Cosam C Joseph

University of Dar es Salaam, Dār es Salām, Dar es Salaam, Tanzania

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Publications (33)38.48 Total impact

  • [Show abstract] [Hide abstract] ABSTRACT: Candidiasis is one of the most frequent opportunistic infections in individuals with severe immunosupression and further development of resistance against the available antifungal drugs has created an alarming situation. This requires intensive drug discovery to develop new, more effective, affordable and accessible antifungal agents possessing novel modes of action. Albizia anthelmintica, which is ethno medically used to treat vaginal candidiasis in the Morogoro and coastal regions of Tanzania, on activity guided fractionation and subsequent purification resulted in the isolation and characterization of an isomer of methyl cyclitol (1) and six echinocystic acid saponins (2–7). Saponins 6 and 7 are new and being reported for the first time from nature. Among all the isolated compounds, 3-O-[α-L-arabinopyranosyl (12)][α-L-arabinopyranosyl (16)]-2-acetamido-2-deoxy-β-D-glucopyranosyl echinocystic acid (4), 3-O-[α-L-arabinopyranosyl (12)] [α-L-arabinopyranosyl (16)]-2-amino-2-deoxy-β-D-glucopyranosyl echinocystic acid (6) and 3-O-[β-D-glucopyranosyl (13)] [α-L-arabinopyranosyl (12)] [α-L-arabinopyranosyl (16)]-2-amino-2-deoxy-β-D-glucopyranosyl echinocystic acid (7) and their combinations were active against the various strains of C. albicans with MICs ranging from 12.5 to 125 μg/ml.
    No preview · Article · Jul 2015
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    [Show abstract] [Hide abstract] ABSTRACT: –4, and anticandida activity assay procedures and 1H and 13C-NMR spectroscopic data of 1–4, are available as supporting information .
    No preview · Dataset · Mar 2013
  • [Show abstract] [Hide abstract] ABSTRACT: Azabicycloheptenoylditerpene 1-((2E,6E,10E)-3,7,11,15-tetramethylhexadeca-2,6,10,14-tetraenyl)-2-azabicyclo[2.2.1]hept-5-en-3-one (artamodamide, 1), diphenylpentanoid (E)-1,5-bis(4-hydroxyphenyl)-pent-1-en-3-one (artamenone, 2) and N-methoxy-5-oxoaporphinoid (artamonteirine, 3) were isolated as new metabolites from Artabotrys modestus Diels ssp macranthus Verdc. and Artabotrys monteiroae Oliv. (Annonaceae), together with several known compounds. Structures of the isolated compounds were established based on analysis of their spectroscopic data. Some of the compounds exhibited antimicrobial activity (minimum inhibitory concentration values between 2.5 and 20 µg mL(-1)) and varying levels of mosquito larvicidal potency. These results further indicate the versatility of the family Annonaceae in accumulating bioactive natural products with diverse chemical structures and wide spectra of biological activities, and hence suggesting the need to conserve Annonaceae species that are potentially vulnerable to extinction.
    No preview · Article · Sep 2012 · Natural product research
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    [Show abstract] [Hide abstract] ABSTRACT: Combretum zeyheri Sond (Combretaceae) has been reported to exhibit anticandida activity against Candida kruzei, C. albicans, and C. parapsilosis; however, the active constituents have not been isolated so far. A bioactivity-guided fractionation of MeOH extract of C. zeyheri resulted in the isolation of triterpenoids, ursolic acid (1.1), oleanolic acid (1.2), maslinic acid (2.1), 2α,3β-dihydroxyurs-12-en-28-oic acid (2.2), 6β-hydroxymaslinic acid (3), and terminolic acid (4). These compounds were characterized on the basis of their 1D, 2D NMR, ESI-MS and FT-IR spectroscopic data. All the isolated compounds, 1.2, 2.1, 2.2, 3, and 4 except ursolic acid (1.1) are being reported for the first time from C. zeyheri. Later, the isolated triterpenoids (1–4) were evaluated for their anticandida activity against the three strains of C. albicans and all compounds showed anticandida activity of which terminolic acid (4) was most active. Furthermore, structure–activity relationship of isolated triterpenoids (1–4) was studied, which showed that triterpenoids of oleanane and ursane having 2α,3β,23-trihydroxyl group are more active.
    Full-text · Article · Mar 2012 · Medicinal Chemistry Research
  • [Show abstract] [Hide abstract] ABSTRACT: Toussaintine A (N-cinnamoyl-5,6-dehydro-4-hydroxyindolidin-2,7-dione), toussaintine B (N-cinnamoyl-5,6-dehydro-4,7-dihydroxyindolidin-2-one), toussaintine C (N-cinnamoyl-5,6-dehydro-4-hydroxyindolidin-7-one), toussaintine D (N-cinnamoyl-2-amino-4-hydroxy-7-oxo-2,3,8,9-tetrahydrobenzofuran) and toussaintine E (N-cinnamoyl-1-acetoxymethyl-2-amino-1-hydroxycyclox-5-en-4-one) were isolated as antibacterial and antifungal constituents of the leaves of Toussaintia orientalis Verdc. (Annonaceae) and their structures established from analysis of spectroscopic data. The compounds belong to a series of variously cyclized aminocinnamoyl tetraketide derivatives, showing the importance of rarely occurring Annonaceae species as sources of structurally diverse natural products.
    No preview · Article · Jun 2011 · Phytochemistry
  • [Show abstract] [Hide abstract] ABSTRACT: HIV/AIDS pandemic is currently the most socio-economic challenge that faces Tanzania as it affects mostly the young and most economically productive population. People living with HIV/AIDS in Tanzania are susceptible to fungal and bacterial opportunistic infections, which are a major cause of mortality and morbidity in the country. Despite the government's intervention to provide ARVs to people living with HIV/AIDS, many of them especially those living in the rural areas can neither afford them due to poverty nor access them due to distance to health centers. Moreover, resistance of opportunistic microbial pathogens to conventional medicines and the serious side effects associated with antiretroviral drugs are also a major drawback to the management of HIV/AIDS in the country. Due to these factors, many people opt to use of traditional medicines. This paper highlights the use and conservation of herbal remedies to manage HIV/AIDS pandemic in Tanzania. Ethnobotanical surveys were carried out in Bukoba Rural District to explore the traditional ethno-medical knowledge, the use and conservation of medicinal plants in the management of HIV/AIDS opportunistic infections and to determine whether levels of harvesting are sustainable. The district is currently an epicenter of HIV/AIDS and although over 90% of the population in the district relies on traditional medicines to manage the disease, this traditional knowledge still remains largely unknown. Seventyfive plant species belonging to 66 genera and 40 families were found to be used to treat one or more HIV/AIDS related diseases in the district. Eight plant species were tested in-vitro for their antifungal activity against three major fungal pathogens, Candida albicans (C.P. Robin) Berkhout, Cryptococcus neoformans (San Felice) Vuill., and Aspergillus niger Tiegh. Three of them were further tested in-vivo for their anti-Candida activity. With decreasing natural stocks of medicinal plants, and based on the results, this study further provides concrete recommendations for the conservation of these important non-timber forest products and the region's medicinal plant biodiversity.
    No preview · Article · Jan 2011 · Ethnobotany Research and Applications
  • [Show abstract] [Hide abstract] ABSTRACT: Toussaintine A (N-cinnamoyl-5,6-dehydro-4-hydroxyindolidin-2,7-dione), toussaintine B (N-cinnamoyl-5,6-dehydro-4,7-dihydroxyindolidin-2-one), toussaintine C (N-cinnamoyl-5,6-dehydro-4-hydroxyindoli-din-7-one), toussaintine D (N-cinnamoyl-2-amino-4-hydroxy-7-oxo-2,3,8,9-tetrahydrobenzofuran) and toussaintine E (N-cinnamoyl-1-acetoxymethyl-2-amino-1-hydroxycyclox-5-en-4-one) were isolated as antibacterial and antifungal constituents of the leaves ofToussaintia orientalisVerdc. (Annonaceae) and their structures established from analysis of spectroscopic data. The compounds belong to a series of var-iously cyclized aminocinnamoyl tetraketide derivatives, showing the importance of rarely occurring Annonaceae species as sources of structurally diverse natural products. Keywords: Toussaintia orientalis, Annonaceae, Toussaintines, Indolidinoids, Hydrobenzofuranoid, Antimicrobial
    No preview · Article · Jan 2011 · Phytochemistry
  • [Show abstract] [Hide abstract] ABSTRACT: Plants used in traditional medicine in Tanzania were screened for their cytotoxicity using the brine shrimp and CellTiter-BlueTM cell viability assays. Dichloromethane extracts of Capparis erythrocarpos, Cussonia arborea, Dracaena steudneri, Lannea schimperi, Pseudospondias microcarpa, Rauvolfia vomitoria, Sapium ellipticum and Zehneria scabra exhibited various cytotoxic activities against brine shrimp larvae. Only semi-purified fractions of C. erythrocarpos, C. arborea, D. steudneri, Lannea schimperi and S. ellipticum and one pure compound Lup-20(29)-en-3-one (1) from S.ellipticum were tested against K562 Leukaemia cell line using the CellTiter-BlueTM cell viability assay method. In the brine shrimp lethality assay, P. microcarpa was the most toxic plant with an LC50 value of 1.9 μg/ml (95%CI, 1.6-2.2 μg/ml) , while Z. scabra was the least toxic plant with LC50 value of 179.4 μg/ml (95%CI, 156.1-213.9 μg/ml). In the CellTiter-BlueTM cell viability assay, the mean % cell vitality growth for the fractions of each of the five plant species C. arborea, C. erythrocarpos, D. steudneri, L. schimperi and S. ellipticum were 43.1%, 67.2%, 82.1%, 52.3% and 87.6% respectively, with P<0.0001 and 95% confidence intervals (CI) of 54.746-81.082 μg/ml. The IC50 concentration for compound Lup-20(29)-en-3-one (1) was 1.747x10-6 μM with 95% confidence intervals (CI) of 3.019x10-7 to 1.011x10-4 μM. Results indicate that most of the extracts tested were relatively non-toxic hence supporting the inherent use of these plants in traditional medicine.
    No preview · Article · Jan 2011
  • C Kihampa · Mhh Nkunya · C Joseph · S Magesa
    [Show abstract] [Hide abstract] ABSTRACT: The phenylpropenoids O-methyleugenol, O-methylisoeugenol and 2,3-dimethoxycinnamaldehyde, have been isolated as the antimosquitocidal principles of the stem and root bark extracts of Uvariodendron pycnophyllum (Diels) R.E. Fr. The extracts and compounds exhibited activity with LC50 values in the range 17-59 ppm against the Anopheles gambiae s.s Giles mosquito larvae, while the constituent phenylpropenoids showed long term mortality effects to adult An. gambiae mosquito on impregnated bednets, and mosquito repellency that was stronger than the activity of the standard repellent DEET.
    No preview · Article · Oct 2010
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    [Show abstract] [Hide abstract] ABSTRACT: In traditional African communities, repellent volatiles from certain plants generated by direct burning or by thermal expulsion have played an important role in protecting households against vectors of malaria and other diseases. Previous research on volatile constituents of plants has shown that some are good sources of potent mosquito repellents. In this bioprospecting initiative, the essential oil of leaves of the tree, Suregada zanzibariensis Verdc. (Angiospermae: Euphobiaceae) was tested against the mosquito, Anopheles gambiae s.s. Giles (Diptera: Culicidae) and found to be repellent. Gas chromatography (GC), GC-linked mass spectrometry (GC-MS) and, where possible, GC-co-injections with authentic compounds, led to the identification of about 34 compounds in the essential oil. About 56% of the constituents were terpenoid ketones, mostly methyl ketones. Phenylacetaldehyde (14.4%), artemisia ketone (10.1%), (1S)-(-)-verbenone (12.1%) and geranyl acetone (9.4%) were the main constituents. Apart from phenylacetaldehyde, repellent activities of the other main constituents were higher than that of the essential oil. The blends of the main constituents in proportions found in the essential oil were more repellent to An. gambiae s.s. than was the parent oil (p < 0.05), and the presence of artemisia ketone in the blend caused a significant increase in the repellency of the resulting blend. These results suggested that blends of some terpenoid ketones can serve as effective An. gambiae s.s. mosquito repellents.
    Full-text · Article · Jun 2010 · Journal of Insect Science
  • [Show abstract] [Hide abstract] ABSTRACT: The new aristolactam alkaloid toussalactam {2-hydroxy-1,6-dimethoxy-5H-dibenzo[cdf]indol-4-one} and the known ones, namely aristolactam AII, aristolactam BII, piperolactam C and aristolactam FII; 1-(2-C-methyl-beta-D-ribofuranosyl)-uracil, 3,4,5-trimethoxyphenyl-beta-D-glucopyranoside, and three catechinoids were isolated from the cytotoxic Toussaintia orientalis Verdc stem and root bark extracts, and their structures established based on analysis of spectroscopic data. The aristolactams exhibited antimicrobial and antiinflammatory activity, aristolactam FII showing almost the same level of activity as the standard anti-inflammatory agent Indomethacin. The compounds also exhibited either mild or no antiproliferative and cytotoxic activities, except aristolactam FII that showed the same level of cytotoxicity as the standard drug Camptothecin. 1-(2-C-Methyl-beta-D-ribofuranosyl)-uracil, which is being reported for the first time as a natural product, was inactive in the antibacterial, antifungal, antiinflammatory, antiproliferative and cytotoxicity assays.
    No preview · Article · Feb 2010 · Natural product communications
  • [Show abstract] [Hide abstract] ABSTRACT: The clerodane diterpenoids trans-kolavenolic acid, 18-oxocleroda-3,13(E)-dien-15-oic acid, ent-(18-hydroxycarbonyl)-cleroda-3,13(E)-dien-15-oate, 2-oxo-ent-cleroda-3,13(Z)-dien-15-oic acid and trans-2-oxo-ent-cleroda-13(Z)-en-15-oic acid, and the chlorobenzenoid O-(3-hydroxy-4-hydroxycarbonyl-5-pentylphenyl)-3-chloro-4-methoxy-6-pentyl-2-oxybenzoic acid were isolated from Tessmannia martiniana var pauloi and T. martiniana var matiniana. Structures were established based on interpretation of spectroscopic data. Some of the compounds exhibited significant antimosquito, antifungal and antibacterial activities.
    No preview · Article · Feb 2010 · Natural product communications
  • [Show abstract] [Hide abstract] ABSTRACT: The phenylpropenoids O-methyleugenol, O-methylisoeugenol and 2,3- dimethoxycinnamaldehyde, have been isolated as the antimosquitocidal principles of the stem and root bark extracts of Uvariodendron pycnophyllum (Diels) R.E. Fr. The extracts and compounds exhibited activity with LC50 values in the range 17-59 ppm against the Anopheles gambiae s.s Giles mosquito larvae, while the constituent phenylpropenoids showed long term mortality effects to adult An. gambiae mosquito on impregnated bednets, and mosquito repellency that was stronger than the activity of the standard repellent DEET.
    No preview · Article · Jan 2010
  • [Show abstract] [Hide abstract] ABSTRACT: The nor-halimane diterpenoid tessmannic acid and its methyl, 2-methylisopropyl and 1-methylbutyl esters, the unusual isocoumarins 8-hydroxy-6-methoxy-3-pentylisocoumarin and 7-chloro-8-hydroxy-6-methoxy-3-pentylisocoumarin, and 5-pentyl-3-methoxy-N-butylaniline were isolated from the stem and root bark extracts of Tessmannia densiflora Harms (Caesalpiniaceae) that showed mosquito larvicidal activity. The structures were determined on interpretation of spectroscopic data. Tessmannic acid and its methyl ester exhibited antibacterial and antifungal activity. The compounds also caused high larvae and adult Anopheles gambiae mosquitoe mortality effects, and stronger mosquito repellency than that shown by the standard repellent DEET, hence indicating Tessmannia species to be potential sources of bioactive natural products.
    No preview · Article · Sep 2009 · Phytochemistry
  • [Show abstract] [Hide abstract] ABSTRACT: The furanoditerpenoids voucapane, voucapane-6alpha,7alpha-diol, voucapane-18,19-diol and 18-hydroxyvoucapan-19-al were isolated from the cytotoxic stem and root bark extracts of Stuhlmaniamoavi Verdc. (Ceasalpiniaceae) and their structures established based on analysis of spectroscopic data. The compounds exhibited anti-proliferative, cytotoxic, antibacterial and antifungal activities, 18-hydroxyvoucapan-19-al showing the highest anti-proliferative and cytotoxic properties. Voucapane-18,19-diol was only mildly active but the activity was enhanced for its 18,19-di-(4-methyl)-benzenesulphonate. Some of these results thus corroborate the traditional medicinal uses of the crude extracts for the treatment of skin infections.
    No preview · Article · Sep 2009 · Phytochemistry
  • [Show abstract] [Hide abstract] ABSTRACT: The clerodane diterpenoids trans-kolavenolic acid, 18-oxocleroda-3,13(E)-dien-15-oic acid, ent-(18-hydroxycarbonyl)-cleroda3,13(E)-dien-15-oate, 2-oxo-ent-cleroda-3,13(Z)-dien-15-oic acid and trans-2-oxo-ent-cleroda-13(Z)-en-15-oic acid, and the chlorobenzenoid O-(3-hydroxy-4-hydroxycarbonyl-5-pentylphenyl)-3-chloro-4-methoxy-6-pentyl-2-oxybenzoic acid were isolated from Tessmannia martiniana var pauloi and T. martiniana var matiniana. Structures were established based on interpretation of spectroscopic data. Some of the compounds exhibited significant antimosquito, antifungal and antibacterial activities. Keywords: Tessmannia martiniana var pauloi, T. martiniana var martiniana, Caesalpiniaceae, ent-clerodanoids, chlorobenzenoid, anti-mosquitoes, antimicrobials.
    No preview · Article · Aug 2009 · Natural product communications
  • [Show abstract] [Hide abstract] ABSTRACT: The nor-halimane diterpenoid tessmannic acid and its methyl, 2-methylisopropyl and 1-methylbutyl esters, the unusual isocoumarins 8-hydroxy-6-methoxy-3-pentylisocoumarin and 7-chloro-8-hydroxy- 6-methoxy-3-pentylisocoumarin, and 5-pentyl-3-methoxy-N-butylaniline were isolated from the stem and root bark extracts of Tessmannia densiflora Harms (Caesalpiniaceae) that showed mosquito larvicidal activity. The structures were determined on interpretation of spectroscopic data. Tessmannic acid and its methyl ester exhibited antibacterial and antifungal activity. The compounds also caused high larvae and adult Anopheles gambiae mosquitoe mortality effects, and stronger mosquito repellency than that shown by the standard repellent DEET, hence indicating Tessmannia species to be potential sources of bioactive natural products. Keywords: Tessmannia densiflora; Caesalpiniaceae; Nor-halimanoids; Isocoumarins anti-mosquitoes; Antimicrobials
    No preview · Article · Aug 2009 · Phytochemistry
  • [Show abstract] [Hide abstract] ABSTRACT: Fungal infections represent a significant cause of morbidity and mortality especially in immunocompromised patients in the world today. Dichloromethane (DM) and aqueous (W) extracts of nine plants used traditionally for the treatment of fungal infections in Bukoba rural district in Tanzania were screened for antifungal activity against Candida albicans, Cryptococcus neoformans, and Aspergillus niger using agar well and disk diffusion methods. Dichloromethane extracts of Capparis erythrocarpos [CE] Isert (Capparaceae), Cussonia arborea [CA] Hochst. Ex A. Rich (Araliaceae), Dracaena steudneri [DS] Engl. (Dracaenaceae), Lannea schimperi [LS] (A. Rich) Engl. (Anacardiaceae), Rauvolfia vomitoria [RV] Afz (Apocynaceae), and Sapium ellipticum [SE] (Krauss) Pax (Euphorbiaceae) showed activity against all three fungi. Extracts of Rumex usambarensis [RU] (Dammer) Dammer (Polygonaceae) and Zehneria scabra [ZS] (L.f.) Sond. (Cucurbitaceae) had an activity limited to only one or two of the test organisms. Rhoicissus tridentata [RT] (L.f.) Wild & Drum (Vitaceae) was the only plant without activity. Fractions of the active extracts CE, CA, DS, LS, and SE exhibited higher antifungal activity against one or more of the three fungi. Four compounds isolated from S. ellipticum also exhibited antifungal activity against one or more of the three fungi. The minimum inhibitory concentrations (MICs) and minimum fungicidal concentrations (MFCs), determined using the microplate assay method, ranged between 0.4 and 50.0 μg/mL for crude extracts, 1.6 and 50.0 μg/mL for semi-purified fractions, and 0.12 and 1.0 μg/mL for pure compounds, as compared to 0.016–1.5 μg/mL for fluconazole. We confirm the potential of traditionally used plants as a source of new drugs for treatment of fungal infections.
    No preview · Article · Jul 2009 · Pharmaceutical Biology
  • [Show abstract] [Hide abstract] ABSTRACT: Background & objectives: This paper reports the larvicidal activity of seventeen Tanzanian plant species against the malaria vector, Anopheles gambiae s.s. Giles larvae. Some of the plants are used traditionally as sources of insecticidal materials. Methods: The crude extracts from the leaves, stem and root barks of the investigated plants were obtained by solvent extraction and then bio-assayed following WHO protocols showed LC50 values 10 to 400 ppm after 24 h exposure. The structures were determined on interpretation of spectroscopic data. Results: The most active extracts were those from the stem and root barks of Annona squamosa, Uvaria faulknerae, U. kirkii and Uvariodendron pycnophyllum, all of which had LC50 values between 10 and 100 ppm. Long-term exposure beyond 24 h also showed more susceptibility of the larvae to the extracts. Larvae deformities by forming tail-like structures were observed for the methanol extracts of Tessmannia martiniana var pauloi. Interpretation & conclusion: The results suggest that the investigated plant extracts are promising as larvicides against An. gambiae s.s. Giles mosquitoes and could be useful leads in the search for new and biodegradable plant derived larvicide products. Keywords Anopheles gambiae s.s. – botanical mosquitocides – IGR activity
    No preview · Article · Jun 2009 · Journal of vector borne diseases
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    [Show abstract] [Hide abstract] ABSTRACT: This paper reports the larvicidal activity of seventeen Tanzanian plant species against the malaria vector, Anopheles gambiae s.s. Giles larvae. Some of the plants are used traditionally as sources of insecticidal materials. The crude extracts from the leaves, stem and root barks of the investigated plants were obtained by solvent extraction and then bio-assayed following WHO protocols showed LC50 values 10 to 400 ppm after 24 h exposure. The structures were determined on interpretation of spectroscopic data. The most active extracts were those from the stem and root barks of Annona squamosa, Uvaria faulknerae, U. kirkii and Uvariodendron pycnophyllum, all of which had LC50 values between 10 and 100 ppm. Long-term exposure beyond 24 h also showed more susceptibility of the larvae to the extracts. Larvae deformities by forming tail-like structures were observed for the methanol extracts of Tessmannia martiniana var pauloi. The results suggest that the investigated plant extracts are promising as larvicides against An. gambiae s.s. Giles mosquitoes and could be useful leads in the search for new and biodegradable plant derived larvicide products.
    Full-text · Article · Jun 2009 · Journal of vector borne diseases