihydroxy-600,600-dimethylchromano-(7,6,200,300)-flavone and (+)6-(2x-hydroxy- 3-methyl-3-butenyl)-5,7,40-trihydroxyflavone were isolated from the twigs of Dorstenia dinklagei together with the known 6-prenylapigenin, 4-hydroxylonchocarpin, stipulin and 5,40-dihydroxy-600,600-dimethylchromano-(7,6,200,300)-flavone. Their structures were determined on the basis of spectral data and by comparison with data reported in the literature and with authentic specimens for known compounds. URI: http://hdl.handle.net/10311/262 Files in this item: 2
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Ngameni, B.; Ngadjui, B.; Folefoc, G.; Watchueng, J.; Abegaz, B. (Elsevier Ltd; www.elsevier.com/locate/phytochem, NaN, 2003)[more][less]
Abstract: The twigs of Dorstenia barteri var. subtriangularis yielded three diprenylated chalcones: ( )-3-(3,3-dimethylallyl)-50-(2-hydroxy-3- methylbut-3-enyl)-4,20,40-trihydroxychalcone, (+)-3-(3,3-dimethylallyl)-40,50-[2000-(1-hydroxy-1-methylethyl)-dihydrofurano]-4,20- dihydroxychalcone and 3,4-(600,600-dimethyldihydropyrano)-40,50-[2000,-(1-hydroxy-1-methylethyl)-dihydrofurano]-20-hydroxychalcone for which the names bartericins A, B and C, respectively, are proposed. Stipulin, b-sitosterol and its 3-b-D-glucopyranosyl derivative were also isolated. The structures of these secondary metabolites were determined on the basis of spectroscopic analysis, especially, NMR spectra in conjunction with 2D experiments, COSY, HMQC and HMBC. The structural relationship of bartericins B and C was further established by the chemical cyclization of one to the other. URI: http://hdl.handle.net/10311/258 Files in this item: 2
Diprenylated chalcones and other.pdf (3.479Mb)license.txt (1.998Kb) -
Nkoanea, B.B.M.; Wibetoe, G.; Lund, W.; Abegaz, B. (South African Journal of Science, NaN, 2007)[more][less]
Abstract: BLEPHARIS ASPERA WAS COLLECTED FROM A copper–nickel mineralized area in Botswana and examined as a possible Cu–Ni indicator plant for biogeochemical prospecting. Different plant parts and the host soils were analysed using ultrasonic slurry sampling electrothermal atomic absorption spectrometry. All plant parts accumulated Cu and Ni in above-normal amounts, although not in hyperaccumulator concentrations. The leaf to soil Cu concentration ratio varied little with metal concentration in the soil. We propose Blepharis aspera as a Cu indicator plant. URI: http://hdl.handle.net/10311/282 Files in this item: 1
Examination of Blepharis.pdf (1.160Mb) -
Mutanyatta, J.; Bezabih, M.; Abegaz, B.; Dreyer, M.; Brun, R.; Kocher, N.; Bringmann, G (Elsevier Ltd.http://www.elsevier.com/wps/find/journaldescription.cws_home/942/description#description, NaN, 2005)[more][less]
Abstract: From the roots of Bulbine frutescens, the first sulfated phenylanthraquinones were isolated, together with their known sulfate-free analogs. Their structures were elucidated by spectroscopic and chiroptical methods, by acid hydrolysis or by partial synthesis. The new compounds have the usual stereo-orientation at the biaryl axis (i.e., with the acetyl portion above the anthraquinone plane) except for sodium ent-knipholone 60-O-sulfate (and thus, also its hydrolysis product, ent-knipholone), which exhibit an opposite axial configuration. We also describe the first stereoanalysis of natural phenylanthraquinones, some of which were found to be not enantiomerically pure, some even nearracemic. We furthermore, report on the first X-ray structure analysis of a phenylanthraquinone, viz. 40-O-demethylknipholone. URI: http://hdl.handle.net/10311/246 Files in this item: 2
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Mutanyatta, J.; Matapa, B.; Shushu, D.; Abegaz, B. (Elsevier Ltd. www.elsevier.com/locate/phytochem, NaN, 2002)[more][less]
Abstract: Eleven homoisoflavonoids and two xanthones were isolated and characterized from the bulbs of Ledebouria graminifolia. Five of the homoisoflavonoids are new compounds and were identified as: 5-hydroxy-7-methoxy-3-(40-hydroxybenzyl)-4-chromanone, 5-hydroxy-6,7-dimethoxy-3-(40-hydroxybenzyl)-4-chromanone, 5,7,8-trimethoxy-3-(40-hydroxybenzyl)-4-chromanone, 5-hydroxy- 30,40,7-trimethoxyspiro{2H-1-benzopyran-70-bicyclo[4.2.0]octa[1,3,5]-trien}-4-one, 5,7-dihydroxy-30,40-dimethoxyspiro{2H-1-benzopyran- 70-bicyclo[4.2.0]octa[1,3,5]-trien}-4-one. Structures were elucidated by extensive 1D, and 2D NMR spectroscopy and HRMS. A method for tissue culture was developed and the bulbs of mature plants were found to contain all the compounds isolated from the wild specimens of L. graminifolia. URI: http://hdl.handle.net/10311/249 Files in this item: 2
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Kapche, G.; Laatsch, H.; Fotso, S.; Kouam, S.; Wafo, P.; Ngadjui, B.; Abegaz, B. (Elsevier Ltd. www.elsevier.com/locate/biochemsyseco, NaN, 2007)[more][less]
Abstract: The genus Lannea belongs to the family Anacardiaceae and consists of 40 species. Lannea nigritana (Sc. Elliot) Keay is a small tree of 3e6 m of height found in the tropical rain forest (Berhaut, 1971; Letouzey, 1972). It is used in the traditional medicine for the treatment of various infectious diseases (Berhaut, 1971; Burkill, 1985). The stem bark of this plant was collected in Makenene, Centre Province of Cameroon in December 2003. The identification was done by Mr. Nana from the National Herbarium of Yaounde where a voucher specimen (N 40408/HNC) documenting the collection is deposited. URI: http://hdl.handle.net/10311/252 Files in this item: 2
Lanneanol.pdf (2.606Mb)license.txt (1.998Kb) -
Ngadjui, B.; Watchueng, J.; Keumedjio, F.; Ngameni, B.; Simo, I.; Abegaz, B. (Elsevier Ltd. www.elsevier.com/locate/phytochem, NaN, 2004)[more][less]
Abstract: The twigs of Dorstenia angusticornis and Dorstenia barteri var. subtriangularis yielded 16 compounds. Two novel diprenylated chalcones: 3,50-di-(2-hydroxy-3-methylbut-3-enyl)-4,20,40-trihydroxychalcone, 3, 4-(2,2-dimethylpyrano)-30-(2-hydroxy-3-methylbut- 3-enyl)-20,40-dihydroxychalcone and the known stipulin were isolated from both species. 3-(2-Hydroxy-3-methylbut-3-enyl)- 50-(3,3-dimethylallyl)-4,20,40-trihydroxychalcone and the known compounds: 4-hydroxylonchocarpin, kanzonol B, bartericins A, B, C and 30-(2-hydroxy -3-methylbut-3-enyl)-4,20,40-trihydroxychalcone were isolated from D. barteri while the known compounds: gancaonin Q, paratocarpins C, F, and lupeol were obtained from Dorstenia angusticornis. b-Sitosterol and its b-D-glucopyranoside were isolated from both species. Structures of these secondary metabolites were established using spectroscopic analysis, especially, NMR spectra in conjunction with 2D experiments, COSY, HMQC and HMBC. URI: http://hdl.handle.net/10311/253 Files in this item: 2
license.txt (1.998Kb)Prenylated chalcones, flavone.pdf (3.563Mb) -
Ngandeu, F.; Bezabih, M.; Ngamga, D.; Tchinda, A.; Ngadjui, B.; Abegaz, B.; Dufat, H.; Tillequin, F. (Elsevier Ltd. www.elsevier.com/locate/phytochem, NaN, 2007)[more][less]
Abstract: Three prenylated rotenoids, elliptol, 12-deoxo-12a-methoxyelliptone and 6-methoxy-6a,12a-dehydrodeguelin were isolated from the twigs of Millettia duchesnei, together with the known compounds, 6a,12a-dehydrodeguelin, 6-hydroxy-6a,12a-dehydrodeguelin, 6-oxo- 6a,12a-dehydrodeguelin, elliptone, 12a-hydroxyelliptone and eriodictyol. Their structures were elucidated on the basis of spectral data and comparison with information reported in the literature and with authentic specimens for some known compounds. The full NMR data of 6-oxo-6a,12a-dehydrodeguelin and 6-hydroxy-6a,12a-dehydrodeguelin are reported here for the first time. URI: http://hdl.handle.net/10311/243 Files in this item: 2
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Ngamba, D.; Awouafack, M.; Tane, P.; Bezabih, M.; Abegaz, B. (Elsevier Ltd. www.elsevier.com/locate/biochemsyseco, NaN, 2007)[more][less]
Abstract: Gladiolus psittascinus HOOK, an herbaceous plant, is propagated by its bulb. This onion-looking plant occurs in rocky places in western province of Cameroon. The bulbs are used to treat asthma, gonorrhoea, diabetes and intestinal parasites (Adjanohoun et al., 1990). The bulbs of G. psittascinus were collected in Dschang (West Province of Cameroon) in July 2005 and identified by Mr Francois Nana, a botanist at the National Herbarium, Yaounde where a voucher specimen (55925 HCN) is deposited. We report here the isolation and structural elucidation from the chloroform extract of two new anthraquinones namely: 1,6,7-trihydroxy-3-methoxy-8-methyl-anthraquinone (1) and 1-hydroxy-3,6,7-trimethoxy-8-methyl-anthraquinone (2) along with four known compounds. The structures of the compounds were elucidated by spectroscopic analysis, mainly, 1D and 2D NMR and by comparing their physical (mp) and spectroscopic (Table 1) data with those reported in the literature. URI: http://hdl.handle.net/10311/248 Files in this item: 4
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